1. Photosynthesis

2. Introduction Light reaction
Photosynthesis
Introduction
Light reaction

3. Cell Energy:
Energy for living things comes from food. Originally, the energy in food comes from the sun.

4. Organisms that CANNOT use the sun’s energy to make food—heterotrophs
Ex: animals and most microorganisms

5. Organisms that use light energy from the sun to produce food—autotrophs (auto = self)
Ex: plants and some microorganisms (some bacteria and protists)

6. Photosynthetic Organisms are Producers

7. Photosynthesis is the process by which the energy of sunlight is converted into the energy of glucose

8. Photosynthesis occurs on plant leaves

9. Where photosynthesis takes place
Leaf Anatomy
Protects the leaf
Where photosynthesis takes place
Lets CO2 in and O2 out

10. More specifically, photosynthesis occurs in the chloroplasts of leaf
granum

11. Chloroplast Structure: Structure:

12. (These look yellow, orange, and red). As chlorophyll dies in the
The main energy
absorbing molecule
in chloroplasts is
_____________
______________
are plant pigments too.
(These look yellow, orange, and red). As chlorophyll dies in the
fall, the green color fades and is replaced by carotenoids
CHLOROPHYLL
CAROTENOIDS

13. Carotenoids are plant pigments too.
Carotenoids are plant pigments too.
These look yellow, orange, and red.
As chlorophyll dies in the fall, the green color
fades and is replaced by carotenoids

14. Chlorophyll absorbs mostly red and blue wavelengths of light
Red and blue absorbed
Green is reflected

15. Photosynthesis Overview

16. Two Main Stages of Photosynthesis
Light-Independent Reactions (Calvin Cycle)
Light- Dependent Reactions

17. Part 1: Light-Dependent Reaction
Occurs in thylakoids/grana
Sun’s energy is absorbed & changed into chemical energy in ATP & NADPH

18. 5 steps of light rxn
Light strikes thylakoid & hits chlorophyll causing electrons become excited.

19. 5 steps of light rxn
2. Electrons jump from chlorophyll to chlorophyll through thylakoid membrane (electron transport chain). NADP+ picks up high energy e- & H+ to become NADPH.

21. H2O is split by light (photolysis)– electrons are given back to chlorophyll, H+ collects, & O2 is released (waste product you breathe)

22. 4. H+ builds up inside thylakoid. 5
4. H+ builds up inside thylakoid. 5. H+ pass through transport protein (ATP synthase) which adds P to ADP forming ATP.

23. Talk to a Neighbor…
Using the following diagram, walk your partner through the 5 steps of the light- dependent reactions

24. At the end of the Light-Dependent Reactions…

25. Summary of Light Rxn
Video clip
Using light energy ADP NADP+ H2O changed into ATP NADPH H+ & O2