ATP and Enzymes

TerpGal02, ASN · Oct 18, 2008

Well as far as I understand it, and Im no genious by the way, there are 2 main enzymes in muscle contraction. You have the AChE (acetylcholine-esterase) in the motor end plate that degrades ACh after it is used up by the ACh receptors in the sarcolemma during the propogation of the action potential. Then there are the enzymes in the myosin heads of the thick filaments that degrade ATP into ADP and inorganic phosphate that allow the myosin heads to use the energy in the ATP to break the cross bridges and to go back into their "cocked" positions. ATP is used by the chemically and voltage gated channels to first flood the muscle fiber with sodium, generating the action potenial, and then by the voltage gated channels in the terminal cisternae of the sarcoplasmic reticulum to allow Calcium ions into to sarcoplasm which then bonds to troponin and removes the tropomyosin "blockade" from the active sites on G Actin. That lets the myosin heads from the thick filaments to bond to the thin filaments creating the cross bridges. ATP is also used by the myosin heads of the thick filaments. The myosin heads need to break ATP down to get into their "cocked" (facing up toward the M line) position. Once a myosin head binds to the active site on G Actin, the energy from the ATP allows the myosin head to pivot, ratcheting the thin filament toward the M line. Then another ATP molecule binds to the myosin head, releasing the bond between the thick and thin filament. Now the myosin head is in a low energy position, and the enzymes in it break down the ATP and the myosin head uses the energy to go back to its cocked position in order to start the process again. There's a GREAT video on youtube about the sliding filament theory. Just go there and search for sliding filament theory. It really helped me understand.

Snowii · Oct 18, 2008

:yeahthat:

I just had an exam over this

Miss_Piggy.RN · Oct 18, 2008

:redpinkhe Thank you! :)