1. Converting Light Energy into Chemical Energy
Photosynthesis
Converting Light Energy into Chemical Energy

2. How far down the rabbit hole must we go to look at photosynthesis?

4. Photosynthesis Purpose of photosynthesis-
To use sunlight to convert water and carbon dioxide into high-energy carbohydrates and oxygen.
B. Solar energy is converted into chemical energy through photosynthesis.
Light Energy
Sugar + O2
CO2 + H2O

5. Plants use water + carbon dioxide to make sugar
Plants use sugars as material for building cells and energy to run cells
Humans use sugars for:
Food
Shelter
Energy
Clothing
Medicines

6. Location of Photosynthesis
Occurs in the leaves of green plants
Occurs in specific cells in the middle layer of the leaf
Occurs in organelles – called chloroplasts – within the cells of the middle layer of the leaf
Photosynthesis Formula:
(6) CO2 + (6) H2O + light energy (1) C6H12O6 + (6) O2

7. In the chloroplasts of photosynthetic organisms, the energy of sunlight is transformed into the energy stored in chemical bonds of carbohydrates (glucose).
CO2
H2O
Light
Chloroplast O2
Other materials
Chlorophyll absorbs
Calvin
Cycle:
Light-
Dependent
Reactions
Light-
Independent
Reactions
H+ ions
ATP
NADPH
Sugar (Glucose)
C6H12O6

8. F. Two Reactions in Photosynthesis
Light-dependent reactions convert light energy and the splitting of water to chemical energy (ATP) and release H and oxygen.
Light-independent reactions use the energy from the light-dependent reaction to convert CO2 and H to sugar

9. G. Light Dependent Reactions
2. Occurs in the thylakoid membrane
1. Also called light reactions or photochemical reactions

10. Chloroplast structure

11. 3. Sunlight is absorbed by chlorophyll pigments in photosystems located in the thylakoid membranes inside the chloroplast.
Water is split into 2e-, 2 H+ and 1 O2 at Photosystem II.
4. Electrons move through the ETC from PS II to PS I.
Energy from these e- transport H+ from stroma to thylakoid space.

12. 5. Pigments in Photosystem I use energy from light to convert NADP to NADPH.
6. ATP is produced from ADP using the energy in the difference between the sides of the membrane.
7. ATP Synthase is the enzyme that converts ADP to ATP.

13. light dependent reaction
(click on the image to be redirected to the video)

15. Light Reaction (recap)
1. Light Absorption Light energy absorbed by pigments generates electrons that are transferred to chlorophyll a, the primary pigment in photosystems.
Photosystems are bundles of pigments responsible for absorbing sun’s light energy.

16. Light Reaction (recap)
2. Electron Transport Electrons are transported along the ETC within the photosystems. Electrons (-) and hydrogen ions combine with NADP+ to produce NADPH, stored energy!