3.2 Respiration

Basic Process

  • Living organisms obtain energy from organic substances (like glucose).
  • Involves breakdown of food molecules to release energy.
  • Occurs continuously in all living cells.
  • Word Equation: Glucose + Oxygen → Carbon Dioxide + Water + Energy

Respiration as an Energy-Releasing Process

  • Exothermic Process: Releases energy, captured as ATP (Adenosine Triphosphate).
  • Importance: Vital for growth, movement, reproduction, and maintaining body temperature.

Respiration in Plants

  • Plants also respire, taking in oxygen and releasing carbon dioxide, just like animals. Respiration in plants can be of two types:

1. Aerobic Respiration

  • Basic Concept: Occurs in the presence of oxygen.
  • Process: Complete breakdown of glucose into CO₂ and water.
  • Energy Release: Large amount of energy.
  • Equation: Glucose + Oxygen → Carbon Dioxide + Water + Energy (large amount)

Respiration in Plants (Continued)

2. Anaerobic Respiration

  • Basic Concept: Occurs in the absence or limited supply of oxygen.
  • Process: Incomplete breakdown of glucose.
  • Energy Release: Smaller amount of energy.
  • In Plants/Yeast: Alcoholic Fermentation.
  • Equation: Glucose → Ethanol + Carbon Dioxide + Energy (small amount)

Respiration and Photosynthesis in Plants

Feature Photosynthesis Respiration
Process Anabolic (builds up food) Catabolic (breaks down food)
Energy Stores light energy as chemical energy Releases chemical energy from food
Reactants Carbon dioxide, Water Glucose, Oxygen
Products Glucose, Oxygen Carbon dioxide, Water, Energy
Occurrence Only in cells with chlorophyll (e.g., leaves) In all living cells of the plant
Time Occurs during daytime (in presence of light) Occurs continuously (day and night)
Gas Exchange Takes in CO₂, releases O₂ Takes in O₂, releases CO₂