Which statement best describes a typical food chain?
a. An owl has a positive impact on the grass population.
b. An owl has a negative impact on the grass population.
c. A carnivore has a negative effect on primary producers.
d. Energy can flow back and forth between trophic levels.
e. Energy is never lost as it moves from one trophic level to the next.
a
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Which statement below does NOT correctly describe paracrine regulation?
A. Paracrine regulatory molecules include cytokines and growth factors. B. Nitric oxide can function either as a neurotransmitter or a paracrine regulatory molecule. C. Endothelin and bradykinin are paracrine molecules that control blood vessel constriction and dilation. D. Paracrine molecules are released into the circulatory system to affect distant tissues. E. Platelet-derived growth factor and insulin-like growth factor are both paracrine regulatory molecules.
In order to reuse an enzyme after the conclusion of an enzyme-catalyzed reaction, what must occur?
A. The enzyme has to be resynthesized. B. The enzyme must change into an active form C. The enzyme has to decrease entropy. D. The enzyme has to separate itself from the product.
You are studying the effects of specific transcription factors on the activation of gene expression. You notice that one particular transcription factor binds far away from the promoter of its target gene. What can explain this?
A. DNA looping brings the transcription factor closer to the promoter and initiates gene transcription. B. RNA looping brings the transcription factor closer to the promoter and initiates gene transcription. C. The transcription factor tags the enhancer with ubiquitin to stimulate transcription. D. The transcription factor transcribes small RNAs that then bind to the promoter and activate the gene's expression.
RNA in cells differs from DNA in that ___________________
(a) it contains the base uracil, which pairs with cytosine. (b) it is single-stranded and cannot form base pairs. (c) it is single-stranded and can fold up into a variety of structures. (d) the sugar ribose contains fewer oxygen atoms than does deoxyribose.