1. What activates protein kinase A (PKA) in a typical hormone-signaling pathway?
A.
Cyclic AMP (cAMP)
B.
DNA
C.
Glucose
D.
Cholesterol
Correct Answer:
Cyclic AMP (cAMP)
Explanation:
cAMP binds to the regulatory subunits of PKA and activates its catalytic subunits.
2. What type of enzyme is protein kinase A?
A.
A protein kinase
B.
A DNA polymerase
C.
A lipid-digesting enzyme
D.
An RNA molecule
Correct Answer:
A protein kinase
Explanation:
PKA is a protein kinase because it transfers phosphate groups to specific proteins.
3. What does activated PKA usually do to target proteins?
A.
Adds phosphate groups to them
B.
Removes all amino acids from them
C.
Converts them into DNA
D.
Breaks them into glucose
Correct Answer:
Adds phosphate groups to them
Explanation:
Activated PKA phosphorylates target proteins, which can change their activity.
4. In the cAMP pathway, which molecule directly binds to and activates PKA?
A.
cAMP
B.
ATP only
C.
Calcium carbonate
D.
Amino acid
Correct Answer:
cAMP
Explanation:
cAMP is the second messenger that binds to PKA and releases its active catalytic subunits.
5. PKA is commonly present in an inactive form consisting of which parts?
A.
Regulatory and catalytic subunits
B.
DNA and RNA strands
C.
Ribosomes and lysosomes
D.
Lipids and carbohydrates
Correct Answer:
Regulatory and catalytic subunits
Explanation:
Inactive PKA contains regulatory subunits associated with catalytic subunits; cAMP causes their separation.
6. What happens to the catalytic subunits of PKA when cAMP binds to the regulatory subunits?
A.
They are released and become active
B.
They are destroyed immediately
C.
They leave the cell permanently
D.
They change into receptors
Correct Answer:
They are released and become active
Explanation:
Binding of cAMP changes the regulatory subunits and releases the active catalytic subunits of PKA.
7. Which cellular process can be regulated by PKA through phosphorylation of target proteins?
A.
Glycogen breakdown
B.
Formation of the cell wall in bacteria
C.
Digestion of food in the stomach only
D.
Replication of viruses only
Correct Answer:
Glycogen breakdown
Explanation:
PKA can phosphorylate enzymes involved in glycogen metabolism and help regulate glycogen breakdown.
8. What is the main role of cAMP in relation to PKA?
A.
It acts as a second messenger
B.
It forms the cell membrane
C.
It carries oxygen in blood
D.
It stores genetic information
Correct Answer:
It acts as a second messenger
Explanation:
cAMP carries the signal from a hormone-activated receptor to PKA inside the cell.
9. Which molecule can be phosphorylated by activated PKA?
A.
A target protein
B.
A water molecule
C.
A sodium ion
D.
A cholesterol molecule only
Correct Answer:
A target protein
Explanation:
PKA transfers a phosphate group to selected target proteins to regulate their functions.
10. What is the immediate result of PKA activation in a cell?
A.
Phosphorylation of specific proteins
B.
Complete destruction of the nucleus
C.
Permanent stopping of all metabolism
D.
Conversion of proteins into lipids
Correct Answer:
Phosphorylation of specific proteins
Explanation:
Once activated by cAMP, PKA phosphorylates specific proteins, producing cellular responses.
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