AP BIOLOGY

Detailed explanation-1: -Answer is 2-LIGHT REACTIONS ALONE. In the first step of photosynthesis, ATP and NADPH are produced using the light-dependent reactions, Then ATP and NADPH produced by the light reactions are used by the Calvin cycle to make carbohydrates.

Detailed explanation-2: -The reaction center chlorophyll of photosystem I transfers its excited electrons through a series of carriers to ferrodoxin, a small protein on the stromal side of the thylakoid membrane. The enzyme NADP reductase then transfers electrons from ferrodoxin to NADP+, generating NADPH.

Detailed explanation-3: -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. These two energy-storing molecules are then used in the light-independent reactions.

Detailed explanation-4: -Photosynthesis is a series of chemical reactions divided into two stages, the light reactions and the Calvin cycle. ATP and NADPH are generated by two electron transport chains during the light reactions. The Calvin cycle uses CO2 and the energy temporarily stored in ATP and NADPH to make the sugar glucose.

Detailed explanation-5: -NADPH is produced from NADP+. The major source of NADPH in animals and other non-photosynthetic organisms is the pentose phosphate pathway, by glucose-6-phosphate dehydrogenase (G6PDH) in the first step. The pentose phosphate pathway also produces pentose, another important part of NAD(P)H, from glucose.