The immune system consists of two components: ________ and ________.
A) leukocytes : lymphoid tissues
B) plasma cells : cytotoxic T cells
C) lymphocytes : phagocytes
D) leukocytes : lymphocytes
E) antigens : antibodies
Ans: D) leukocytes : lymphocytes
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After the depolarization phase of an action potential, the resting potential is restored by _____
A) the opening of sodium activation gates B) the opening of voltage-gated potassium channels and the closing of sodium channels C) a decrease in the membrane's permeability to potassium and chloride ions D) a brief inhibition of the sodium-potassium pump E) the opening of more voltage-gated sodium channels
Which of the following protein categories facilitates the movement of ions and molecules across membranes?
A. regulatory proteins B. protective proteins C. transport proteins D. cell-signaling proteins E. motor proteins
Fossils are aged by a process that examines the ________ of known radioactive elements
Fill in the blank(s) with correct word
A test used to detect anti-Rickettsia antibodies in a patient's serum is the
A) direct fluorescent-antibody test. B) indirect fluorescent-antibody test.