unit 2 KA2 - cellular respiration

Question 1

what is glycolysis? describe the two stages.

Answer 1

glycolysis is the breakdown of glucose to pyruvate in the cytoplasm. stage one is energy investment and stage two is energy pay off. it does not require oxygen.
energy investment:
- 2 ATP are used up, breaking down into ADP and Pi.
- the first phosphate from the breakdown of ATP is added onto glucose to form intermediate compounds. - this is the first phosphorylation.
energy pay off:
- reactions which follow generate four ATP molecules which results in a net gain of 2 ATP.
- the second phosphorylation occurs which is where the other phosphate is added to the intermediates to form pyruvate.

Question 2

when is pyruvate broken down to an acetyl group

Answer 2

in aerobic conditions

Question 3

describe the citric acid cycle

Answer 3

• pyruvate broken down into an acetyl group
• acetyl combines with coenzyme A to form acetyle coenzyme A
• acetyl from acetyl coA combines with oxaloacetate to form citrate.
• during a series of enzyme controlled steps, citrate is gradually converted back into oxaloacetate
• results in the generation of ATP and release of carbon dioxide.
• occurs in the matrix of the mitochondria.

Question 4

what is the role of dehydrogenase enzymes and NAD in cellular respiration?

Answer 4

the dehydrogenase enzymes remove hydrogen ions and electrons and pass them to the coenzyme NAD, forming NADH. this occurs in both glycolysis and the citric acid cycle. the hydrogen ions and electrons from the NADH are passed to the electron transport chain on the inner mitochondrial membrane.

Question 5

describe the electron transport chain

Answer 5

the electron transport chain is a series of carrier proteins attached to the innter mitochondiral membrane.

• electrons are passed along the electron transport chain releasing energy
• this energy allows hydrogen ions to be pumpued across the inner mitochondrial membrane. the flow of these ions back through the membrane protein ATP synthase results in the production of ATP.
• the hydrogen ions and electrons combine with oxygen to form water.

Question 6

what is the role of ATP

Answer 6

ATP is used to transfer energy to cellular processes which require energy

Question 7

what is fermentation

Answer 7

in the absence of oxygen, fermentation takes place in the cytoplasm. it results in much less ATP being produced than in aerobic respiration

Question 8

describe fermentation in animal cells

Answer 8

in animal cells, pyruvate is converted to lactate in a REVERSIBLE reaction.

Question 9

describe fermentation in plant and yeast cells

Answer 9

in plant and yeast cells, ethanol and CO2 are produced in an IRREVERSIBLE REACTION