In step 4 of the citric acid cycle, the reduction of NAD+ to NADH is coupled to the generation of CO2 and the formation of a high-energy thioester bond. Which molecule provides the sulfhydryl group necessary to form the thioester bond?
(a) pyruvate
(b) acetyl CoA
(c) CoA
(d) cysteine side chain in the catalytic pocket
(c)
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What is the risk associated with amateur mushroom hunting?
a. mycotoxicosis b. ringworm c. mycetismus d. histoplasmosis
Antihistamines dampen the effect of allergic
reactions by a. blocking the production of histamines. b. blocking the release of histamines. c. blocking the effect of histamines. d. enzymatically destroying the histamines. e. none of these.
Why are many digestive enzymes produced in an inactive form and then activated in the lumen of the digestive tract?
A. It helps to break down macromolecules(proteins, carbohydrates, nucleic acids, lipids) faster. B. The temperature of organism changes when food falls into digestive tract, that helps to activate digestive enzymes. C. Digestive enzyme should have an inactive period, only after that period they could be activated. D. Digestive enzymes would destroy the cells that produce and secrete them if they were produced in an active form.
Without knowing the genetic basis, humans have selectively bred for:
a) increased body size in cattle. b) transgenic tomatoes. c) increased milk production. d) both a) and b). e) both a) and c).