1. Small charged molecules, often biogenic amines function as

A. hormones
B. neurotransmitters
C. both (a) and (b)
D. none of these

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2. SH₂ domains specifically bind to

A. phosphorylated serine residues
B. phosphorylated tyrosine residues
C. GDP
D. Ca²⁺

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3. In paracrine signaling, the signaling molecules affects only

A. target cells close to the cell from which it was secreted
B. target cells distant from its site of synthesis in cells of an endocrine organ
C. both (a) and (b)
D. none of the above

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4. Simple nerve reflexes use signaling molecules called

A. neurotransmitters
B. nitric oxides
C. G proteins
D. proteases

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5. Which of the following is not a type of signaling molecule?

A. Testosterone
B. Insulin
C. Thyroxin
D. Adenylate cyclase

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