Cell Membrane Structure
Which of the following activities is most important function of glycoproteins and glycolipids of animal cell membranes?
A. maintaining membrane fluidity at low temperatures
B. ability to distinguish one type of neighboring cell from another
C. active transport of molecules against their concentration gradients
D. facilitated diffusion of molecules down their concentration gradients
B. ability to distinguish one type of neighboring cell from another
What type of transport is described as an unassisted movement of solutes from higher to lower concentration across the phospholipid membrane?
simple diffusion
A plant cell whose cytoplasm has a concentration of 0.02 molar glucose is placed in a test tube of water containing 0.02 molar glucose. Assuming that glucose is not actively transported into the cell, which of the following terms BEST describes the cell's appearance?
A. flaccid
B. normal
C. plasmolyzed
D. shriveled
A. flaccid
Which type of transport mechanism requires the cell to expend metabolic energy directly to a pump?
primary active transport
Doctors examine cells lining the small intestine. They observe the cells taking in large amounts of dissolved nutrients and extracellular fluid all at once in small vesicles. Which bulk transport process is being used?
pinocytosis
What chemical property characterizes the interior of the phospholipid bilayer?
hydrophobic
What kind of molecules pass through the phospholipid layer of the cell membrane easily?
A. macromolecules
B. positively charged ions
C. large uncharged non-polar molecules
D. small uncharged non-polar molecules
D. small uncharged non-polar molecules
What will happen to a red blood cell when placed in a hypertonic solution?
shrink/shriveled
Which of the following situations is NOT an example of active transport?
A. A white blood cell engulfs a bacterium as you fight off an infection.
B. The lung cells of a victim who drowned in fresh water are swollen due to water entering the cells.
C. Salivary gland cells produce the enzyme salivary amylase and secrete it into the salivary ducts to be delivered to the mouth.
D. Cells of the stomach wall transport hydrogen ions through an ATP-dependent membrane protein to the inside of the stomach, producing a pH of 1.5. The pH of the cytoplasm of stomach wall cells is approximately at pH 7.
B. The lung cells of a victim who drowned in fresh water are swollen due to water entering the cells.
After a viral infection, immune cells consume leftover viral particles and dead cell debris through vesicles that merge with lysosomes for digestion. Which bulk transport process is being used?
phagocytosis
Why is the presence of cholesterol important in the plasma membranes of some animals?
A. enables the animal to add hydrogen atoms to unsaturated phospholipids
B. enables the animal to remove hydrogen atoms from saturated phospholipids
C. enables the membrane to stay fluid more easily when cell temperature drops
D. makes the membrane less flexible, allowing it to sustain greater pressure from within the cell
C. enables the membrane to stay fluid more easily when cell temperature drops
Which of the following statements correctly describes the difference between carrier proteins and channel proteins?
A. Carrier proteins assist molecules in osmosis while channel proteins assist molecules in active transport.
B. Channel proteins are attracted to glycolipids and carrier proteins change shape slightly when a specific molecule binds to help.
C. Channel proteins change shape when a specific molecule binds to move it across the membrane while carrier proteins provide corridors for specific molecules to pass through.
D. Carrier proteins change shape when a specific molecule binds to move it across the membrane while channel proteins provide corridors for specific molecules to pass through.
D. Carrier proteins change shape when a specific molecule binds to move it across the membrane while channel proteins provide corridors for specific molecules to pass through.
Which of the following statements correctly describes a cell when placed in a hypotonic solution?
A. Salts will move into the cell from the surrounding solution.
B. Salts will move out of the cell into the surrounding solution.
C. Water will move into the cell from the surrounding solution.
D. Water will move out of the cell into the surrounding solution.
C. Water will move into the cell from the surrounding solution.
How are primary active and secondary active transport related?
A. They both use ATP to move molecules.
B. Primary active transport moves one molecule, but secondary active transport moves two.
C. Secondary active transport uses the concentration gradient established by primary active transport.
D. Primary active transport establishes a concentration gradient, but secondary active transport does not.
C. Secondary active transport uses the concentration gradient established by primary active transport.
A patient has dangerously high LDL cholesterol because their liver cells fail to take in LDL particles. Test results reveal that the receptors for LDL on the membrane are defective, so LDL cannot be internalized. Which bulk transport process is being disrupted?
receptor-mediated endocytosis
Which of the following molecules would likely move through the lipid bilayer of a plasma membrane most rapidly?
A. CO2
B. Na+
C. H2O
D. sucrose
A. CO2
How can molecules pass through a closed gate such as in ligand-gated channel protein?
A. The ligand-gated channel protein is always open, and it does need any stimulus.
B. Receptor must receive electrical signals to open the gate.
C. Receptor must receive pressure to open the gate.
D. Receptor must receive signals from the neurotransmitter to open the gate.
D. Receptor must receive signals from the neurotransmitter to open the gate.
A patient who has had severe bleeding accidentally receives a large transfusion of distilled water directly into a major blood vessel. Which of the following events can be expected with this mistake?
A. no unfavorable effect if the water is free of bacteria
B. serious to fatal consequences because the red blood cells could shrink
C. serious to fatal consequences because there would be too much fluid to pump
D. serious to fatal consequences because the red blood cells could swell and burst
D. serious to fatal consequences because the red blood cells could swell and burst
Which of the following membrane activities requires energy from ATP hydrolysis?
A. movement of water using aquaporin
B. absorption of dissolved nutrients in the small intestine
C. transport of oxygen through the phospholipid layer
D. water uptake of plants from roots to shoots
B. absorption of dissolved nutrients in the small intestine
During a neurological exam, scientists see neurons releasing neurotransmitters into the synapse so that messages can pass from one nerve cell to another. The chemicals exit via vesicles fusing with the membrane. Which bulk transport process is being used?
exocytosis
An animal cell that can alter the composition of saturated and unsaturated fatty acids in its membrane lipids is adapted to a cold environment. How will the animal cell react if it is shifted to a warmer environment?
A. It will alter the amount of protein present in the membrane.
B. It will increase the percentage of saturated fatty acids in its membrane.
C. It will decrease the percentage of saturated fatty acids in its membrane.
D. It will increase the percentage of unsaturated fatty acids in its membrane.
B. It will increase the percentage of saturated fatty acids in its membrane.
Facilitated diffusion and active transport both rely on proteins embedded in the phospholipid bilayer of the cell. Which of the following statements provides the BEST explanation of the differences between active transport and facilitated diffusion?
A. Active transport is powered by ADP phosphorylation while facilitated diffusion is powered by the hydrolysis of ATP.
B. Active transport is powered by the hydrolysis of ATP while facilitated diffusion is powered by anabolic reactions of cells.
C. Facilitated diffusion moves molecules down their concentration gradient; active transport uses ATP hydrolysis to move molecules against concentration gradient.
D. Facilitated diffusion moves molecules up their concentration gradient until equilibrium is reached; active transport moves molecules against their concentration gradient.
C. Facilitated diffusion moves molecules down their concentration gradient; active transport uses ATP hydrolysis to move molecules against concentration gradient.
A wilted flower placed in a vase of freshwater for several hours became stiff and stood erect. When it was placed in a salt solution, it wilted. From this information, which of the following statements BEST describes the cells of the flower?
A. hypotonic to freshwater but hypertonic to the salt solution
B. hypertonic to freshwater but hypotonic to the salt solution
C. hypertonic to both the freshwater and the salt solution
D. hypotonic to both freshwater and the salt solution
A. hypotonic to freshwater but hypertonic to the salt solution
Plants must uptake mineral salts from the surrounding soil. The mineral salts, however, are more abundant inside the plant and therefore must use ATP in order to move the salts across the membrane, against their concentration gradient. Which method of movement does this describe?
primary active transport
Which of the following CORRECTLY states the difference between pinocytosis and receptor-mediated endocytosis?
A. Pinocytosis requires cellular energy, but receptor-mediated endocytosis does not.
B. Pinocytosis can concentrate substances from the extracellular fluid, but receptor-mediated endocytosis cannot.
C. Pinocytosis increases the surface area of the plasma membrane whereas receptor -mediated endocytosis decreases the plasma membrane surface area.
D. Pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis offers more selectivity.
D. Pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis offers more selectivity.