Correct Option
The correct option is (b) 2 only.
Explanation
Cellular respiration is a vital biochemical process occurring in the cells of organisms. It involves the enzymatic breakdown of glucose to release energy, which is trapped in the form of ATP (Adenosine Triphosphate) for use in various cellular activities.
Statement-wise Analysis
- Statement 1 is Incorrect. Cellular respiration is a catabolic process involving the breakdown of food sources (like glucose) to release energy. The process of synthesizing food using energy is called photosynthesis (an anabolic process), which occurs in plants and certain bacteria.
- Statement 2 is Correct. Cellular respiration takes place in the cells of all living organisms, including plants, animals, and microorganisms. It is essential for maintaining life as it provides the energy required for all metabolic activities.
- Statement 3 is Incorrect. The breakdown of food does not always occur in the absence of oxygen. Respiration is classified based on oxygen requirement:
- Aerobic Respiration: Occurs in the presence of oxygen, leading to the complete breakdown of glucose into carbon dioxide and water.
- Anaerobic Respiration: Occurs in the absence of oxygen, leading to partial breakdown (e.g., fermentation in yeast or lactic acid formation in muscles).
Key Takeaway
Cellular respiration is the energy-releasing breakdown of glucose that occurs in all living cells. It is distinct from photosynthesis (food synthesis) and can occur either aerobically (with oxygen) or anaerobically (without oxygen).