What might be the advantage to an ancestral cell if it maintained a photosynthetic bacterium within its cytoplasm rather than digest it?
A. It could now live in a highly oxygenated environment.
B. It could now utilize hydrogen sulfide as an energy source.
C. It could now use glucose as an energy source.
D. It could now use photosynthesis to make its food.
Answer: D
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Which of the following bacteria is least likely to be the cause of septic shock?
A) Escherichia coli B) Haemophilus influenzae C) Mycoplasma pneumoniae D) Neisseria meningitidis
The RNA world proposal suggests that the first information molecules were ____
a. transfer RNA b. ribosomes c. messenger RNA d. ribozymes e. unpaired strands of DNA
Microorganisms that typically live on human sur¬faces, including the interior tubes and cavities of the digestive and respiratory tracts, are called ____________.
A. normal flora B. acne C. biofilm D. commensal organisms E. parasitic organisms
Which of the following statements regarding antigens and antibodies is false?
A) An antibody usually recognizes and binds to an antigenic determinant. B) A single antigen may stimulate the immune system to make several distinct antibodies to it. C) Most antigens are proteins or large polysaccharides on the surfaces of viruses or foreign cells. D) Each antibody has only one antigen-binding site.