1. The Reactions of…
Photosynthesis

2. Inside a Chloroplast The organelle in which Photosynthesis takes place
Thylakoids = saclike photosynthetic membranes
Contain chlorophyll, other pigments, proteins
Granum = stack of thylakoids
Stroma = the region outside the thylakoid membranes

3. Inside a Chloroplast

4. Photosynthesis Overview
Two stages:
Light-dependent Reactions
Within the thylakoid
Uses Light & Water to Make ATP, NADPH, and O2
Calvin Cycle
Within the stroma
Uses CO2 , ATP, and NADPH to Make Sugars

5. What is NADPH?
An electron carrier that transfers high-energy electrons and their energy from chlorophyll to other molecules
Traps some energy from sunlight as chemical energy (2 e- and 1 H+)
High-energy electrons are used to help plant cells build molecules like glucose

6. Light-dependent Reactions
1. Chlorophyll in Photosystem II absorbs light and sends its excited electrons to the Electron Transport Chain.
2. ETC uses energy from the electrons to pump H+ into the thylakoid.
3. Light re-energizes the electrons at Photosystem I and sends them to NADP+ to become NADPH.
4. H+ cross the membrane through ATP synthase due to the difference in charge across the membrane, and produces ATP.

8. Calvin Cycle
Uses CO2 and organic molecules to generate sugars and other compounds through a series of reactions
For each “turn” of the Calvin Cycle, most of the organic molecules are used to begin the cycle again
Plants use sugars for energy and for building more complex carbohydrates like starch and cellulose

10. Factors Affecting Photosynthesis
Water
Shortage slows or stops PS
Temperature
Above or below 0-35 deg. C, enzymes do not work well… slows or stops PS
Light
Intensity… more is better, but PS does have a maximum rate for each plant type