Respiration and Kreb's Cycle

[param]

hi.........just wondering is there anyone out there that can help me understand Krebs cycle and the electron transport chain and not forgetting the chemiosmotic hypothesis................

please need help........

[Jesskat14]

I hope I can write this in a way that makes sense!

You have Acetyl coenzyme A (2 carbons) from the link reaction.
The Acetyl coenzyme A binds with an acid acceptor (4 carbons) producing an acid (6 carbons).
2 molecules of CO2 are removed producing the initial acid acceptor (4 carbons) and is able to be used again.
This part is the decarboxylation.

At the same time oxidations occur:
Electrons are transferred onto NAD and FAD to form reduced NAD and FAD (or NADH and FADH).
3 molecules of NADH and 1 molecule of FADH is produced in one cycle.
1 molecule of ATP is also produced.

The electron transport chain:
In the mitochondrial phospholipid membranes there are electron carriers, these carry electrons given by the FADH and NADH.
When the electrons are transferred, active transport of hydrogen ions from the outer mitochondrial space to the inner mitochondrial space can occur.
The hydrogen ions that are moved have to pass through an enzyme before they can enter the inner mitochondrial space.
When the ion passes through the enzyme it attaches Pi groups onto ADP to form ATP.
There are 3 electron carriers in the chain and so 3 molecules of ATP are made from one molecule of NADH (only 2 are made from FADH).
The electron acceptor, oxygen, accepts the electron pair as well as 2 hydrogen ions to form water, which is a by-product.

I really hope that helps it took me a while to get my head round it!
Sorry I'm not really sure on the chemiosmotic hypothesis.

[part23]

by the way.
The oxidation of NADH occurs in a stepwise manner involving an electron transport chain. Reducing equivalents go via a series of carriers to oxygen. Electrons flow downhill, energetically. Energy released in this process is used to generate the Proton Motive Force which is used by the cell to make ATP.

http://electron-transport-chain.com/