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RayBio RayBio
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10 years ago
Write a unified response addressing the following aspects of mitochondrial myopathy.
A) Most aerobic cellular respiration takes place in the mitochondria of the muscle.
1) Explain, in general terms, aerobic cellular respiration as it takes place in a skeletal muscle
2) Describe the role myoglobin plays in this reaction. (Note: You do not have to provide the biochemical pathways involved in your answer.)

B) Explain, using a diagram, the sliding filament model of a muscle contraction, and describe how mitochondrial myopathy would disrupt the contraction of a skeletal muscle.

C) Predict the impact on the daily life of a person who has mitochondrial myopathy, and identify two technologies that could be used to assist people with this condition.
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10 years ago Edited: 10 years ago, nite_n_day
1) Explain, in general terms, aerobic cellular respiration as it takes place in a skeletal muscle

Aerobic cellular respiration is the series of reactions that, with the help of oxygen, make ATP (cellular energy) by completely breaking down glucose into inorganic molecules of carbon dioxide and water.

The reactions of cellular respiration occur as four sub-pathways, which include:

1) Glycolysis
2) Synthesis of Acetyl-CoA
3) Krebs cycle
4) The electron transport chain (aerobic part)

Electron Transport Chain

The most significant production of ATP occurs through a stepwise release of energy from the series of oxidation-reduction reactions in the electron transport chain.

The electron transport chain consists of several membrane-bound carrier molecules that pass electrons from one to another and ultimately to final electron acceptor, oxygen (O2). We need to breathe in oxygen in order to complete electron transport.

Energy from electrons is used to pump protons (H+) across the inner membrane of the mitochondria, establishing a proton gradient, a difference in ion concentration on either side of a membrane. Proton gradients have potential energy available for cellular work.

Protons flow down this gradient, through protein channels that phosphorylate adenosine diphosphate (ADP), adding energy to create adensoine triphosphate ATP.

By the end of aerobic cellular respiration, a total of 38 molecules of ATP are formed from one molecule of glucose.

2) Describe the role myoglobin plays in this reaction. (Note: You do not have to provide the biochemical pathways involved in your answer.)

Myoglobin is the protein that carries oxygen to skeletal muscles.

B) Explain, using a diagram, the sliding filament model of a muscle contraction, and describe how mitochondrial myopathy would disrupt the contraction of a skeletal muscle.

The sliding filament theory describes a process used by muscles to contract. It is a cycle of repetitive events that cause a thin filament to slide over a thick filament and generate tension in the muscle.

Myosin is a molecular motor that acts like an active ratchet. Chains of actin proteins form high tensile passive 'thin' filaments that transmit the force generated by myosin to the ends of the muscle. Myosin also forms 'thick' filaments. Each myosin 'paddles' along an actin filament repeatedly binding, ratcheting and letting go, sliding the thick filament over the thin filament. Calcium ions are released. This calcium bonds to troponin, allowing the myosin head to bind with the binding site.

1) ATP binds to myosin and is hydrolyzed by ATPase into ADP and phosphate. The energy released by this process activates the myosin head and cocks it into a high-energy, extended position.
2) The cocked myosin head binds to a newly exposed active site on the thin filament, generating a cross-bridge between actin and myosin.
3) Myosin releases the ADP and phosphate and returns to a low-energy position, pulling the thin filament along, and this movement is called a power stroke. Shortening occurs when the extensible region pulls the filaments across each other (like the shortening of a spring). Myosin remains attached to the actin.
4) The binding of ATP destabilizes the myosin-actin bond, allowing myosin to detach from actin. While detached, ATP hydrolysis occurs "recharging" the myosin head. If the actin binding sites are still available, myosin can bind actin again.
5) The collective bending of numerous myosin heads (all in the same direction), combine to move the actin filament relative to the myosin filament. This results in muscle contraction.

C) Predict the impact on the daily life of a person who has mitochondrial myopathy, and identify two technologies that could be used to assist people with this condition.

Mitochondrial myopathy is a type of myopathy associated with mitochondrial disease. On biopsy, the muscle tissue of patients with this disease usually demonstrate "ragged red" muscle fibers. These ragged-red fibers contain mild accumulations of glycogen and neutral lipids, and may show an increased reactivity for succinate dehydrogenase and a decreased reactivity for cytochrome c oxidase.

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