AP BIOLOGY

Detailed explanation-1: -This process requires light to be absorbed twice, once in each photosystem, and it makes ATP . In fact, it’s called photophosphorylation because it involves using light energy (photo) to make ATP from ADP (phosphorylation).

Detailed explanation-2: -The light-dependent reactions convert light energy into chemical energy. The goal of the light-dependent reactions of photosynthesis is to collect energy from the sun and break down water molecules to produce ATP and NADPH.

Detailed explanation-3: -ATP is also synthesized by the light-dependent reactions, via chemiosmosis. The transthylakoid pH gradient needed to drive chemiosmosis is generated by two mechanisms: (1) the oxidation of one molecule of water produces two free protons, and (2) proton pumping via the PQ pool.

Detailed explanation-4: -In non-cyclic photophosphorylation, cytochrome b6f uses the energy of electrons from PSII to pump hydrogen ions from the lumen to the stroma; this energy allows ATP synthase to attach a third phosphate group to ADP, which forms ATP.

Detailed explanation-5: -ATP and NADPH are produced during the light dependent reaction, and are reactants necessary for the light independent reaction (Calvin Cycle) to occur. During the light independent reaction, ATP and NADPH are used to convert phosphoglycerate molecules (PGA) to glyceraldehyde-3-phosphate molecules (G3P).