Chapter 5 Test File
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The compounds in biological membranes that form a barrier to the movement of hydrophilic materials across the membrane are
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Integral membrane proteins.
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Carbohydrates.
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Lipids.
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Nucleic acids.
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Peripheral membrane proteins.
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The 'Chapter 5 Test File' assesses knowledge on biological membranes, focusing on their composition and function. Topics include lipid barriers, protein roles, and membrane fluidity, crucial for students in advanced biology courses.
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- 2.
Biological membranes are composed of
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A. nucleotides and nucleosides.
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B. enzymes, electron acceptors, and electron donors.
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C. fatty acids.
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D. monosaccharides.
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E. lipids, proteins, and carbohydrates.
Correct Answer
A. D. monosaccharides. -
- 3.
Which of the following statements about the proteins of the plasma membrane and the proteins of the inner mitochondrial membrane is true?
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A. Both membranes have only peripheral proteins.
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B. Only the mitochondrial membrane has integral proteins.
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C. Only the mitochondrial membrane has peripheral proteins.
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D. All of the proteins from both membranes are hydrophilic.
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E. The two membranes differ in their lipid composition.
Correct Answer
A. E. The two membranes differ in their lipid composition.Explanation
The correct answer is e. The two membranes differ in their lipid composition. This means that the proteins of the plasma membrane and the proteins of the inner mitochondrial membrane have different types or amounts of lipids associated with them. This difference in lipid composition likely contributes to the different functions and properties of these two membranes.Rate this question:
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- 4.
4. The plasma membrane of animals contains carbohydrates
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A. on the inner side of the membrane, facing the cytosol.
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B. on the outer side of the membrane, protruding into the environment.
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C. on both sides of the membrane.
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D. on neither side of the membrane.
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E. within the membrane.
Correct Answer
A. B. on the outer side of the membrane, protruding into the environment.Explanation
The correct answer is b. on the outer side of the membrane, protruding into the environment. The plasma membrane of animals contains carbohydrates on the outer side of the membrane, which helps in cell recognition and cell signaling. These carbohydrates are attached to proteins and lipids on the outer surface of the membrane, forming glycoproteins and glycolipids. This outer layer of carbohydrates is involved in various cellular processes, such as immune responses and cell-cell interactions.Rate this question:
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- 5.
5. In biological membranes, the phospholipids are arranged in a
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A. bilayer, with the fatty acids pointing toward each other.
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B. bilayer, with the fatty acids facing outward.
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C. single layer, with the fatty acids facing the interior of the cell.
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D. single layer, with the phosphorus-containing region facing the interior of the cell.
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E. bilayer, with the phosphorus groups in the interior of the membrane.
Correct Answer
A. A. bilayer, with the fatty acids pointing toward each other.Explanation
In biological membranes, the phospholipids are arranged in a bilayer, with the fatty acids pointing toward each other. This arrangement is due to the polar nature of the phospholipids, which have a hydrophilic (water-loving) head and a hydrophobic (water-repelling) tail. The hydrophilic heads of the phospholipids face outward towards the aqueous environment, while the hydrophobic tails face inward, creating a barrier between the interior and exterior of the cell. This bilayer arrangement provides stability and allows for the selective permeability of the membrane.Rate this question:
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- 6.
6. Cholesterol molecules act to
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A. help hold a membrane together.
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B. transport ions across membranes.
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C. attach to carbohydrates.
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D. disrupt membrane function.
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E. alter the fluidity of the membrane.
Correct Answer
A. E. alter the fluidity of the membrane.Explanation
Cholesterol molecules are known to alter the fluidity of the membrane. They do this by inserting themselves between the phospholipids in the membrane, which reduces the movement of the phospholipids and makes the membrane less fluid. This helps to maintain the integrity and stability of the membrane, preventing it from becoming too rigid or too fluid. Cholesterol also plays a role in regulating the fluidity of the membrane in response to changes in temperature, ensuring that the membrane remains functional under different conditions.Rate this question:
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- 7.
7. Peripheral membrane proteins have
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A. hydrophobic regions within the lipid portion of the bilayer.
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B. hydrophilic regions that protrude in aqueous environments on either side of the membrane.
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C. lateral but not vertical movement within the bilayer.
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D. control over the rate of diffusion.
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E. polar regions that interact with similar regions of integral membrane proteins.
