cell signaling mcq
1.Hormones: a) are secreted by exocrine glands.
b) act only on neighboring cells.
c) are always peptides.
d) are secreted into the blood. 2.Prostaglandins: a) are secreted by exocytosis.
b) are blood-borne chemical signals.
c) re synthesized from membrane lipids.
d) activate nuclear receptors. 3.Hormone receptors: a) have a high affinity for their natural ligand.
b) are always linked to G proteins.
c) are lipids.
d) are always located in the plasma membrane of their target cells. 4.G activation: a) leads to changes in gene expression.
b) always causes an increase in cyclic AMP.
c) leads to the generation of second messengers.
d) always results in a decrease in cyclic AMP. 5.Steroid hormones such as aldosterone: a) bind to nuclear receptors to regulate gene expression.
b) activate G cascades.
c) activate receptors on the cell membrane.
d) directly regulate synthesis. Answer 1.d) are secreted into the blood. Feedback:Hormones are blood borne chemical signals secreted by endocrine glands. They act on cells remote from the point of secretion. The secretion of most hormones is regulated by negative feedback. 2.c) re synthesized from membrane lipids. Feedback:Prostaglandins are synthesized as required and act as paracrine signaling agents. As they are
highly lipophilic, they cannot be stored
in membrane bound vesicles but are secreted by diffusion across the plasma membrane. They act on G linked receptors. 3.a) have a high affinity for their natural ligand. Feedback:Hormone receptors are always proteins but they may be located on the plasma membrane or inside the cell. Many hormone receptors do activate G proteins but others activate membrane bound or bind to nuclear receptors. 4.c) leads to the generation of second messengers. Feedback:G proteins link extracellular signals to the control of intracellular metabolism via the generation of second messengers. Second messengers include cyclic AMP, inositol
trisphosphate (IP3) and diacyl glycerol
(DAG). 5.a) bind to nuclear receptors to regulate gene expression