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- 1. © 2012 Pearson Education, Inc. Lecture by Edward J. Zalisko PowerPoint Lectures for Campbell Biology: Concepts & Connections, Seventh Edition Reece, Taylor, Simon, and Dickey Chapter 3Chapter 3 The Molecules of Cells
- 2. Figure 3.0_1 Chapter 3: Big Ideas Introduction to Organic Compounds Carbohydrates Lipids Proteins Nucleic Acids
- 3. 3.1 Life’s molecular diversity is based on the properties of carbon Diverse molecules found in cells are composed of carbon bonded to – other carbon atoms and – atoms of other elements. Carbon-based molecules are called: – organic compounds. © 2012 Pearson Education, Inc.
- 4. 3.1 By sharing electrons, carbon can – bond to four other atoms and – branch in up to four directions. Methane (CH4) is one of the simplest organic compounds. – Four covalent bonds link four hydrogen atoms to the carbon atom. – Each of the four lines in the formula for methane represents a pair of shared electrons. © 2012 Pearson Education, Inc.
- 5. Figure 3.1A Structural formula Ball-and-stick model Space-filling model The four single bonds of carbon point to the corners of a tetrahedron.
- 6. 3.1 Methane and other compounds composed of only carbon and hydrogen are called hydrocarbons. Carbon, with attached hydrogens, can bond together in chains of various lengths. © 2012 Pearson Education, Inc.
- 7. 3.2 A few chemical groups are key to the functioning of biological molecules An organic compound has unique properties that depend upon the – size and shape of the molecule and – groups of atoms (functional groups) attached to it. Compounds containing functional groups are hydrophilic (water-loving). © 2012 Pearson Education, Inc.
- 8. Table 3.2_1
- 9. Table 3.2_2
- 10. 3.2 An example of similar compounds that differ only in functional groups is sex hormones. – Male and female sex hormones differ only in functional groups. – The differences cause varied molecular actions. – The result is distinguishable features of males and females. © 2012 Pearson Education, Inc.
- 11. 3.3 Cells make a huge number of large molecules from a limited set of small molecules There are four classes of molecules important to organisms: – carbohydrates, – proteins, – lipids, and – nucleic acids. © 2012 Pearson Education, Inc.
- 12. 3.3 The four classes of biological molecules contain very large molecules. – They are often called macromolecules because of their large size. – They are also called polymers because they are made from identical building blocks strung together. – The building blocks of polymers are called monomers. © 2012 Pearson Education, Inc.
- 13. A cell makes a large number of polymers from a small group of monomers. For example, – proteins are made from only 20 different amino acids and – DNA is built from just four kinds of nucleotides. 3.3 © 2012 Pearson Education, Inc.
- 14. 3.3 Monomers are linked together to form polymers through dehydration reactions, which remove water. Polymers are broken apart by hydrolysis, the addition of water. All biological reactions of this sort are mediated by enzymes, which speed up chemical reactions in cells. © 2012 Pearson Education, Inc. Animation: Polymers
- 15. Figure 3.3A_s1 Short polymer Unlinked monomer
- 16. Figure 3.3A_s2 Short polymer Unlinked monomer Dehydration reaction forms a new bond Longer polymer
- 17. Figure 3.3B_s1
- 18. Figure 3.3B_s2 Hydrolysis breaks a bond
- 19. CARBOHYDRATES © 2012 Pearson Education, Inc.
- 20. 3.4 Monosaccharides are the simplest carbohydrates Carbohydrates range from small sugar molecules (monomers) to large polysaccharides. Sugar monomers are monosaccharides, such as those found in honey, – glucose, and – fructose. Monosaccharides can be hooked together to form – more complex sugars and – polysaccharides. © 2012 Pearson Education, Inc.
- 21. 3.4 Monosaccharides are the simplest carbohydrates The carbon skeletons of monosaccharides vary in length. – Glucose and fructose are six carbons long. – Others have three to seven carbon atoms. Monosaccharides are – the main fuels for cellular work and – used as raw materials to manufacture other organic molecules. © 2012 Pearson Education, Inc.
- 22. 3.4 Monosaccharides are the simplest carbohydrates Many monosaccharides form rings. The ring diagram may be – abbreviated by not showing the carbon atoms at the corners of the ring and – drawn with different thicknesses for the bonds, to indicate that the ring is a relatively flat structure with attached atoms extending above and below it. © 2012 Pearson Education, Inc.
- 24. 3.5 Two monosaccharides are linked to form a disaccharide Two monosaccharides (monomers) can bond to form a disaccharide in a dehydration reaction. The disaccharide sucrose is formed by combining – a glucose monomer and – a fructose monomer. The disaccharide maltose is formed from two glucose monomers. © 2012 Pearson Education, Inc. Animation: Disaccharides
- 27. 3.6 CONNECTION: What is high-fructose corn syrup, and is it to blame for obesity? Sodas or fruit drinks probably contain high-fructose corn syrup (HFCS). Fructose is sweeter than glucose. To make HFCS, glucose atoms are rearranged to make the glucose isomer, fructose. © 2012 Pearson Education, Inc.
- 28. 3.6 CONNECTION: What is high-fructose corn syrup, and is it to blame for obesity? High-fructose corn syrup (HFCS) is – used to sweeten many beverages and – may be associated with weight gain. Good health is promoted by – a diverse diet of proteins, fats, vitamins, minerals, and complex carbohydrates and – exercise. © 2012 Pearson Education, Inc.
- 29. Figure 3.6
- 30. 3.7 Polysaccharides are long chains of sugar units Polysaccharides are – macromolecules and – polymers composed of thousands of monosaccharides. Polysaccharides may function as – storage molecules or – structural compounds. © 2012 Pearson Education, Inc.
- 31. 3.7 Polysaccharides are long chains of sugar units Starch is – a polysaccharide, – composed of glucose monomers, and – used by plants for energy storage. Glycogen is – a polysaccharide, – composed of glucose monomers, and – used by animals for energy storage. © 2012 Pearson Education, Inc.
- 32. 3.7 Polysaccharides are long chains of sugar units Cellulose – is a polymer of glucose and – forms plant cell walls. Chitin is – a polysaccharide and – used by insects and crustaceans to build an exoskeleton. © 2012 Pearson Education, Inc.
- 33. Figure 3.7 Starch granules in potato tuber cells Glycogen granules in muscle tissue Glycogen Glucose monomer Starch Cellulose Hydrogen bonds Cellulose molecules Cellulose microfibrils in a plant cell wall
- 34. 3.7 Polysaccharides are long chains of sugar units Polysaccharides are usually hydrophilic (water- loving). Bath towels are – often made of cotton, which is mostly cellulose, and – water absorbent. © 2012 Pearson Education, Inc. Animation: Polysaccharides
- 35. 3.8 Fats are lipids that are mostly energy-storage molecules Lipids – are water insoluble (hydrophobic, or water-fearing) compounds, – are important in long-term energy storage, – contain twice as much energy as a polysaccharide, and – consist mainly of carbon and hydrogen atoms linked by nonpolar covalent bonds. © 2012 Pearson Education, Inc.
- 36. Figure 3.8A
- 37. 3.8 Fats are lipids that are mostly energy-storage molecules Lipids differ from carbohydrates, proteins, and nucleic acids in that they are – not huge molecules and – not built from monomers. Lipids vary a great deal in – structure and – function. © 2012 Pearson Education, Inc.
- 38. 3.8 Fats are lipids that are mostly energy-storage molecules We will consider three types of lipids: – fats, – phospholipids, and – steroids. A fat is a large lipid made from two kinds of smaller molecules, – glycerol and – fatty acids. © 2012 Pearson Education, Inc.
- 39. 3.8 Fats are lipids that are mostly energy-storage molecules A fatty acid can link to glycerol by a dehydration reaction. A fat contains one glycerol linked to three fatty acids. Fats are often called triglycerides because of their structure. © 2012 Pearson Education, Inc. Animation: Fats
- 42. 3.8 Fats are lipids that are mostly energy-storage molecules Some fatty acids contain one or more double bonds, forming unsaturated fatty acids that – have one fewer hydrogen atom on each carbon of the double bond, – cause kinks or bends in the carbon chain, and – prevent them from packing together tightly and solidifying at room temperature. Fats with the maximum number of hydrogens are called saturated fatty acids. © 2012 Pearson Education, Inc.
