Please help me, I am deeply confused in this class and trying so hard to underst

Question

Please help me, I am deeply confused in this class and trying so hard to understand. Please give detailed answers. I know some of these might be confusing but your help will really help me learn. The teacher requires very very detailed answers and he gives nearly no (and I mean literally nearly zero) partial credit so I'm dying here. Thank you sooooooo much, you have no idea.

Also, I am nearly leaglly blind and I am dyslexic so if you could please write clear it would help so much. I just want to learn like everyone else. SUPER SUPER THANK YOU

3. Oxidative phosphorylation and the light reaction both involve electron transport to generate ATP. Compare and contrast these processes. [10 pts] Where do the electrons for oxidative phosphorylation come from? What about for the light reaction? [2 pts] a. b. Describe how both systems convert the energy from electrons into the chemical energy stored in ATP. [2 pts] c. Would you characterize ATP synthase as being involved as an electrorn acceptor? Why or why not? [2 pts]

Explanation / Answer

Ans. #a. Source of electrons in Oxidative phosphorylation: It is food (organic) molecules, like glucose, fatty acids, amino acids, etc. The electrons released from these organic molecules during cellular respiration is first trapped in form of NADH and FADH2. NADH and FADH2 then transfer the electrons to ETC system in mitochondria.

Source of electrons in Light reaction: Water. Photolysis of water releases electrons for the light reaction during photosynthesis.

#b. Oxidative phosphorylation: The electron transport chain (ETC) converts the energy of high-energy electrons (released during oxidation of NADH and FADH2) into the electrochemical potential energy of proton gradient – when the high energy electrons sequentially move through ETC complexes from their higher to lower energy state.

# During the process, the energy of NADH and FADH2 is finally harvested in form of proton gradient across the inner mitochondrial membrane with higher [H+] being in the intermembrane space. The potential energy (chemical and electrical) of proton gradient is further used to form ATP by the ATP synthase (oxidative phosphorylation).

Light reaction: Movement of electrons from water to NADP via non-cyclic or cyclic electron flow system in chloroplast harvest the chemical energy of electrons into proton gradient across the thylakoid membrane. Chloroplast ATP synthase further harvest the potential energy of proton gradient to synthesize ATP from ADP and Pi.

#c. No. ATP synthase does NOT act as an electrons acceptor. It facilitates the transfer of H+ from its higher to lower concertation across the membrane simultaneously with harvesting the potential energy of proton gradient to form ATP. [See, #e.]

#d. Quinones are lipid-soluble small molecules. Being lipid-soluble, they can move from one to another place in the hydrophobic core of the lipid bilayer (inner membrane of mitochondria, thylakoid membrane of chloroplast). Therefore, they can act as electron shuttle by accepting electrons from one complex (large, immobile) and donate it to the other immobile complex.

#e. Final electron acceptor in Oxidative phosphorylation: O2

Final electron acceptor in Light reaction: NADP

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