Sun14November1246PM 43

Second messenger systems relay signals received at receptors on the cell surface which in turn activate intracellular effectors.

Which second messenger is the most abundant in the human body?

(Please select 1 option)

Diacylglycerol (DAG)

Inositol triphosphate

Cyclic AMP (cAMP)

Cyclic GMP (cGMP)

Calcium ions Correct

Explanation

When an agonist interacts with a receptor on the cell surface, second messengers relay signals to target molecules in the cytoplasm or nucleus. They also amplify the strength of the signal. Calcium is the most ubiquitous and abundant second messenger that regulates multiple cellular functions in the body.

These include:

Muscle contraction (skeletal, smooth and cardiac)

Exocytosis (neurotransmitter release at synapses and insulin secretion)

Apoptosis

Cell adhesion to the extracellular matrix

Activation of lymphocytes

Biochemical changes mediated by protein kinase C.

cAMP is either inhibited or stimulated by G proteins.

The receptors in the body that G stimulating (Gs) increase cAMP include:

Beta (ß1, ß2, and ß3)

Dopamine (D1 and D5)

Histamine (H2)

Glucagon

Vasopressin (V2).

cGMP is the second messenger for the action of nitric oxide (NO) and atrial natriuretic peptide (ANP).

IP3 and DAG are the second messengers for angiotensin and thyroid stimulating hormone.

Answer Statistics

1

2%

2

1%

3

64%

4

5%

5

29%

Times answered: 243