- 43. 3.8 Fats are lipids that are mostly energy-storage molecules Unsaturated fats include corn and olive oils. Most animal fats are saturated fats. Hydrogenated vegetable oils are unsaturated fats that have been converted to saturated fats by adding hydrogen. This hydrogenation creates trans fats associated with health risks. © 2012 Pearson Education, Inc.
- 44. 3.9 Phospholipids and steroids are important lipids with a variety of functions Phospholipids are – structurally similar to fats and – the major component of all cells. Phospholipids are structurally similar to fats. – Fats contain three fatty acids attached to glycerol. – Phospholipids contain two fatty acids attached to glycerol. © 2012 Pearson Education, Inc.
- 45. Figure 3.9A-B Water Hydrophobic tails Water Hydrophilic heads Symbol for phospholipid Phosphate group Glycerol
- 46. Figure 3.9A Hydrophobic tail Hydrophilic head Phosphate group Glycerol
- 47. 3.9 Phospholipids and steroids are important lipids with a variety of functions Phospholipids cluster into a bilayer of phospholipids. The hydrophilic heads are in contact with – the water of the environment and – the internal part of the cell. The hydrophobic tails band in the center of the bilayer. © 2012 Pearson Education, Inc.
- 48. Figure 3.9B Water Hydrophobic tail Water Hydrophilic head Symbol for phospholipid
- 49. 3.9 Phospholipids and steroids are important lipids with a variety of functions Steroids are lipids in which the carbon skeleton contains four fused rings. Cholesterol is a – common component in animal cell membranes and – starting material for making steroids, including sex hormones. © 2012 Pearson Education, Inc.
- 50. Figure 3.9C
- 51. 3.10 CONNECTION: Anabolic steroids pose health risks Anabolic steroids – are synthetic variants of testosterone, – can cause a buildup of muscle and bone mass, and – are often prescribed to treat general anemia and some diseases that destroy body muscle. © 2012 Pearson Education, Inc.
- 52. 3.10 CONNECTION: Anabolic steroids pose health risks Anabolic steroids are abused by some athletes with serious consequences, including – violent mood swings, – depression, – liver damage, – cancer, – high cholesterol, and – high blood pressure. © 2012 Pearson Education, Inc.
- 53. Figure 3.10
- 54. 3.11 Proteins are made from amino acids linked by peptide bonds Proteins are – involved in nearly every dynamic function in your body and – very diverse, with tens of thousands of different proteins, each with a specific structure and function, in the human body. Proteins are composed of differing arrangements of a common set of just 20 amino acid monomers. © 2012 Pearson Education, Inc.
- 55. 3.11 Proteins are made from amino acids linked by peptide bonds Amino acids have – an amino group and – a carboxyl group (which makes it an acid). Also bonded to the central carbon is – a hydrogen atom and – a chemical group symbolized by R, which determines the specific properties of each of the 20 amino acids used to make proteins. © 2012 Pearson Education, Inc.
- 57. 3.11 Proteins are made from amino acids linked by peptide bonds Amino acid monomers are linked together – in a dehydration reaction, – joining carboxyl group of one amino acid to the amino group of the next amino acid, and – creating a peptide bond. Additional amino acids can be added by the same process to create a chain of amino acids called a polypeptide. © 2012 Pearson Education, Inc.
- 59. Figure 3.11C_s2 Carboxyl group Amino group Amino acidAmino acid Dipeptide Peptide bond Dehydration reaction
- 60. 3.12 A protein’s specific shape determines its function Probably the most important role for proteins is as enzymes, proteins that – serve as metabolic catalysts and – regulate the chemical reactions within cells. © 2012 Pearson Education, Inc.
- 61. 3.12 A protein’s specific shape determines its function Other proteins are also important. – Structural proteins provide associations between body parts. – Contractile proteins are found within muscle. – Defensive proteins include antibodies of the immune system. – Signal proteins are best exemplified by hormones and other chemical messengers. – Receptor proteins transmit signals into cells. – Transport proteins carry oxygen. – Storage proteins serve as a source of amino acids for developing embryos. © 2012 Pearson Education, Inc.
- 62. Figure 3.12A
- 63. 3.12 A protein’s specific shape determines its function A polypeptide chain contains hundreds or thousands of amino acids linked by peptide bonds. The amino acid sequence causes the polypeptide to assume a particular shape. The shape of a protein determines its specific function. © 2012 Pearson Education, Inc.
- 66. 3.12 A protein’s specific shape determines its function If a protein’s shape is altered, it can no longer function. In the process of denaturation, a polypeptide chain – unravels, – loses its shape, and – loses its function. Proteins can be denatured by changes in salt concentration, pH, or by high heat. © 2012 Pearson Education, Inc.
- 67. 3.13 A protein’s shape depends on four levels of structure A protein can have four levels of structure: – primary structure – secondary structure – tertiary structure – quaternary structure © 2012 Pearson Education, Inc.
- 68. 3.13 A protein’s shape depends on four levels of structure The primary structure of a protein is its unique amino acid sequence. – The correct amino acid sequence is determined by the cell’s genetic information. – The slightest change in this sequence may affect the protein’s ability to function. © 2012 Pearson Education, Inc.
- 69. 3.13 A protein’s shape depends on four levels of structure Protein secondary structure results from coiling or folding of the polypeptide. – Coiling results in a helical structure called an alpha helix. – A certain kind of folding leads to a structure called a pleated sheet, which dominates some fibrous proteins such as those used in spider webs. – Coiling and folding are maintained by regularly spaced hydrogen bonds between hydrogen atoms and oxygen atoms along the backbone of the polypeptide chain. © 2012 Pearson Education, Inc.
- 70. Figure 3.13_1
- 72. 3.13 A protein’s shape depends on four levels of structure The overall three-dimensional shape of a polypeptide is called its tertiary structure. – Tertiary structure generally results from interactions between the R groups of the various amino acids. – Disulfide bridges may further strengthen the protein’s shape. © 2012 Pearson Education, Inc.
- 73. 3.13 A protein’s shape depends on four levels of structure Two or more polypeptide chains (subunits) associate providing quaternary structure. – Collagen is an example of a protein with quaternary structure. – Collagen’s triple helix gives great strength to connective tissue, bone, tendons, and ligaments. © 2012 Pearson Education, Inc. Animation: Secondary Protein Structure Animation: Primary Protein Structure Animation: Quaternary Protein Structure Animation: Tertiary Protein Structure Animation: Protein Structure Introduction
- 74. Figure 3.13A_s1 Primary structure Amino acids Amino acids Four Levels of Protein Structure
- 75. Figure 3.13A-B_s2 Primary structure Amino acids Amino acids Four Levels of Protein Structure Beta pleated sheet Alpha helix Hydrogen bond Secondary structure
- 76. Figure 3.13A-C_s3 Primary structure Amino acids Amino acids Four Levels of Protein Structure Beta pleated sheet Alpha helix Hydrogen bond Secondary structure Tertiary structure Transthyretin polypeptide
- 77. Figure 3.13A-D_s4 Primary structure Amino acids Amino acids Four Levels of Protein Structure Beta pleated sheet Alpha helix Hydrogen bond Secondary structure Tertiary structure Transthyretin polypeptide Quaternary structure Transthyretin, with four identical polypeptides
- 78. 3.14 DNA and RNA are the two types of nucleic acids The amino acid sequence of a polypeptide is programmed by a discrete unit of inheritance known as a gene. Genes consist of DNA(deoxyribonucleic acid), a type of nucleic acid. DNA is inherited from an organism’s parents. DNA provides directions for its own replication. DNA programs a cell’s activities by directing the synthesis of proteins. © 2012 Pearson Education, Inc.
- 79. 3.14 DNA and RNA are the two types of nucleic acids DNA does not build proteins directly. DNA works through an intermediary, ribonucleic acid (RNA). – DNA is transcribed into RNA. – RNA is translated into proteins. © 2012 Pearson Education, Inc.
- 83. 3.15 Nucleic acids are polymers of nucleotides DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are composed of monomers called nucleotides. Nucleotides have three parts: – a five-carbon sugar called ribose in RNA and deoxyribose in DNA, – a phosphate group, and – a nitrogenous base. © 2012 Pearson Education, Inc.
