respiration and fermentation

Question 1

how do our cells release energy?

Answer 1

• the chemical stored in glucose must be released by all cells through a series of enzyme controlled reactions called respiration.
• the energy released from the breakdown of glucose is used to generate ATP
• the energy transferred by ATP can be used for cellular activities such as muscle cell contraction, cell division, protein synthesis and transmission of nerve impulses

Question 2

describe the first stage of respiration (break down of glucose into pyruvate)

Answer 2

the first stage of respiration occurs in the cytoplasm of a cell and does not need oxygen. Glucose is broken down into two molecules of pyruvate, releasing enough energy to yield two molecules of ATP.

Question 3

describe the second stage of respiration ( break down of pyruvate into carbon dioxide and water using oxygen)

Answer 3

if oxygen is present in the cell, aerobic respiration takes place. Each pyruvate molecule diffuses into a mitochondrion and is broken down completely to carbon dioxide and water, releasing enough energy to yield 36 ATP molecules.

during the complete aerobic breakdown of one molecule of glucose (stages 1 & 2 ) enough energy is released to produce 38 ATP molecules.

Question 4

where does aerobic respiration take place?

Answer 4

the mitochondria, cells that need a lot of energy have a large number of mitochondria eg sperm & muscle cells.

Question 5

what is fermentation?

Answer 5

in the absence of oxygen, the fermentation pathway takes place. During fermentation glucose is only partly broken down. Fermentation takes place in the cytoplasm of the cell.

Question 6

fermentation in animal cells.

Answer 6

In animals, the fermentation pathway occurs when no oxygen is available or when the oxygen supply runs out. The pyruvate molecules are converted into lactate. When pyruvate is converted into lactate this causes muscle fatigue.

Question 7

fermentation in plant & fungal cells

Answer 7

in plant and yeast cells, the fermentation pathway occurs when no oxygen is available. e.g when root hair cells become water logged. The pyruvate molecules are broken down/ converted into ethanol and carbon dioxide

Question 8

what is a respirometer?

Answer 8

A respirometer is a piece of apparatus which is used to measure the rate of respiration. A respirometer can measure the consumption of oxygen and some can also measure the production of carbon dioxide.