Cellular Respiration

and Metabolism

What is Photosynthesis?

The process of using sunlight to

convert CO2 and water into

glucose and oxygen

CO2 + H2O C6H12O6 + O2

Reaction takes place in

the chloroplast

Early Experiments with Photosynthesis

• Van Helmont (1643) - plant growth does not come from soil

• Joseph Priestley (1771) - plants produce oxygen

• Jan Ingenhousz (1779) - plants need light to produce oxygen

Granum

Interior of Chloroplast

Thylakoid(contain chlorophyll)

Stroma -fluidwith enzymes

Granum

Converting Solar Energy

• Plants trap the sun’s energy using a green pigment called chlorophyll

• Chlorophyll is inside the chloroplast in the thylakoid membrane

• Solar energy is used to transform CO2 into sugars

Why are leaves green?

Only green light is

reflected

All other colors are absorbed

Chlorophyll Absorption

http://www.cbu.edu/~seisen/ChlorophyllAbsorption.jpg

Factors that Affect

Photosynthesis• Water availability

• Light intensity (varies from species to species)

• Temperature (extremes slow down photosynthesis - below 0oC and above 35oC)

Photosynthesis is divided into two processes:

Overview of Light Dependent Reactions

• Take place in thylakoidmembranes

• Require light to occur

• Produce oxygen gas

• Produce ATP and NADPH

Photosystems I and II

Clusters of light absorbing chlorophylls, other pigments and

proteins found in thylakoid membrane.

Each photosystem is connected to each other by an electron transport

chain that produces ATP

Overview of Light-Dependent Reactions

1. Light strikes Photosystem II. Energy from light excites e-

2. e- are passed through ETC to Photosystem I. Their energy is used to produce ATP (goes to the Calvin cycle)

3. Photosystem I captures light energy to re-energize e-

4. High energy e- are picked up by NADP+ to form e- carrier NADPH (goes to the Calvin cycle)

Overall schematic view of light-dependent reactions

1

4

3

2

The Calvin Cyclehappens in the stroma

Uses energy stored in ATP and

NADPH to produce glucose from

CO2.

* Six CO2 molecules from the

atmosphere are needed to

produce one glucose molecule

Summary of the Reactions of

Photosynthesis

thylakoid

stroma