- 85. 3.15 Nucleic acids are polymers of nucleotides DNA nitrogenous bases are – adenine (A), – thymine (T), – cytosine (C), and – guanine (G). RNA – also has A, C, and G, – but instead of T, it has uracil (U). © 2012 Pearson Education, Inc.
- 86. 3.15 Nucleic acids are polymers of nucleotides A nucleic acid polymer, a polynucleotide, forms – from the nucleotide monomers, – when the phosphate of one nucleotide bonds to the sugar of the next nucleotide, – by dehydration reactions, and – by producing a repeating sugar-phosphate backbone with protruding nitrogenous bases. © 2012 Pearson Education, Inc.
- 88. 3.15 Nucleic acids are polymers of nucleotides Two polynucleotide strands wrap around each other to form a DNA double helix. – The two strands are associated because particular bases always hydrogen bond to one another. – A pairs with T, and C pairs with G, producing base pairs. RNA is usually a single polynucleotide strand. © 2012 Pearson Education, Inc.
- 89. Figure 3.15C Base pair A C T GC C G T A C G A T TA G C TA TA AT
- 90. 3.16 EVOLUTION CONNECTION: Lactose tolerance is a recent event in human evolution The majority of people – stop producing the enzyme lactase in early childhood and – do not easily digest the milk sugar lactose. Lactose tolerance represents a – relatively recent mutation in the human genome and – survival advantage for human cultures with milk and dairy products available year-round. © 2012 Pearson Education, Inc.
- 91. 3.16 EVOLUTION CONNECTION: Lactose tolerance is a recent event in human evolution Researchers identified three mutations that keep the lactase gene permanently turned on. The mutations appear to have occurred – about 7,000 years ago and – at the same time as the domestication of cattle in these regions. © 2012 Pearson Education, Inc.
- 92. Figure 3.16
- 93. You should now be able to 1. Describe the importance of carbon to life’s molecular diversity. 2. Describe the chemical groups that are important to life. 3. Explain how a cell can make a variety of large molecules from a small set of molecules. 4. Define monosaccharides, disaccharides, and polysaccharides and explain their functions. 5. Define lipids, phospholipids, and steroids and explain their functions. © 2012 Pearson Education, Inc.
- 94. You should now be able to 6. Describe the chemical structure of proteins and their importance to cells. 7. Describe the chemical structure of nucleic acids and how they relate to inheritance. 8. Explain how lactose tolerance has evolved in humans. © 2012 Pearson Education, Inc.
Notes de l'éditeur
- Figure 3.0_1 Chapter 3: Big Ideas
- Student Misconceptions and Concerns General biology students might not have previously taken a chemistry course. The concept of molecular building blocks that cannot be seen can be abstract and difficult to comprehend for such students. Concrete examples from our diets and good images will increase comprehension. Students might need to be reminded about the levels of biological organization. The relationship between atoms, monomers, and polymers can be confusing as each is discussed. Consider noting these relationships somewhere in the classroom (such as on the board) where students can quickly glance for reassurance. Teaching Tips One of the great advantages of carbon is its ability to form up to four bonds, permitting the assembly of diverse components and branching configurations. Challenge your students to find another element that might also permit this sort of adaptability. (Like carbon, silicon has four electrons in its outer shell.) Toothpicks and gumdrops (or any other pliable small candy) permit the quick construction of chemical models. Different candy colors can represent certain atoms. The model of the methane molecule in Figure 3.1 can thus easily be demonstrated (and consumed)!
- Student Misconceptions and Concerns General biology students might not have previously taken a chemistry course. The concept of molecular building blocks that cannot be seen can be abstract and difficult to comprehend for such students. Concrete examples from our diets and good images will increase comprehension. Students might need to be reminded about the levels of biological organization. The relationship between atoms, monomers, and polymers can be confusing as each is discussed. Consider noting these relationships somewhere in the classroom (such as on the board) where students can quickly glance for reassurance. Teaching Tips One of the great advantages of carbon is its ability to form up to four bonds, permitting the assembly of diverse components and branching configurations. Challenge your students to find another element that might also permit this sort of adaptability. (Like carbon, silicon has four electrons in its outer shell.) Toothpicks and gumdrops (or any other pliable small candy) permit the quick construction of chemical models. Different candy colors can represent certain atoms. The model of the methane molecule in Figure 3.1 can thus easily be demonstrated (and consumed)!
- Figure 3.1A Three representations of methane (CH 4 )
- Student Misconceptions and Concerns General biology students might not have previously taken a chemistry course. The concept of molecular building blocks that cannot be seen can be abstract and difficult to comprehend for such students. Concrete examples from our diets and good images will increase comprehension. Students might need to be reminded about the levels of biological organization. The relationship between atoms, monomers, and polymers can be confusing as each is discussed. Consider noting these relationships somewhere in the classroom (such as on the board) where students can quickly glance for reassurance. Teaching Tips One of the great advantages of carbon is its ability to form up to four bonds, permitting the assembly of diverse components and branching configurations. Challenge your students to find another element that might also permit this sort of adaptability. (Like carbon, silicon has four electrons in its outer shell.) Toothpicks and gumdrops (or any other pliable small candy) permit the quick construction of chemical models. Different candy colors can represent certain atoms. The model of the methane molecule in Figure 3.1 can thus easily be demonstrated (and consumed)!
- Student Misconceptions and Concerns General biology students might not have previously taken a chemistry course. The concept of molecular building blocks that cannot be seen can be abstract and difficult to comprehend for such students. Concrete examples from our diets and good images will increase comprehension. Teaching Tips A drill with interchangeable drill bits is a nice analogy to carbon skeletons with different functional groups. The analogy relates the role of different functions to different structures.
- Table 3.2_1 Important chemical groups of organic compounds (part 1)
- Table 3.2_2 Important chemical groups of organic compounds (part 2)
- Student Misconceptions and Concerns General biology students might not have previously taken a chemistry course. The concept of molecular building blocks that cannot be seen can be abstract and difficult to comprehend for such students. Concrete examples from our diets and good images will increase comprehension. Teaching Tips A drill with interchangeable drill bits is a nice analogy to carbon skeletons with different functional groups. The analogy relates the role of different functions to different structures.
- Student Misconceptions and Concerns General biology students might not have previously taken a chemistry course. The concept of molecular building blocks that cannot be seen can be abstract and difficult to comprehend for such students. Concrete examples from our diets and good images will increase comprehension. Teaching Tips 1. Train cars linking together to form a train is a nice analogy to linking monomers to form polymers. Consider adding that as the train cars are joined, a puff of steam appears—a reference to water production and a dehydration reaction when linking molecular monomers. 2. The authors note that the great diversity of polymers mainly results from the arrangement of polymers, the different sequences made possible by combinations or permutations of the same monomers. Consider illustrating this by simply asking students how many different ways can we arrange the letters A, B, and C, using each letter, and only once, to form 3-lettered words. The answer is 6 permutations: ABC, ACB, BAC, BCA, CBA, CAB (the factorial of 3). And if letters can be repeated, the answer is 27 (= 3 3 ): AAA, BBB, CCC, ABB, ACC, etc.
- Student Misconceptions and Concerns General biology students might not have previously taken a chemistry course. The concept of molecular building blocks that cannot be seen can be abstract and difficult to comprehend for such students. Concrete examples from our diets and good images will increase comprehension. Teaching Tips 1. Train cars linking together to form a train is a nice analogy to linking monomers to form polymers. Consider adding that as the train cars are joined, a puff of steam appears—a reference to water production and a dehydration reaction when linking molecular monomers. 2. The authors note that the great diversity of polymers mainly results from the arrangement of polymers, the different sequences made possible by combinations or permutations of the same monomers. Consider illustrating this by simply asking students how many different ways can we arrange the letters A, B, and C, using each letter, and only once, to form 3-lettered words. The answer is 6 permutations: ABC, ACB, BAC, BCA, CBA, CAB (the factorial of 3). And if letters can be repeated, the answer is 27 (= 3 3 ): AAA, BBB, CCC, ABB, ACC, etc.
