Interacting systems of molecules enclosed in compartments called __________ evolved 3.8 billion years ago in living organisms.
A. cells
B. organs
C. microspheres
D. tissues
Answer: A. cells
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Humans are unable to get metabolic energy from cellulose because:
A. cellulose contains very little chemical energy. B. cellulose is not part of a normal diet. C. cellulose digesting enzymes are absent from the human gut. D. cellulose does not taste good. E. cellulose is present in large quantities in the gut.
This type of cell is closely associated with a companion cell
a. sieve tube member b. tracheid c. vessel elements d. sclerenchyma e. collenchyma
What is the most important role of bacteria in the environment?
A) as disease-causing agents B) as fungal control C) as decomposers D) as a source of restriction enzymes
Which of the following is NOT characteristic of RNA?
A) It is a helical polymer. B) It is usually double-stranded. C) Its "backbone" is composed of pentoses and phosphates. D) It contains both purines and pyrimidines. E) It can function as a catalyst.