The document summarizes cellular metabolism and metabolic pathways. There are two types of metabolic reactions: anabolism and catabolism. Anabolism uses energy to form larger molecules from smaller ones, while catabolism releases energy by breaking down larger molecules. The main metabolic pathways discussed are glycolysis, the citric acid cycle, and the electron transport chain. Glycolysis breaks down glucose to form pyruvic acid. The citric acid cycle further breaks down pyruvic acid and produces ATP and electrons. The electron transport chain uses these electrons to power ATP synthesis through oxidative phosphorylation.

1. Edited by Brenda Holmes MSN/Ed, RN Associate Professor South Arkansas Community College

2. Chapter 4 Cellular Metabolism Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

6. Amino acid N H H C C H R Dipeptide molecule + + Peptide bond Amino acid N H H C C H H H R H O N H H C C H R H O N H C C OH R H O O N H H C C H R N H C C OH R H O O Water Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. O O H 2 O H C H Glycerol 3 fatty acid molecules + OH HO H C OH HO H C C C C OH HO H O O C C C O O O H C H Fat molecule (triglyceride) + H C H C O O O H 3 water molecules (CH 2 ) 14 CH 3 (CH 2 ) 14 CH 3 (CH 2 ) 14 CH 3 (CH 2 ) 14 CH 3 (CH 2 ) 14 CH 3 (CH 2 ) 14 CH 3 H 2 O H 2 O H 2 O Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. O

8. Amino acid N H H C C H R Dipeptide molecule + + Peptide bond Amino acid N H H C C H H H R H O N H H C C H R H O N H C C OH R H O O N H H C C H R N H C C OH R H O O Water Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. O O H 2 O H C H Glycerol 3 fatty acid molecules + OH HO H C OH HO H C C C C OH HO H O O C C C O O O H C H Fat molecule (triglyceride) + H C H C O O O H 3 water molecules (CH 2 ) 14 CH 3 (CH 2 ) 14 CH 3 (CH 2 ) 14 CH 3 (CH 2 ) 14 CH 3 (CH 2 ) 14 CH 3 (CH 2 ) 14 CH 3 H 2 O H 2 O H 2 O Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. O

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27. Glycolysis Cytosol Mitochondrion A T P 2 Glucose High-energy electrons (e – ) High-energy electrons (e – ) High-energy electrons (e – ) 2e – and 2H + A T P 2 H 2 O O 2 A T P 32–34 CO 2 Pyruvic acid Pyruvic acid 2 CO 2 Acetyl Co A Citric acid Oxaloacetic acid 1 3 4 2 Glycolysis The 6-carbon sugar glucose is broken down in the cytosol into two 3-carbon pyruvic acid molecules with a net gain of 2 ATP and release of high-energy electrons. Citric Acid Cycle The 3-carbon pyruvic acids generated by glycolysis enter the mitochondria. Each loses a carbon (generating CO 2 and is combined with a coenzyme to form a 2-carbon acetyl coenzyme A (acetyl CoA). More high-energy electrons are released. Each acetyl CoA combines with a 4-carbon oxaloacetic acid to form the 6-carbon citric acid, for which the cycle is named. For each citric acid, a series of reactions removes 2 carbons (generating 2 CO 2 ’s), synthesizes 1 ATP, and releases more high-energy electrons. The figure shows 2 ATP, resulting directly from 2 turns of the cycle per glucose molecule that enters glycolysis. Electron Transport Chain The high-energy electrons still contain most of the chemical energy of the original glucose molecule. Special carrier molecules bring the high-energy electrons to a series of enzymes that convert much of the remaining energy to more ATP molecules. The other products are heat and water. The function of oxygen as the final electron acceptor in this last step is why the overall process is called aerobic respiration. Electron transport chain Citric acid cycle Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

