(i) Phosphorylation - Hexokinase, Phospho fructokinase and glyceraldehyde - 3 phosphate dehydrogenase
(ii) De-Phosphorylation - Phospho glycerate Kinase and Pyruvate Kinase

	Alcoholic fermentation	Lactic acid fermentation
1	It providuces alcohol and releases CO2 from pyruvic acid.	It produces lactic acid and does not release CO2 from pyruvic acid.
2	It takes place in two steps	It takes place in single step.
3	It involves two enzymes, pyruvate decarboxylase with Mg++ and alcohol dehydrogenase.	It uses one enzyme, lactate dehydrogenase with Zn++.
4	It forms acetaldehyde as intermediate compound.	Does not form any intermediate compound.
5	It commonly occurs in yeast.	Occurs in bacteria, some fungi and vertebrate muscles.

Experiment to demonstrate the production of CO₂ in aerobic respiration:
1) Take small quantity of any seed (groundnut or bean seeds) and allow them to germinate by imbibing them. While they are germinating place them in a conical flask. A small glass tube containing 4 ml of freshly prepared. Potassium hydroxide (KOH) solution is hung into the conical flask with the help of a thread and tightly close the one holed cork (Figure).
2) Take a bent glass tube, the shorter end of which is inserted into the conical flask through the hole in the cork, while the longer end is dipped in a beaker containing water. Observe the position of initial water level in bent glass tube.
3) This experimental setup is kept for two hours and the seeds are allowed to germinate. After two hours, the level of water rises in the glass tube. It is because, the CO₂ evolved during aerobic respiration by germinating seeds will be absorbed by KOH solution and the level of water will rise in the glass tube.
CO₂+2KOH⟶K₂CO₃+H₂O

4)In the case of ground nut or bean seeds, the rise , of water is relatively lesser because these seeds use fat and proteins as respiratory substrate and release a very small amount of CO₂, But in the case of wheat grains, the rise in water level is greater because they use carbohydrate as respiratory substrate. When carbohydrates are used as substrate, equal amounts of CO₂ and O₂ are evolved and consumed.

Demonstration of alcoholic fermentation:
1) Take a Kuhne's fermentation tube which consists of an upright glass tube with side bulb. Pour 10% sugar solution mixed with baker's yeast into the fermentation tube so that it is filled and plug the mouth with cotton. After some time, the glucose solution will be fermented.
2) The solution will give out an alcoholic smell and level of solution in glass column will fall due to the accumulation of CO₂ gas.

3) It is due to the presence of zymase enzyme in yeast which converts the glucose solution into alcohol and CO₂. Now introduce a pellet of KOH into the tube, the KOH will absorb CO₂ and the level of solution will rise in upright tube.

Significance of Krebs cycle:
1) TCA cycle is to provide energy in the form of ATP for metabolism in plants.
2) It provides carbon skeleton or raw material for various anabolic processes.
3) Many intermediates of TCA cycle are further metabolized to produce amino acids, proteins and nucleic acids.
4) Succinyl CoA is raw material for formation of chlorophylls, cytochrome, phytochrome and other pyrrole substances.
5) a-ketoglutarate and oxaloacetate undergo reductive amination and produce amino acids.
6) It acts as metabolic sink which plays a central role in intermediary metabolism.

Industrial uses of alcoholic fermentation:
1) In bakeries, it is used for preparing bread, cakes, biscuits.
2) In beverage industries for preparing wine and alcoholic drinks.
3) In producing vinegar and in tanning, curing of leather.
4) Ethanol is used to make gasohol (a fuel that is used for cars in Brazil).

A plant or tissue transferred from water to salt solution will increase the rate of respiration. It is called salt respiration.

Kuhne's fermentation tube experiment demonstrates the process of alcoholic fermentation.

1) RQ value indicates which type of respiration occurs in living cells, either aerobic or anaerobic.
2) It also helps to know which type of respiratory substrate is involved.