Photosynthesis

“The light and dark reactions”

General formula for photosynthesis Light + water + carbon dioxide = glucose + oxygen

Two steps Light-dependent

(sometimes called the “light reactions”)

Light-independent (sometimes called the Calvin-Benson cycle, the Calvin cycle, the Carbon Fixation cycle or the C3 dark reactions)

Light-dependent reactions Water and sunlight are the reactants ATP & NADPH are the products Water is split (photolysis) “Excited” electrons are involved Two different chlorophyll molecules are

involved

Light-independent reactions ATP and NADPH from the light reactions

combined with carbon dioxide are the reactants

Glucose and waste oxygen are the main products

Carbon dioxide is “fixed” into a usable form

Where does all this happen? Light reactions take

place on the membrane of the thylakoids within a chloroplast.

Light-absorbing pigments and enzymes are there to help.

“Dark” reactions take place in the stroma of the chloroplast.

Enzymes needed for this pathway to proceed are in the stroma as well.

Why should You care about photosynthesis?

You like to eat.

You like to breathe.