Fun for all eukaryotic organisms….

Cell Respiration

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• Cell respiration (C.R.) occurs in the mitochondria.

• It occurs in ALL eukaryotic cells.

• The purpose is to use glucose to make 36 ATP molecules.

Background

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• C6H1206 + 6 O2 6 CO2 + 6 H20 + 36ATP

• Hmmmm…does this look familiar?

• What are the reactants?

• What are the products?

Equation for Cell Respiration

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• Where does it occur?– In the cytoplasm of the cell

• Does it need oxygen?– No! This part of C.R. is “anaerobic”

• An- = without• -aerobic = oxygen

• What happens?– Glucose is broken in half to create 2 pyruvic acid

molecules.– 4 ATP are produced, but 2 are used in the process of

glycolysis, leaving a net gain of 2 ATP.

1. Glycolysis:

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• Where does it occur?– In the mitochondria

• Does it require oxygen?– YES!!! (It is an aerobic process)

• What happens?– The pyruvic acids (produced in glycolysis) are

broken down and CO2 is released was waste– Result: 2 ATP are produced.

2. Krebs Cycle

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– Where does it occur?• In the mitochondria

– Does it need oxygen?• YES!!! (It is an aerobic process)

– What happens?• In glycolysis and the Krebs cycle, high energy

electrons were produced. These electrons are used to make 32 ATP molecules.

3. Electron Transport Chain

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• Glycolysis: 2 ATP molecules

• Krebs Cycle: 2 ATP molecules

• Electron Transport Chain: 32 ATP molecules

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So, where do the 36 ATP molecules come from??

• Then “Lactic Acid Fermentation” occurs.– After glycolysis, if there is a lack of O2 (perhaps due to

increased exercise), the pyruvic acid cannot enter the Krebs Cycle.

– Instead, the pyruvic acids are changed into lactic acid, which when used by your cells gives 2 ATP.

– Problem: lactic acid is poison for the cells, which you feel as “burning” when you exercise.

– You cannot continue for long with this burning, so typically, you slow down and breathe more to get oxygen.

What happens if there is a lack of oxygen?

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• Alcohol Fermentation:– Occurs in yeast when making bread and beer.– Yeast produces alcohol as a waste product when

there is low oxygen levels.• Yes, THAT kind of alcohol.

– THIS DOES NOT HAPPEN IN YOUR CELLS!• If it did, people would exercise to get drunk.

– All of our students who skip class would be at the track running laps!

Another fermentation…not in your cells.

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Lets review:Comparison Photosynthesis Cell Respiration

Function:

Location:

Equation: 6 CO2 + 6 H20 + light C6H12O6 + 6 O2

C6H1206 + 6 O2 6 CO2 + 6 H20 + 36ATP

Reactants:

Products:

Glucose production

Energy (ATP) Production

Chloroplasts Mitochondria

CO2; H20; light Glucose & O2

Glucose & O2CO2; H20; 36 ATP

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