1. Photosynthesis and Cellular Respiration
Chapters 8 & 9
Photosynthesis and Cellular Respiration

2. Energy: the ability to do work
Cells work: growth, repair, active transport, and reproduction
Organisms get energy from food
How do organisms get food?
1. Make it
2. Eat it

3. Autotrophs & Heterotrophs
Autotrophs: make their own food
1. Most are photosynthetic
- use sunlight as an energy source
- examples: plants & algae

4. 2. A few are chemosynthetic
- use inorganic compounds as an energy source
- example: bacteria deep in ocean

5. B. Heterotrophs: cannot make their own food (also called consumers)
1. Eat autotrophs or other heterotrophs
2. Examples: animals, fungi

6. III. ATP
Cells store energy in the form of a molecule called adenosine triphosphate (ATP)
Parts of ATP
1. Adenine – a nucleotide
2. Ribose – 5 carbon sugar
3. 3 phosphate groups (PO4)

7. Adenosine
Bonds broken to release energy

8. - adenosine+PO4=AMP
(adenosine monophosphate)
- adenosine+PO4+PO4=ADP
(adenosine diphosphate)
- adenosine+PO4+PO4+PO4=ATP

9. ATP Cycle
1. Food energy is used to make ATP in cellular respiration
2. ATP is broken down to release energy for the cell

10. ATP
Energy for cell
Food energy
ADP

12. IV. Photosynthesis
Photosynthesis occurs in chloroplasts (organelles inside plants)

13. Overview of Photosynthesis
1. Uses light as the source of energy
2. Makes glucose (C6H12O6)
3. Uses water and carbon dioxide as reactants

14. 4. Chlorophyll is the catalyst
Gives off oxygen as a by-product
6. Equation:
6CO2 + 6H20
C6H12O6 + 6O2

15. Photosynthetic pigments
1. Chlorophyll: primary pigment; appears green

16. Carotenoids: secondary pigments; can appear yellow, red, or orange

17. Chloroplast Structure
1. Double membrane (inner=folded, outer=smooth)

18. grana: stacks of thylakoids
thylakoid: 1 disc
stroma: gel-like material between thylakoids

19. 2. Light dependent reactions occur in the grana
3. Light independent reactions (Calvin Cycle) occur in the stroma

20. Summary of Photosynthesis
1. Light dependent reactions: a. light causes electrons in chlorophyll to become excited
b. light energy is also used to split water

21. c. oxygen is released as a by-product
d. hydrogen is passed to the Calvin Cycle
e. ATP is made - this is used as an energy source for the Calvin Cycle

22. 2. The light independent reactions (also called the Calvin Cycle)
a. CO2 from the air combines with the hydrogen from the light dependent reactions to make sugar (C6H12O6)
b. ATP made in light dependent reactions is used as an energy source

23. 3. Summary equation:
6CO2 + 6H20 C6H12O6 + 6O2
- light is required as an energy source
- chlorophyll is required as a catalyst

24. V. Cellular Respiration
Respiration occurs in mitochondria (organelles in all eukaryotic cells)

25. Overview of Respiration
1. Usually uses oxygen
2. Breaks down glucose into energy

26. 3. Gives off carbon dioxide and water as by-products
4. Equation:
C6H12O6 + 6O2
6CO2 + 6H20 + energy

27. C. Steps of Respiration
1. Glycolysis: glucose is converted to pyruvic acid
a. 2 molecules of ATP required
b. oxygen not required
c. glucose (6 carbons) is broken down into molecules of pyruvic acid (3 carbons)

28. d. 4 molecules of ATP released
e. An energy-rich molecule called NADH is made – this will be used later to make ATP

29. Aerobic respiration: occurs if oxygen is present
a. pyruvic acid is broken down into acetyl Coenzyme A
b. acetyl Coenzyme A enters the Krebs Cycle

30. c. In the Krebs Cycle:
1. CO2 is released
2. 2 molecules of ATP are produced
3. Energy rich molecules of NADH and FADH2 are produced – these will be used later to make ATP

31. d. The electron transport chain
1. Electrons from NADH and FADH2 are passed along the electron transport chain
2. Energy from these electrons is used to make ATP

32. 3. Hydrogen from NADH and FADH2 is combined with oxygen to produce H2O

33. 3. Anaerobic respiration: occurs if oxygen is not present
a. 2 types:
1. Alcoholic fermentation
2. Lactic acid fermentation

34. b. Alcoholic fermentation
1. Pyruvic acid is converted to carbon dioxide and alcohol
2. Equation:
pyruvic acid + NADH
alcohol + CO2 + NAD+

35. 3. Used to make bread (yeast), wine, beer, ethanol

36. c. Lactic acid fermentation
1. Pyruvic acid is converted to lactic acid
2. Equation:
pyruvic acid + NADH
lactic acid + NAD+

37. Occurs in animal cells
- after strenuous exercise, there is a shortage of oxygen going to the muscles
- a build-up of lactic acid causes muscle fatigue and soreness