1. Photosynthesis!! Do Now (on handout)
What 3 things are inputs to photosynthesis?
What 2 things are produced?

3. Photosynthesis Happens in Chloroplasts
Thylakoid
Stroma

4. Chloroplasts: Another Look
Thylakoid: membranes where light is absorbed by chlorophyll.
Stroma: solution inside chloroplasts where sugars are built.

5. Chlorophyll is the green pigment that green plants use to capture light energy

6. Chlorophyll is the green chemical that captures photons of light

7. Part 1: The Light Reactions
The light reactions of photosynthesis are responsible for capturing the energy of light, and storing it in chemicals like ATP.
Those chemicals are then used by the Calvin Cycle to build sugars the plant needs to grow and survive.

8. Step 1: Chlorophyll in the chloroplast captures light energy
Light strikes chlorophyll
Electrons are knocked out of chlorophyll by light… they travel to step 2
Electrons are replaced when water is split
Light
electrons
Chlorophyll
2 H + O
H2O

9. Step 2: The Electron Transport Chain Makes a Hydrogen Gradient
Stroma H+ H+ H+
Inside
thylakoid H+ H+
Electrical energy allows ACTIVE transport from high concentration to low. H+ H+

10. H+ is at a high concentration in the thylakoids

11. Step 3: ATP is made by the enzyme ATP synthase
Inside
Thylakoid
The energy to make ATP from ADP + P comes from the concentration gradient of hydrogen ions across the thylakoid membrane.
ATPsynthase is a key enzyme that makes ATP
Stroma

12. Light Reaction Summary
Light energy is captured by chlorophyll in the chloroplast.
Light energy is stored in ATP and other molecules.
The electrons used in the process come from the splitting of water. This is why plants make oxygen.

13. The Calvin Cycle In the Calvin Cycle build sugars from CO2.
The energy for the process comes from ATP made during the light reaction.
This process also happens in the chloroplast (specifically, the stroma).

14. Calvin Cycle… it’s complicated
What you need to know:
CO2 molecules are combined to make sugar (C6H12O6)
Requires lots of ATP

16. Homework Tonight’s homework will count as a small quiz grade!
Use chapter 6 of your textbook if you need more help.