- Student Misconceptions and Concerns General biology students might not have previously taken a chemistry course. The concept of molecular building blocks that cannot be seen can be abstract and difficult to comprehend for such students. Concrete examples from our diets and good images will increase comprehension. Teaching Tips 1. Train cars linking together to form a train is a nice analogy to linking monomers to form polymers. Consider adding that as the train cars are joined, a puff of steam appears—a reference to water production and a dehydration reaction when linking molecular monomers. 2. The authors note that the great diversity of polymers mainly results from the arrangement of polymers, the different sequences made possible by combinations or permutations of the same monomers. Consider illustrating this by simply asking students how many different ways can we arrange the letters A, B, and C, using each letter, and only once, to form 3-lettered words. The answer is 6 permutations: ABC, ACB, BAC, BCA, CBA, CAB (the factorial of 3). And if letters can be repeated, the answer is 27 (= 3 3 ): AAA, BBB, CCC, ABB, ACC, etc.
- Student Misconceptions and Concerns General biology students might not have previously taken a chemistry course. The concept of molecular building blocks that cannot be seen can be abstract and difficult to comprehend for such students. Concrete examples from our diets and good images will increase comprehension. Teaching Tips 1. Train cars linking together to form a train is a nice analogy to linking monomers to form polymers. Consider adding that as the train cars are joined, a puff of steam appears—a reference to water production and a dehydration reaction when linking molecular monomers. 2. The authors note that the great diversity of polymers mainly results from the arrangement of polymers, the different sequences made possible by combinations or permutations of the same monomers. Consider illustrating this by simply asking students how many different ways can we arrange the letters A, B, and C, using each letter, and only once, to form 3-lettered words. The answer is 6 permutations: ABC, ACB, BAC, BCA, CBA, CAB (the factorial of 3). And if letters can be repeated, the answer is 27 (= 3 3 ): AAA, BBB, CCC, ABB, ACC, etc.
- Figure 3.3A_s1 Dehydration reaction building a polymer chain (step 1)
- Figure 3.3A_s2 Dehydration reaction building a polymer chain (step 2)
- Figure 3.3B_s1 Hydrolysis breaking down a polymer (step 1)
- Figure 3.3B_s2 Hydrolysis breaking down a polymer (step 2)
- Student Misconceptions and Concerns 1. Consider reinforcing the three main sources of calories with food items that clearly represent each group. Bring clear examples to class as visual references. For example, a can of Coke or a bag of sugar for carbohydrates, a tub of margarine for lipids, and some beef jerky for protein (although some fat and carbohydrates might also be included). 2. The abstract nature of chemistry can be discouraging to many students. Consider starting out this section of lecture by examining the chemical groups on a food nutrition label. Candy bars with peanuts are particularly useful, as they contain significant amounts of all three sources of calories (carbohydrates, proteins, and lipids). Teaching Tips If your lectures will eventually include details of glycolysis and aerobic respiration, this is a good point to introduce the basic concepts of glucose as fuel. Just introducing this conceptual formula might help: eating glucose and breathing oxygen produces water and usable energy (used to build ATP) plus heat and carbon dioxide exhaled in our breath.
- Student Misconceptions and Concerns 1. Consider reinforcing the three main sources of calories with food items that clearly represent each group. Bring clear examples to class as visual references. For example, a can of Coke or a bag of sugar for carbohydrates, a tub of margarine for lipids, and some beef jerky for protein (although some fat and carbohydrates might also be included). 2. The abstract nature of chemistry can be discouraging to many students. Consider starting out this section of lecture by examining the chemical groups on a food nutrition label. Candy bars with peanuts are particularly useful, as they contain significant amounts of all three sources of calories (carbohydrates, proteins, and lipids). Teaching Tips If your lectures will eventually include details of glycolysis and aerobic respiration, this is a good point to introduce the basic concepts of glucose as fuel. Just introducing this conceptual formula might help: eating glucose and breathing oxygen produces water and usable energy (used to build ATP) plus heat and carbon dioxide exhaled in our breath.
- Student Misconceptions and Concerns 1. Consider reinforcing the three main sources of calories with food items that clearly represent each group. Bring clear examples to class as visual references. For example, a can of Coke or a bag of sugar for carbohydrates, a tub of margarine for lipids, and some beef jerky for protein (although some fat and carbohydrates might also be included). 2. The abstract nature of chemistry can be discouraging to many students. Consider starting out this section of lecture by examining the chemical groups on a food nutrition label. Candy bars with peanuts are particularly useful, as they contain significant amounts of all three sources of calories (carbohydrates, proteins, and lipids). Teaching Tips If your lectures will eventually include details of glycolysis and aerobic respiration, this is a good point to introduce the basic concepts of glucose as fuel. Just introducing this conceptual formula might help: eating glucose and breathing oxygen produces water and usable energy (used to build ATP) plus heat and carbon dioxide exhaled in our breath.
- Figure 3.4C Three representations of the ring form of glucose
- Student Misconceptions and Concerns Consider reinforcing the three main sources of calories with food items that clearly represent each group. Bring clear examples to class as visual references. For example, a can of Coke or a bag of sugar for carbohydrates, a tub of margarine for lipids, and some beef jerky for protein (although some fat and carbohydrates might also be included). Teaching Tips Learning the definitions of word roots is invaluable when learning science. Learning the meaning of the prefix word roots “mono ” (one), “di ” (two), and “poly ” (many) helps to distinguish the structures of various carbohydrates.
- Figure 3.5_s1 Disaccharide formation by a dehydration reaction (step 1)
- Figure 3.5_s2 Disaccharide formation by a dehydration reaction (step 2)
- Student Misconceptions and Concerns Consider reinforcing the three main sources of calories with food items that clearly represent each group. Bring clear examples to class as visual references. For example, a can of Coke or a bag of sugar for carbohydrates, a tub of margarine for lipids, and some beef jerky for protein (although some fat and carbohydrates might also be included). Teaching Tips 1. The widespread use of high-fructose corn syrup can be surprising to students. Consider asking each student to bring to class a product label that indicates the use of high-fructose corn syrup (HFCS) as an ingredient. 2. Consider an assignment for students to access the Internet and find reliable sources that discuss high rates of sugar consumption in the modern diet. The key, of course, is in the quality of the resource. Consider limiting their search to established nonprofit organizations (American Cancer Society, American Heart Association, etc.) and peer-reviewed journals.
- Student Misconceptions and Concerns Consider reinforcing the three main sources of calories with food items that clearly represent each group. Bring clear examples to class as visual references. For example, a can of Coke or a bag of sugar for carbohydrates, a tub of margarine for lipids, and some beef jerky for protein (although some fat and carbohydrates might also be included). Teaching Tips 1. The widespread use of high-fructose corn syrup can be surprising to students. Consider asking each student to bring to class a product label that indicates the use of high-fructose corn syrup (HFCS) as an ingredient. 2. Consider an assignment for students to access the Internet and find reliable sources that discuss high rates of sugar consumption in the modern diet. The key, of course, is in the quality of the resource. Consider limiting their search to established nonprofit organizations (American Cancer Society, American Heart Association, etc.) and peer-reviewed journals.
- Figure 3.6 High-fructose corn syrup (HFCS), a main ingredient of soft drinks and processed foods
- Student Misconceptions and Concerns Consider reinforcing the three main sources of calories with food items that clearly represent each group. Bring clear examples to class as visual references. For example, a can of Coke or a bag of sugar for carbohydrates, a tub of margarine for lipids, and some beef jerky for protein (although some fat and carbohydrates might also be included). Teaching Tips 1. A simple exercise demonstrates the enzymatic breakdown of starches into sugars. If students place an unsalted cracker in their mouths, holding it in their mouths while it mixes well with saliva, they might soon notice that a sweeter taste begins to emerge. The salivary enzyme amylase begins the digestion of starches into disaccharides, which may be degraded further by other enzymes. These disaccharides are the source of the sweet taste. 2. The text notes that cellulose is the most abundant organic molecule on Earth. Ask your students why this is true. 3. The cellophane wrap often used to package foods is a biodegradable material derived from cellulose. Consider challenging students to create a list of other cellulose-derived products (such as paper.) 4. An adult human may store about a half of a kilogram of glycogen in the liver and muscles of the body, depending up recent dietary habits. A person who begins dieting might soon notice an immediate weight loss of 2–4 pounds (1–2 kilograms) over several days, reflecting reductions in stored glycogen, water, and intestinal contents (among other factors).
