The molecule (molecules) that fits into the active site of an enzyme and reacts with the enzyme is
A. always a protein.
B. an analog.
C. always a carbohydrate.
D. a substrate.
E. always broken down by the enzyme.
Answer: D. a substrate.
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Why isn't the oxygenase function of rubisco active under normal environmental conditions?
a. the oxygenase activity of the enzyme requires more energy b. the affinity of the enzyme favors the binding of CO2 c. the oxygenase activity of the enzyme is inhibited by O2 d. the binding site of the enzyme is allosterically inhibited under normal conditions e. the oxygenase binding site has a higher affinity for ATP
The sperm produced by mosses require _____ to reach an archegonium.
a) animals b) light c) the development of a flower d) wind e) moisture
In a cell that has a diploid number of 8 chromosomes, how many chromatids will be present at the beginning of mitosis?
A) 8 B) 16 C) 32 D) 4 E) 2
The 1985 Nobel Prize in Physiology or Medicine was awarded to Michael Brown and Joseph Goldstein for their work on cholesterol metabolism. Brown and Goldstein investigated the cause of remarkably high levels of circulating cholesterol found in certain
families. Just as remarkable was the high incidence of heart disease in these families. What Brown and Goldstein found was not what might be expected–these individuals did not make too much cholesterol. Instead, most of these people had defects in receptor-mediated endocytosis (RME). What could possibly link high cholesterol levels in the blood and defective RME in these patients? A) Cholesterol was not transported into cells by active transport proteins and therefore accumulated in the blood. B) Cholesterol was not transported into cells by RME and therefore accumulated in the blood. C) Cholesterol was being secreted from cells by RME at too high a rate and therefore accumulated in the blood. D) Cholesterol was not transported into cells by facilitated diffusion and therefore accumulated in the blood. E) Cholesterol was being secreted by facilitated diffusion at too high a rate and therefore accumulated in the blood.