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Cell Membrane Structure and Function
Chapter 5 Cell Membrane Structure and Function Notes: One of challenges in this chapter is distinguishing the different types of membrane proteins and determining whether they function in passive or energy-requiring modes of transport. Although students understand the definition of a concentration gradient, they have difficulty understanding why water moves one way or the other across a membrane. Students also have a hard time with tonicity and understanding hypertonic vs. hypotonic.
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Which of the following is nonpolar?
Fatty acid tails Water channels Water Phospholipid heads Question: 5-1 Answer: 1 Diff: Moderate Text Ref: Section 5.1 Skill: Factual Also relates to: Chapter 2 Notes: Water and all membrane proteins are polar molecules. The phospholipid head groups are also polar owing to their inherent charge. Only the fatty acid tails, which extend deep into the lipid bilayer, are nonpolar.
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Which of the following is nonpolar?
Fatty acid tails Water channels Water Phospholipid heads Question: 5-1 Answer: 1 Diff: Moderate Text Ref: Section 5.1 Skill: Factual Also relates to: Chapter 2 Notes: Water and all membrane proteins are polar molecules. The phospholipid head groups are also polar owing to their inherent charge. Only the fatty acid tails, which extend deep into the lipid bilayer, are nonpolar.
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The term “fluid mosaic model” refers to:
An experiment that shows the function of the cell membrane. The dynamic flow of proteins and lipids within the membrane. The cell membrane’s ability to communicate with the fluid portions of the cell. The cell’s ability to communicate with the fluid portions of the membrane. Question: 5-2 Answer: 2 Diff: Easy Text Ref: Section 5.1 Skill: Factual Notes: Students are often amazed that the phospholipids are fluid and that the proteins float and move within them. Learning this reinforces that there are thousands of different kinds of proteins that have different structures and functions.
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The term “fluid mosaic model” refers to:
An experiment that shows the function of the cell membrane. The dynamic flow of proteins and lipids within the membrane. The cell membrane’s ability to communicate with the fluid portions of the cell. The cell’s ability to communicate with the fluid portions of the membrane. Question: 5-2 Answer: 2 Diff: Easy Text Ref: Section 5.1 Skill: Factual Notes: Students are often amazed that the phospholipids are fluid and that the proteins float and move within them. Learning this reinforces that there are thousands of different kinds of proteins that have different structures and functions.
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An organism living at the equator has more saturated phospholipids in its cell membranes than an organism living at the South Pole. Why? In cold climates, more unsaturated fats with kinked tails are needed to maintain the fluidity of the cell membranes. In cold climates, more saturated fats with kinked tails are needed to maintain the fluidity of the cell membranes. In warm climates, more unsaturated fats with kinked tails are needed to maintain the fluidity of the cell membranes. In warm climates, more saturated fats with kinked tails are needed to maintain the fluidity of the cell membranes. Question: 5-3 Answer: 1 Diff: Easy Text Ref: Section 5.1 Skill: Conceptual Also relates to: Chapter 3 Notes: Unsaturated fats have double bonds in the tails, making the tails kinked (instead of straight, as in saturated fats). The kinked structure of the unsaturated phospholipids makes them more fluid. This is very important in colder environments, where the molecules tend to move slower. Organisms living in warm environments have fewer unsaturated fats in their cell membranes than organisms living in cold environments. This question will help students remember Chapter 3, where saturated and unsaturated fats were introduced, and help them see the application of these different kinds of lipids.
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An organism living at the equator has more saturated phospholipids in its cell membranes than an organism living at the South Pole. Why? In cold climates, more unsaturated fats with kinked tails are needed to maintain the fluidity of the cell membranes. In cold climates, more saturated fats with kinked tails are needed to maintain the fluidity of the cell membranes. In warm climates, more unsaturated fats with kinked tails are needed to maintain the fluidity of the cell membranes. In warm climates, more saturated fats with kinked tails are needed to maintain the fluidity of the cell membranes. Question: 5-3 Answer: 1 Diff: Easy Text Ref: Section 5.1 Skill: Conceptual Also relates to: Chapter 3 Notes: Unsaturated fats have double bonds in the tails, making the tails kinked (instead of straight, as in saturated fats). The kinked structure of the unsaturated phospholipids makes them more fluid. This is very important in colder environments, where the molecules tend to move slower. Organisms living in warm environments have fewer unsaturated fats in their cell membranes than organisms living in cold environments. This question will help students remember Chapter 3, where saturated and unsaturated fats were introduced, and help them see the application of these different kinds of lipids.
