Study Guides/Biology/Cellular Respiration Class 10
Study Guide · Biology

Cellular Respiration

Cellular respiration is a fundamental biochemical process where living cells break down glucose (food) to release energy. This energy is stored in the form of ATP (Adenosine Triphosphate) molecules. In Class 10 Biology under the chapter Life Processes, we study how respiration occurs in different organisms and the pathways through which glucose is broken down.

Question (Click to Flip)

Why is ATP called the energy currency of the cell?

Answer

ATP stores the energy released during respiration. When the cell needs energy to perform any activity, ATP is broken down to release a fixed amount of energy, acting like a currency.

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Key Facts

Respiration is an exothermic and biochemical process.

ATP is the energy currency of the cell.

Aerobic respiration produces 38 ATP per glucose molecule.

Anaerobic respiration produces only 2 ATP per glucose molecule.

Muscle cramps occur due to the accumulation of lactic acid during anaerobic respiration.

1. What is Cellular Respiration?

Cellular respiration is the process of oxidizing food molecules, like glucose, to carbon dioxide and water. The energy released is trapped in the form of ATP for use by all the energy-consuming activities of the cell. It takes place in the cytoplasm and mitochondria of the cells.

2. Types of Respiration

  • Aerobic Respiration: Takes place in the presence of oxygen. It completely breaks down glucose into carbon dioxide and water, releasing a large amount of energy (38 ATP). It occurs in the mitochondria.
  • Anaerobic Respiration: Takes place in the absence of oxygen. It partially breaks down glucose into lactic acid (in muscle cells) or ethanol and carbon dioxide (in yeast), releasing much less energy (2 ATP). It occurs in the cytoplasm.

3. Breakdown of Glucose by Various Pathways

The first step is the breakdown of a 6-carbon glucose molecule into a 3-carbon molecule called pyruvate. This happens in the cytoplasm. Further breakdown depends on oxygen:

  • Absence of Oxygen (in yeast): Pyruvate converts to ethanol + carbon dioxide + energy (fermentation).
  • Lack of Oxygen (in muscle cells): Pyruvate converts to lactic acid + energy (causes muscle cramps).
  • Presence of Oxygen (in mitochondria): Pyruvate breaks down completely into carbon dioxide + water + much energy.

Questions and Answers

Why is ATP called the energy currency of the cell?+

ATP stores the energy released during respiration. When the cell needs energy to perform any activity, ATP is broken down to release a fixed amount of energy, acting like a currency.

Why do we get muscle cramps after heavy exercise?+

During heavy exercise, there is a lack of oxygen in our muscle cells. Anaerobic respiration takes place, breaking down pyruvate into lactic acid. The accumulation of lactic acid causes muscle cramps.

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