24. An enzyme-catalyzed reaction was carried out with the substrate concentration initially a thousand times greater than the Km for that substrate. After 9 minutes, 1% of the substrate had been converted to product, and the amount of product formed in the reaction mixture was 12 mol. If, in a separate experiment, one-third as much enzyme and twice as much substrate had been combined, how long would it take for the same amount (12 mol) of product to be formed? (A) 1.5 min (B) 3 min (C) 6 min (D) 13.5 min (E) 27 min

9. Which of the following statements is not true? (1) In muscle, the activity of phosphofructokinase is regulated by pH value. (2) Lactase deficiency cause many adults are intolerant of milk. (3) In vertebrate liver, fructokinase is bypassed during fructose metabolism, often leading to conversion of excess fructose into fat. (4) Ethanol is metabolized in the cytosol of liver that will elevate the [NADH]/[NAD+ ] ratio, and inhibit glycolysis and gluconeogenesis. (5) Compared to hexokinase, glucokinase displays sigmoidal kinetics for glucose uptake and higher glucose affinity. (A) 1 and 3, (B) 2 and 4, (C) 3 and 5, (D) only 3, (E) only 5.

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