8.2 & 3 The Process of Photosynthesis

Key QuestionsWhat happens during the Light

Dependent Reactions?

What happens during the Light Independent Reactions?

What factors affect photosynthesis?

What are electron carrier molecules?

What are the reactants and products in photosynthesis?

Photosynthesis is a biochemical pathway

Two parts

1. Light dependent reaction

2. Light independent reaction (Calvin Cycle)

3 Stages of Photosynthesis

Stage 1: Energy is captured from sunlight

Stage 2: Light energy is converted to chemical energy (ATP + NADPH)

Stage 3: Energy is used to form glucose

High Energy Electrons

Energy carriers—

Oven Mitt/Bucket analogy

NADP+ NADP+, 2e-, H+

Light Dependent ReactionPhotosystem II

p. 237

Thylakoids

Chlorophyll--blue and red absorbed

-green and yellow reflected

Carotenoids

-red and orange reflected

Light splits water molecule into:4H+ + 4e- + O2

Light Dependent ReactionElectron Transport chain

Excited e- are passed along thylakoid membrane

Light Dependent ReactionPhotosystem I

Light Absorbed Again

NADP+ takes a H+ ion and 2 e- becomes NADPH

Minimal amount of ATP made (to be used later)

Diffuse H+ into stroma

Light Independent ReactionCalvin Cycle

p. 238

Stroma

No light required

ATP, NADPH come in from light reactions

CO2 comes in from the atmosphere

ADP, NADP+ and C6H12O6 (Glucose) made

Rate of Photosynthesis

Dependent on:

Light intensity (most import)

CO2, H2O

Temperature