Q: Which of the following best describes the role of calcium ions ($$\text{Ca}^{2+}) in $$muscle contraction?

$$\text{Ca}^{2+}$$ binds to troponin C, exposing actin binding sites

Question 1

Which muscle fiber type is most resistant to fatigue and primarily uses fatty acids as its main fuel source?

Accepted Answer

Type I (Slow-Twitch, Oxidative)

Question 2

During the initial 10 seconds of intense exercise, which pathway is primarily responsible for rapid ATP regeneration in skeletal muscle?

Accepted Answer

Creatine phosphate system (phosphocreatine)

Question 3

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

Accepted Answer

Acetylcholine release → Depolarization of sarcolemma → Action potential travels down T-tubules → Calcium release from sarcoplasmic reticulum

Question 4

Which enzyme catalyzes the reaction $$	ext{Phosphocreatine} + 	ext{ADP} \leftrightarrow 	ext{Creatine} + 	ext{ATP} in $$muscle cells?

Accepted Answer

Creatine kinase

Question 5

A sprinter completes a 100-meter dash in under 10 seconds. Which metabolic pathway is most responsible for ATP supply during this activity?

Accepted Answer

Phosphocreatine system

Question 6

Which of the following best describes the role of calcium ions ($$	ext{Ca}^{2+}) in $$muscle contraction?

Accepted Answer

$$	ext{Ca}^{2+}$$ binds to troponin C, exposing actin binding sites

Question 7

Which regulatory effect does high citrate concentration have on muscle metabolism at rest?

Accepted Answer

Inhibits glycolysis by inhibiting PFK-1

Question 8

During prolonged aerobic exercise, which hormone is primarily responsible for activating hormone-sensitive lipase in adipose tissue, leading to increased blood fatty acids?

Accepted Answer

Epinephrine

Question 9

Which of the following is a direct effect of AMP accumulation in exercising muscle?

Accepted Answer

AMP activates AMPK, which stimulates glycolysis and glycogenolysis

Question 10

What is the fate of lactate produced during anaerobic glycolysis in skeletal muscle?

Accepted Answer

It is exported to the liver for gluconeogenesis via the Cori cycle

Question 11

Which metabolic adaptation is most likely to occur in skeletal muscle after endurance training?

Accepted Answer

Increase in oxidative enzyme activity

Question 12

Which of the following correctly describes the mechanism by which epinephrine stimulates glycogenolysis in muscle?

Accepted Answer

Epinephrine binds to a receptor, activating a Gs protein, which increases cAMP and activates PKA, leading to phosphorylation of glycogen phosphorylase

Question 13

Which fuel source is preferred by resting skeletal muscle under normal conditions?

Accepted Answer

Fatty acids

Question 14

During long-duration exercise, which process becomes increasingly important for maintaining blood glucose levels after initial glycogen stores are depleted?

Accepted Answer

Hepatic gluconeogenesis

Question 15

Which of the following is a direct effect of AMPK activation in exercising muscle?

Accepted Answer

Phosphorylation of acetyl-CoA carboxylase, decreasing malonyl-CoA and increasing fatty acid entry into mitochondria

Question 16

Which step in the muscle contraction cycle requires ATP hydrolysis?

Accepted Answer

Detachment of myosin from actin

Question 17

Which of the following changes is NOT typically observed in skeletal muscle after endurance training?

Accepted Answer

Decreased mitochondrial biogenesis

Question 18

Which of the following best explains why Type IIb muscle fibers fatigue quickly during intense exercise?

Accepted Answer

They have low myoglobin and primarily use glycolysis for ATP production

Question 19

Which process is stimulated by a rise in AMP/ADP ratio during muscle activity?

Accepted Answer

Activation of AMPK, enhancing fatty acid oxidation and glucose uptake

Question 20

A patient with a deficiency in creatine kinase would most likely experience which symptom during short, intense bursts of exercise?

Accepted Answer

Rapid fatigue due to inability to rapidly regenerate ATP from phosphocreatine

Biochemistry of Skeletal Muscle: Integrated Musculoskeletal System

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