16. A macromolecule that regulates the fluidity of animal cell membranes by stif
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16. A macromolecule that regulates the fluidity of animal cell membranes by stiffening the membrane at higher temperatures and the freezing at lower temperature. preventing the membrane from A nucleic acid D. C. cholesterol B. enzyme 17. Proteins in a membrane are: A peripheral if they are bound to the surface of the membrane B. integral if they are embedded in the membrane and span both surfaces of the blayer C. integral if they are embedded in the membrane and protrude from only one surface of the bilayser D. All of the choices are correct 18. what type of molecule can dissolve in the lipid blayer and pass through the membrane rapidy? A. small hydrophilic 8. large ionic C. large hydrophobic D. large amphipathic 19. Which of the following statements about diffusion is true? A. It is very rapid over long distances. B. It requires an expenditure of energy by the cell. C. It is an active process in which molecules move from a region of lower concentration to a region of higher concentration. D. It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration. 20. Which of the following is a reasonable explanation for why unsaturated fatty acids help keep a membrane more fluid at lower The double bonds form kinks in the fatty acid tails, preventing adjacent lpids from packing tighthy A. B. Unsaturated fatty acids have a higher cholesterol content and, therefore, more cholesterol in membranes. Unsaturated fatty acids are more polar than saturated fatty acids. D. The double bonds block interaction among the hydrophilic head groups of the lipids. -21. Which of the following is a characteristic feature of a carrier protein in a plasma membrane? A It exhibits a specificity for a particular type of molecule. 8. It requires the expenditure of cellular energy to function C. It works against diffusion D. It has no hydrophobic 22. The diffusion of water across a selectively permeable membrane B. active transpont C. facilitative diffusion D. concentration gradient A. osmosis 23. The force driving simple diffusion while the energy source for active transpont is_ A. the concentration gradient; ADP B. the concentration gradient;ATP C. transmembrane pumps; electron transport D. phosphorylated protein carriers; ATP solution occurs when the solute concentration on the outside of a cell is the same as that inside 24. A the cell. NO net water movement occurs across the plasma membrane. A Hypotoric C. Isotonic D. Hypnotic B. Hypertonic 25. The mechanism by which a cell transports vesicles to the membrane, fuses the vesicle with the 26. The second law of thermodynamics states that energy transfer or transformation increases the of the universe. 27. Which of the following is an example of chemical (potential) rather than kinetic energy contents outside of a cell. D. pinocytosis B. cell drinking C. exocytosis D. Direction A. Order B. EntropY C. Stability A. water rushing over Niagara Fall C. a molecule of glucose B. light flashes emitted by a firefly D. a crawling beetle foraging for food 28. All of the biochemical pathways in a cell constitute B. free energy D. metabolism. C. endergonic reactions only A. coupling reactions. 29. Which term most precisely describes the cellular process of breaking down large molecules into smaller ones? A. anabolism (anabolic pathways) C. catabolism (catabolic pathways) B. metabolism D. dehydrationExplanation / Answer
16) Option C, i.e., cholesterol is the correct answer.
The mosaic nature of the membrane, its phospholipid chemistry, and the presence of cholesterol contribute to membrane fluidity.
17) Option D, i.e., all of the above are the correct answer.
Membrane proteins are of two types, surface proteins and integral proteins.Surface proteins are preipheral proteins associated with the plasma membrane surface and integral or intrinsic proteins are that span the membrane and protrude at either one end or both of the plasma membrane.
18) Option C, i.e., Hydrophobic is the correct answer.
The solubility of a molecule is depepndant on the nature of solute as well as the solvent. lipid bilayer of membrane is composed of phospholipids and is hydrophobic in nature. To be able to pass through the membrane by dissolving in it, the molecule should be hydrophobic in nature similar to membrane lipids.
19) Option D is the correct answer.
Diffusion is a passive process in which molecules move along the concentration gradient without expenditure of energy.
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