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What do you think of when you
hear “respiration”?
Cellular Respiration
Probably breathing!
Date: ____________
But that’s not exactly correct…
Cellular Respiration
• Purpose: convert sugar (chemical energy)
into ATP (different chemical energy)
– ATP is then used to fuel cellular metabolic
processes
• ANY food (organic) molecule or nutrient can
be used as a source of energy for ATP
– Most common are CARBOHYDRATES
– Nutrients + oxygen  water + carbon dioxide +
energy (ATP)
Cellular Respiration Equation
C6H12O6 + 6O2  6CO2 +
6H2O
• Notice something?
• It’s a mirror image of
photosynthesis!
–6CO2 + 6H2O  C6H12O6 + 6O2
Mitochondria
Where does cellular
respiration occur?
• Site of cellular respiration
• Located in plant AND animal cells!
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Types of Cellular Respiration
• Aerobic cellular respiration
–Requires oxygen
• Anaerobic cellular respiration
–Occurs when no
oxygen is present
Aerobic Cellular Respiration
• 3 steps
–Glycolysis
–Krebs cycle
–Electron transport chain
Step One: Glycolysis
• Takes place in the cytoplasm
• Is actually an anaerobic process
–Does NOT require oxygen!
• Glucose is broken down into…
–2 pyruvic acid molecules
–2 ATP molecules
Step Three: Electron
Transport Chain
• Takes place in the mitochondria
• Aerobic process – REQUIRES OXYGEN!
• Most ATP is formed during this part of the cycle
– 32 – 34 ATP molecules are made
• The whole purpose of breathing oxygen is to
form water at the very end of this process!
Oxygen is called the final electron acceptor in
this metabolic pathway.
• Water are released as a waste product
Step Two: Krebs Cycle
• Also called the citric acid cycle
• Takes place in the mitochondria
• Aerobic process – REQUIRES
OXYGEN!
• 2 pyruvic acid are converted into…
–Carbon dioxide
–2 ATP
Total Glucose Yield
• During aerobic cellular
respiration, ONE molecule of
glucose will make 34-36 ATP
molecules!
• ATP goes on to do
work in the cell
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Focus Questions
1.
2.
3.
4.
5.
6.
7.
8.
What is the purpose of cellular respiration?
What is the equation for cellular respiration?
Where does cell respiration occur?
What are the two types of respiration? How are
they different?
What are the three steps of aerobic cellular
respiration?
Where does each step occur?
Give a brief description of each step.
How much ATP do we get from one molecule of
glucose?
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