QuestionSBA
QuestionChoice
In high calcium conditions, calcium binds to troponin (on tropomyosin) and the positions of troponin and tropomyosin on actin are altered, making the binding sites available for myosin to attach to.
10003841
a
Troponin
QuestionChoice
Tropomyosin proteins block myosin binding sites on the actin filament (in low calcium conditions). On tropomyosin proteins, there are troponin complexes and it is these that bind calcium.
10003842
b
Tropomyosin
QuestionChoice
Actin (and myosin) are contractile proteins found in every cell. However, they are found in much higher quantities in muscle cells. During muscle contraction, the myosin head attaches to the myosin-binding site on actin, forming a cross-bridge. The myosin head then pivots from a 90-degree to a 45-degree angle, and actin slides past myosin.
10003844
d
Actin
QuestionChoice
Myosin (and actin) are contractile proteins found in every cell. However, they are found in much higher quantities in muscle cells. During muscle contraction, the myosin head attaches to the myosin-binding site on actin, forming a cross-bridge. The myosin head then pivots from a 90-degree to a 45-degree angle, and actin slides past myosin.
10003843
c
Myosin
QuestionChoice
Myofibrils are bundles of myofilaments (actin and myosin). Bundles of myofibrils make up a muscle fibre. Myofibrils do not bind calcium.
10003845
e
Myofibril
Concept
Chapter
2693
3966
Muscle physiology
Topic
183
Physiology & Pathology of Bone
13315
A 27-year-old athlete presents to their General Practitioner with pain in the anterior aspect of their thigh, which is worse on movement. The GP suspects a muscle strain.

During muscle contraction, what does calcium bind to?
a