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

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

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

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

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

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)

Adenosine Bonds broken to release energy

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

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

ATP Energy for cell Food energy ADP

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

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

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

Photosynthetic pigments 1. Chlorophyll: primary pigment; appears green

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

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

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

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

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

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

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

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

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

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

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

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 2 molecules of pyruvic acid (3 carbons)

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

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

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

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 32 ATP

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

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

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

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

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

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