- Student Misconceptions and Concerns Consider reinforcing the three main sources of calories with food items that clearly represent each group. Bring clear examples to class as visual references. For example, a can of Coke or a bag of sugar for carbohydrates, a tub of margarine for lipids, and some beef jerky for protein (although some fat and carbohydrates might also be included). Teaching Tips 1. A simple exercise demonstrates the enzymatic breakdown of starches into sugars. If students place an unsalted cracker in their mouths, holding it in their mouths while it mixes well with saliva, they might soon notice that a sweeter taste begins to emerge. The salivary enzyme amylase begins the digestion of starches into disaccharides, which may be degraded further by other enzymes. These disaccharides are the source of the sweet taste. 2. The text notes that cellulose is the most abundant organic molecule on Earth. Ask your students why this is true. 3. The cellophane wrap often used to package foods is a biodegradable material derived from cellulose. Consider challenging students to create a list of other cellulose-derived products (such as paper.) 4. An adult human may store about a half of a kilogram of glycogen in the liver and muscles of the body, depending up recent dietary habits. A person who begins dieting might soon notice an immediate weight loss of 2–4 pounds (1–2 kilograms) over several days, reflecting reductions in stored glycogen, water, and intestinal contents (among other factors).
- Student Misconceptions and Concerns Consider reinforcing the three main sources of calories with food items that clearly represent each group. Bring clear examples to class as visual references. For example, a can of Coke or a bag of sugar for carbohydrates, a tub of margarine for lipids, and some beef jerky for protein (although some fat and carbohydrates might also be included). Teaching Tips 1. A simple exercise demonstrates the enzymatic breakdown of starches into sugars. If students place an unsalted cracker in their mouths, holding it in their mouths while it mixes well with saliva, they might soon notice that a sweeter taste begins to emerge. The salivary enzyme amylase begins the digestion of starches into disaccharides, which may be degraded further by other enzymes. These disaccharides are the source of the sweet taste. 2. The text notes that cellulose is the most abundant organic molecule on Earth. Ask your students why this is true. 3. The cellophane wrap often used to package foods is a biodegradable material derived from cellulose. Consider challenging students to create a list of other cellulose-derived products (such as paper.) 4. An adult human may store about a half of a kilogram of glycogen in the liver and muscles of the body, depending up recent dietary habits. A person who begins dieting might soon notice an immediate weight loss of 2–4 pounds (1–2 kilograms) over several days, reflecting reductions in stored glycogen, water, and intestinal contents (among other factors).
- Figure 3.7 Polysaccharides
- Student Misconceptions and Concerns Consider reinforcing the three main sources of calories with food items that clearly represent each group. Bring clear examples to class as visual references. For example, a can of Coke or a bag of sugar for carbohydrates, a tub of margarine for lipids, and some beef jerky for protein (although some fat and carbohydrates might also be included). Teaching Tips 1. A simple exercise demonstrates the enzymatic breakdown of starches into sugars. If students place an unsalted cracker in their mouths, holding it in their mouths while it mixes well with saliva, they might soon notice that a sweeter taste begins to emerge. The salivary enzyme amylase begins the digestion of starches into disaccharides, which may be degraded further by other enzymes. These disaccharides are the source of the sweet taste. 2. The text notes that cellulose is the most abundant organic molecule on Earth. Ask your students why this is true. 3. The cellophane wrap often used to package foods is a biodegradable material derived from cellulose. Consider challenging students to create a list of other cellulose-derived products (such as paper.) 4. An adult human may store about a half of a kilogram of glycogen in the liver and muscles of the body, depending up recent dietary habits. A person who begins dieting might soon notice an immediate weight loss of 2–4 pounds (1–2 kilograms) over several days, reflecting reductions in stored glycogen, water, and intestinal contents (among other factors).
- Student Misconceptions and Concerns 1. Students may struggle with the concept that a pound of fat contains more than twice the calories of a pound of sugar. It might seem that a pound of food would potentially add on a pound of weight. Other students may have never understood the concept of calories in the diet, simply following general guidelines of avoiding fatty foods. Furthermore, fiber and water have no caloric value but add to the weight of food. Consider class discussions that explore student misconceptions about calories, body weight, and healthy diets. 2. Students might struggle to extrapolate the properties of lipids to their roles in an organism. Ducks float because their feathers repel water instead of attracting it. Hair on our heads remains flexible because of oils produced in our scalp. Examples such as these help connect the abstract properties of lipids to concrete examples in our world. Teaching Tips 1. The text in Module 3.8 notes the common observation that vinegar and oil do not mix in this type of salad dressing. A simple demonstration can help make this point. In front of the class, mix together colored water and a yellow oil (corn or canola oil work well). Shake up the mixture and then watch as the two separate. (You may have a mixture already made ahead of time that remains separated; however, the dye may bleed between the oil and the water.) Placing the mixture on an overhead projector or other well-illuminated imaging device makes for a dramatic display of hydrophobic activity! 2. The text notes that a gram of fat stores more than twice the energy of a gram of polysaccharide, such as starch. You might elaborate with a simple calculation to demonstrate how a person’s body weight would vary if the energy stored in body fat were stored in carbohydrates instead. If a 100-kg man carried 25% body fat, he would have 25 kg of fat in his body. Fat stores about 2.25 times more energy per gram than carbohydrate. What would be the weight of the man if he stored the energy in the fat in the form of carbohydrate? (2.25 x 25 = 56.25 kg of carbohydrate + 75kg (nonfat body weight) = 131.25 kg, an increase of 31.25%) 3. Margarine in stores commonly comes in liquid squeeze containers, in tubs, and in sticks. These forms reflect increasing amounts of hydrogenation, gradually increasing the stiffness from a liquid, to a firmer spread, to a firm stick of margarine. As noted in the text, recent studies have suggested that unsaturated oils become increasingly unhealthy as they are hydrogenated. Students might therefore remember that as margarine products increase in stiffness, they generally become less healthy. Public attention to hydrogenation and the health risks of the resulting trans fats are causing changes in the use of products containing trans fats.
- Figure 3.8A Water beading on the oily coating of feathers
- Student Misconceptions and Concerns 1. Students may struggle with the concept that a pound of fat contains more than twice the calories of a pound of sugar. It might seem that a pound of food would potentially add on a pound of weight. Other students may have never understood the concept of calories in the diet, simply following general guidelines of avoiding fatty foods. Furthermore, fiber and water have no caloric value but add to the weight of food. Consider class discussions that explore student misconceptions about calories, body weight, and healthy diets. 2. Students might struggle to extrapolate the properties of lipids to their roles in an organism. Ducks float because their feathers repel water instead of attracting it. Hair on our heads remains flexible because of oils produced in our scalp. Examples such as these help connect the abstract properties of lipids to concrete examples in our world. Teaching Tips 1. The text in Module 3.8 notes the common observation that vinegar and oil do not mix in this type of salad dressing. A simple demonstration can help make this point. In front of the class, mix together colored water and a yellow oil (corn or canola oil work well). Shake up the mixture and then watch as the two separate. (You may have a mixture already made ahead of time that remains separated; however, the dye may bleed between the oil and the water.) Placing the mixture on an overhead projector or other well-illuminated imaging device makes for a dramatic display of hydrophobic activity! 2. The text notes that a gram of fat stores more than twice the energy of a gram of polysaccharide, such as starch. You might elaborate with a simple calculation to demonstrate how a person’s body weight would vary if the energy stored in body fat were stored in carbohydrates instead. If a 100-kg man carried 25% body fat, he would have 25 kg of fat in his body. Fat stores about 2.25 times more energy per gram than carbohydrate. What would be the weight of the man if he stored the energy in the fat in the form of carbohydrate? (2.25 x 25 = 56.25 kg of carbohydrate + 75kg (nonfat body weight) = 131.25 kg, an increase of 31.25%) 3. Margarine in stores commonly comes in liquid squeeze containers, in tubs, and in sticks. These forms reflect increasing amounts of hydrogenation, gradually increasing the stiffness from a liquid, to a firmer spread, to a firm stick of margarine. As noted in the text, recent studies have suggested that unsaturated oils become increasingly unhealthy as they are hydrogenated. Students might therefore remember that as margarine products increase in stiffness, they generally become less healthy. Public attention to hydrogenation and the health risks of the resulting trans fats are causing changes in the use of products containing trans fats.