30. High energy electrons carried by NADH and FADH 2 Breakdown of simple molecules to acetyl coenzyme A accompanied by production of limited ATP and high energy electrons H 2 O 2e – and 2H + Waste products – NH 2 CO 2 CO 2 Citric acid cycle Electron transport chain Amino acids Acetyl coenzyme A Simple sugars (glucose) Glycerol Fatty acids Proteins (egg white) Carbohydrates (toast, hashbrowns) Food Fats (butter) Pyruvic acid ATP ATP Breakdown of large macromolecules to simple molecules Glycolysis 1 2 3 ATP Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. © Royalty Free/CORBIS. ½ O 2 High energy electrons carried by NADH and FADH 2 Complete oxidation of acetyl coenzyme A to H 2 O and CO 2 produces high energy electrons (carried by NADH and FADH 2 ), which yield much ATP via the electron transport chain Breakdown of simple molecules to acetyl coenzyme A accompanied by production of limited ATP and high energy electrons H 2 O 2e – and 2H + Waste products – NH 2 CO 2 CO 2 Citric acid cycle Electron transport chain Amino acids Acetyl coenzyme A Simple sugars (glucose) Glycerol Fatty acids Proteins (egg white) Carbohydrates (toast, hashbrowns) Food Fats (butter) Pyruvic acid ATP ATP Breakdown of large macromolecules to simple molecules Glycolysis 1 2 3 ATP © Royalty Free/CORBIS. ½ O 2

33. DNA Profiling Frees A Prisoner

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38. Nucleic Acid Amplification

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44. Messenger RNA 1 DNA information is copied, or transcribed, into mRNA following complementary base pairing 2 mRNA leaves the nucleus and attaches to a ribosome 3 Translation begins as tRNA anticodons recognize complementary mRNA codons, thus bringing the correct amino acids into position on the growing polypeptide chain 4 As the ribosome moves along the mRNA, more amino acids are added 5 At the end of the mRNA, the ribosome releases the new protein 6 Amino acids attached to tRNA Polypeptide chain Cytoplasm DNA double helix DNA strands pulled apart Transcription (in nucleus) Translation (in cytoplasm) Nucleus C Codon 1 Codon 2 Codon 3 Codon 4 Codon 5 Codon 6 Codon 7 G G G G G A A A U U C C C C C C G G G A Methionine Glycine Amino acids represented Serine Alanine Threonine Alanine Glycine DNA strand Messenger RNA A T A A T T T A T A T A T A T A T U A U A U A G C C G C G C G C G C G C G C G G C C G C C G U A C G C G G G G G G G G G G C C C C C C C C C C A A A A A T T A A T A T A T A T C G G C G C G C T A T A T A C G A T G C T A C G T A C G C G G C A T T A C G G C T T G C G C G C G C G C G C G C G C G Nuclear pore tRNA molecules can pick up another molecule of the same amino acid and be reused Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. G C C G A G G C U C T C C G A G

45. Next amino acid Anticodon Codons Growing polypeptide chain 1 1 2 2 3 3 4 4 5 5 6 6 7 C U G G Ribosome 1 1 2 2 3 3 7 4 4 5 5 6 7 C C C G U C U G C G U Next amino acid Anticodon Codons 1 1 2 2 3 3 4 4 5 5 6 6 7 Peptide bond C U G C G U C C G C G U 6 Messenger RNA Transfer RNA Next amino acid 1 1 2 2 3 3 4 4 5 5 6 7 6 7 U C G G A A A A A A G G G G G G G G C C C C C C C U U U C G G A A A A A A G G G G G G G G C C C C C C C U U U C G G A A A A A A G G G G G G G G C C C C C C C U U U C G G A A A A A A G G G G G G G G C C C C C C C U U The transfer RNA molecule for the last amino acid added holds the growing polypeptide chain and is attached to its complementary codon on mRNA. A second tRNA binds complementarily to the next codon, and in doing so brings the next amino acid into position on the ribosome. A peptide bond forms, linking the new amino acid to the growing polypeptide chain. The tRNA molecule that brought the last amino acid to the ribosome is released to the cytoplasm, and will be used again. The ribosome moves to a new position at the next codon on mRNA. A A new tRNA complementary to the next codon on mRNA brings the next amino acid to be added to the growing polypeptide chain. 2 1 3 4 Messenger RNA Transfer RNA Next amino acid Transfer RNA Messenger RNA Transfer RNA Growing polypeptide chain Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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47. MicroRNAs and RNA Interference

52. The Human Metabolome

57. Quiz 4 Complete Quiz 4 now! Read Chapter 5.