When the muscle is at rest, _____ is disposed in such a way that it covers the sites on the _____ chain where the head of _____ becomes attached.
Correct answer: A. tropomyosin: actin: myosin
- A. tropomyosin: actin: myosin
- B. myosin: actin: tropomyosin
- C. actin: tropomyosin: myosin
- D. actin: myosin: tropomyosin
Explanation
At rest, tropomyosin lies along the actin filament and covers the binding sites where the myosin heads would attach, so no cross bridges can form. When calcium binds troponin, tropomyosin shifts and exposes these sites, letting myosin bind to actin and pull.
This question appeared on the UHS MDCAT 2026 paper, which you can sit online with every answer explained.
Report an error
The more specific you are, the faster it gets fixed. A source beats an opinion.
Prefer email? [email protected]
About Muscle Contraction
Muscle contraction is explained by the sliding filament model, in which myosin heads pull actin filaments within sarcomeres using ATP. The topic covers calcium, troponin, tropomyosin, the neuromuscular junction and relaxation, with attention to how filament length stays almost constant while the sarcomere shortens.
Practise Support and Movement
745 free Support and Movement MCQs from Biology, each with the correct answer and an explanation. Unlimited attempts, no account needed.
Discussion
Stuck on an option, or know a faster way to get there? Ask or explain it here.
No comments yet. Be the first to explain this one.
Exams that ask Biology questions like this
Biology is on 8 papers prepared for on TestUstad, and all of them draw the same bank, so this question is worth knowing for every one of them.
More Muscle Contraction questions
Upon arrival of nerve impulse, which of the following allows calcium ions to enter the cytosol?
Muscle fatigue results due to deficiency of _ and excess accumulation of _.
According to the sliding filament hypothesis, the release of_ from the sarcoplasmic reticulum causes the reorientation of certain components in the thin filament, permitting them to bind with extension from the thick myosin filaments:
The sarcomere is the region of a myofibril between two successive: