What percentage of the species that have ever existed on Earth are probably now extinct?
a. less than 10%
b. more than 99.9%
c. about 80%
d. about 25%
e. about 75%
ANSWER: b
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You have isolated a previously unstudied protein, identified its complete structure in detail, and determined that it catalyzes the breakdown of a large substrate. You notice it has two binding sites
One of these is large, apparently the bonding site for the large substrate; the other is small, possibly a binding site for a regulatory molecule. What do these findings tell you about the mechanism of this protein? A) It is probably a structural protein that is involved in cell-to-cell adhesion. B) It is probably an enzyme that works through allosteric regulation. C) It is probably an enzyme that works through competitive inhibition. D) It is probably a cell membrane transport protein-like an ion channel. E) It is probably a structural protein found in cartilage or skeletal tissue.
Why is ultraviolet radiation damaging?
a. Because it consists of wavelengths that are longer than visible light, the energy of the photons of ultraviolet light is greater and more damaging to biological molecules. b. Because it consists of wavelengths that are shorter than visible light, the energy of the photons of ultraviolet light is greater and more damaging to biological molecules. c. Because it consists of wavelengths that are shorter than visible light, the energy of the photons of ultraviolet light is lesser and more damaging to biological molecules. d. Because it consists of wavelengths that are shorter than visible light, the energy of the photons of ultraviolet light is lesser and less damaging to biological molecules.
Which of the following statements about NAD+ is false?
A) NAD+ is reduced to NADH during both glycolysis and the citric acid cycle. B) NAD+ has more chemical energy than NADH. C) NAD+ is reduced by the action of dehydrogenases. D) NAD+ can receive electrons for use in oxidative phosphorylation. E) In the absence of NAD+, glycolysis cannot function.
A viroid is a completely developed infectious agent composed of nucleic acid and surrounded by a capsid
Indicate whether the statement is true or false