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The phospholipid tails of the membrane face one another because:
They are hydrophilic—repelled by water. They are hydrophobic—attracted to water. They are hydrophilic—attracted to water. They are hydrophobic—repelled by water. Question: 5-4 Answer: 4 Diff: Easy Text Ref: Section 5.1 Skill: Factual Also relates to: Chapter 2 Notes: The concepts of hydrophilic and hydrophobic are introduced at the end of Chapter 2, but they are more appropriately explained in the context of the plasma membrane.
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The phospholipid tails of the membrane face one another because:
They are hydrophilic—repelled by water. They are hydrophobic—attracted to water. They are hydrophilic—attracted to water. They are hydrophobic—repelled by water. Question: 5-4 Answer: 4 Diff: Easy Text Ref: Section 5.1 Skill: Factual Also relates to: Chapter 2 Notes: The concepts of hydrophilic and hydrophobic are introduced at the end of Chapter 2, but they are more appropriately explained in the context of the plasma membrane.
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Which of the following is NOT a function of cell membrane proteins?
To move hydrophilic substances across the plasma membrane To communicate with other cells To isolate the inside of the cell from the outside To identify cell type Question: 5-5 Answer: 3 Diff: Easy Text Ref: Section 5.1 Skill: Factual Notes: Students should understand that the proteins play many roles in the cell membrane but that the phospholipids provide the isolating function.
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Which of the following is NOT a function of cell membrane proteins?
To move hydrophilic substances across the plasma membrane To communicate with other cells To isolate the inside of the cell from the outside To identify cell type Question: 5-5 Answer: 3 Diff: Easy Text Ref: Section 5.1 Skill: Factual Notes: Students should understand that the proteins play many roles in the cell membrane but that the phospholipids provide the isolating function.
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Which is NOT a form of active transport?
Pinocytosis Receptor-mediated transport Phagocytosis Osmosis Question: 5-6 Answer: 4 Diff: Easy Text Ref: Section 5.1 Skill: Factual Notes: Pinocytosis, receptor-mediated transport, and phagocytosis are all energy-requiring processes for the uptake of substances into cells. Osmosis is a passive transport process dependent only on a transmembrane water concentration gradient.
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Which is NOT a form of active transport?
Pinocytosis Receptor-mediated transport Phagocytosis Osmosis Question: 5-6 Answer: 4 Diff: Easy Text Ref: Section 5.1 Skill: Factual Notes: Pinocytosis, receptor-mediated transport, and phagocytosis are all energy-requiring processes for the uptake of substances into cells. Osmosis is a passive transport process dependent only on a transmembrane water concentration gradient.
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Which cell has the highest surface area/volume ratio?
A cell with a radius of 10 units A cell with a radius of 20 units A cell with a radius of 50 units A cell with a radius of 100 units Question: 5-7 Answer: 1 Diff: Easy Text Ref: Section 5.1 Skill: Application Also relates to: Chapter 2 Notes: The cell with the smallest radius will have the largest surface area/volume ratio. However, the largest cell will have the highest absolute volume. It is therefore easier for a smaller cell to transport materials into and out of its cytoplasm than it is for a larger cell with more cytoplasm through which the transported material has to move.
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Which cell has the highest surface area/volume ratio?
A cell with a radius of 10 units A cell with a radius of 20 units A cell with a radius of 50 units A cell with a radius of 100 units Question: 5-7 Answer: 1 Diff: Easy Text Ref: Section 5.1 Skill: Application Also relates to: Chapter 2 Notes: The cell with the smallest radius will have the largest surface area/volume ratio. However, the largest cell will have the highest absolute volume. It is therefore easier for a smaller cell to transport materials into and out of its cytoplasm than it is for a larger cell with more cytoplasm through which the transported material has to move.
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Side A will be hypertonic to side B.
A semipermeable membrane separates two solutions, permitting water, but not larger molecules, to pass. Side A contains a 20% sugar solution. Side B contains a 40% sugar solution. At equilibrium, what condition is true? Side A will be hypertonic to side B. Side A will be hypotonic to side B. Side A will be isotonic to side B. Side B will be hypotonic to side A. Question: 5-8 Answer: 3 Diff: Hard Text Ref: Section 5.2 Skill: Application Notes: Water will flow by osmosis from the side with greater water concentration (side A) to the side with less water concentration (side B). Water will continue to flow to side B until the solution in side B is isotonic to that in side A, and at that point equilibrium will have been established.
