1. Photosynthesis – Stage 1
Also known as Light Reactions/Light Dependent Reactions
take place in thylakoids
require sunlight
involves converting sunlight energy and H2O into chemical energy (ATP & NADPH) temporarily
Reason: to make temporary energy (ATP & NADPH) to use in Stage Two

2. Energy
All organisms need energy for all of life’s functions in the form of ATP
The following two nucleic acids are temporary energy packets formed during stage one of photosynthesis. The energy to “charge” them comes from the sun.
ATP = adenosine triphosphate (charged)
ADP = adenosine diphosphate (uncharged)
NADPH - (charged)
NADP - (unchared)

3. Adenosine Triphosphate
the molecule that can store and transport the energy needed for survival
made of…
1 sugar – ribose
1 base – adenine
3 phosphates
sugar
phosphates
base

4. Releasing Energy from ATP

5. ATP
breaking the bond between the last two phosphates is how the energy is released from ATP
ATP  ADP + P
once the energy is released, the ADP returns to the mitochondria to be rebuilt into ATP (storing energy again)

6. ATP is like a rechargeable battery

7. The sun’s light energy shines down on the leaves of a plant.

8. The sunlight is absorbed by the leaf.

9. Specifically, the plant cells in the leaf absorb the sunlight.

10. If we take a look inside that plant cell, we see chloroplasts.

11. Those chloroplasts inside the plant cell absorb the sunlight.

12. Chlorophyll is the main pigment that absorbs the sunlight
Chlorophyll is the main pigment that absorbs the sunlight. It is found on the thylakoid membranes.

13. 1. Sunlight shines down on the chlorophyll molecules (green ovals) embedded in the thylakoid membranes (black line).

14. 2. Sunlight excites electrons that jump off of the chlorophyll molecule.

15. 3. Water from the plant’s roots comes to replace the lost electron.

16. 4. Water breaks apart to give the chlorophyll back the missing electron (one of the hydrogen atoms from water fills this gap in the chlorophyll where the electron left).

17. 5. Oxygen from the water will join another oxygen to form O2 (oxygen gas), which we breathe in.

18. 6. In the mean time, the lost electrons are being used to “charge up” ATP and NADPH. These two temporary energy storage molecules are sent into the stroma of the chloroplast to be used in Stage 2.

19. Reactants (Ingredients)
Summary of Stage One
Sunlight (activation energy)
Reactants (Ingredients)
Products
Water (H20)
ADP (uncharged)
NADP (uncharged)
Oxygen Gas (02)
ATP (charged)
NADPH (charged)