Cellular Respiration

Making Energy for the Cell

Energy

• ALL organisms use energy!
• Unicellular, multicellular, prokaryotic, eukaryotic, plants, animals, protists, bacteria, fungi
• ALL
• Different organisms get their energy in different ways.
• Producers produce is (through photosynthesis).
• Consumers consume it.

Energy

• The form of energy that we get by making it (producers) or eating it (consumers) is not useable to our cells.
• Where does photosynthesis take place?
• Chloroplast
• What organelle produces energy for all eukaryotic cells?
• Mitochondria

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Energy

• Cellular respiration is the process that creates energy that the cell can use.
• What is the form of energy that the cell can use?
• ATP
• What kind of cells use energy?
• ALL!!
• What kind of cells undergo cellular respiration?
• ALL!!

The Equation

Recall the chemical formula for photosynthesis:

6 CO₂ + 6 H₂O + energy → C₆H₁₂O₆ + 6 O₂

Flip that sucker around and you’ve got the chemical formula for cellular respiration!

C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O + energy

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ATP

Glycolysis

• Series of reactions which break the 6-carbon glucose molecule down into two 3-carbon molecules called pyruvate.
• All organisms from simple bacteria to humans perform it the same way.
• Yields 2 ATP molecules for every one glucose molecule broken down.

• Next, the pyruvate will go down one of two paths, depending on if they have oxygen.
• No oxygen 🡪 anaerobic
• Oxygen 🡪 aerobic

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Anaerobic

• Some organisms live in environments with little or no oxygen
• Marshes, bogs, gut of animals, sewage treatment ponds
• No oxygen used = ‘an’aerobic
• Results in no more ATP. It’s done. It only gets 2 ATP.
• Single cell fungi do this (alcoholic fermentation) and we get beer, wine, bread.
• Our muscle cells do this (lactic acid fermentation) when we work out too fast without breathing.

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Aerobic

• Oxygen required=aerobic
• 2 more sets of reactions which occur in a specialized structure within the cell called the mitochondria
• 1. Kreb’s Cycle
• 2. Electron Transport Chain

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Kreb’s Cycle

• Completes the breakdown of glucose
• Takes the pyruvate (3-carbons) and breaks it down, the carbon and oxygen atoms end up in CO₂ and H₂O.
• Hydrogens and electrons are stripped and loaded onto NAD⁺ and FAD to produce NADH and FADH2
• Production of only 2 more ATP but loads up the coenzymes with H⁺ and electrons which move to the 3^rd stage

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Electron Transport Chain

• Electron carriers loaded with electrons and protons from the Kreb’s cycle move to this chain.
• Energy is released to form a total of 32 ATP.

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Aerobic vs. Anaerobic

• Glycolysis 2 ATP

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• Kreb’s 2 ATP

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• Electron Transport 32 ATP

36 ATP

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Glucose

Glycolysis

🡪 Pyruvate

Oxygen

No Oxygen

Aerobic

Fermentation

(Anaerobic)

Lactic Acid Fermentation

(muscles and some bacteria)

Alcoholic Fermentation (yeast)

Electron Transport Chain

Kreb’s Cycle

2 ATP

2 ATP

2 ATP

32 ATP