Q: Which equation best represents the ATP hydrolysis reaction that powers muscle contraction?

$\mathrm{ATP} + \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{ADP} + \mathrm{P}_i + \text{energy}$

Question 1

Which type of tissue, in addition to muscular tissue, is found in skeletal muscle?

Accepted Answer

Connective tissue

Question 2

Arrange the following structures from largest to smallest in the organization of a skeletal muscle: fascicle, myofibril, muscle fiber, sarcomere.

Accepted Answer

Fascicle > muscle fiber > myofibril > sarcomere

Question 3

Which layer of connective tissue surrounds an individual muscle fiber?

Accepted Answer

Endomysium

Question 4

What is a myofibril?

Accepted Answer

A contractile organelle within a muscle fiber composed of repeating sarcomeres

Question 5

Which organelle in muscle fibers stores calcium ions necessary for contraction?

Accepted Answer

Sarcoplasmic reticulum

Question 6

Where are the RYR (ryanodine receptor), SERCA (sarcoplasmic/endoplasmic reticulum Ca2+ ATPase), and DHPR (dihydropyridine receptor) primarily found in muscle fibers?

Accepted Answer

Within the sarcoplasmic reticulum and T-tubules

Question 7

What is the function of calcium ions during muscle contraction?

Accepted Answer

They bind to troponin, causing a conformational change that exposes myosin-binding sites on actin

Question 8

Which protein forms the thick filaments in a sarcomere?

Accepted Answer

Myosin

Question 9

During muscle contraction, which sarcomere band remains unchanged in length?

Accepted Answer

A-band

Question 10

Which component of the sarcomere serves as the boundary between adjacent sarcomeres?

Accepted Answer

Z-line

Question 11

Which protein anchors thick filaments to the Z-line and contributes to the elasticity of muscle?

Accepted Answer

Titin

Question 12

What is the role of troponin in muscle contraction?

Accepted Answer

It binds calcium and moves tropomyosin away from actin's myosin-binding sites

Question 13

Which of the following best describes the change in the sarcomere during muscle contraction?

Accepted Answer

Both the I-band and H-band shorten, while the A-band remains the same

Question 14

A patient with a mutation in the SERCA pump would most likely experience which of the following symptoms?

Accepted Answer

Impaired muscle relaxation due to inability to re-sequester calcium

Question 15

Which equation best represents the ATP hydrolysis reaction that powers muscle contraction?

Accepted Answer

$\mathrm{ATP} + \mathrm{H}_2\mathrm{O} ightarrow \mathrm{ADP} + \mathrm{P}_i + 	ext{energy}$

Question 16

If a muscle fiber is unable to release calcium from the sarcoplasmic reticulum, which step of contraction will be directly affected?

Accepted Answer

Myosin binding to actin

Question 17

Which of the following is the correct sequence of events in excitation-contraction coupling in skeletal muscle?

Accepted Answer

Acetylcholine release > action potential > calcium release > cross-bridge formation

Question 18

A muscle biopsy reveals a lack of troponin. Which process would be most directly impaired?

Accepted Answer

Exposure of myosin-binding sites on actin

Question 19

Which of the following best describes the role of the DHPR (dihydropyridine receptor) in skeletal muscle contraction?

Accepted Answer

It acts as a voltage sensor in the T-tubule membrane, triggering RYR-mediated calcium release

Question 20

During a sustained muscle contraction, which protein prevents overstretching of the sarcomere?

Accepted Answer

Titin

Skeletal Muscle Structure and Sarcomere Components: Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards