What is the role of ATP in synthesis of molecules, chemiosmosis and fermentation?

Regarding Chemiosmosis, I quote to you from page 176 of Kingsley Stern's 10th edition of introductory plant biology (Co-Author Jim Bidlack). I'll also break this down into my own words at the end of this brief excerpt.

The oxygen-evolving complex on the inside of a thylakoid membrane catalyzes the splitting of water molecules , producing protons and electrons, as well as oxygen gas. These electrons used to replenish those excited in chlorophyll are then transferred in bucket-brigade fashion through an electron transport system, ultimately reducing NADP to NADPH. As electrons travel through this transport system, additional protons move from the stroma to the inside of the thylakoid membrane in specific oxidation-reduction reactions when electrons pass from photosystem II to PQ (plastoquinone). These protons join with the protons from the split water molecules and thereby contribute to an accumulation of four protons toward the inside of the thylakoid membrane (an area also known as the thylakoid lumen).

Although some protons are used in the production of NADPH on the stroma side of the thylakoid membrane, there is still a net accumulation of protons in the thylakoid lumen from the splitting of water molecules and electron transport. This establishes a proton gradient, giving special proteins in the thylakoid membrane the potential for moving protons from the thylakoid lumen back to the stroma. Movement of protons across the membrane is thought to be a source of energy for the snthesis of ATP. The action has been described as similar to the movement of molecules during osmosis, and has been called chemiosmosis, or the Mitchell Theory, after its author, Peter Mitchell. In this concept, protons move across a thylakoid membrane through protein channels called ATPase. With the proton movement, ADP and phosphate (P) combine, producing ATP. This chemiosmotic mechanism for connecting electron flow with conversion of ADP to ATP is essentially the same as that of oxidative phosphorylation in mitochondria, except that in mitochondria, oxygen (instead of NADP) is the terminal electron acceptor.

So, in a nutshell, you're using photolysis to split water, and creating a proton gradient on one side of the thylakoid membrane. These protons want to get out to the other side of the membrane (think diffusion). To do this they must pass through ATP synthase. (Think revolving door.) As they pass through each time, they "turn" the door, and in the process, a terminal phosphate is attached to the ADP molecule, rendering ATP.

Hope that helps with part of it.

Ben Haizlip

Pre AP Biology Teacher

Moore West Junior High School

Oklahoma City, OK

the basically element that i will imagine of is that the hydride ion from NADH is well known becuase of reactivity and length (small and detrimental charge on one proton). that is because H- is competing with inorganic phosphate which has a resonance stabalized detrimental charge, so Pi is a worse nucleophile (plus steric factors of a huge Pi vs. small H). yet i'm not totally certaint what the electrophile is doing.

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plain simple it is energy