The document discusses cell membrane structure and models. It provides revision questions about phospholipid and cholesterol structure in membranes. Specifically, it asks students to:
1) Draw and label structures of phospholipids, membranes, and the plasma membrane.
2) Outline the Davson-Danielli and Singer-Nicholson models of membrane structure and the evidence used to support and refute each.
3) Explain how evidence from techniques like freeze-fracture and protein extraction refuted the Davson-Danielli model and supported the fluid mosaic model.
1. Revision questions 1.3. Membrane structure
Dr. Miltiadis Kitsos, DP Biology, Platon School, mailto:biology.kitsos@gmail.com
Understandings, Applications and Skills
Understandings:
• Phospholipids form bilayers in water due to the amphipathic properties of
phospholipid molecules.
• Membrane proteins are diverse in terms of structure, position in the
membrane and function.
• Cholesterol is a component of animal cell membranes.
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Applications and skills:
• Application: Cholesterol in mammalian membranes reduces membrane
fluidity and permeability to some solutes.
• Skill: Drawing of the fluid mosaic model.
• Skill: Analysis of evidence from electron microscopy that led to the proposal
of the Davson-Danielli model.
• Skill: Analysis of the falsification of the Davson-Danielli model that led to the
Singer-Nicolson model.
2. Revision questions 1.3. Membrane structure
Dr. Miltiadis Kitsos, DP Biology, Platon School, mailto:biology.kitsos@gmail.com
1. Draw and label a diagram of a single phospholipid molecule.
2. Draw and label a phospholipid monolayer and a bilayer.
3. Revision questions 1.3. Membrane structure
Dr. Miltiadis Kitsos, DP Biology, Platon School, mailto:biology.kitsos@gmail.com
3. Draw and label a diagram of the plasma membrane.
4. Outline the structure of the Davson-Danielli model of the cell membrane. Outline the evidence
used to support it.
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5. Outline the main points of the freeze-fracture
technique and explain how evidence from this
method, like this micrograph, were used to
refute the Davson-Danielli model
4. Revision questions 1.3. Membrane structure
Dr. Miltiadis Kitsos, DP Biology, Platon School, mailto:biology.kitsos@gmail.com
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6. Improvements in biochemical techniques allowed proteins to be extracted from membranes.
Outline how evidence from these methods were used to refute the Davson-Danielli model?
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5. Revision questions 1.3. Membrane structure
Dr. Miltiadis Kitsos, DP Biology, Platon School, mailto:biology.kitsos@gmail.com
7. In the following image you may see two integral proteins and some notes on their affinity with
water. This evidence falsifies the Davson-Danielli model. Explain how
Hydrophilic region
Hydrophobic region
6. Revision questions 1.3. Membrane structure
Dr. Miltiadis Kitsos, DP Biology, Platon School, mailto:biology.kitsos@gmail.com
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8. Outline the Singer-Nicholson fluid mosaic model of the cell membrane.
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http://www.ib.bioninja.com.au/_Media/tracie_med.jpeg
9. List the six main functions of the membrane proteins.
T :
7. Revision questions 1.3. Membrane structure
Dr. Miltiadis Kitsos, DP Biology, Platon School, mailto:biology.kitsos@gmail.com
R :
A :
C :
I :
E :
10. Outline the functions of glycoproteins found in the plasma membrane
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8. Revision questions 1.3. Membrane structure
Dr. Miltiadis Kitsos, DP Biology, Platon School, mailto:biology.kitsos@gmail.com
11. Cholesterol is a type of lipid, but it is not a fat or oil. What group does it belong to?
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12. Outline the structure of cholesterol and its position in the membrane. You may sketch the relative
position if you wish.
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13. Explain how cholesterol affects the fluidity of the membrane.
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