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Troponin Complex
MCQ questions and answers.
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10
MCQ Questions
1. How many protein subunits are present in the troponin complex?
A.
Two
B.
Three
C.
Four
D.
Five
Correct Answer:
Three
Explanation:
The troponin complex has three subunits: troponin T, troponin I, and troponin C.
2. Which troponin subunit binds to tropomyosin?
A.
Troponin C
B.
Troponin I
C.
Troponin T
D.
Troponin M
Correct Answer:
Troponin T
Explanation:
Troponin T attaches the troponin complex to tropomyosin on the thin filament.
3. Which troponin subunit binds calcium ions?
A.
Troponin T
B.
Troponin I
C.
Troponin C
D.
Troponin A
Correct Answer:
Troponin C
Explanation:
Troponin C binds calcium ions, initiating changes that help expose the myosin-binding sites on actin.
4. What is the main function of troponin I?
A.
To bind calcium ions
B.
To inhibit actin-myosin interaction
C.
To attach the complex to tropomyosin
D.
To form thick filaments
Correct Answer:
To inhibit actin-myosin interaction
Explanation:
Troponin I has an inhibitory role and helps prevent actin-myosin interaction when the muscle is relaxed.
5. The troponin complex is associated mainly with which muscle filament?
A.
Thick filament
B.
Thin filament
C.
Intermediate filament
D.
Elastic filament
Correct Answer:
Thin filament
Explanation:
The troponin complex is attached to the thin filament, which contains actin and tropomyosin.
6. What happens when calcium binds to troponin C?
A.
Tropomyosin moves away from actin's myosin-binding sites
B.
Myosin filaments dissolve
C.
Troponin leaves the muscle fibre
D.
Actin changes into myosin
Correct Answer:
Tropomyosin moves away from actin's myosin-binding sites
Explanation:
Calcium binding to troponin C changes the troponin complex and shifts tropomyosin, exposing binding sites on actin.
7. In a relaxed skeletal muscle fibre, the troponin-tropomyosin complex helps to do what?
A.
Expose all myosin-binding sites on actin
B.
Block myosin-binding sites on actin
C.
Break down actin filaments
D.
Produce calcium ions
Correct Answer:
Block myosin-binding sites on actin
Explanation:
When calcium levels are low, the troponin-tropomyosin complex covers the myosin-binding sites on actin and prevents contraction.
8. Which subunit of the troponin complex is directly responsible for sensing calcium levels?
A.
Troponin T
B.
Troponin I
C.
Troponin C
D.
Troponin X
Correct Answer:
Troponin C
Explanation:
Troponin C acts as the calcium-sensing subunit because it binds calcium ions during muscle contraction.
9. What is the role of troponin T in the troponin complex?
A.
It binds calcium
B.
It binds tropomyosin
C.
It breaks down ATP
D.
It forms the myosin head
Correct Answer:
It binds tropomyosin
Explanation:
Troponin T connects the troponin complex with tropomyosin on the thin filament.
10. Which sequence correctly describes the role of the troponin complex during skeletal muscle contraction?
A.
Calcium binds troponin C, causing tropomyosin to move and expose actin sites
B.
Calcium binds troponin T, causing actin to become myosin
C.
Calcium binds troponin I, causing the thick filament to disappear
D.
Calcium removes troponin from the thin filament, stopping contraction
Correct Answer:
Calcium binds troponin C, causing tropomyosin to move and expose actin sites
Explanation:
Calcium binding to troponin C changes the complex and shifts tropomyosin away from actin's myosin-binding sites, allowing contraction to begin.
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Troponin Complex
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