Question

What is proposed as a reason for decreased muscle force when the speed of contraction increases?

a. Increased cross-bridge attachment
b. Rapid myosin head binding to actin
c. Finite time for cross-bridge attachment
d. Enhanced ATP production

What happens to the ADP of a myosin head that fails to bind during muscle contraction?
a. It is immediately reused without changes
b. It gets permanently attached to actin
c. It is released and recycled for future use
d. It forms a complex with ATP irreversibly

Why is the decrease in muscle force at higher contraction velocities explained in terms of cross-bridge attachment time?
a. Cross-bridges attach more quickly at higher velocities
b. Faster velocities lead to increased ATP production
c. Shorter attachment times result in fewer cross-bridges
d. Higher velocities facilitate ADP recycling

For a myosin head to be useful again, what does it need to get rid of?
a. Actin
b. ATP
c. Calcium ions
d. ADP

How does the ATP consumption relate to the force-velocity curve during muscle contraction?
a. It follows an asymmetric curve with higher consumption at higher velocities
b. It remains constant regardless of contraction velocity
c. It mirrors the force-velocity curve in a reverse parabola
d. It increases linearly with contraction velocity

Answer 1

The reason for decreased muscle force at higher contraction velocities is the finite time for cross-bridge attachment. ADP is released and recycled when a myosin head fails to bind during muscle contraction. The ATP consumption increases linearly with contraction velocity.

Step-by-step explanation:

The reason for decreased muscle force when the speed of contraction increases is c. Finite time for cross-bridge attachment. At higher contraction velocities, cross-bridges have shorter attachment times, resulting in fewer cross-bridges and decreased muscle force.

When a myosin head fails to bind during muscle contraction, the ADP is released and recycled for future use (option c). It does not get permanently attached to actin or form a complex with ATP.

The decrease in muscle force at higher contraction velocities is explained in terms of cross-bridge attachment time because shorter attachment times result in fewer cross-bridges (option c). Higher contraction velocities do not lead to increased ATP production or facilitate ADP recycling (options b and d).

For a myosin head to be useful again, it needs to get rid of ADP (option d). Actin, ATP, and calcium ions are not necessary to get rid of for the myosin head to be useful again.

The ATP consumption during muscle contraction increases linearly with contraction velocity (option d). It does not follow an asymmetric curve, remain constant, or mirror the force-velocity curve.