Correct Answer
A. E. polar regions that interact with similar regions of integral membrane proteins.Explanation
Peripheral membrane proteins are proteins that are not embedded within the lipid bilayer but are attached to the membrane surface. They have hydrophilic regions that interact with the aqueous environment on either side of the membrane. These hydrophilic regions can also interact with similar regions of integral membrane proteins, which are proteins that are embedded within the lipid bilayer. This interaction allows peripheral membrane proteins to perform various functions, such as facilitating the transport of molecules across the membrane or transmitting signals between the cell's interior and exterior. Therefore, the correct answer is e. polar regions that interact with similar regions of integral membrane proteins.Rate this question:
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- 8.
8. The functional roles for different proteins found in membranes include all except
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A. allowing movement of molecules that would otherwise be excluded by the lipid components of the membrane.
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B. transferring signals from outside the cell to inside the cell.
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C. maintaining the shape of the cell.
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D. facilitating the transport of macromolecules across the membrane.
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E. stabilizing the lipid bilayer.
Correct Answer
A. E. stabilizing the lipid bilayer.Explanation
The functional roles for different proteins found in membranes include allowing movement of molecules that would otherwise be excluded by the lipid components of the membrane, transferring signals from outside the cell to inside the cell, maintaining the shape of the cell, and facilitating the transport of macromolecules across the membrane. However, stabilizing the lipid bilayer is not a function of proteins in the membrane. Proteins can interact with the lipid bilayer, but their primary function is not to stabilize it.Rate this question:
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- 9.
9. Houseplants adapted to indoor temperatures may die when accidentally left outdoors in the cold because their
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A. DNA cannot function.
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B. membranes lack adequate fluidity.
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C. photosynthesis is impaired.
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D. chloroplasts malfunction.
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E. membranes need more cholesterol.
Correct Answer
A. B. membranes lack adequate fluidity.Explanation
Houseplants that are adapted to indoor temperatures may die when accidentally left outdoors in the cold because their membranes lack adequate fluidity. Membranes are made up of lipids, which can become rigid and less fluid in cold temperatures. This can disrupt the normal functioning of the membranes, affecting various cellular processes such as nutrient uptake, water transport, and waste removal. As a result, the houseplant may not be able to properly maintain its physiological functions and eventually die.Rate this question:
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- 10.
10. A protein that forms an ion channel through a membrane is most likely to be
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A. a peripheral protein.
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B. a transmembrane protein.
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C. a phospholipid.
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D. an enzyme.
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E. entirely outside the phospholipid bilayer.
Correct Answer
A. B. a transmembrane protein.Explanation
A protein that forms an ion channel through a membrane is most likely to be a transmembrane protein because transmembrane proteins span the entire phospholipid bilayer of the membrane. This allows them to create a channel or pore through which ions can pass, facilitating the movement of ions across the membrane. Peripheral proteins are located on the surface of the membrane and do not span the entire bilayer, making them less likely to form an ion channel. Phospholipids are a type of lipid molecule that make up the bilayer itself, and enzymes are proteins that catalyze chemical reactions, neither of which are directly involved in forming ion channels.Rate this question:
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- 11.
11. The hydrophilic regions of a membrane protein are most likely to be found
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A. only in muscle cell membranes.
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B. associated with the fatty acid region of the lipids.
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C. in the interior of the membrane.
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D. exposed on the surface of the membrane.
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E. either on the surface or inserted into the interior of the membrane.
Correct Answer
A. D. exposed on the surface of the membrane.Explanation
The hydrophilic regions of a membrane protein are most likely to be found exposed on the surface of the membrane because hydrophilic regions are attracted to water and therefore will be oriented towards the aqueous environment on either side of the membrane. This allows the hydrophilic regions to interact with water molecules and participate in various cellular processes such as transport of ions and molecules across the membrane.Rate this question:
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- 12.
12. A characteristic of plasma membranes that helps them fuse during vesicle formation and phagocytosis is the
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A. ratio of one protein molecule for every 25 phospholipid molecules.
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B. capacity of lipids to associate and maintain a bilayer organization
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C. constant fatty acid chain length and degree of saturation.
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D. ability of phospholipid molecules to flip over and trade places with other phospholipid molecules.
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E. asymmetrical distribution of membrane proteins.
