13. When placed in a hypertonic solution, animal cells
D. transport water out.
14-According to the fluid mosaic model of cell membranes, which of the following is a true statement about membrane phospholipids?
A. They can move laterally along the plane of the membrane.
B. They frequently flip-flop from one side of the membrane to the other.
C. They occur in an uninterrupted bilayer, with membrane proteins restricted to the surface of the membrane.
D. They are free to depart from the membrane and dissolve in the surrounding aqueous solution.
E. They have hydrophilic tails in the interior of the membrane.
15. The reversibility of ligand‒receptor binding
A. ensures that the ligands are not metabolized.
B. maintains the specificity of the receptor.
C. prevents the receptor from being continuously stimulated.
D. initiates a cellular response.
E. controls the number of ligand‒receptor interactions.
16. Which of the following statements about plasma membrane receptors is false?
A. Their ligands attach to the extracellular domains of the receptor.
B. They move extracellular chemical signals into the cytoplasm.
C. Protein kinase receptors are a type of membrane receptor in mammals.
D. Ion channels can be membrane receptors.
E. Their ligands are polar and lipid insoluble.
17. Consider the equation ΔG = ΔH - TΔS. If ΔG of a chemical reaction is negative and the change in entropy, ΔS, is positive, you can conclude that the reaction
A. requires energy.
B. is endergonic.
C. is exergonic.
D. will not reach equilibrium.
E. decreases the disorder in the system.
18. Which of the following statements about enzymes is false?
A. Some enzymes change shape when they bind to their substrate.
B. Enzymes lower the activation energy for a chemical reaction.
C. Enzymes are highly specific for their substrates.
D. An enzyme may orient substrates, induce strain, or temporarily add chemical groups.
E. Most enzymes are much smaller than their substrates