6.3 Muscles Flashcards
(13 cards)
What is an antagonistic muscle pair?
Muscles which oppose the action of each other. When one muscle contracts, the other muscle relaxes
Label the diagram of skeletal muscle:
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This diagram shows the myosin and actin filaments in a relaxed and contracted muscle:
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What is the role of actin in muscle contraction?
- The myosin head forms a cross-bridge with the actin filament
- The actin filaments are pulled towards the centre of the sarcomere by myosin filaments
What is the role of myosin in muscle contraction?
- Forms cross-bridge with actin filament
- The head moves to pull actin filament
- ATP is used and myosin head detaches from actin so it can bind to the next site on the actin filament
What is the role of calcium ions in muscle contraction?
- Binds to troponin, moving tropomyosin
- So binding site on actin is exposed and myosin heads can bind (forming the actin-myosin cross bridge)
- Also activates ATPase
What is the role of ATP in muscle contraction?
- Binds to the myosin head so cross-bridge breaks
* Hydrolysed to provide energy source for movement of myosin head
What is the role of tropomyosin in muscle contraction?
- When calcium ions are present
- It is removed from the myosin-head-binding-site on the actin, so the site is exposed and cross bridges can form
- This allows actin to be pulled to the centre of the sarcomere
Write a series of steps to describe how muscle contraction takes place following the entry of Calcium ions into the sarcoplasm
- Calcium ions enter the sarcoplasm (from the sarcoplasmic reticulum)
- Calcium ions bind to the troponin and this causes the tropomyosin to move
- so the binding site on the actin filament is exposed
- the myosin head binds to the actin filament
- ADP and Pi are released from the myosin head
- The myosin head does the ‘power stroke’ and pulls the actin towards the centre of the sarcomere
- A new ATP molecule binds to the myosin head
- This causes the myosin head to detach from the actin filament (so the cross-bridge is broken)
- ATPase is activated by Ca2+ ions
- ATPase hydrolyses the ATP
- The myosin head re-cocks (moves back to its original position)
- The myosin head binds the next binding site along the actin filament and the process repeats
Write an equation to show how phosphocreatine is formed
ATP + creatine ADP + phosphocreatine
Write an equation to show how phosphocreatine is used to form ATP
ADP + phosphocreatine ATP + creatine
What is the function of phosphocreatine?
Phosphocreatine allows ATP to be formed quickly without the need for respiration
Fast a slow twitch
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