- Student Misconceptions and Concerns 1. Students may struggle with the concept that a pound of fat contains more than twice the calories of a pound of sugar. It might seem that a pound of food would potentially add on a pound of weight. Other students may have never understood the concept of calories in the diet, simply following general guidelines of avoiding fatty foods. Furthermore, fiber and water have no caloric value but add to the weight of food. Consider class discussions that explore student misconceptions about calories, body weight, and healthy diets. 2. Students might struggle to extrapolate the properties of lipids to their roles in an organism. Ducks float because their feathers repel water instead of attracting it. Hair on our heads remains flexible because of oils produced in our scalp. Examples such as these help connect the abstract properties of lipids to concrete examples in our world. Teaching Tips 1. The text in Module 3.8 notes the common observation that vinegar and oil do not mix in this type of salad dressing. A simple demonstration can help make this point. In front of the class, mix together colored water and a yellow oil (corn or canola oil work well). Shake up the mixture and then watch as the two separate. (You may have a mixture already made ahead of time that remains separated; however, the dye may bleed between the oil and the water.) Placing the mixture on an overhead projector or other well-illuminated imaging device makes for a dramatic display of hydrophobic activity! 2. The text notes that a gram of fat stores more than twice the energy of a gram of polysaccharide, such as starch. You might elaborate with a simple calculation to demonstrate how a person’s body weight would vary if the energy stored in body fat were stored in carbohydrates instead. If a 100-kg man carried 25% body fat, he would have 25 kg of fat in his body. Fat stores about 2.25 times more energy per gram than carbohydrate. What would be the weight of the man if he stored the energy in the fat in the form of carbohydrate? (2.25 x 25 = 56.25 kg of carbohydrate + 75kg (nonfat body weight) = 131.25 kg, an increase of 31.25%) 3. Margarine in stores commonly comes in liquid squeeze containers, in tubs, and in sticks. These forms reflect increasing amounts of hydrogenation, gradually increasing the stiffness from a liquid, to a firmer spread, to a firm stick of margarine. As noted in the text, recent studies have suggested that unsaturated oils become increasingly unhealthy as they are hydrogenated. Students might therefore remember that as margarine products increase in stiffness, they generally become less healthy. Public attention to hydrogenation and the health risks of the resulting trans fats are causing changes in the use of products containing trans fats.
- Student Misconceptions and Concerns 1. Students may struggle with the concept that a pound of fat contains more than twice the calories of a pound of sugar. It might seem that a pound of food would potentially add on a pound of weight. Other students may have never understood the concept of calories in the diet, simply following general guidelines of avoiding fatty foods. Furthermore, fiber and water have no caloric value but add to the weight of food. Consider class discussions that explore student misconceptions about calories, body weight, and healthy diets. 2. Students might struggle to extrapolate the properties of lipids to their roles in an organism. Ducks float because their feathers repel water instead of attracting it. Hair on our heads remains flexible because of oils produced in our scalp. Examples such as these help connect the abstract properties of lipids to concrete examples in our world. Teaching Tips 1. The text in Module 3.8 notes the common observation that vinegar and oil do not mix in this type of salad dressing. A simple demonstration can help make this point. In front of the class, mix together colored water and a yellow oil (corn or canola oil work well). Shake up the mixture and then watch as the two separate. (You may have a mixture already made ahead of time that remains separated; however, the dye may bleed between the oil and the water.) Placing the mixture on an overhead projector or other well-illuminated imaging device makes for a dramatic display of hydrophobic activity! 2. The text notes that a gram of fat stores more than twice the energy of a gram of polysaccharide, such as starch. You might elaborate with a simple calculation to demonstrate how a person’s body weight would vary if the energy stored in body fat were stored in carbohydrates instead. If a 100-kg man carried 25% body fat, he would have 25 kg of fat in his body. Fat stores about 2.25 times more energy per gram than carbohydrate. What would be the weight of the man if he stored the energy in the fat in the form of carbohydrate? (2.25 x 25 = 56.25 kg of carbohydrate + 75kg (nonfat body weight) = 131.25 kg, an increase of 31.25%) 3. Margarine in stores commonly comes in liquid squeeze containers, in tubs, and in sticks. These forms reflect increasing amounts of hydrogenation, gradually increasing the stiffness from a liquid, to a firmer spread, to a firm stick of margarine. As noted in the text, recent studies have suggested that unsaturated oils become increasingly unhealthy as they are hydrogenated. Students might therefore remember that as margarine products increase in stiffness, they generally become less healthy. Public attention to hydrogenation and the health risks of the resulting trans fats are causing changes in the use of products containing trans fats.
- Figure 3.8B A dehydration reaction linking a fatty acid molecule to a glycerol molecule
- Figure 3.8C A fat molecule (triglyceride) consisting of three fatty acids linked to glycerol
- Student Misconceptions and Concerns 1. Students may struggle with the concept that a pound of fat contains more than twice the calories of a pound of sugar. It might seem that a pound of food would potentially add on a pound of weight. Other students may have never understood the concept of calories in the diet, simply following general guidelines of avoiding fatty foods. Furthermore, fiber and water have no caloric value but add to the weight of food. Consider class discussions that explore student misconceptions about calories, body weight, and healthy diets. 2. Students might struggle to extrapolate the properties of lipids to their roles in an organism. Ducks float because their feathers repel water instead of attracting it. Hair on our heads remains flexible because of oils produced in our scalp. Examples such as these help connect the abstract properties of lipids to concrete examples in our world. Teaching Tips 1. The text in Module 3.8 notes the common observation that vinegar and oil do not mix in this type of salad dressing. A simple demonstration can help make this point. In front of the class, mix together colored water and a yellow oil (corn or canola oil work well). Shake up the mixture and then watch as the two separate. (You may have a mixture already made ahead of time that remains separated; however, the dye may bleed between the oil and the water.) Placing the mixture on an overhead projector or other well-illuminated imaging device makes for a dramatic display of hydrophobic activity! 2. The text notes that a gram of fat stores more than twice the energy of a gram of polysaccharide, such as starch. You might elaborate with a simple calculation to demonstrate how a person’s body weight would vary if the energy stored in body fat were stored in carbohydrates instead. If a 100-kg man carried 25% body fat, he would have 25 kg of fat in his body. Fat stores about 2.25 times more energy per gram than carbohydrate. What would be the weight of the man if he stored the energy in the fat in the form of carbohydrate? (2.25 x 25 = 56.25 kg of carbohydrate + 75kg (nonfat body weight) = 131.25 kg, an increase of 31.25%) 3. Margarine in stores commonly comes in liquid squeeze containers, in tubs, and in sticks. These forms reflect increasing amounts of hydrogenation, gradually increasing the stiffness from a liquid, to a firmer spread, to a firm stick of margarine. As noted in the text, recent studies have suggested that unsaturated oils become increasingly unhealthy as they are hydrogenated. Students might therefore remember that as margarine products increase in stiffness, they generally become less healthy. Public attention to hydrogenation and the health risks of the resulting trans fats are causing changes in the use of products containing trans fats.
