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12 Cards in this Set
- Front
- Back
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What is 'ATP'? (Don't have to say what it stands for, just what its function is) |
Molecular currency. Contains chemical energy which is essential for muscular contraction. |
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Where is it made? |
In the mitochondria of muscle cells. |
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What is the 'sarcoplasmic reticulum'? |
A specialised version of endoplasmic reticulum for muscle cells. Its walls contain calcium pumps which store calcium ions. |
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What is the sarcoplasmic reticulum studded with? And what are they linked to? |
Calcium channels. These are linked to voltage sensitive proteins in the membrane of the muscle cell. |
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What happens when you try to move your arm? |
Your brain sends an action potential along the motor neurone until its synapses with a muscle cell in the arm. The receptors on that muscle cell send out a signal that releases the stored calcium ions from the sarcoplasmic reticulum. |
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At this point, what is stopping the actin from binding with the myosin? |
Troponin and Tropomyosin are acting as guards, covering the actin strands, and require calcium ions to be moved. |
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And so, when the action potential is sent to the muscle, how does this allow the binding of actin and myosin? |
The Troponin and tropomyosin proteins bind with the newly released (due to the action potential) calcium ions. This means that they change shape, and are lifted away from the actin site which the myosin head needs to bind with. |
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What does a myosin head need in order to bind to the actin site? |
ATP, which is then broken down into ADP and the remaining phosphate. |
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What does this conversion (ATP to ADP + phosphate) do to the myosin head? |
It changes its shape, resembling a stretched spring, storing the energy that was released during the conversion. |
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What happens when that stored energy is finally released? |
ACTIN AND MYSOIN FINALLY BIND! The myosin changes shape. It pulls on the actin strand, shrinking the entire sarcomere, thus contracting the muscle. |
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What does the changing shape of the myosin head cause to happen? (hint: changing shape allows proteins to bind/unbind with stuff) |
The ADP and the phosphate unbind with it, letting fresh ATP bind in its place, causing another shape change in which the myosin unbinds with the actin, before once again breaking down its ATP into ADP + phosphate and going back into the stretched spring-like position |
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Meanwhile, what's happening with the Calcium? |
The Calcium pumps are restocking the calcium in the sarcoplasmic reticulum, removing the calcium ion from the troponin. This shape change puts the tropomyosin guards back over the actin site, restarting the entire process. |
