Question

1) Define "substrate-level phosphorylation." (One clear complete sentence will work as an answer.) B) The reaction ADP + Pi → ATP is highly endergonic. In the case of substrato-level phosphorylation, where does the energy required for ATP synthesis come from? (Not the sun. I mean most immediately in the phosphorylation reaction itself.) C) Define "oxidative phosphorylation." (One clear complete sentence will work as an answer.) D) The reaction ADP - Pi → ATP is highly endergonic. In the case of oxidkive phosphorylation, where does the energy required for ATP synthesis come from? (Not the sun. I mean most immediately in the phosphorylation reaction itself. It's OK if this overlaps your answer to part C.) E) In terms of the energy that drives ATP synthesis, what is the difference between axidative phosphorylation and photophosphorylation? (One clear and specific sentence will work as an answer.) F) In the case of most animal cells, such as most of your cells, where does the majority of ATP that is used in reactions in the cytosol and nucleus come from? (State the location where most of this ATP is made, AND whether it is substrate-level phosphorylation, oxidative phosphorylation, or photophosphorylation.) G) In the case of the leaf cells of a plant, where does the majority of ATP that is used in reactions in the cytosol and nucleus some from? (State the location where most of this ATP is made, AND whether it is substrate-level phosphorylation, oxidative phosphorylation, or photophosphorylation.)

Answer 1

A) substrate-level phosphorylation is the synthesis of ATP by phoshorylation of ADP in a coupled reaction that can occur in any metabolic pathway. Substrate-level phosphorylation can occur in any organelle of a cell.

B) In the case of substrate-level phosphorylation, the energy commes from the coupled exergonic reaction.

C) Oxidative phosphorylation- Oxidation of NADH and FADH2 leads to phosphorylation of ADP to synthesize ATP.

D) In caseof oxidative phosphorylation. the energy comes from proton motive force (PMF), which is a result of chemical gradient (change in pH) and electrical gradient (change in charge). The PMF pushes the protons from intermembrane space of mitochondria to the mitochondrial matrix.

E) The energy that drives ATP synthesis in case of oxidative phosphorylation comes from oxidation of NADH and FADH2, while in case of photophosphorylation, it comes from light energy from photosynthesis.

F) In the case of most animal cells, majority of the ATP comes from mitochondrial matrix. (oxidative phosphorylation)

G) In the case of leaf cells of a plant, majority of the ATP comes from chloroplast stroma. (photophosphorylation)