Differentiate between:
(i) Respiration and Combustion
(ii) Aerobic and Anaerobic respiration.

Respiration

Combustion

1. Respiration being a biological process occurs in living cells.

1. Combustion is a non-biological process and hence it is non-cellular.

2. Respiration is the slow oxidation of organic substances (glucose) which results in stepwise release of energy.

2. Combustion is a rapid oxidation of a substrate (like coal) and results in the release of the energy abruptly.

3. The heat evolved during respiration is stepwise, hence it does not harm the cells and organelles.

3. The heat evolved during combustion is abrupt hence it raises the temperature which results in fire.

4. The heat energy evolved is either made available to the cells or is stored as chemical energy in the form of ATP.

4. The heat energy evolved is made use of at the time of evolution and is not stored.

5. Respiration reactions are catalysed by enzymes.

5. Enzymes are not used in combustion.

Aerobic respiration

Anaerobic respiration

1. Aerobic respiration takes place in the presence of oxygen.

1. It takes place in the absence of oxygen.

2. In aerobic respiration complete oxidation of glucose takes place.

2. In anaerobic respiration the glucose molecule is incompletely broken down.

3. End products of aerobic respiration are CO₂, water and energy.

3. End product of anaerobic respiration are ethyl alcohol (or lactic acid) CO₂ and a little energy.

4. Large amount of energy is released i.e., 38 molecules of A.T.P. per glucose molecule.

4. Small amount of energy is released i.e., 2 A.T.P. molecules per glucose molecule.

5. First step of aerobic respiration (glycolysis) takes place in cytoplasm while second (Kreb’s cycle) and third (Electron transport chain) steps take place in mitochondria.

5. Complete anaerobic respiration occurs in cytoplasm.