Importance of step-wise release of energy :
Step-wise oxidation of food in cells is advantageous in following ways :
I. Due to step-wise release of chemical bond energy, a maximum proportion of it is used in the synthesis of ATP molecules.
2. Temperature of cell does not rise as total energy is not produced at one time.
3. The rate of energy output can be controlled according to cells requirement by increasing or decreasing the action of the enzymes at different steps.
4. Intermediates of the pathway can be used for the synthesis of other biomolecules like amino acids.
Oxidative phosphorylation. It is the synthesis of ATP molecules from ADP and iP (inorganic phosphate) during aerobic respiration. ADP + i P + energy ----> ATP
The energy is evolved during electron transport chain and H+ shift from the outer chamber of mitochondria into inner chamber through F0-F1 particles. When electron is passing through F1 particle or head of oxysome then its energy is taken by ADP + iP to form ATP. Therefore oxysome acts as ATPase.
When one molecule of NADH is oxidized then 3 ATP molecules are produced. When one molecule of FADH2 in oxidized, 2 ATP molecule are produced.
In eucaryotic cells, one molecule of glucose on oxidation produces 36 ATP molecules.
During aerobic oxidation in prokaryotic cell, of one glucose molecule 38 ATP molecules are produced. ATP’s are the energy currency of the cell.
Distinguish between the following :
(a) Aerobic respiration and anaerobic respiration.
May or may not be released.
Provides less energy.
Yeasts, parasites, anaerobic bacteria.
Provides more energy.
Most of the plants and animals.
Citric acid cycle or Krebs’ cycle
1. It occurs in cytoplasm.
2. It is a straight pathway.
3. Glycolysis is the first step of respiration.
4. In glycolysis glucose is broken down to pyruvate.
5. It occurs in aerobic and anaerobic modes of respiration.
6. It degades a molecule of glucose into two molecules of an organic substance,
8. No carbon dioxide is evolved in glycolysis.
9. It is not connected with oxidative phosphorylation
1. it occurs inside mitochondria.
2. It is a cyclic pathway.
3. Citric cycle is the second step in respiration.
4. In this, acetyl group is broken down completely.
5. It occurs only in aerobic respiration.
6. It degrades acetyl CoA completely into C02+ H20.
7. The net gain of energy is equal to 24 molecules of ATP.
8. Carbon dioxide is evolved in citric acid cycle.
9. Citric acid cycle is connected with oxidative phosphorylation.
1.In glycolysis, starting material is glucose.
2. End product is pyruvate.
3. Two ATP molecules are formed from one glucose molecule.
4. Two NADP molecules are produced in glycolysis.
5. It is a complicated process.
6. It is common to aerboic and anaerobic respiration.
1. In fermentation starting material is pyruvic acid.
2. End product is ethyl alcohol and C02.
3. No ATP molecules are formed.
4. NADH is consumed in fermentation.
5. It is a simple process.
6. It is the second step in the anaerobic respiration.