Correct Answer
A. B. capacity of lipids to associate and maintain a bilayer organizationExplanation
The capacity of lipids to associate and maintain a bilayer organization is a characteristic of plasma membranes that helps them fuse during vesicle formation and phagocytosis. This is because the lipid bilayer structure allows for the fusion of membranes, as the lipids can easily associate and reorganize. This characteristic allows for the formation of vesicles and the engulfment of particles during phagocytosis. The ratio of protein to phospholipid molecules, the fatty acid chain length and degree of saturation, and the asymmetrical distribution of membrane proteins are not directly related to the fusion of plasma membranes during vesicle formation and phagocytosis.Rate this question:
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- 13.
13. The plasma membranes of winter wheat are able to remain fluid when it is extremely cold by
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A. increasing the number of cholesterol molecules present.
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B. closing protein channels.
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C. decreasing the number of hydrophobic proteins present.
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D. replacing saturated fatty acids with unsaturated fatty acids.
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E. using fatty acids with longer tails.
Correct Answer
A. D. replacing saturated fatty acids with unsaturated fatty acids.Explanation
The plasma membranes of winter wheat are able to remain fluid when it is extremely cold by replacing saturated fatty acids with unsaturated fatty acids. Unsaturated fatty acids have double bonds in their carbon chains, which introduces kinks and prevents the fatty acids from packing tightly together. This increases the fluidity of the membrane, allowing it to remain functional even at low temperatures.Rate this question:
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- 14.
14. Which type of membrane protein would likely be most easily removed in a laboratory experiment?
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A. Integral proteins
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B. Channel proteins
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C. Peripheral proteins
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D. Transmembrane proteins
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E. Gated channels
Correct Answer
A. C. Peripheral proteinsExplanation
Peripheral proteins are loosely attached to the surface of the cell membrane and can be easily removed in a laboratory experiment. They are not embedded within the lipid bilayer like integral proteins or transmembrane proteins. Channel proteins and gated channels are types of integral proteins, so they would not be easily removed. Therefore, the most likely answer is c. Peripheral proteins.Rate this question:
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- 15.
15. When a mouse cell and a human cell are fused, the membrane proteins of the two cells become uniformly distributed over the surface of the hybrid cell. This occurs because
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A. many proteins can move around within the bilayer.
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B. all proteins are anchored within the membrane.
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C. proteins are asymmetrically distributed within the membrane.
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D. all proteins in the plasma membrane are peripheral.
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E. different membranes contain different proteins.
Correct Answer
A. A. many proteins can move around within the bilayer.Explanation
The correct answer is a. many proteins can move around within the bilayer. This is because the membrane proteins are not fixed in place, but rather they have the ability to move within the lipid bilayer of the cell membrane. This movement allows for the proteins from the mouse cell and the human cell to become uniformly distributed over the surface of the hybrid cell when they are fused together. This phenomenon is due to the fluidity of the lipid bilayer, which allows for the proteins to freely move and mix with each other.Rate this question:
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- 16.
16. The LDL receptor is an integral protein that crosses the plasma membrane, with portions of the protein extending both outside and into the interior of the cell. The amino acid side chains (R groups) in the region of the protein that crosses the membrane are most likely
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A. charged.
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B. hydrophilic.
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C. hydrophobic.
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D. carbohydrates.
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E. lipids.
Correct Answer
A. C. hydrophobic.Explanation
The correct answer is c. hydrophobic. The question states that the protein crosses the plasma membrane, which is composed of a lipid bilayer. Hydrophobic amino acid side chains are nonpolar and repel water, making them more likely to interact with the hydrophobic interior of the membrane. This allows the protein to anchor itself in the membrane and span across it. Charged and hydrophilic amino acid side chains would be more likely to interact with the aqueous environment inside or outside the cell, respectively. Carbohydrates and lipids are not mentioned in the context of the question.Rate this question:
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- 17.
17. When a membrane is prepared by freeze-fracture and examined under the electron microscope, the exposed interior of the membrane bilayer appears to be covered with bumps. These bumps are
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A. integral membrane proteins.
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B. ice crystals.
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C. platinum.
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D. organelles.
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E. vesicles.
