1. “How Plants Eat Sunshine”
Photosynthesis or
“How Plants Eat Sunshine”

2. Plants don’t eat cheeseburgers.
Where do plants get the food to create the energy they need to grow and reproduce?
PHOTOSYNTHESIS!

3. What do you already know about Photosynthesis?
It produces Oxygen.
It uses CO2.
It happens in plants.
Uses light.
Chloroplasts.
Chlorophyll
Starch is produced.

4. What have we learned in lab?
Photosynthesis (O2 production) occurs in the light.
Photosynthesis takes place where chlorophyll is present - the green parts
Photosynthesis produces starch

5. How does Photosynthesis work?
Photosynthesis is the process of TRANSFORMING LIGHT ENERGY into CHEMICAL ENERGY (food, or GLUCOSE).
Light Glucose
BUT HOW??

6. Let’s look at a plant cell.
Here’s the chloroplast.

7. Chloroplasts…
Have stacks of thylakoids –a stack of thylakoids is called grana.
Have a stroma-
Space
surrounding the
thylakoids

8. Chloroplasts are GREEN so…
Sunlight is part of the VISIBLE spectrum
White light can be separated by wavelengths.
Wavelengths correspond to different colors.
The colors you see are being RFLECTED.

9. Chloroplasts are GREEN so…
CHLOROPHYLL is the pigment molecule that makes plants green and is responsible for photosynthesis.
GREEN IS BEING REFLECTED.
Light that is ABSORBED is used during photosynthesis.
ALL OTHER LIGHT IS USED FOR PHOTOSYNTHESIS.

10. The Light Dependent Reaction: uses water and produces O2

11. Step 1: the ETC (light DEPENDENT reactions)
An electron Transport Chain (ETC) is an electron conveyer belt.
Electrons (e-) move down the chain and are picked up and make new molecules.
The ETC is located in the THYLAKOID MEMBRANE.

12. Step 1: the ETC (light DEPENDENT reactions)
Light hits chlorophyll and excites an e-. The e- starts moving down the chain. This leaves an empty space.
ETC e-
Chlorophyll

13. Step 1: the ETC (light DEPENDENT reactions)
H2O is split. O2 donates an electron to fill the empty space in the chain and diffuses out. H+ stays in
the thylakoid,
making an H+
gradient.
The OXYGEN
is released! e-
O- + H+ H+

14. Step 1: the ETC (light DEPENDENT reactions)
H+ diffuses out through ATP synthase, to make ATP. e-
H+ H+ H+ H+ H+ H+ H+ H+ H+
ATP Synthase H+
ATP!!

15. Step 1: the ETC (light DEPENDENT reactions)
Electrons are picked up from the ETC and used to take H+ to the CALVIN CYCLE.
NADP+e-+H+NADPH e-
H+ H+ H+ H+ H+ H+ H+ H+ H+ H+
ATP!!

16. http://highered. mcgraw-hill

17. The CALVIN CYCLE aka THE DARK REACTIONS: Consume CO2 and produce Glucose (C6H12O6)

18. Step 2: The Calvin Cycle (Light INdependent reactions)
H+ is transferred to the CALVIN CYCLE in the stroma.
Stroma: the dark middle part of the thylakoid.

19. Step 2: the Calvin Cycle (the DARK reactions)
CO2 diffuses into the chloroplast
And enters the
Calvin Cycle.
CALVIN CYCLE
CO2

20. Step 2: the Calvin Cycle (the DARK reactions)
H+ enters the Calvin Cycle.
Energy from ATP created during the Light Dependent Reactions is used to ...
combine 6 molecules of CO2 and 12 H+ to make …
GLUCOSE (C6H12O6)!

21. Step 2: the Calvin Cycle (the DARK reactions)
CO2
C6H12O6 H+

22. Step 1 and Step 2:

23. The Bottom Line... Photosynthesis occurs in plants.
Photosynthesis uses sunlight to make starch.
Photosynthesis takes place in the chloroplast using chlorophyll.
Oxygen released from plants comes from WATER – NOT CO2
CO2 and H+ (also from water) are used to make C6H12O6.

24. The Bottom Line... Photosynthesis has 2 reactions:
LIGHT DEPENDENT and LIGHT INDEPENDENT.
Light Dependent Reactions = Thylakoid
Light INdependent Reactions = Stroma
CO2 + H2O + ATP SUNLIGHT C6H12O6 + O2

25. So… why should we save the rainforest?
We need the Oxygen to make our own energy – ATP – during cellular respiration!
Coming up next in Biology...
How do our cells use Oxygen from plants to make ATP??