Photosynthesis requires the input of energy in the form of light to create a good electron donor (H2O) and acceptor (NADP+).

Chlorophyll molecules are green pigments with polycyclic structures in thylakoid membranes. It shows strong absorption in the visible region of the spectrum; they have high molar extinction coefficients and can absorb light well. Chlorophyll a and b have different absorption spectra that complement each other's range of light absorption for more visible light absorption.

1. Energy from a photon of light is absorbed by the molecule chlorophyll, then exciton transferred to neighboring chlorophyll until it is transferred to chlorophyll of a reaction center pair.

2. The reaction center passes an electron to the electron acceptor, creating a hole that is filled by an electron from an electron donor.

Review: Exam 2 chapter 20