Photosynthesis
Photosynthesis = Two Steps ➢ Light Reactions • Requires light. • Produces ATP and NADPH (energy stored in chemical bonds) to be used in CO2 fixation. ➢ Carbon-Fixation Reactions • ATP and NADPH produced in the light reactions are used to fix and reduce carbon into simple sugars
The Light Reactions
The Light Reactions ➢ Also called the: • thylakoid reactions. • light-dependent reactions. • energy-transduction reactions. ➢ Overall Function: • Uses light energy to make ATP and NADPH (energy stored in chemical bonds) to be used in CO2 fixation
The Light Reactions Stroma Intermembrane space lamellae Thylakoid Outer envelope Grana lamellae Thylakoid Stroma Thylakoid Inner lumen Stroma envelope Granum lamella
The Light Reactions ➢ Occur on the thylakoid membrane
The Light Reactions
The Light Reactions ➢ Consists of two photosystems: • Photosystem II : P680 • Photosystem I : P700 ➢ Each has ~ 250 to 400 pigment molecules. • Antenna complex– funnel e- to the reaction center. • Reaction center– protein & 2 special chlorophyll a molecules that convert light energy to chemical energy
Light reactions
Light reactions ➢ Primary reaction: ▪ Energy transfer: light to electric energy ▪ Oxidation/reduction: ➢ Electron transport and photophosphorylation ▪ ATP and NADPH produced