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Name: ______________________ Date: _______________ Period: _______
Chapter 5 Section 3
Cellular Respiration
How do we get energy?
• We all need energy to function and we get this energy from the food we
eat.
• Cellular respiration is the process by which chemical energy of “food”
molecules is released and captured as ATP.
• All types of food (carbohydrates, fats, and proteins) can be used as fuel
to produce ATP.
• However, glucose is most commonly used.
Cellular Respiration = Metabolism
• Metabolism is the sum of all chemical reactions that occur in the
organism.
During cell respiration, the breaking down of food contributes to
metabolism.
Cellular respiration in the presence of oxygen is known as aerobic
respiration.
3 Metabolic Processes of Aerobic Cellular Respiration
• 1. Glycolysis which occurs in the cytoplasm.
• 2. Krebs cycle/Citric cycle which occurs inside of the mitochondria.
• 3. Electron transport chain which occurs inside the mitochondria
membrane.
Glycolysis
• Literally means “sugar breakdown”.
• In glycolysis, the 6-carbon sugar, glucose is broken down into two 3carbon molecules called pyruvate.
• 2 ATP are used as activation energy for glycolysis.
• However, it produces 4 ATP and 2 NADH.
What is NADH?
• It helps produce energy!
• Acts like a spark plug in a cell.
Krebs/Citric Cycle
• Only occurs if O2 is present!
• The pyruvate from glycolysis will be used to generate a pool of
chemical energy which includes:
▫ 2 ATP
▫ 8 NADH
▫ 2 FADH2 - similar to NADH
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Electron Transport Chain
• The ETC allows the release of large amounts of chemical energy stored
in NADH and FADH2.
• The ETC produces up to 30 more ATP for the cell.
• Net gain of aerobic respiration 36-38 ATP!
If oxygen is not present, the Krebs cycle won’t function.
• When the cell lacks O2, fermentation (which is a type of anaerobic
respiration) recycles the NAD+ so the cell can make ATP!
Aerobic vs. Anaerobic Respiration
• The chemical energy stored in glucose generates far more ATP in
aerobic respiration (36-38 ATP) compared to anaerobic respiration (2
ATP)!
Two types of fermentation:
• Lactic acid – recycles NAD+, but produces lactic acid as a by-product.
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Bacteria, fungi and animals use this process!
Alcoholic – recycles NAD+, but produces alcohol as a by-product.
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All other organisms!
Especially yeast!