Textbook Question
Some hormones act by:
a. Increasing the synthesis of enzymes
b. Converting an inactive enzyme into an active enzyme
c. Affecting only specific target organs
d. All of these
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16. The Endocrine System
Membrane Bound Receptors and Secondary Messengers
Multiple Choice
Which of these acts as a second messenger in cellular signaling pathways?
A
Insulin
B
cAMP (cyclic Adenosine Monophosphate)
C
Phospholipase C
D
G-protein
Verified step by step guidance1
Understand the concept of second messengers: Second messengers are molecules that relay signals received at receptors on the cell surface to target molecules inside the cell, in the cytoplasm or nucleus.
Identify the role of cAMP: Cyclic Adenosine Monophosphate (cAMP) is a common second messenger used in many biological processes. It is derived from ATP and is involved in the activation of protein kinases.
Differentiate between primary and secondary messengers: Primary messengers are extracellular signaling molecules like hormones and neurotransmitters, while secondary messengers like cAMP are intracellular signaling molecules.
Recognize the function of cAMP in signaling pathways: cAMP is synthesized from ATP by the enzyme adenylate cyclase, which is activated by G-proteins. It then activates protein kinase A (PKA), leading to a cascade of cellular responses.
Conclude why cAMP is the correct answer: Among the options provided, cAMP is the only molecule that acts as a second messenger, relaying signals from the cell surface to the inside of the cell.
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