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What is the step-by-step process of respiration?

Verified Answer

Respiration is a multi-stage biochemical process in which glucose is broken down to release energy in the form of ATP. It occurs in three main stages: glycolysis, Krebs cycle, and electron transport chain.

Step-by-step process of respiration:

1. Glycolysis (in cytoplasm)

  • Glucose (6-carbon) is split into two molecules of pyruvate (3-carbon each).

  • A small amount of energy (ATP) and NADH is produced.

  • Does not require oxygen (can occur in both aerobic and anaerobic conditions).

2. Link reaction (transition step)

  • Pyruvate enters mitochondria and is converted into acetyl-CoA.

  • Carbon dioxide is released and NADH is formed.

3. Krebs cycle (Citric Acid Cycle – in mitochondria)

  • Acetyl-CoA is completely broken down.

  • Produces:

    • Carbon dioxide (CO₂)

    • NADH and FADH₂ (electron carriers)

    • A small amount of ATP

4. Electron Transport Chain (ETC – inner mitochondrial membrane)

  • NADH and FADH₂ donate electrons.

  • Energy released is used to produce a large amount of ATP.

  • Oxygen acts as the final electron acceptor and forms water.

Total outcome (aerobic respiration):

  • High ATP production

  • CO₂ and H₂O as by-products

In anaerobic conditions:

  • Only glycolysis occurs

  • Pyruvate is converted into lactic acid (in muscles) or alcohol (in yeast)

  • Much less ATP is produced

In simple terms: Respiration breaks glucose step by step—first in cytoplasm, then in mitochondria—to release energy stored as ATP.