All of the following are mechanical/physical defense mechanisms EXCEPT:

a. tears
b. mucus
c. stomach acid
d. urine


Answer: c. stomach acid

Biology & Microbiology

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Organisms that are found together and interact on a more or less permanent basis are in a relationship termed

A. mutualism. B. parasitism. C. symbiosis. D. transient microbiota.

Biology & Microbiology

L-lysine is an essential amino acid and must be supplied in the diet. By comparison, the stereoisomer D-lysine is not biologically active. Why can your body only utilize one form?

A. Antibodies recognize the D form and destroy it before your body can use it for nutritional purposes. B. Since the L form and D form are chiral molecules, they will bind together and inhibit utilization of the D form. C. Enzymes can only recognize a single, specific stereoisomer. D. Since the L form and D form are enantiomers, they will bind together and inhibit utilization of the D form.

Biology & Microbiology

The location where a disease-causing organism is normally found is called the ________.

Fill in the blank(s) with the appropriate word(s).

Biology & Microbiology

In many mammalian species, including bats and most non-human primates, a bone in the penis, called

the ____, helps to maintain it in an erect state.

a. pendulum b. baculum c. colostrum d. gametogonium e. marsupium

Biology & Microbiology