6. Zinc is an essential trace element for most organisms. Zinc is required in the active site of the enzyme carboxypeptidase where it most likely functions in which of the following ways?
(A) as a noncompetitive inhibitor of the enzyme
(B) as an allosteric activator of the enzyme
(C) as a cofactor necessary for enzyme activity
(D) as a coenzyme derived from a vitamin

2. A salamander relies on hydrogen bonding to stick to various surfaces. Therefore, a salamander would have the greatest difficulty clinging to a_____. (A)slightly damp surface (B)surface of hydrocarbons (C) surface of mostly carbon-oxygen bonds (D) surface of mostly carbon-nitrogen bonds

3. Sulfur is in the same column of the periodic table as oxygen but it is less electronegative than oxygen. Compared to water molecules, how will the H2S molecules behave? (A)have greater cohesion to other H2S molecules (B)have a greater tendency to form hydrogen bonds with each other (C)have a higher capacity to absorb heat for the same change in temperature (D) not be able to form hydrogen bonds with each other

4.Which of the following identifies the chemical relationship between glucose and fructose? (A) They are isotopes. (B) They are enantiomers. (C) They are cis-trans isomers. (D) They are structural isomers.

5. During a 12-hour fast in a human, the first macromolecule to get depleted is typically_____. (A)glucose (B) protein (C)glycogen (D) starch

7. The liver is involved in the detoxification of many poisons and drugs. Which of the following structures is abundant in liver cells and primarily responsible for detoxification processes? (A) rough endoplasmic reticulum (B) smooth endoplasmic reticulum (C)Golgi apparatus (D) nuclear envelope

8. In some cells, there are many different ion electrochemical gradients across the plasma membrane even though there are usually only one or two types of proton pumps present in the membrane. The gradients of the other ions are most likely established by which of the following? (A)co-transport proteins (B) ion channels (C)pores in the plasma membrane (D)passive diffusion across the plasma membrane

9. Which of the following responses is stimulated by cell signaling the formation of biofilms? (A) formation of mating complexes (B) aggregation of bacteria (C)secretion of substances that inhibit the growth of foreign bacteria (D) inhibition of quorum sensing

10. Which of the following reactions produces the majority of the COz released by the complete oxidation of glucose? (A) glycolysis (B)electron transport (C)oxidation of pyruvate to acetyl-CoA (D)the citric acid cycle

複選題11. Carotenoids are often found in foods that are considered to have antioxidant properties in human nutrition. Which of the following statements best describes a related function they serve in plants? (A)They serve as accessory pigments to increase light absorption. (B) They protect against oxidative damage from excessive light energy. (C)They shield the sensitive chromosomes of the plant from harmful ultraviolet radiation. (D) They reflect orange light and enhance red light absorption by chlorophyll.

12. One difference between cancer cells and normal cells is that cancer cells________. (A)are unable to synthesize DNA (B)are arrested at the S phase of the cell cycle (C)continue to divide even when they are tightly packed together (D) cannot function properly because they are affected by density-dependent inhibition