Cell Biology - Respiration T3

Question 1

Respiration

Answer 1

Respiration is the process by which plant and animal cells release the chemical energy stored in glucose (the respiratory substrate). Respiration is a series of reactions that are controlled by enzymes.
Aerobic respiration is the release of energy from glucose in the presence of oxygen. It can be summarised by the word equation:

GLUCOSE + OXYGEN ——> CARBON DIOXIDE + WATER + ENERGY

Question 2

ATP

Answer 2

ATP (adenosine triphosphate) is formed when ADP (adenosine diphosphate) and an inorganic phosphate (Pi) are joined together by a chemical bond. This bonds acts like an energy store and when the energy is required the bond is broken to release it.

Question 3

Storage of ATP

Answer 3

It is not necessary for organisms to store large quantities of ATP as it is continually generated (it is built up at the same time as it broken down).

Question 4

First stage of aerobic respiration

Answer 4

The first stage of aerobic respiration takes place in the cytoplasm of the cell and it splits one glucose molecule into two pyruvate molecules. 2 ATP molecules are also produced during this stage.

Question 5

Second Stage of aerobic respiration

Answer 5

The second stage of aerobic respiration takes place in the mitochondria of the cell and the pyruvate from stage one is broken down to produce carbon dioxide and water.

Question 6

Fermentation

Answer 6

There will be times when oxygen is absent or in short supply and when this happens fermentation (respiration without oxygen) will occur. Unlike aerobic respiration that has the same end products in both animal and plant cells, the end products in each type of cell are different in the absence of oxygen. The glucose is broken down into pyruvate in the cytoplasm with 2 ATP produced as happened in aerobic respiration. However, in the absence of oxygen fermentation does not move into the mitochondria and is completed in the cytoplasm.