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Edexcel A2 Biology Unit 5 (6BIO5) - 22/06/2011- OFFICIAL THREAD !

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Reply 3540
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iesians
6
Original post by pandoraclaire
• Ca2+ attaches to the troponin causing it to move
• Tropomyosin on the actin in moved exposing the myosin binding sites
• Myosin heads bind with the myosin binding sites forming cross bridges
• ADP and Pi on the myosin head are released
• Myosin changes shape moving the actin over the myosin
• ATP binds to the myosin head causing it to detach
• ATPase on the myosin head hydrolyses the ATP forming ADP and Pi
• Hydrolysis causes the myosin head to return to its original position and the cycle starts again. This causes the sarcomere to shorten and the muscle contracts.

so i think basically it breaks the ATP into ADP and Pi which moves the myosin head back to where it was :smile:
hope that helped!


what ? it doesnt move it back to where it was . it bends it forward resulting in a power stroke.
Reply 3541
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iesians
6
Original post by wam-bam
..


lol wam bam you givign this too ! good to see you ....again :tongue:
Reply 3542
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wam-bam
1
Original post by iesians
lol wam bam you givign this too ! good to see you ....again :tongue:


yup :frown: soo worried about it, had chem this afternoon, and got C4 on thursday ... you?
Original post by iesians
what ? it doesnt move it back to where it was . it bends it forward resulting in a power stroke.


the use of ATPase is after the power stroke, the power stroke was a couple bullet points before. After that the ATP joins with the myosin head and the ATPase hydrolyses it to make ADP and Pi. The energy from that moves the head back to where it was in order to make more power strokes.
Reply 3544
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iesians
6
Original post by wam-bam
yup :frown: soo worried about it, had chem this afternoon, and got C4 on thursday ... you?


WTHH why you givin both maths and bio ?!
i personally think chem was okiesh ! now i can concentrate on bio ! and then v r done !!!!
Reply 3545
Avatar for iesians
iesians
6
Original post by pandoraclaire
the use of ATPase is after the power stroke, the power stroke was a couple bullet points before. After that the ATP joins with the myosin head and the ATPase hydrolyses it to make ADP and Pi. The energy from that moves the head back to where it was in order to make more power strokes.


well, i was taught that ATP results in detachment of myosin head.
and ATPase is involved in its HYDROLYSIS.
so how can it possibly help in the detachment of myosin head when it is ACTUALLY hydrolysing ATP ( which is needed)
Original post by iesians
well, i was taught that ATP results in detachment of myosin head.
and ATPase is involved in its HYDROLYSIS.
so how can it possibly help in the detachment of myosin head when it is ACTUALLY hydrolysing ATP ( which is needed)


no thats not what im saying, the ATP attachment causes the myosin head to detach while the hydrolysis of it creates energy to move the head back up ready for another power stroke, its in the orange textbook page 142 :smile:
Reply 3547
Avatar for iesians
iesians
6
Original post by pandoraclaire
no thats not what im saying, the ATP attachment causes the myosin head to detach while the hydrolysis of it creates energy to move the head back up ready for another power stroke, its in the orange textbook page 142 :smile:


well. to get the head moved back wouldnt it DETACH from the actin and then come back ??!
Original post by iesians
well. to get the head moved back wouldnt it DETACH from the actin and then come back ??!


... yes it does detach... it detaches when the ATP binds to it, it goes back to a straight position after hydrolysis down to the ATPase
Reply 3549
Avatar for ghogho
ghogho
Original post by hannah_27
It recombines ATP + Pi to make ATP which releases the myosin head from the binding site once it has completed one movement.
It then returns to it's original position and the process begins again.


noo
ATPase break down ATP into ADP and Pi in the bulb head of myosin in order to break down the the actomyosin bridge
Reply 3550
Avatar for ghogho
ghogho
Original post by iesians
well, i was taught that ATP results in detachment of myosin head.
and ATPase is involved in its HYDROLYSIS.
so how can it possibly help in the detachment of myosin head when it is ACTUALLY hydrolysing ATP ( which is needed)


u r ryt iesians this is the role of ATPase
Reply 3551
Avatar for ghogho
ghogho
Original post by iesians
well. to get the head moved back wouldnt it DETACH from the actin and then come back ??!


ya it break down actomyosin bridge and this requires ATP
Reply 3552
Avatar for wam-bam
wam-bam
1
Original post by iesians
WTHH why you givin both maths and bio ?!
i personally think chem was okiesh ! now i can concentrate on bio ! and then v r done !!!!


& physics :tongue: silly me
Reply 3553
Avatar for iesians
iesians
6
Original post by pandoraclaire
... yes it does detach... it detaches when the ATP binds to it, it goes back to a straight position after hydrolysis down to the ATPase


so apparantly you are sayin that hydrolysis happens twice ?
once for the power stroke
and second for the detach and STRAIGHTENING of myosin head.

can you give a reference . i dont have the orange book.
Original post by iesians
so apparantly you are sayin that hydrolysis happens twice ?
once for the power stroke
and second for the detach and STRAIGHTENING of myosin head.

can you give a reference . i dont have the orange book.


• Ca2+ attaches to the troponin causing it to move
• Tropomyosin on the actin in moved exposing the myosin binding sites
• Myosin heads bind with the myosin binding sites forming cross bridges
• ADP and Pi on the myosin head are released
• Myosin changes shape moving the actin over the myosin
• ATP binds to the myosin head causing it to detach
• ATPase on the myosin head hydrolyses the ATP forming ADP and Pi
• Hydrolysis causes the myosin head to return to its original position and the cycle starts again. This causes the sarcomere to shorten and the muscle contracts.

that's the whole process with the role of ATPase in hydrolysing the ATP. I have the feeling we are saying the same thing in different ways...
Original post by iesians
so apparantly you are sayin that hydrolysis happens twice ?
once for the power stroke
and second for the detach and STRAIGHTENING of myosin head.

can you give a reference . i dont have the orange book.


also just to clarify I didn't say it hydrolyses for the power stroke :smile: i said it happens after the power stroke
Reply 3556
Avatar for iesians
iesians
6
Original post by ghogho
ya it break down actomyosin bridge and this requires ATP


right ! well someone above said that ATP is then hydrolysed as it moves back to its original position !! DUH ! i never even heard that
Reply 3557
Avatar for iesians
iesians
6
Original post by pandoraclaire
also just to clarify I didn't say it hydrolyses for the power stroke :smile: i said it happens after the power stroke


after the power stroke ? how does that even make sense ?
Reply 3558
Avatar for iesians
iesians
6
Original post by pandoraclaire
• Ca2+ attaches to the troponin causing it to move
• Tropomyosin on the actin in moved exposing the myosin binding sites
• Myosin heads bind with the myosin binding sites forming cross bridges
• ADP and Pi on the myosin head are released
• Myosin changes shape moving the actin over the myosin
• ATP binds to the myosin head causing it to detach
• ATPase on the myosin head hydrolyses the ATP forming ADP and Pi
• Hydrolysis causes the myosin head to return to its original position and the cycle starts again. This causes the sarcomere to shorten and the muscle contracts.

that's the whole process with the role of ATPase in hydrolysing the ATP. I have the feeling we are saying the same thing in different ways...


did you write it or can you give a credible reference for it (not the orange book)
because it doesnt make sense why would energy be needed to bring the myosin head to its original position ? it will just SPRING back once it is released from the actin.
Original post by iesians
after the power stroke ? how does that even make sense ?


if you read the step by step that is exactly how it happens, also when the other person said it breaks down the bridge, that is what i am saying, what do you think happens in the sliding filament theory?? i thinks its exactly the same as me but in different words tbh.

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