Major Concepts to Review for AP Biology

Cell Respiration


Cell respiration involves 3 processes

Glycolysis (anaerobic) ------makes 2 ATP's

Fermentation (anaerobic)----returns NAD for use in glycolysis.

Citric Acid cycle -------------uses oxygen to complete oxidation of glucose and make 34 ATP's (includes the electron transport chain and the ATP synthase as part of the F0F1 complex



  • uses 2 ATP's
  • makes 4 ATP's (net of 2 ATP molecules)
  • converts glucose into 2 pyruvates
  • makes NADH (necessary for electron transport or for fermentation)
  • is anaerobic and occurs in the cytoplasm
  • is found in all living things


Citric acid cycle:

  • begins when acetyl-CoA combines with a 4-carbon molecule resident within the citric acid cycle (acetyl group + oxaloacetic acid = citric acid)
  • oxidizes "food" molecules to produce electrons and Hydrogen ions
  • generates per cycle or one pyruvate the following

2 CO2


double each per 1 glucose molecule



  • sends the electrons to the electron transport chain in the inner membrane of the mitochondria.


Electron Transport Chain

  • uses electrons from oxidation of food molecules
  • uses proton pumps to generate proton gradient
  • oxygen acts as the final electron acceptor and is reduced to water


Muscles and Energy

  • Muscles have lots of mitochondria and need and use lots of ATP
  • If ATP is used up they can continue because creatine phosphate is a second energy source
  • glycolysis can supply quick energy and
  • lactate fermentation recycles needed NAD from NADH creating a oxygen debt.
  • Being "in shape" decreases the time necessary to pay off an oxygen debt because of:
    • enlarged lung capacity
    • heart has greater stroke volume
    • more blood cells increases oxygen carring capacity
    • greater muscle mass and improved vascularization (more capillaries)


Fats and proteins can be used as alternate fuels - hydrolysis and other metabolic steps can turn most molecules into pyruvate or acetyl-CoA

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