- Student Misconceptions and Concerns 1. Students may struggle with the concept that a pound of fat contains more than twice the calories of a pound of sugar. It might seem that a pound of food would potentially add on a pound of weight. Other students may have never understood the concept of calories in the diet, simply following general guidelines of avoiding fatty foods. Furthermore, fiber and water have no caloric value but add to the weight of food. Consider class discussions that explore student misconceptions about calories, body weight, and healthy diets. 2. Students might struggle to extrapolate the properties of lipids to their roles in an organism. Ducks float because their feathers repel water instead of attracting it. Hair on our heads remains flexible because of oils produced in our scalp. Examples such as these help connect the abstract properties of lipids to concrete examples in our world. Teaching Tips 1. The text in Module 3.8 notes the common observation that vinegar and oil do not mix in this type of salad dressing. A simple demonstration can help make this point. In front of the class, mix together colored water and a yellow oil (corn or canola oil work well). Shake up the mixture and then watch as the two separate. (You may have a mixture already made ahead of time that remains separated; however, the dye may bleed between the oil and the water.) Placing the mixture on an overhead projector or other well-illuminated imaging device makes for a dramatic display of hydrophobic activity! 2. The text notes that a gram of fat stores more than twice the energy of a gram of polysaccharide, such as starch. You might elaborate with a simple calculation to demonstrate how a person’s body weight would vary if the energy stored in body fat were stored in carbohydrates instead. If a 100-kg man carried 25% body fat, he would have 25 kg of fat in his body. Fat stores about 2.25 times more energy per gram than carbohydrate. What would be the weight of the man if he stored the energy in the fat in the form of carbohydrate? (2.25 x 25 = 56.25 kg of carbohydrate + 75kg (nonfat body weight) = 131.25 kg, an increase of 31.25%) 3. Margarine in stores commonly comes in liquid squeeze containers, in tubs, and in sticks. These forms reflect increasing amounts of hydrogenation, gradually increasing the stiffness from a liquid, to a firmer spread, to a firm stick of margarine. As noted in the text, recent studies have suggested that unsaturated oils become increasingly unhealthy as they are hydrogenated. Students might therefore remember that as margarine products increase in stiffness, they generally become less healthy. Public attention to hydrogenation and the health risks of the resulting trans fats are causing changes in the use of products containing trans fats.
- Student Misconceptions and Concerns Students might struggle to extrapolate the properties of lipids to their roles in an organism. Ducks float because their feathers repel water instead of attracting it. Hair on our heads remains flexible because of oils produced in our scalp. Examples such as these help connect the abstract properties of lipids to concrete examples in our world. Teaching Tips Before explaining the properties of a polar molecule such as a phospholipid, have students predict the consequences of adding phospholipids to water. See if the class can generate the two most common configurations: (1) a lipid bilayer encircling water (water surrounding the bilayer and water contained internally) and (2) a micelle (polar heads in contact with water and hydrophobic tails clustered centrally).
- Figure 3.9A-B Detail of a phospholipid membrane
- Figure 3.9A Chemical structure of a phospholipid molecule
- Student Misconceptions and Concerns Students might struggle to extrapolate the properties of lipids to their roles in an organism. Ducks float because their feathers repel water instead of attracting it. Hair on our heads remains flexible because of oils produced in our scalp. Examples such as these help connect the abstract properties of lipids to concrete examples in our world. Teaching Tips Before explaining the properties of a polar molecule such as a phospholipid, have students predict the consequences of adding phospholipids to water. See if the class can generate the two most common configurations: (1) a lipid bilayer encircling water (water surrounding the bilayer and water contained internally) and (2) a micelle (polar heads in contact with water and hydrophobic tails clustered centrally).
- Figure 3.9B Section of a phospholipid membrane
- Student Misconceptions and Concerns Students might struggle to extrapolate the properties of lipids to their roles in an organism. Ducks float because their feathers repel water instead of attracting it. Hair on our heads remains flexible because of oils produced in our scalp. Examples such as these help connect the abstract properties of lipids to concrete examples in our world. Teaching Tips Before explaining the properties of a polar molecule such as a phospholipid, have students predict the consequences of adding phospholipids to water. See if the class can generate the two most common configurations: (1) a lipid bilayer encircling water (water surrounding the bilayer and water contained internally) and (2) a micelle (polar heads in contact with water and hydrophobic tails clustered centrally).
- Figure 3.9C Cholesterol, a steroid
- Student Misconceptions and Concerns Students might struggle to extrapolate the properties of lipids to their roles in an organism. Ducks float because their feathers repel water instead of attracting it. Hair on our heads remains flexible because of oils produced in our scalp. Examples such as these help connect the abstract properties of lipids to concrete examples in our world. Teaching Tips The consequences of steroid abuse will likely be of great interest to your students. However, the reasons for the damaging consequences might not be immediately clear. As time permits, consider noting the diverse homeostatic mechanisms that normally regulate the traits affected by steroid abuse.
- Student Misconceptions and Concerns Students might struggle to extrapolate the properties of lipids to their roles in an organism. Ducks float because their feathers repel water instead of attracting it. Hair on our heads remains flexible because of oils produced in our scalp. Examples such as these help connect the abstract properties of lipids to concrete examples in our world. Teaching Tips The consequences of steroid abuse will likely be of great interest to your students. However, the reasons for the damaging consequences might not be immediately clear. As time permits, consider noting the diverse homeostatic mechanisms that normally regulate the traits affected by steroid abuse.
- Figure 3.10 Bodybuilder
- Teaching Tips 1. Many analogies help students appreciate the diversity of proteins that can be made from just 20 amino acids. The authors note that our language uses combinations of 26 letters to form words. Proteins are much longer “words,” creating even more diversity. Another analogy is to trains. This builds upon the earlier analogy when polymers were introduced. Imagine making different trains about 100 cars long, using any combination of 20 types of railroad cars. Mathematically, the number of possible trains is 20 100 , a number beyond imagination. 2. The authors note that the difference between a polypeptide and a protein is analogous to the relationship between a long strand of yarn and a sweater knitted from yarn. Proteins are clearly more complex!
- Teaching Tips 1. Many analogies help students appreciate the diversity of proteins that can be made from just 20 amino acids. The authors note that our language uses combinations of 26 letters to form words. Proteins are much longer “words,” creating even more diversity. Another analogy is to trains. This builds upon the earlier analogy when polymers were introduced. Imagine making different trains about 100 cars long, using any combination of 20 types of railroad cars. Mathematically, the number of possible trains is 20 100 , a number beyond imagination. 2. The authors note that the difference between a polypeptide and a protein is analogous to the relationship between a long strand of yarn and a sweater knitted from yarn. Proteins are clearly more complex!
- Figure 3.11A General structure of an amino acid
- Teaching Tips 1. Many analogies help students appreciate the diversity of proteins that can be made from just 20 amino acids. The authors note that our language uses combinations of 26 letters to form words. Proteins are much longer “words,” creating even more diversity. Another analogy is to trains. This builds upon the earlier analogy when polymers were introduced. Imagine making different trains about 100 cars long, using any combination of 20 types of railroad cars. Mathematically, the number of possible trains is 20 100 , a number beyond imagination. 2. The authors note that the difference between a polypeptide and a protein is analogous to the relationship between a long strand of yarn and a sweater knitted from yarn. Proteins are clearly more complex!
- Figure 3.11C_s1 Peptide bond formation (step 1)
- Figure 3.11C_s2 Peptide bond formation (step 2)
- Student Misconceptions and Concerns The functional significance of protein shape is an abstract molecular example of form and function relationships, which might be new to some students. The binding of an enzyme to its substrate is a type of molecular handshake, which permits specific interactions. To help students think about form and function relationships, share some concrete analogies in their lives—perhaps flathead and Phillips screwdrivers that match the proper type of screws or the fit of a hand into a glove. Teaching Tips Most cooking results in changes in the texture and color of food. The brown color of a cooked steak is the product of the denaturation of proteins. Fixatives such as formalin also denature proteins and cause color changes. Students who have dissected vertebrates will realize that the brown color of the muscles makes it look as if the animal has been cooked.
- Student Misconceptions and Concerns The functional significance of protein shape is an abstract molecular example of form and function relationships, which might be new to some students. The binding of an enzyme to its substrate is a type of molecular handshake, which permits specific interactions. To help students think about form and function relationships, share some concrete analogies in their lives—perhaps flathead and Phillips screwdrivers that match the proper type of screws or the fit of a hand into a glove. Teaching Tips Most cooking results in changes in the texture and color of food. The brown color of a cooked steak is the product of the denaturation of proteins. Fixatives such as formalin also denature proteins and cause color changes. Students who have dissected vertebrates will realize that the brown color of the muscles makes it look as if the animal has been cooked.
- Figure 3.12A Structural proteins make up hair, tendons, and ligaments; contractile proteins are found in muscles.
- Student Misconceptions and Concerns The functional significance of protein shape is an abstract molecular example of form and function relationships, which might be new to some students. The binding of an enzyme to its substrate is a type of molecular handshake, which permits specific interactions. To help students think about form and function relationships, share some concrete analogies in their lives—perhaps flathead and Phillips screwdrivers that match the proper type of screws or the fit of a hand into a glove. Teaching Tips Most cooking results in changes in the texture and color of food. The brown color of a cooked steak is the product of the denaturation of proteins. Fixatives such as formalin also denature proteins and cause color changes. Students who have dissected vertebrates will realize that the brown color of the muscles makes it look as if the animal has been cooked.
