Molecular Mechanisms of Skeletal Muscle Contraction Quiz

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What is the primary function of creatine phosphate in the formation of ATP in muscle fibers?

To act as a storage form of high-energy phosphate bonds (correct)

To serve as a cofactor for the enzyme creatine kinase

To provide a rapid source of phosphate for the glycolytic pathway

To catalyze the oxidative phosphorylation of ADP in the mitochondria

Which of the following statements about the role of creatine phosphate in ATP formation is correct?

Creatine phosphate is the primary source of ATP for muscle contraction. (correct)

Creatine phosphate is formed through the oxidative phosphorylation of ADP in the mitochondria.

The concentration of creatine phosphate increases at the start of muscle contraction.

The breakdown of creatine phosphate is an irreversible reaction.

How does the concentration of ATP and ADP change in a muscle fiber at the start of contraction?

Both ATP and ADP concentrations remain constant.

ATP concentration increases while ADP concentration also increases.

ATP concentration increases while ADP concentration decreases.

ATP concentration decreases while ADP concentration increases. (correct)

What is the primary limitation of the creatine phosphate system in providing ATP for muscle contraction?

The concentration of creatine phosphate in the cell is limited. Signup and view all the answers

Which of the following best describes the reversible reaction catalyzed by creatine kinase?

Creatine phosphate + ADP → Creatine + ATP Signup and view all the answers

What is the primary advantage of the creatine phosphate system in providing ATP for muscle contraction?

It can generate ATP more rapidly than glycolysis or oxidative phosphorylation. Signup and view all the answers

What is the function of the H zone in skeletal muscle?

It is a space between the opposing ends of two sets of thin filaments in each sarcomere. Signup and view all the answers

What does the M line in skeletal muscle correspond to?

Proteins that link together the central region of adjacent thick filaments. Signup and view all the answers

What is the relationship between contraction and muscle fiber shortening?

Contraction refers to activation of force-generating sites, but does not necessarily mean shortening. Signup and view all the answers

Which type of neurons innervate skeletal muscle fibers?

Alpha motor neurons Signup and view all the answers

What is the advantage of myelinated axons in motor neurons?

They allow faster propagation of action potentials. Signup and view all the answers

What is a motor unit?

A single motor neuron and all the muscle fibers it innervates. Signup and view all the answers

What determines the maximal rate of cross-bridge cycling in skeletal muscle fibers?

The type of myosin subtype present in the fiber Signup and view all the answers

Which type of skeletal muscle fibers have myosin with low ATPase activity?

Slow-twitch fibers Signup and view all the answers

What are the two main subtypes of fast myosin distinguished based on structure?

Type 2A and Type 2X Signup and view all the answers

Which type of myosin has about four times higher ATPase activity than the other?

Type 2X myosin Signup and view all the answers

How are skeletal muscle fibers classified based on their major pathway to form ATP?

Based on oxidative or glycolytic pathway usage Signup and view all the answers

What contributes to extra oxygen requirement in muscles after contraction has stopped?

Accumulation of lactate Signup and view all the answers

Which type of muscle fibers contain numerous mitochondria and have high oxidative capacity?

Slow-oxidative fibers Signup and view all the answers

What is responsible for the dark red color of oxidative muscle fibers?

High myoglobin content Signup and view all the answers

Which type of muscle fibers have few mitochondria but a high concentration of glycolytic enzymes?

Fast-glycolytic fibers Signup and view all the answers

What gives glycolytic muscle fibers their pale color?

Lack of myoglobin Signup and view all the answers

Which characteristic distinguishes slow-oxidative muscle fibers?

High myosin-ATPase activity and high oxidative capacity Signup and view all the answers

Which type of muscle fibers are often referred to as white muscle fibers?

Fast-glycolytic fibers Signup and view all the answers

What type of muscle fibers combine high myosin-ATPase activity with high oxidative capacity and intermediate glycolytic capacity?

Fast-oxidative-glycolytic fibers (type 2A) Signup and view all the answers

Which type of muscle fibers are resistant to fatigue and can maintain contractile activity for long periods with little tension loss?

Slow-oxidative fibers Signup and view all the answers

Which type of skeletal muscle fibers are used for quick bursts of strong activation, like jumping or sprinting?

Fast-glycolytic fibers (type 2X) Signup and view all the answers

In whole-muscle contraction, what is true about the muscle fibers within a single motor unit?

They are all of the same fiber type. Signup and view all the answers

Which statement accurately describes the composition of most skeletal muscles?

They consist of all three motor unit types interspersed with each other. Signup and view all the answers

What distinguishes fast-glycolytic skeletal muscles in terms of fatigue resistance?

They fatigue rapidly. Signup and view all the answers