Physiology Question?

Question

Protein, polypeptide and catecholamine hormes stimulate their target cells by?
A. Stimulating RNA synthesis in the nucleus
B. Stimulating the synthesis of intracellular cAMP
C. Directly combing with inactive enzymes in the cytoplasm, and
and thus activating these enzymes
D. Stimulating DNA synthesis

Answer 1

The correct answer is B. On the suface of the target cell are receptors specific for the hormone involved. These are connected to intracellular components which are activated by the binding of the hormone for the receptor. A conformational change occurs and the activated G-protein (that's the intracellular portion for the receptor) catalyzes the formation of the second messenger (the 1st messenger being your hormone). There are various types of second messengers in different cells of the body. cAMP (cyclic adenosine monophosphate) is one of them. The others include IP3 (inositol triphosphate) and Ca ions. The second messenger then induces the production of whatever effect is intended. Thus, the answer to your question is B.

Choice C is wrong because the hormones you mentioned are hydrophylic, so generally, they cannot cross the cell membrane.
Choice D is wrong, again for the same reasons. Steroid hormones (which are lipophylic are the hormones that function like this.
Choice A is wrong. I'm about 99.9% sure that there is no hormone that acts directly to stimulate RNA synthesis. The steroid hormones do this, though indirectly. The DNA synthesis leads to increased DNA replication which is the middle pathway to produce your proteins that will be the final effector in the process.

Answer 2

The answer is B - because it utilizes the binding at the cell surface which involves cAMP

Answer 3

B, cyclic AMP.. ewwww, I remember that.

Answer 4

C. but I'm just guessing.