biology : class11 Cyclic AMP : Receptors, Second Messengers, Gene Regulation : Hormone Action MCQ Questions and Answers
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Cyclic AMP
MCQ questions and answers.
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MCQ Questions
1. What does cAMP stand for?
A.
Cyclic adenosine monophosphate
B.
Cyclic adenosine diphosphate
C.
Calcium adenosine monophosphate
D.
Cytoplasmic adenine monophosphate
Correct Answer:
Cyclic adenosine monophosphate
Explanation:
cAMP stands for cyclic adenosine monophosphate and functions as a second messenger in hormone action.
2. What is the main role of cAMP in hormone action?
A.
It acts as a second messenger inside the cell
B.
It carries oxygen in the blood
C.
It forms the cell membrane
D.
It digests proteins outside the cell
Correct Answer:
It acts as a second messenger inside the cell
Explanation:
cAMP carries signals from activated cell-surface receptors to intracellular targets, so it is called a second messenger.
3. Which enzyme produces cAMP from ATP?
A.
Adenylyl cyclase
B.
Protein kinase
C.
Phosphodiesterase
D.
Pepsin
Correct Answer:
Adenylyl cyclase
Explanation:
Adenylyl cyclase converts ATP into cAMP after activation of certain hormone receptors.
4. Which molecule is converted into cAMP by adenylyl cyclase?
A.
ATP
B.
DNA
C.
Glucose
D.
Amino acid
Correct Answer:
ATP
Explanation:
Adenylyl cyclase uses ATP as the starting molecule to form cyclic AMP.
5. Where is cAMP mainly formed during its role as a second messenger?
A.
Inside the cytoplasm of the target cell
B.
Inside the nucleus of a red blood cell
C.
Outside the cell in the bloodstream
D.
Inside the stomach lumen
Correct Answer:
Inside the cytoplasm of the target cell
Explanation:
After receptor activation at the cell membrane, cAMP is formed inside the target cell, mainly in the cytoplasm.
6. Which enzyme breaks down cAMP and helps stop its signal?
A.
Phosphodiesterase
B.
Adenylyl cyclase
C.
RNA polymerase
D.
Amylase
Correct Answer:
Phosphodiesterase
Explanation:
Phosphodiesterase breaks down cAMP, reducing its concentration and terminating the cAMP signal.
7. cAMP commonly activates which type of enzyme?
A.
Protein kinase
B.
Digestive protease
C.
DNA helicase
D.
Cellulose synthase
Correct Answer:
Protein kinase
Explanation:
cAMP commonly activates protein kinase A, which phosphorylates target proteins and produces cellular responses.
8. In a cAMP signaling pathway, what is the first messenger?
A.
The hormone outside the cell
B.
cAMP inside the cell
C.
Protein kinase A
D.
Phosphodiesterase
Correct Answer:
The hormone outside the cell
Explanation:
The hormone is the first messenger because it carries the signal to the cell, while cAMP acts as the second messenger.
9. What is a likely result of increased cAMP inside a target cell?
A.
Activation of specific cellular proteins
B.
Immediate destruction of the cell membrane
C.
Conversion of cAMP into DNA
D.
Complete stopping of all enzyme activity
Correct Answer:
Activation of specific cellular proteins
Explanation:
Increased cAMP can activate protein kinase A, which modifies specific proteins and helps produce the hormone's effect.
10. Which sequence correctly describes a basic cAMP pathway?
A.
Hormone binds receptor, adenylyl cyclase forms cAMP, and cAMP activates protein kinase
B.
cAMP binds DNA, ATP leaves the cell, and the receptor is destroyed
C.
Protein kinase forms ATP, the hormone enters the nucleus, and cAMP leaves the cell
D.
Phosphodiesterase forms cAMP, the receptor digests the hormone, and DNA becomes ATP
Correct Answer:
Hormone binds receptor, adenylyl cyclase forms cAMP, and cAMP activates protein kinase
Explanation:
This sequence summarizes the basic cAMP pathway: hormone-receptor binding activates adenylyl cyclase, cAMP is produced, and cAMP activates protein kinase.
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