Photosynthesis

Chapter 8

Organisms that use Photosyntheis

• Anozygenic– Purple bacteria

– Green sulfur bacteria

– Green nonsulfur bacteria

– Heliobacteria

• Oxygenic– Cyanobacteria

– Some algae

– All land plants

Where does photosynthesis happen?

Parts of the Chloroplast

• Thylakoid Membrane – where photosystems are found

• Grana

• Chlorophyll

• Stroma

3 Stages of Photosynthesis

• 1. Capturing energy from sunlight

• 2. Using the energy to make ATP and to reduce the compound NADP+ to NADPH

• 3. Using the ATP and NADPH to power the synthesis or organic molecules from CO2 in the air

Story Time- History of Photosynthesis

• Helmont

• Priestly

• Jan Ingen-Housz

• F.F. Blackman

• C.B. van Niel

Pigments• Photons- Short wavelength vs Long

Wavelength– Can cause photoelectric effect

Chlorophyll Absorption Spectra

• Chlorophyll a

• Chlorophyll b• Both can’t absorb 500-600nm…what color do you

think this is?

Accessory Pigments

• Caroteniods- ex Beta-carotene

• Phycobiloproteins

Photosystem Organization

• Antenna Complex

• Reactions Ceneter

Antenna Complex

• Captures photons from sunlight and channels them to the reactions center chlorophylls

Reaction Center

• Figure 8.10

• In plants water serves as an electron donor, when water is oxidized oxygen is released along with two protons

Light-Dependant Reactions

• Primary Photoevent

• Charge Separation

• Electron Transport

• Chemiosmosis– ALL OCCUR IN THE THYLAKOID

MEMBRANE!!!!!!!!!!!!

Photosystems

• Chloroplasts have two photosystems…sulfur bacteria have 1 what does this suggest.

• Photosystem 1- 700nm

• Photosystem 2- 680 nm

• Cytochrome b6-f complex– Cyclic vs noncyclic

Video Break

• Photosystems

And Now for a Video Break

• Photosynthetic Electron Transport System and ATP Synthase

So What is made?

• For every Electron Pair 1 molecule of ATP is made…but this is not enough to drive carbon fixation…how do they cope?

• NADPH is also Made

Carbon Fixation

• Converts inorganic carbon into organic molecules

• Calvin cycle– 3 phases

• Carbon Fixation

• Reduction

• Regeneration of RuBP

Calvin Cycle

• Calvin Cycle

Photorespiration

• Releases CO2

• Reduces the yield or photosynthesis

• As Temperature rises C3 respiration becomes less favorable

Coping with High Temperatures

• C4 pathway- Captures CO2 in one cell and the decarboxylation occurs in an adjacent cell. – Corn, sugarcane, grasses.

• CAM pathway- stomata open during the night and close during the day– Cacti, pineapples, and some other plants