0
When the sarcomere is at rest what is covering the active sites on actin?
Wiki User
∙ 11y ago
Troponin
Wiki User
∙ 11y ago
Add your answer:
Earn +20 pts
Myosin cross bridges attach to active sites of?
actin (thin) filaments
When a muscle is at rest the active sites on the actin are blocked by?
TROPOMYOSIN MOLECULES ( troponin hold the tropomyosin in place)
ADP molecules on the surface of actin serve as active sites for the formation of cross bridges with molecules of?
ATP not ADP binds to actin-myosin and is cleaved by to ADP.
What are the steps in sliding filament theory?
Before contraction:1) no nerve impulse to myoneural junction.2) Ca++ in the sarcoplasmic reticulum3) combining of actin and myosin is prevented by a tropomyosin-troponin complex that attatches to the actin.Contraction:1) an action potential (nerve impulse) travels along a neural axon to a myoneural junction (synapse)2) Acetylcholine (neurotransmitter) is released from the synaptic vesicles of the neuron.3) acetylcholine diffuses over into the sacrolemma and the t-tubules.4) Ca++mis released from the sarcoplasmic reticulum.5) the Ca++ then binds to the actin degrading the tropomyosin-troponin complex to expose myosin attatchment sights6) the heads of the myosin myofilaments attatch to the exposed attatchment sights on actin filament7) ATP binds to the heads of the myosin filaments. breakdown of the ATP to ADP+p releases energy and causes a bending of myosin heads.8) another ATP binds to the myosin head causing it to release the actin filament then attatch again with the head unbent. again the ATP breaks down and the process continues.To relax:1) nerve impulse stops2) active transport returns Ca++ to the sarcoplasmic reticulum3) ATP's are reformed (ADP+P+energy=ATP)4) Tropomyosin-troponin complex reforms causing the myosin to release the actin5) when the filaments release each other they slide back to the resting position.
What happens when calcium ions bind to troponin?
When Ca2+ ions are released from the sarcoplasmic reticulum, They combine with troponin, and this cause the tropomyosin threads to shift their position
What mineral is needed to allow actin and myosin to interact?
In order for myosin to connect to actin's active sites, Ca ions must be released from storage in the sarcoplasmic reticulum into the sarcoplasm. A nerve impulse stimulates the release of Ca ions from the sarcoplasmic reticulum. Once the Ca ions are released into the sarcoplasm, they bind to troponin. Once they bind to troponin, troponin no longer is bound to tropomyosin. Tropomyosin is now no longer covering up actin's active sites, thus allowing myosin to attach to actin's active sites.
During muscle contraction myosin cross bridges attach to which active sites?
actin filaments
Myosin cross bridges attach to active sites of?
actin (thin) filaments
What happens to a sarcomere when muscle length changes?
1. Arrangement of thick and thin filaments: In each sarcomere two sets of actin filaments extend partway toward the center. The myosin filaments are arranged such that they partially overlap the actin filaments. Myosin heads on each side point away from the center of the sarcomere.2. During contraction, the interaction of myosin heads with the actin filaments pulls the thin filaments toward the center of the sarcomere. The actin and myosin filaments slide past each other.3. Cross-bridges = attachement betwn myosin heads and binding sites on actin filaments.4. When a muscle cell is stimulated, myosin heads are energized by ATP. They attach to adjacent actin filaments, and tilt in a short "power stroke" toward the center of the sarcomere. Each power sroke requires an ATP. With many power strokes in rapid succession, the actin filaments are made to slide past the myosin filaments.
What is the protein that regulates muscle contraction by controlling the availability of active sites on actin called?
tropomyosin
During skeletal muscle contraction myosin cross bridges attach to active sites of?
During skeletal muscle contraction myosin cross bridges attach to active sites of actin filaments. Actin filaments bind ATP. Their growth is regulated by thymosin and profilin.
When a muscle is at rest the active sites on the actin are blocked by?
TROPOMYOSIN MOLECULES ( troponin hold the tropomyosin in place)
ADP molecules on the surface of actin serve as active sites for the formation of cross bridges with molecules of?
ATP not ADP binds to actin-myosin and is cleaved by to ADP.
What does myosin attach to?
During muscle contraction, myosin cross bridges attach to active sites of ACTIN FILAMENTS.
Active sites on the actin become available for binding when?
C: Calcium binds to troponin. The troponin is a filament in the actin strand, and the active site needs to be uncovered so that the myosin head can bond and therefore pull the muscle to contract it.
What blocks the myosin binding sites on the actin molecule preventing cross bridge formation?
The tropomyosin molecule blocks the active sites of the actin. Troponin is a molecule that is bound to the tropomyosin. Troponin needs CA+ (calcium ions) to bind to it in order to rotate the tropomyosin molecule and expose the actin molecules for the myosin heads to interact for muscle contraction.
What role does tropomyosin play in cross bridge cycle?
The displacement of tropomyosin exposes the active sites of actin allowing cross bridge to form.
