Lactic Acid Fermentation on Muscle Cells

What is lactic acid fermentation in muscle cells?

• Breakdown of glucose only in mitochondria

• Partial breakdown of glucose into lactic acid and energy

• Complete breakdown of glucose with oxygen

• Conversion of lactic acid to ethanol

Answer explanation

Occurs in cytoplasm when muscles lack oxygen.

Why do muscles switch to lactic acid fermentation during intense exercise?

• To generate water quickly

• Oxygen supply is insufficient to meet ATP demand

• To produce more CO₂

• Because mitochondria are inactivated

Answer explanation

This provides quick ATP when O₂ limited.

What is the typical ATP yield per glucose via lactic fermentation in muscle cells?

• ~0 ATP

• ~2 ATP

• ~150 ATP

• ~38 ATP

Answer explanation

Fermentation yields only 2 ATP per glucose.

What causes muscle cramps during heavy exercise?

• Oxygen surplus

• Accumulation of lactic acid

• Ethanol buildup in muscles

• CO₂ shortage

Answer explanation

Lactic acid buildup leads to fatigue and cramps.

What is oxygen debt?

• Oxygen lost through exhalation

• Oxygen stored in muscles

• Extra oxygen needed to oxidise lactic acid after exercise

• Oxygen needed to start glycolysis

Answer explanation

O₂ debt repays lactic acid oxidation post-exercise.

Where does lactic acid fermentation occur in muscle cells?

• Nucleus

• Cytoplasm

• Cell membrane

• Mitochondria

Answer explanation

It occurs in the cytoplasm outside mitochondria.

What happens to accumulated lactic acid post-exercise?

• Converted to ethanol in muscles

• Transformed into glucose in muscles

• Oxidised to CO₂ and H₂O using extra oxygen

• Remains and causes permanent damage

Answer explanation

O₂ debt allows lactic acid to be broken down later.