1. Photosynthesis
Part I

2. Photo (light)-synthesis (putting things together)
Remember:
- To make a large molecule (glucose) you need Energy
- When you break down a large molecule (glucose) you
generate Energy

3. 2 Steps of Photosynthesis
1. Light-dependent reactions: convert the sun's energy into chemical energy - generate the energy needed for the next step
2. Light-independent reactions: use the energy from step 1. and Carbon dioxide to make glucose (food)

4. 2 Steps

5. Step 1
Occurs in two different areas of the thylakoid – Photosystem I and Photosystem II
Photosystem – light collecting unit of the chloroplast
Photosystem has Chlorophyll and Electron Transport System ( a chain of Carrier Proteins)

6. Light electrons
- The more Energy an electron has , the further away from the protons it can get;
- Given enough energy it can escape
altogether leaving behind a (+) charged
particle – ion
- When an electron falls closer to protons, it releases energy
- When Hydrogen (picture) looses 1 electron, it becomes a H+ ion

8. Step 1 – getting that energy from the sun
Light-dependent – reactions need light
Requires water and sunlight
Chlorophyll absorbs the energy from the sun – (high energy particles called photons) – with enough energy 2 electrons will pop off from chlorophyll
To replace these lost electrons, Chlorophyll using photons will split water into oxygen, hydrogen ions and electrons – O H e-

9. Step 1 – Photosystem II
The 2 electrons from Chlorophyll will travel down the electron transport chain (ETC) – a chain of carrier proteins that will use the energy form the electrons to transport H+ across the membrane – result high concentration of H+ inside the thylakoid
H+ ions build up inside the thylakoid from the break down of water and the ETC

10. ATP formation
H+ wants to move from high to low concentration (Diffusion) but it needs help from a protein in the cell membrane called ATP synthetase
As H+ passes through, ATP synthetase is forced to turn and when it does it adds a phosphate group to ADP to make ATP

12. Step 1 – Photosystem I
The electrons from photosystem II lost energy when they pumped H+ across the membrane
In photosystem I light gives electrons energy again
Then they go through another ETC
Here they are used to make NADPH which goes on to the next set of reactions

13. Summary of Light dependent reactions
Require water and sunlight, have 2 parts: photosystem II and photosystem I
As light shines on Chlorophyll it looses 2 electrons, and replaces them with 2 electrons from water
As the plant uses the electrons from water H+ and O2 are left behind
Oxygen gas is given off in photosystem II and ATP is made
NADPH is made in photosystem I

15. Step 2 – Light-independent reactions
Also called Dark reactions or the Calvin cycle
Takes place in the stroma of the chloroplast
Need carbon dioxide to build carbohydrates
Use ATP and NADPH (energy) from light dependent reactions and carbon dioxide to make carbohydrates/glucose

16. Dark Side of Photosynthesis
To be Continued