The correct option is 1 and 2 only.
Explanation
Cellular respiration is the process by which organisms break down nutrients to release energy. Glycolysis is the foundational stage of this process, occurring in the cytoplasm, and involves the partial oxidation of glucose.
Statement-wise Analysis:
- Statement 1 is Correct: Obligate anaerobes are organisms that are unable to survive in the presence of oxygen. They rely strictly on anaerobic processes for energy production. Examples include bacteria such as Clostridium botulinum.
- Statement 2 is Correct: Facultative anaerobes are organisms that can survive in both the presence and absence of oxygen. They perform aerobic respiration when oxygen is available but switch to anaerobic respiration (fermentation) when oxygen is depleted. Yeast is a classic example.
- Statement 3 is Incorrect: All living organisms retain the enzymatic machinery to partially oxidize glucose without the help of oxygen. This universal process is known as glycolysis. Therefore, organisms do possess the necessary enzymes for this anaerobic partial oxidation.
- Statement 4 is Incorrect: The breakdown of glucose to pyruvate is specifically termed Glycolysis (or the EMP pathway). Fermentation is the subsequent anaerobic process where pyruvate is converted into products like lactic acid or ethanol and carbon dioxide to regenerate NAD+.
Key Takeaway:
Glycolysis is a universal metabolic pathway occurring in the cytoplasm of all living organisms, involving the partial oxidation of glucose to pyruvate without the requirement of oxygen.