3.7: Cell respiration Flashcards

1
Q

Define cell respiration

A

Cell respiration is the controlled release of energy from organic compounds in cells to form ATP.

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2
Q

State that, in cell respiration, glucose in the cytoplasm is broken down by glycolysis into pyruvate, with a small yield (2) of ATP.

A

In cell respiration, glucose in the cytoplasm is broken down by glycolysis into pyruvate with small yield of ATP.

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3
Q

Explain that, during anaerobic cell respiration, pyruvate can be converted in the cytoplasm into lactate, or ethanol and carbon dioxide, with no further yield of ATP.

A

Anaerobic respiration occurs in the absence of a ready supply of oxygen (e.g. during intense physical activity, when oxygen reserves are depleted).

  • In order to generate the small amounts of energy provided by glycolysis, the end product (pyruvate) must be converted into another substance before more glucose can be used
  • This is because the conversion of pyruvate replenishes the levels of the hydrogen acceptor (NAD+) needed for glycolysis to occur

The conversion of pyruvate occurs in the cytoplasm of the cell and the products are:
+ Lactate (3C) in animal cells
+ Ethanol (2C) and carbon dioxide (CO2) in plants, fungi (e.g. yeast) and bacteria
+ The conversion of pyruvate into ethanol and CO2 is also known as fermentation

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4
Q

Explain that, during aerobic cell respiration, pyruvate can be broken down in the mitonchondrion into carbon dioxide and water with a large yield of ATP.

A

Aerobic respiration occurs in the presence of oxygen and takes place in the mitochondrion.

  • Pyruvate is broken down into carbon dioxide and water and a large amount of ATP is formed (34 - 36 molecules)
  • Although this process begins with glycolysis (to break down glucose into pyruvate), glycolysis does not require oxygen and is an anaerobic process.
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