1. PHOTOSYNTHESIS: Converting solar energy into chemical energy (SUGARS).
CELLS AND ENERGY Part 2
PHOTOSYNTHESIS: Converting solar energy into chemical energy (SUGARS).

2. AN OVERVIEW OF PHOTOSYNTHESIS
Photosynthesis is the process by which autotrophic organisms use light energy to make sugar and oxygen gas from carbon dioxide and water.
Carbon dioxide
Water
Glucose
Oxygen gas
PHOTOSYNTHESIS

3. How Does Photosynthesis Work?
2 Reactions
Light-Dependent Reactions
Occurs in the Thylakoid Membrane
Light-Independent Reactions
Occurs in the Stroma
Calvin Cycle

4. Light-Dependent Reactions
Occurs in the Thylakoid Membrane
Uses Photosystem II and Photosystem I
P680 – PSII (chlorophyll a)
P700 – PSI (chlorophyll a)
Uses water to provide electrons.
Electrons move through the Electron Transport Chain (ETC)
Generates O2, ATP and NADPH

5. Where do the Light-Dependent Reactions take place in the Chloroplast?
Light-Dependent Reactions take place in the Thylakoid Membrane of the Chloroplast.

6. Light-Independent Reactions The Calvin Cycle
Occurs in the Stroma
Uses ATP and NADPH from the light-dependent reactions as ENERGY.
Uses atmospheric Carbon Dioxide (CO2)
Carbon Dioxide enters the leaves through pores called STOMATA
Produces Sugars that the plant uses for energy and structure (cellulose)

7. AN OVERVIEW OF PHOTOSYNTHESIS
The light reactions convert solar energy to chemical energy
Produce Oxygen, ATP & NADPH
Light
Chloroplast
NADP
ADP
+ P
Calvin
cycle
The Calvin cycle makes sugar from carbon dioxide
ATP generated by the light reactions provides the energy for sugar synthesis
The NADPH produced by the light reactions provides the electrons for the reduction of carbon dioxide to glucose
Light
reactions

8. The Calvin cycle takes place in the STROMA of the Chloroplast.
Where does the Calvin cycle take place in the Chloroplast?
The Calvin cycle takes place in the STROMA of the Chloroplast.

9. Light-Dependent Reactions Step - by - Step
Sunlight (photons) hits Photosystem II.
Chlorophyll a (inside Photosystem II) absorbs wavelength 680 and sends electrons to Electron Transport Chain (ETC).
Water is split to provide electrons – Oxygen is a by-product of splitting water.
Electrons move through the Electron Transport Chain to Photosystem I, losing energy as they move from molecule to molecule.

10. Light-Dependent Reactions Step – by – Step Continued
Sunlight hits Photosystem I.
Chlorophyll a (inside Photosystem I) absorbs wavelength 700 and sends electrons to enzyme to make NADPH.
ATP is produced by enzyme called ATP Synthase.

12. Oxygen, ATP and NADPH are made during the Light-Independent Reactions.
What products are made during the Light-Dependent Reactions?
Oxygen, ATP and NADPH are made during the Light-Independent Reactions.

13. Diagram of Light-Dependent Reactions
Let’s Draw!

14. Light-Independent Reactions The Calvin cycle Step – by - Step
Carbon Dioxide (CO2) enters into the plant leaves and into the STROMA of the Chloroplast
The Carbon from CO2 becomes a sugar molecule through several enzymatic reactions.
Energy from ATP and electrons from NADPH are used to make SUGARS.
6 CO2 molecules make 1 GLUCOSE molecule

16. Light-Independent Reactions
The Calvin cycle

17. Sugar is made in the Calvin cycle.
What product is made in the Calvin cycle?
Sugar is made in the Calvin cycle.

18. What is the original source of Carbon for the Calvin cycle and where does it come from?
Carbon Dioxide from the atmosphere is the original source for the Calvin cycle.

19. 6 CO2 molecules are needed to make 1 molecule of Glucose.
How many molecules of Carbon Dioxide (CO2) are needed to make one molecule of Glucose?
6 CO2 molecules are needed to make 1 molecule of Glucose.