- Figure 3.12B Ribbon model of the protein lysozyme
- Figure 3.12C Space-filling model of the protein lysozyme
- Student Misconceptions and Concerns The functional significance of protein shape is an abstract molecular example of form and function relationships, which might be new to some students. The binding of an enzyme to its substrate is a type of molecular handshake, which permits specific interactions. To help students think about form and function relationships, share some concrete analogies in their lives—perhaps flathead and Phillips screwdrivers that match the proper type of screws or the fit of a hand into a glove. Teaching Tips Most cooking results in changes in the texture and color of food. The brown color of a cooked steak is the product of the denaturation of proteins. Fixatives such as formalin also denature proteins and cause color changes. Students who have dissected vertebrates will realize that the brown color of the muscles makes it look as if the animal has been cooked.
- Teaching Tips An examination of the fabrics and weave of a sweater might help students understand the levels of protein structure. Although not a perfect analogy, levels of organization can be better appreciated. Teasing apart a single thread reveals a simpler organization of smaller fibers woven together. In turn, threads are interlaced into a connected fabric, which may be further twisted and organized into a pattern or structural component of a sleeve. Challenge students to identify the limits of this analogy and identify aspects of protein structure not included (such as the primary structure of a protein, its sequence of amino acids).
- Teaching Tips An examination of the fabrics and weave of a sweater might help students understand the levels of protein structure. Although not a perfect analogy, levels of organization can be better appreciated. Teasing apart a single thread reveals a simpler organization of smaller fibers woven together. In turn, threads are interlaced into a connected fabric, which may be further twisted and organized into a pattern or structural component of a sleeve. Challenge students to identify the limits of this analogy and identify aspects of protein structure not included (such as the primary structure of a protein, its sequence of amino acids).
- Teaching Tips An examination of the fabrics and weave of a sweater might help students understand the levels of protein structure. Although not a perfect analogy, levels of organization can be better appreciated. Teasing apart a single thread reveals a simpler organization of smaller fibers woven together. In turn, threads are interlaced into a connected fabric, which may be further twisted and organized into a pattern or structural component of a sleeve. Challenge students to identify the limits of this analogy and identify aspects of protein structure not included (such as the primary structure of a protein, its sequence of amino acids).
- Figure 3.13_1 Spider web
- Figure 3.13_2 Collagen
- Teaching Tips An examination of the fabrics and weave of a sweater might help students understand the levels of protein structure. Although not a perfect analogy, levels of organization can be better appreciated. Teasing apart a single thread reveals a simpler organization of smaller fibers woven together. In turn, threads are interlaced into a connected fabric, which may be further twisted and organized into a pattern or structural component of a sleeve. Challenge students to identify the limits of this analogy and identify aspects of protein structure not included (such as the primary structure of a protein, its sequence of amino acids).
- Teaching Tips An examination of the fabrics and weave of a sweater might help students understand the levels of protein structure. Although not a perfect analogy, levels of organization can be better appreciated. Teasing apart a single thread reveals a simpler organization of smaller fibers woven together. In turn, threads are interlaced into a connected fabric, which may be further twisted and organized into a pattern or structural component of a sleeve. Challenge students to identify the limits of this analogy and identify aspects of protein structure not included (such as the primary structure of a protein, its sequence of amino acids).
- Figure 3.13A_s1 Four Levels of Protein Structure (step 1)
- Figure 3.13A-B_s2 Four Levels of Protein Structure (step 2)
- Figure 3.13A-C_s3 Four Levels of Protein Structure (step 3)
- Figure 3.13A-D_s4 Four Levels of Protein Structure (step 4)
- Student Misconceptions and Concerns Module 3.14 is the first time the authors present the concept of transcription and translation, discussed extensively in later chapters. The basic conceptual flow of information from DNA to RNA to proteins is essential to these later discussions. Teaching Tips The “NA ” in the acronyms DNA and RNA stands for “Nucleic acid. ” Students often do not make this association without assistance.
- Student Misconceptions and Concerns Module 3.14 is the first time the authors present the concept of transcription and translation, discussed extensively in later chapters. The basic conceptual flow of information from DNA to RNA to proteins is essential to these later discussions. Teaching Tips The “NA ” in the acronyms DNA and RNA stands for “Nucleic acid. ” Students often do not make this association without assistance.
- Figure 3.14_s1 The flow of genetic information in the building of a protein (step 1)
- Figure 3.14_s2 The flow of genetic information in the building of a protein (step 2)
- Figure 3.14_s3 The flow of genetic information in the building of a protein (step 3)
- Teaching Tips When discussing the sequence of nucleotides in DNA and RNA, consider challenging your students with the following questions based upon prior analogies. If the 20 possible amino acids in a polypeptide represent “words ” in a long polypeptide sentence, how many possible words are in the language of a DNA molecule? (Answer: Four nucleotides, GCAT, are possible). Are these the same “words ” used in RNA? (Answer: No. Uracil substitutes for thymine.)
- Figure 3.15A A nucleotide, consisting of a phosphate group, a sugar, and a nitrogenous base
- Teaching Tips When discussing the sequence of nucleotides in DNA and RNA, consider challenging your students with the following questions based upon prior analogies. If the 20 possible amino acids in a polypeptide represent “words ” in a long polypeptide sentence, how many possible words are in the language of a DNA molecule? (Answer: Four nucleotides, GCAT, are possible). Are these the same “words ” used in RNA? (Answer: No. Uracil substitutes for thymine.)
- Teaching Tips When discussing the sequence of nucleotides in DNA and RNA, consider challenging your students with the following questions based upon prior analogies. If the 20 possible amino acids in a polypeptide represent “words ” in a long polypeptide sentence, how many possible words are in the language of a DNA molecule? (Answer: Four nucleotides, GCAT, are possible). Are these the same “words ” used in RNA? (Answer: No. Uracil substitutes for thymine.)
- Figure 3.15B Part of a polynucleotide
- Teaching Tips When discussing the sequence of nucleotides in DNA and RNA, consider challenging your students with the following questions based upon prior analogies. If the 20 possible amino acids in a polypeptide represent “words ” in a long polypeptide sentence, how many possible words are in the language of a DNA molecule? (Answer: Four nucleotides, GCAT, are possible). Are these the same “words ” used in RNA? (Answer: No. Uracil substitutes for thymine.)
- Figure 3.15C DNA double helix
- Student Misconceptions and Concerns The evolution of lactose tolerance within human groups in East Africa does not represent a deliberate decision, yet this evolutionary change appears logical. Many students perceive adaptations as deliberate events with purpose. As students develop a better understanding of the mechanisms of evolution, it will be important to point out that mutations arise by chance, with the culling hand of natural selection favoring traits that convey an advantage. Organisms cannot plan evolutionary change. Teaching Tips The research revealing the separate evolution of lactose tolerance into human adulthood in several parts of the world provide another opportunity to help students understand the process of natural selection. Consider using this example to walk students through the steps of this evolutionary change. Help students to understand that people did not choose to be lactose tolerant as adults. Instead, the environment of nutritious dairy products created an adaptive advantage for those people fortunate enough to possess the lactose tolerant mutation.
- Student Misconceptions and Concerns The evolution of lactose tolerance within human groups in East Africa does not represent a deliberate decision, yet this evolutionary change appears logical. Many students perceive adaptations as deliberate events with purpose. As students develop a better understanding of the mechanisms of evolution, it will be important to point out that mutations arise by chance, with the culling hand of natural selection favoring traits that convey an advantage. Organisms cannot plan evolutionary change. Teaching Tips The research revealing the separate evolution of lactose tolerance into human adulthood in several parts of the world provide another opportunity to help students understand the process of natural selection. Consider using this example to walk students through the steps of this evolutionary change. Help students to understand that people did not choose to be lactose tolerant as adults. Instead, the environment of nutritious dairy products created an adaptive advantage for those people fortunate enough to possess the lactose tolerant mutation.
- Figure 3.16 A prehistoric European cave painting of cattle