2. PHOTOSYNTHESIS

3. KEY CONCEPT Photosynthesis is a series of chemical reactions that transform light energy into chemical energy stored in food.

4. Chemical Equation of Photosynthesis
Sunlight Energy
6CO2 + 6H2O C6H12O6 + 6O2
Carbon dioxide + Water Glucose + Oxygen
REACTANTS PRODUCTS
Carbon dioxide Glucose (sugar)
Water Oxygen
Sunlight Energy

5. CO2 enters a leaf through guard cell/stomata by diffusion

6. H2O enters roots through osmosis.

7. Chloroplasts
In plants, Photosynthesis occurs in chloroplasts

8. Structure of the Chloroplast Organelle
Thylakoids- coin shaped compartments
surrounded by a membrane filled
with chlorophyll
Grana –
Stacks of thylakoids
Chlorophyll – green colored molecule
in thylakoid membrane
Stroma –
Fluid filled space between grana
chloroplast
stroma
grana (thylakoids)

9. . Chloroplast vs. Chlorophyll
leaf cell
leaf
Chloroplast = Organelle where photosynthesis occurs
Chlorophyll = Green colored molecule that “fills” the chloroplast

10. 2 Stages of Photosynthesis Reactions
1. Light Dependent Reactions
*Require light energy
2.Light Independent Reactions
*Do NOT require light energy

11. Requires Light energy and Water as reactants *Occur in the thylakoid
Light-Dependent Reactions .
Requires Light energy and Water as reactants
*Occur in the thylakoid
*Produces high energy molecules that will transfer their energy to the Light Independent Rxns.
*Waste product is Oxygen

12. Stage 1: LIGHT DEPENDENT REACTIONS

13. Steps of the Light Dependent Reactions
1. Light energy “excites” electrons in a chlorophyll molecule. 2. The “excited”, high energy electrons are passed from one protein molecule to another along the electron transport chain in the thylakoid membrane and are used to make 2 energy carrier molecules 3. Enzymes split the water molecule: H2O 2H+ + 2e- + O- * The 2e- replace the electrons the chlorophyll molecule lost * Oxygen gas is released

14. Light-Independent Reactions (Calvin Cycle)
Do NOT require light energy – can happen in the dark
Source of Energy: the energy stored in high E molecules made in the light rxns
Occurs in the stroma fluid

15. *CO2 is needed – it diffuses across the chloroplast
membrane into the stroma.
*CO2 is rearranged using H+ from the breakdown of water and Energy from energy carrying molecules made in the light dependent reactions to make GLUCOSE.

16. Making the Energy Storing
GLUCOSE
Is the #1 Job of PHOTOSYNTHESIS

17. Big Picture of Energy Transformation in Photosynthesis
Light Dependent Reactions –
Chlorophyll molecule captures and transforms Light Energy into Chemical energy temporarily stored in energy carrier molecules.
Light Independent Reactions –
Chemical E from the energy carrier molecules made in
Light Dependent reactions is transformed and stored as
chemical energy in glucose

18. Photosynthesis plays a role in carbon cycling
Inorganic Carbon in CO2 gas from the atmosphere
gets “fixed” into organic compounds like carbohydrates,
lipids and proteins.

19. The Big Picture
Write the chemical equation for Photosynthesis using logic or memory – No Notes Allowed!!

20. 6CO2 + 6H2O C6H12O6 + 6O2 The Big Picture
Write the chemical equation for Photosynthesis using logic or memory – No Notes Allowed!!
6CO2 + 6H2O C6H12O6 + 6O2

21. Sample Exam Question
Using a microscope, a student observes a small, green organelle in a plant cell.
What is the name of this organelle?
Which energy transformation occurs first within the organelle?
A. ATP to light
B. Light to Chemical
C. Heat to Electrical
D. Chemical to Chemical

22. Sample Exam Question
Using a microscope, a student observes a small, green organelle in a plant cell.
What is the name of this organelle? Chloroplast
Which energy transformation occurs first within the organelle?
A. ATP to light
B. Light to Chemical
C. Heat to Electrical
D. Chemical to Chemical

23. Photosynthesis is series of chemical reactions that involve the transformation of energy from one form to another. The many reactions of photosynthesis are grouped into two set of reactions. Name each reaction set. Explain the energy transformation that occurs in each.

24. Photosynthesis is series of chemical reactions that involve the transformation of energy from one form to another. The many reactions of photosynthesis are grouped into two set of reactions. Name each reaction set. Explain the energy transformation that occurs in each.
Light Dependent Rxns
Light Energy .> Chemical E stored in energy carrying molecules
Chemical E in energy carriers > Chemical E stored in glucose

25. Overall Energy Transformation in Photosynthesis
Light Energy > Chemical Energy stored in Glucose

26. Sample Exam Question
Photosynthesis and cellular respiration are two major processes in which carbon atoms are cycled through the bodies of living things.

27. The equation for the overall process is:
6CO2 + 6H2O  C6H12O6 + 6O2
C6H12O6
granum (stack of thylakoids)
thylakoid
sunlight
1 six-carbon sugar
6H2O
6CO2
6O2
chloroplast 1 2 4 3
energy
stroma (fluid outside the thylakoids)

28. Water is absorbed by osmosis through the roots