AP BIOLOGY

Detailed explanation-1: -Light reaction is the first stage of photosynthesis process in which solar energy is converted into chemical energy in the form of ATP and NADPH.

Detailed explanation-2: -The first step in photosynthesis is the photo excitation of chlorophyll by a photon of light.

Detailed explanation-3: -In the first part of photosynthesis, the light-dependent reaction, pigment molecules absorb energy from sunlight. The most common and abundant pigment is chlorophyll a. A photon strikes photosystem II to initiate photosynthesis.

Detailed explanation-4: -The light reaction of photosynthesis produces ATP and NADPH which in turn serve as the energy source to drive the second phase of photosynthesis (dark reactions) during which carbohydrate synthesis takes place.

Detailed explanation-5: -Steps of the Light Reactions The light reactions occur in several steps, all of which take place in the thylakoid membrane. 0 Step 1: Units of sunlight, called photons, strike a molecule of chlorophyll in photosystem II of the thylakoid membrane.