Question

Differentiate between:
(a) Respiration and Combustion 
(b) Glycolysis and Krebs’ cycle 
(c) Aerobic respiration and Fermentation

Answer 1

(a) Difference between Respiration and Combustion 

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Respiration	Combustion
It is a slow, enzyme-controlled process.	It is a rapid and uncontrolled process.
Occurs in living cells.	Occurs outside living systems.
Energy is released in a stepwise manner.	Energy is released suddenly as heat and light.
Does not produce flame.	Usually produces flame.

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(b) Difference between Glycolysis and Krebs’ Cycle

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Glycolysis	Krebs’ Cycle
Occurs in the cytoplasm of the cell.	Occurs in the mitochondrial matrix.
Glucose is broken down into pyruvate.	Acetyl-CoA is completely oxidised to CO2.
Does not require oxygen directly.	Operates only under aerobic conditions.
Produces a small amount of ATP.	Produces reduced coenzymes (NADH, FADH2) for ATP synthesis.

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(c) Difference between Aerobic Respiration and Fermentation 

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Aerobic Respiration	Fermentation
Takes place in the presence of oxygen.	Takes place in the absence of oxygen.
Complete oxidation of glucose occurs.	Incomplete oxidation of glucose occurs.
End products are CO2 and H2O.	End products are ethanol and CO2 or lactic acid.
Large amount of energy (ATP) is released.	Very small amount of energy is released.

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Conclusion:

These differences highlight how biological processes vary in their mechanisms, energy yield, and dependence on oxygen.