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Side A will be hypertonic to side B.
A semipermeable membrane separates two solutions, permitting water, but not larger molecules, to pass. Side A contains a 20% sugar solution. Side B contains a 40% sugar solution. At equilibrium, what condition is true? Side A will be hypertonic to side B. Side A will be hypotonic to side B. Side A will be isotonic to side B. Side B will be hypotonic to side A. Question: 5-8 Answer: 3 Diff: Hard Text Ref: Section 5.2 Skill: Application Notes: Water will flow by osmosis from the side with greater water concentration (side A) to the side with less water concentration (side B). Water will continue to flow to side B until the solution in side B is isotonic to that in side A, and at that point equilibrium will have been established.
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Water movement through channels Oxygen diffusion through the membrane
Which membrane process requires molecules to bind to a membrane protein? Water movement through channels Oxygen diffusion through the membrane Receptor-mediated transport Lipid movement across membranes Question: 5-9 Answer: 3 Diff: Easy Text Ref: Section 5.2 Skill: Factual Notes: This question provides an example of a protein-assisted form of transport involving the binding of the transported molecule to a membrane receptor before it moves across the membrane. All the other examples of transfer across biological membranes do not require the attachment of the transported molecule to a membrane protein.
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Water movement through channels Oxygen diffusion through the membrane
Which membrane process requires molecules to bind to a membrane protein? Water movement through channels Oxygen diffusion through the membrane Receptor-mediated transport Lipid movement across membranes Question: 5-9 Answer: 3 Diff: Easy Text Ref: Section 5.2 Skill: Factual Notes: This question provides an example of a protein-assisted form of transport involving the binding of the transported molecule to a membrane receptor before it moves across the membrane. All the other examples of transfer across biological membranes do not require the attachment of the transported molecule to a membrane protein.
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Facilitated diffusion uses what kind of protein?
Recognition Enzyme Attachment Carrier Question: 5-10 Answer: 4 Diff: Easy Text Ref: Section 5.2 Skill: Application Also relates to: Chapter 2 Notes: This will reinforce that facilitated diffusion can be accomplished only by carrier proteins without expending energy. It can also lead to a more in-depth discussion on the different functions of all membrane proteins.
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Facilitated diffusion uses what kind of protein?
Recognition Enzyme Attachment Carrier Question: 5-10 Answer: 4 Diff: Easy Text Ref: Section 5.2 Skill: Application Also relates to: Chapter 2 Notes: This will reinforce that facilitated diffusion can be accomplished only by carrier proteins without expending energy. It can also lead to a more in-depth discussion on the different functions of all membrane proteins.
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Transport salt into the cell.
The salt concentration of the fluid surrounding a cell is more concentrated than the fluid inside the cell. The cell will: Shrink. Swell. Stay the same. Transport salt into the cell. Question: 5-11 Answer: 1 Diff: Moderate Text Ref: Section 5.2 Skill: Application Notes: Students have a hard time with the concept of tonicity. They need to remember water follows solute. If they can remember this, they can understand in what direction the water will move. The most immediate effect here is for water to move OUT of the cell, resulting in the cell’s shrinking. However, over a more extended period of time the cell may transport salt into its cytoplasm, preventing additional water loss.
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Transport salt into the cell.
The salt concentration of the fluid surrounding a cell is more concentrated than the fluid inside the cell. The cell will: Shrink. Swell. Stay the same. Transport salt into the cell. Question: 5-11 Answer: 1 Diff: Moderate Text Ref: Section 5.2 Skill: Application Notes: Students have a hard time with the concept of tonicity. They need to remember water follows solute. If they can remember this, they can understand in what direction the water will move. The most immediate effect here is for water to move OUT of the cell, resulting in the cell’s shrinking. However, over a more extended period of time the cell may transport salt into its cytoplasm, preventing additional water loss.
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What type of cell junctions are needed for a tissue that must prevent fluids from leaking across its cell layer? Desmosomes Tight junctions Gap junctions Plasmodesmata Question: 5-12 Answer: 2 Diff: Hard Text Ref: Section 5.2 Skill: Application Notes: All organs that must retain fluids have their cells joined by tight junctions to make a strong seal. Other types of junctions provide for more loose connections or for cell-to-cell transfer of ions or small molecules.
