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  1. What are phospholipids composed of?
  2. In isomerization reactions, the reactants and the products have the same ________ but different ________.
  3. Why is FADH2 produced at one step in the citric acid cycle?
  4. How are ATP and ADP molecules different?
  5. What is the final product of the electron transport chain in cellular respiration?
  6. Account for the 36 ATP produced during cellular respiration.
  7. Explain why 36 ATP are produced under ideal conditions.
  8. Explain why it is essential that muscle cells, during anaerobic respiration, convert pyruvate into lactic acid, even though the cell obtains very little energy in this process and the accumulation of lactic acid causes muscle fatigue and pain.


  1. Phospholipids are composed of glycerol backbone, phosphorylated alcohol, and fatty acids.
  2. ...the same chemical formula but different formation.
  3. Because that stem does not release quite enough energy to reduce NADH.
  4. ADP has less stored energy.
  5. A molecule of water.

  6. The following chart accounts for the 36 ATP in cellular respiration:

Number of ATP Produced



2 NADH x3


=4 (-2 from moving into mitochondria)

Oxidation of Pyruvate

2 NADH x3 =6

Citric Acid Cycle

6 NADH x3

2 FADH2 x2






  1. ATP will leave depending on the conditions of the cell.  If there isn't enough oxygen, the cell changes to aerobic respiration, sometimes our body will produce more ATP because of more energy needed by our bodies, some ATP is used towards other parts of our bodies and performed in other life functions like going to form fats and proteins.
  2. It is essential that muscle cells during anaerobic respiration, convert pyruvate to lactic acid incase there isn't any more oxygen produced.  When there isn't oxygen present, NADH can't be recycled, therefore glycolysis can't continue.  In order to produce energy, our bodies need to rely on another system.  The lactic acid system, which doesn't require oxygen, can still produce energy.