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AP Biology
Reading Guide
Chapter 5 – Cell Transport and Communication
Chapters 37.1 and 5.1-5.4 – Membrane Structure and Function; Transport
Across Membranes
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OBJECTIVES
 Describe the function of the plasma membrane.
 Describe the structure of the plasma membrane and the fluid mosaic model.
 Describe the fluid properties of the cell membrane and explain how membrane fluidity is influenced
by membrane composition.
 Explain how hydrophobic and hydrophilic interactions determine membrane structure and function.
 Describe how proteins are spatially arranged in the cell membrane and how they contribute to
membrane function.
 Describe factors that affect selective permeability of membranes.
 Define diffusion; explain what causes it and why it is a spontaneous process.
 Understand factors that affect rates of diffusion and Fick’s law.
 Explain what regulates the rate of passive transport.
 Explain why a concentration gradient across a membrane represents potential energy.
 Define osmosis and predict the direction of water movement based upon differences in solute
concentration.
 Describe how living cells with and without walls regulate water balance.
 Explain how transport proteins are similar to enzymes.
 Describe one model for facilitated diffusion.
 Explain how active transport differs from diffusion.
 Explain the function of the Na-K pump as an example of active transport.
 Explain how active transport systems can generate a membrane potential or electrochemical
gradient.
 Explain how large molecules are transported across the cell membrane by vesicular transport
mechanisms.
 Give an example of receptor-mediated endocytosis.
 Explain how membrane proteins interface with and respond to changes in the extracellular
environment.
 Describe the structure and list some functions of the extracellular matrix in animal cells.
 Describe the structure of intercellular junctions found in plant and animal cells, and relate structure
with function.
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AP Biology
Reading Guide
Chapter 5 – Cell Transport and Communication
QUESTIONS – Membrane Structure
1. Describe the fluid-mosaic membrane model proposed by Singer and Nicolson.
2. Sketch a generic phospholipid. Identify the position of the
hydrophobic and hydrophilic regions. Recall what functional
group provides for a polar head group – what charge does it
contribute? Would this create a net negative or net positive
charge to the cell surface?
3. Match the structure with the correct letter from the diagram.
__________ Cholesterol
__________ Hydrophobic end of phospholipids
__________ Cytoskeleton
__________ Integral protein
__________ Glycolipid
__________ Lipid bilayer
__________ Glycoprotein
__________ Oligosaccharides
__________ Peripheral protein
__________ Hydrophilic end of phospholipids
4. Explain what is meant by the phrase ‘membranes are bifacial (asymmetric).’
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AP Biology
Reading Guide
Chapter 5 – Cell Transport and Communication
5. What components of the cell membrane contribute to the fluid quality of the cell membrane?
6. Explain how composition of the membrane may affect fluidity of the membrane.
7. Describe the experiment and results that provided evidence that proteins drift through the
membrane.
8. How are integral proteins different from peripheral proteins?
Integral Proteins
Peripheral Proteins
9. What is another term to describe an integral protein?
10. What types of amino acid side chains would you predict interface with the fatty acid core of the
membrane versus the extracellular and intracellular regions?
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AP Biology
Reading Guide
Chapter 5 – Cell Transport and Communication
11. Define each of the following terms:
Term
Definition
Glycoprotein
Glycolipid
12. What are some possible roles of carbohydrates on the surface of the cell membrane?
QUESTIONS – Cell Transport
13. Why is the plasma membrane described as selectively permeable?
14. What types of molecules can passively cross a membrane and which types are excluded?
Freely permeable
Impermeable
15. Describe the process of diffusion. What drives the diffusion process? Why is it spontaneous?
16. Name a physiologically relevant process that occurs by simple diffusion.
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AP Biology
Reading Guide
Chapter 5 – Cell Transport and Communication
17. Write the equation for Fick’s Law below. Define all terms of the equation.
18. Describe how each of the following affects the rate of diffusion.
MOLECULAR SIZE
TEMPERATURE
CONCENTRATION
GRADIENT
19. Define osmosis and osmotic pressure.
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Page 5 of 10
AP Biology
Reading Guide
Chapter 5 – Cell Transport and Communication
20. Examine the diagrams below. The arrows
indicate the direction of net water movement.
Answer the following questions.
A
a. Which panel shows a hypertonic environment?
B
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b. Which panel shows a cell hypertonic to its environment?
c. Which panel shows an isotonic environment?
C
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d. Describe what is happening to the plant and animal cells in Panel B (use the terms crenation and
plasmolysis).
e. Explain why this is happening.
f.
Describe what is happening to the plant and animal cells in Panel C (use the terms cytolysis and
turgor pressure).
21. How do substances that cannot readily diffuse through the cell membrane transported across?
22. Define facilitated diffusion.
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AP Biology
Reading Guide
Chapter 5 – Cell Transport and Communication
23. Compare and contrast a channel protein and a carrier protein. Why can the rate of facilitated
diffusion using a carrier protein become saturated as concentration of solute increases?
24. What is a gated channel? Distinguish between a ligand-gated and voltage-gated channel.
25. Is there a specific water channel protein? Explain why the discovery of this channel does not
discount the generally observation that transport of water is a passive process.
26. Contrast movement by facilitated diffusion with movement by active transport.
27. Why is active transport directional, whereas simple diffusion and facilitated diffusion bidirectional
processes?
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AP Biology
Reading Guide
Chapter 5 – Cell Transport and Communication
Describe what is occurring during the functioning of the Na-K Pump.
28. Why does the action of the Na-K pump result in the formation of an electric gradient?
29. Distinguish between primary active transport and secondary active transport? Give an example of
each. Then discuss how primary active transport provides the energy required for secondary active
transporter.
Describe and Contrast the Three Methods of Endocytosis
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AP Biology
Reading Guide
Chapter 5 – Cell Transport and Communication
Phagocytosis
Pinocytosis
ReceptorMediated
Endocytosis
30. Explain how selectivity can be achieved by receptor-mediated endocytosis. Give a physiologically
relevant example of this process.
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AP Biology
Reading Guide
Chapter 5 – Cell Transport and Communication
31. Distinguish between various transport processes in a cell by completing the following chart:
Type of
transport
Energy
Required?
Direction
Requirements
Examples
Diffusion
Osmosis
Facilitated
transport
Active
transport
Exocytosis
Endocytosis
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