1. Photosynthesis
Biology 2
D. Mitchell

2. All life requires energy.
2/25/2019
All life requires energy.
Almost all energy for life is derived from the sun.
Energy from the sun enters living systems when autotrophs absorb sunlight. .

3. Autotrophs (producers)-Organisms that can make their own food
Autotrophs (producers)-Organisms that can make their own food. Examples – plants, algae, and some bacteria

4. Heterotrophs (consumers) -must feed on autotrophs, one another, or organic wastes in order to obtain energy. -cannot make their own food. Examples: other bacteria, many protists, fungi and animals.

5. Photosynthesis
Process by which plants, algae and some bacteria use light energy to make organic compounds (sugar-glucose).

6. EQUATION FOR PHOTOSYNTHESIS
Light ENERGY
6CO2 +
6H2O
C6H12O6 +
6O2
CARBON DIOXIDE
WATER
GLUCOSE
OXYGEN Gas
Reactants
Products
The equation is read six molecules of carbon dioxide is added to six molecules of water which yields one molecule of glucose and six molecules of oxygen gas.

7. 2/25/2019
Photosynthesis takes place in the chloroplast of plants and the cytoplasm of bacteria.
Chloroplasts are the specialized organelles in plants and some algae where photosynthesis occurs.
Most chloroplasts are in leaf cells that are specialized for photosynthesis.

8. Thylakoids: disc-shaped stacks (granum) inside the chloroplast.
Parts of the chloroplast:
Thylakoids: disc-shaped stacks (granum) inside the chloroplast.
Stroma: dark fluid that surrounds the grana inside the chloroplast

9. Chloroplast
Thylakoid membrane
Stroma (fluid)

10. Pigments involved in Photosynthesis
The primary pigment - chlorophyll
Plants contain two types of chlorophyll -chlorophyll a and chlorophyll b
Each pigment absorbs certain wavelengths of light (red and blue) and reflects others (green and yellow).

11. Photosynthesis: The Process
Occurs in 2 main phases
Light Dependent Reactions
Photosystem II
Photosystem I
Light Independent (Calvin Cycle) Reactions

12. Light Dependent Reactions
Occur in the thylakoids of the chloroplasts during times of light
Purpose is to absorb sunlight and convert it to ATP that can be used in the Calvin cycle.

13. Summary of Light Dependent
Sunlight enters the chloroplast when pigments in the thylakoids absorb the light.
Some excited electrons are released.
Water molecules are split into H+ and Oxygen gas (O2) .

14. Summary of Light Dependent
Some excited electrons pass to the Electron Transport Chain and travel across the thylakoid membranes.
Energy provided in the ETCs is used to make ATP.

15. Some excited electrons travel down another electron transport chain.
Energy is used to make NADPH

16. And now what….
The ATP and the NADPH of the light dependent reactions are used for the next main step, the Calvin cycle (Light independent reactions)

17. Light Independent Reactions
USES Carbon dioxide (CO2), H+, and the energy in ATP and NADPH
CO2 is fixed/mixed with the Hydrogen ions to make glucose.
Occurs in the stroma in the chloroplast

18. the most common method of carbon-dioxide fixation
Calvin Benson Cycle
the most common method of carbon-dioxide fixation
function -to produce a single molecule of glucose (C6H12O6)

19. 3 phases:
Carbon Fixation
Reduction
Regeneration of RuBP

20. Summary of Light Independent Reactions
Using ATP and NADPH from the light dependent reactions, Carbon dioxide (CO2) is used to make glucose (C6H12O6).

21. Environmental factors that affect photosynthesis are:
Light quality
Light intensity
Light availability
Carbon dioxide availability
Water availability