1. Energy Generation in Chloroplasts
Chapter 13 & 14
Energy Generation in Chloroplasts

2. Chloroplasts and Photosynthesis
Photosynthesis is process using the energy in sunlight and CO2 to create the organic materials required of present day cells
The chloroplast is the special organelle in plants responsible for photosynthesis

3. Chloroplasts Similar to mitochondria Uses a proton pump to create ATP
Stroma instead of matrix
Has own RNA, DNA and ribosomes
Difference is that the e- transport chain is in the thylakoid membrane – 3rd membrane that makes up the thylakoids, a sac-like structure, so have a thylakoid space
Granum – stack of thylakoids
Chloroplasts

4. Chloroplasts vs Mitochondria

5. Light and Dark Reactions
Light or photosynthetic e- transfer reactions
Sunlight energizes e- in chlorophyll which then moves down the e- transport chain in the thylakoid membrane
e- gotten from H2O to make O2
Electrochemical gradient is made in the stroma across the thylakoid membrane making ATP
Generate NADPH from NADP+
Dark or carbon-fixation reactions
ATP and NADPH produced in light reaction used as energy and reducing power to take CO2 and convert it to a carbohydrate – sucrose

6. Photosynthesis Reactions

7. Chlorophyll
Sunlight is composed of many different wavelengths ranging from violet to red
Chlorophyll is green because it absorbs all the wavelengths but green
The e- in chlorophyll gain a higher energy level when a wavelength is absorbed and then bounce around the ring – porphyrin (blue)

8. Photosystem
Chlorophylls are in a multiprotein complex called a photosystem
Antenna is many molecules of chlorophyll that capture the sunlight’s energy that ultimately goes to the reaction center

9. Reaction Center Set of proteins in the thylakoid membrane
Special chlorophyll molecule that is an irreversible trap for an excited e-
Transfers the e- to a more stable environment

10. ATP and NADPH
The light reaction makes the ATP and NADPH (reducing power) to synthesize the sugar
ATP made with the first photon of light absorbed and NADPH is made from the second photon of light

11. Summary of Light Reactions
Electron from chlorophyll in photsystem II is donated to NADPH
The replacement electron comes from the splitting of water
When 4 electrons are removed (4 photons hit chlorophyll) O2 is released

12. Carbon Fixation

13. Carbon-Fixation or Calvin Cycle
CO2 joins with a ribulose 1,5-bisphosphate (5 C) by a carboxylase called rubisco
Rubisco is slow compared to other enzymes so therefore there is a large amount in the cell to compensate for this
1 molecule of glyceraldehyde 3-phosphate (net product ) is generated and goes to make the sugar
A large amount of energy goes to regenerating the ribulose 1,5-bisphosphate
3 ATP and 2 NADPH required for each CO2 molecule converted to carbohydrate

14. Glyceraldehyde 3-phosphate
Converted into sucrose
Can be shuttled into the glycolytic pathway in the mitochondria of plants to become pyruvate and eventually ATP
Excess is converted into starch in the stroma which can be used at night as an energy source