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What type of cell junctions are needed for a tissue that must prevent fluids from leaking across its cell layer? Desmosomes Tight junctions Gap junctions Plasmodesmata Question: 5-12 Answer: 2 Diff: Hard Text Ref: Section 5.2 Skill: Application Notes: All organs that must retain fluids have their cells joined by tight junctions to make a strong seal. Other types of junctions provide for more loose connections or for cell-to-cell transfer of ions or small molecules.
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In active transport, the energy source that moves a molecule against its concentration gradient is:
Glucose. NADPH. NADH. ATP. Question: 5-13 Answer: 4 Diff: Easy Text Ref: Section 5.2 Skill: Factual Also relates to: Chapters 3, 6, 7, & 8 Notes: This is the first application of the function of ATP, which was introduced in Chapter 3. It is useful to revisit the structure of ATP and how it gives off energy as the last phosphate group is broken off. Students will learn more about the role of ATP as an energy carrier in Chapters 6, 7, and 8.
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In active transport, the energy source that moves a molecule against its concentration gradient is:
Glucose. NADPH. NADH. ATP. Question: 5-13 Answer: 4 Diff: Easy Text Ref: Section 5.2 Skill: Factual Also relates to: Chapters 3, 6, 7, & 8 Notes: This is the first application of the function of ATP, which was introduced in Chapter 3. It is useful to revisit the structure of ATP and how it gives off energy as the last phosphate group is broken off. Students will learn more about the role of ATP as an energy carrier in Chapters 6, 7, and 8.
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Animal cells communicate with one another through:
Desmosomes. Tight junctions. Gap junctions. Plasmodesmata. Question: 5-14 Answer: 3 Diff: Easy Text Ref: Section 5.3 Skill: Factual Notes: This question can reinforce the difference between gap junctions in animals and plasmodesmata in plants.
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Animal cells communicate with one another through:
Desmosomes. Tight junctions. Gap junctions. Plasmodesmata. Question: 5-14 Answer: 3 Diff: Easy Text Ref: Section 5.3 Skill: Factual Notes: This question can reinforce the difference between gap junctions in animals and plasmodesmata in plants.
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Which of the transport processes in the figure below results in the movement of molecules from a high to a low concentration? Only a Only c a and c a, b, c, and d Question: 5-15 Answer: 4 Diff: Easy Text Ref: Section 5.2 Skill: Factual Notes: This slide shows that a number of different transport mechanisms can result in the transport of molecules down a concentration gradient across a biological membrane. Some of these mechanisms result in diffusion through the lipid bilayer or through aqueous channel proteins and water channels, while others involve the binding of molecules to carrier proteins, followed by their diffusion through the membrane. Figure 5-7
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Which of the transport processes in the figure below results in the movement of molecules from a high to a low concentration? Only a Only c a and c a, b, c, and d Question: 5-15 Answer: 4 Diff: Easy Text Ref: Section 5.2 Skill: Factual Notes: This slide shows that a number of different transport mechanisms can result in the transport of molecules down a concentration gradient across a biological membrane. Some of these mechanisms result in diffusion through the lipid bilayer or through aqueous channel proteins and water channels, while others involve the binding of molecules to carrier proteins, followed by their diffusion through the membrane. Figure 5-7
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In the figure below, what is the correct association?
Trunk lipids: high fatty acid fluidity Trunk lipids: unsaturated fatty acids Leg lipids: low fatty acid fluidity Leg lipids: unsaturated fatty acids Question: 5-16 Answer: 4 Diff: Moderate Text Ref: Section 5.1 Skill: Factual Notes: An adaptation to the cold is to synthesize lipids with unsaturated fatty acids, which provide increased membrane fluidity for cells in appendages exposed to the lowest temperatures. Figure E5-1
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In the figure below, what is the correct association?
Trunk lipids: high fatty acid fluidity Trunk lipids: unsaturated fatty acids Leg lipids: low fatty acid fluidity Leg lipids: unsaturated fatty acids Question: 5-16 Answer: 4 Diff: Moderate Text Ref: Section 5.1 Skill: Factual Notes: An adaptation to the cold is to synthesize lipids with unsaturated fatty acids, which provide increased membrane fluidity for cells in appendages exposed to the lowest temperatures. Figure E5-1 33
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