Correct Answer
A. A. integral membrane proteins.Explanation
When a membrane is prepared by freeze-fracture and examined under the electron microscope, the exposed interior of the membrane bilayer appears to be covered with bumps. These bumps are actually integral membrane proteins. This is because integral membrane proteins are embedded within the lipid bilayer of the membrane, and when the membrane is fractured, these proteins are exposed on the fractured surface, appearing as bumps under the electron microscope. Ice crystals, platinum, organelles, and vesicles are not typically observed in this context.Rate this question:
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- 18.
18. When vesicles from the Golgi apparatus deliver their contents to the exterior of the cell, they add their membranes to the plasma membrane. The plasma membrane does not increase in size, because
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A. some vesicles from the Golgi apparatus fuse with the lysosomes.
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B. membrane vesicles carry proteins from the endoplasmic reticulum to the Golgi apparatus.
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C. membrane is continually being lost from the plasma membrane by endocytosis.
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D. new phospholipids are synthesized in the endoplasmic reticulum.
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E. the phospholipids become more tightly packed together in the membrane.
Correct Answer
A. C. membrane is continually being lost from the plasma membrane by endocytosis. -
- 19.
19. Protein movement within a membrane may be restricted by
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A. glycolipids and glycoproteins.
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B. closure of gated channels.
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C. the cytoskeleton and lipid rafts.
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D. cell adhesion.
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E. tight junctions and desmosomes.
Correct Answer
A. C. the cytoskeleton and lipid rafts.Explanation
Protein movement within a membrane may be restricted by the cytoskeleton and lipid rafts. The cytoskeleton is a network of protein filaments that provides structural support to the cell and can act as a barrier to protein movement. Lipid rafts are specialized regions of the membrane that contain high concentrations of cholesterol and sphingolipids, and they can also restrict protein movement by creating a more rigid environment. Together, the cytoskeleton and lipid rafts play a role in maintaining the organization and integrity of the cell membrane.Rate this question:
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- 20.
20. Which of the following functions as a recognition signal for interactions between cells?
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A. RNA
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B. Phospholipids
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C. Cholesterol
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D. Fatty acids
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E. Glycolipids
Correct Answer
A. E. GlycolipidsExplanation
Glycolipids function as recognition signals for interactions between cells. They are composed of a carbohydrate chain attached to a lipid molecule. These molecules are located on the cell surface and play a crucial role in cell-cell recognition and communication. Glycolipids are involved in various cellular processes, including immune responses, cell adhesion, and cell signaling. They can act as receptors for signaling molecules and facilitate cell-cell adhesion by binding to specific proteins on neighboring cells. Therefore, glycolipids are essential for mediating interactions between cells.Rate this question:
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- 21.
21. Which of the following represents the correct pathway for the synthesis and secretion of insulin, a protein secreted by the cells of the pancreas?
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A. Rough ER; Golgi apparatus; vesicle; plasma membrane
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B. Golgi apparatus; rough ER; lysosome
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C. Lysosome; vesicle; plasma membrane
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D. Plasma membrane; coated vesicle; lysosome
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E. Rough ER; cytoplasm; plasma membrane
Correct Answer
A. A. Rough ER; Golgi apparatus; vesicle; plasma membraneExplanation
The correct pathway for the synthesis and secretion of insulin involves the protein being synthesized in the rough endoplasmic reticulum (ER), then transported to the Golgi apparatus for further processing. From the Golgi apparatus, the insulin is packaged into vesicles, which then fuse with the plasma membrane to release the insulin outside the cell. Therefore, option a. Rough ER; Golgi apparatus; vesicle; plasma membrane is the correct answer.Rate this question:
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- 22.
22. Which of the following are not specialized cell junctions?
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A. Gap junctions
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B. Tight junctions
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C. Desmosomes
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D. Cytoplasmic plaques
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E. Both a and b
Correct Answer
A. D. Cytoplasmic plaquesExplanation
Cytoplasmic plaques are not specialized cell junctions. Gap junctions are specialized cell junctions that allow for direct communication between adjacent cells, while tight junctions are specialized cell junctions that create a barrier between cells to prevent the movement of molecules between them. Desmosomes are specialized cell junctions that provide mechanical strength to tissues. Cytoplasmic plaques, on the other hand, are structures within desmosomes that anchor intermediate filaments to the cell membrane, but they are not considered specialized cell junctions themselves. Therefore, the correct answer is d. Cytoplasmic plaques.Rate this question:
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