Question

In: Anatomy and Physiology

List the proteins that make the thin and thick filament and their function. Please explain in...

List the proteins that make the thin and thick filament and their function. Please explain in detail.

Expert Solution

Ans.There are two types of filament, thick and thin through which myofibrils is made, theses myofibrils provide striped appreance to the muscles.

Thick filaments contain myosin

Thin filaments contain actin( actin is major component of thin filament), troponin and tropomyosin are two other muscles protiens which is present in thin filament.

Muscles contract by sliding the thick (myosin) and thin (actin) filaments along each other.

The myofibrillar proteins, consist mainly of myosin heavy chains (HC), actin, α-actinin, tropomyosin, troponin-T, and myosin light chains (LC)

These protiens account for 2/3rd of average total protien of muscles.

In thin filament the tropomysine which is protien stranded and stablises actin and troponine bind to actin and tropomysine which is affected by Ca++.

The functions of the actin based thin filament

Two strands of fibrous (F) actin form a double helix extending the length of the myofilament, attached at either end at sarcomere composed of G actin monomers each of which has a myosine binding site

Actin site can bind myosin during muscle contraction.

Tropomyosin: an elongated protein winds along the groove of the F actin double helix.

Troponin is composed of three

subunits:

• Tn-A : binds to actin

• Tn-T binds to tropomyosin.

• Tn-C binds to calcium ions.

(1) interaction with myosin to produce force.

(2) regulation of force generation in response to Ca2+ concentration; and

(3) transmission of the force to the ends of the cell.

Function of thick filament

Thick filament plays role in muscle contraction

Each thick filaments is consisit of many myosin molecules whose head protude to the opposite end of the filament.

Single filament contains roughly 300 myosin molecules

Molecule consists of two heavy myosin molecules wound together to form a rod portion lying parallel to the myosin myofilament and two heads that extend laterally.

Myosin heads Can bind to active sites on the actin molecules to lorm cross-bridges. (Actin binding site)

Attached to the rod portion by a hinge region that can bend and straighten during contraction have ATPase activity that breaks down adenosine triphosphate (ATP), releasing energy.

Part of the energy is used to bend the hinge region of the myosin molecule during contraction.

Sydney Mullin answered 2 months ago

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