22. During glycolysis molecules of glucose are__?
(A) broken down in oxidation, liberating the carbon atoms as CO2；
(B) bonded in a reduction to form three molecules of pyruvate；
(C) bonded covalently to form two molecules of pyruvate；
(D) broken down by enzymes to form two molecules of pyruvate.

18. The molecular reactants for photosynthesis are__? (A) glucose and carbon dioxide；(B) glucose and sunlight；(C) glucose and water；(D) water and carbon dioxide.

19. Your liver produces 90% of the cholesterol found in your body. When cholesterol levels get too high, the first enzyme in the pathway of cholesterol synthesis is inhibited. This is an example of__? (A) positive feedback；(B) denaturation；(C) negative feedback；(D) equilibrium.

20. Which of the following is NOT a net product or reactant of photosynthesis? (A) oxygen；(B) glucose；(C) carbon dioxide；(D) ATP

21. The main reason that cellular aerobic respiration needs to occur step by step instead of a single, big reaction is__? (A) cells produce the enzymes needed for cellular respiration very slowly； (B) too much energy would be released as heat, and destroy the cell；(C) cells don't store enough oxygen to absorb all the energy in one release；(D) cells don't have enough mitochondria to catalyze the larger, single reaction.

23. The Krebs cycle runs__? (A) six times for each glucose, because each carbon pulled from the original molecule will power the Krebs cycle；(B) 12 times for each glucose, because all of these processes are associated with the Krebs cycle；(C) three times for each glucose, to power the electron transport proteins in hydrogen transport；(D) twice for each glucose, acting on the two-carbon molecule fragments from glycolysis, carried as acetyl CoA.

24. Fermentation is most common in__? (A) fungi, decomposing dead plants；(B) human muscle cells；(C) both human muscle cells, and intestinal bacteria；(D) bacteria, in mammal intestines.

25. Glycolysis does not require__? (A) oxygen；(B) ATP；(C) NAD+；(D) glucose.

26. Muscle cells use lactic acid fermentation to__? (A) allow an animal to survive for long periods of time in the absence of oxygen；(B) generate NAD+ so that glycolysis can continue in the absence of oxygen；(C) produce less CO2；(D) produce ATP in the presence of oxygen.

27. The first steps in glycolysis involve__? (A) reducing glucose；(B) both the addition of two phosphates to glucose, and then splitting glucose；(C) adding two phosphates from ATP to glucose；(D) splitting glucose into two three-carbon molecules.

28. The net ATP production in glycolysis is only two because__? (A) two ATPs are used to "activate" glucose, while 4 ATPs are produced in remaining glycolysis steps；(B) two ATPs are used to donate electrons, in order to move NADH into the mitochondria；(C) None of the answer choices are correct, because six ATPs are the net yield from glycolysis；(D) that is the needed number of ATPs to power the reactions of the Krebs cycle.