Fermentation and Factors Affecting Cell Respiration

(2) Lactic acid fermentation: It occurs during curd formation. 

(3) Acetic acid fermentation: This is aerobic fermentation 

(4) Butyric acid fermentation:

In rancid butter, butyric acid fermentation takes place. Also in jute fiber.     


Other example are curring of tea, tanning of leather, retting of fibers, processing of Tobacco 

• Resouratory Quotient (R.Q.)

The ratio of the volume of CO₂ released to the volume of O₂ taken in respiration is called RQ.

Value of RQ depends upon the type of respiratory substrate used & measured by Ganong's respirometer.

1. Carbohydrates: R.O. = 1

C₆H₁₂O₆ + 6O₂ + 6H₂O ® 6CO₂ + 12H₂O + E

2. Fat/Oil: RQ = 0.70 or R.Q. < 1

2C₅₁H₉₈O₆ + 145O₂ ® 102 CO₂ + 98 H₂O + E

Fatty seeds germination-castor, RQ. < 1

At the time of formation of fatty seeds, (maturing fatty seed) RQ. is more than 1 because more CO₂ is released than 02 consumed.

3. Organic acids: (In succulent xerophytes at day time)

Malic acid:

C₄-H₆O₅ + 3O₂ → 4CO₂ + 3H₂O + Energy

Oxalic acid R.Q. = 4

Citric acid RQ. = 1.3

4. Incomplete oxidation of carbohydrates:

In CAM plants during night: RQ. = 0

2C₆H₁₂O₆  + 3O₂ → 3C₄H₆O₅ + 3H₂O + Energy

5. Protein: R.Q. = 0.8 or 0.9 or < 1

6. Anaerobic respiration: RQ = ¥

• Factors Effecting Cell Respiration

1. Temperature:

Optimum temp for respiration is between 20-35°C

Maximum temp. is around 45°C

At low temp respiration is low due to inactivation of enzymes {Freeze preserve the food) while at very high temp. decreases. as enzyme get denatured.

Q₁₀ = 2 to 3 for respiration.

Production of potato crop is high on the hill areas due to low temp throughout year.

CRPI (Central. potato Research Institute is situated at Kufri-Shimla (H.P.)

2. Oxygen:

The inhibition of anaerobic respiration by O₂ concentration is called as Pasteur's effect.

The minimum amount of oxygen, at which aerobic respiration takes place & anaerobic respiration become extinct is called as extinction point.

Oxygen concentration at which both aerobic & anaerobic respiration take place Simultaneously is called as transition point.

3. CO₂: If CO₂ concentration increases, then rate of respiration decreases in plants, (because stomata get closed).

4. Salts: If a plant is transferred from water to salt solution, it's respiration increases, this is known as salt respiration. Because absorption of ions requires metabolic energy.

5. Hormones:

IAA, GA & cytokinin Increase the respiration rate. The rapid increase in rate of respiration during ripening of fruits and senescence of leaves and plant organs is called as "Climacteric respiration". This rate is decrease after sometime.

It is due to production of ethylene hormone:

6. Light: Rate of respiration increases with increase in light intensity.

Light controls the stomatal opening & influence on temp and also produce respiratory substrates.

7. Injury, disease & wounds: The respiration increases due to injury wounding & infection.

8. Inhibitors: CN, azides. DNP (Dinitrophenol), CO, rotenone, antimycin, amytal, etc inhibit the respiration.

9. Age: Rate of respiration is more in young cells.

Rate of respiration at meristem apex is high.

10. Water: Seeds are slow respiring part of plants, because dry seeds are deficient of H₂O.  

Note:

Difference Between Glycolysis and Kreb's Cycle

Nicotinamide adenine dinucleotide phosphate/ Nicotinamide adenine dinucleotide (NADP/ NAD): It is called universal hydrogen acceptor, produced during aerobic respiration (glycolysis + Krebs cycle) and also in anaerobic respiration, work as coenzyme in ATP generation Via electron transport system. NADP have one additional phosphate.

NAD plays a crucial role in dehydrogenation processes. Some dehydrogenases do not work with NAD, but react with NADP (Nicotinamide adenine dinucleotide phosphate). Formerly called Coenzyme II or Triphosphopyddine nucleotide = TPN Nicotinamide is a vitamin of B group.

First NAD and NADP both functions as hydrogen acceptors. Later H ions and electrons (e^-) from these are transported through a chain of carriers and after being released at the end of a chain react with O₂ and from H₂O (see Electron Transport chain). During the release of 2 electron from 2H⁺ atoms from NAD. 2H and their reaction with O₂ to form water, 3 ATP molecules are synthesized. 

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