Question

Read the following statements:
i. In endogenous metabolism by aerobic bacteria, electron acceptor is present inside the cells.
ii. In endogenous metabolism by aerobic bacteria, electron acceptor is dissolved oxygen.
iii. The endogenous metabolism is linked to fermentative metabolism.
iv. In exogenous metabolism by aerobic bacteria, enzyme mediated electron transfer happens within the cells.
The correct choice is:

• A. (i) is correct; (iii) is correct
• B. (ii) is correct; (iii) is incorrect
• C. (iii) is incorrect; (iv) is incorrect
• D. (iii) is correct; (iv) is correct

Hint:

- Endogenous metabolism = cell consumes its own reserve using dissolved O$_2$.
- Exogenous metabolism = cell consumes external substrate.
- Fermentation is unrelated to endogenous metabolism in aerobes.

Answer 1

The Correct Option is B

Step 1: Recall definition of endogenous metabolism.
- Endogenous metabolism occurs when external substrate is absent. - Cells use their own stored material as an energy source. - In aerobic bacteria, the electron acceptor is dissolved oxygen from the environment, not inside the cells. Thus, statement (i) is incorrect, statement (ii) is correct.
Step 2: Check link with fermentation.
Fermentative metabolism occurs in the absence of oxygen. But endogenous metabolism in aerobic bacteria is linked to aerobic respiration using oxygen, not fermentation. So, statement (iii) is incorrect.
Step 3: Evaluate exogenous metabolism.
- Exogenous metabolism = when bacteria utilize external substrate (e.g., glucose). - The energy extraction involves enzyme-mediated electron transfer within the cells. So, statement (iv) is correct.
Step 4: Match with options.
- (ii) is correct. - (iii) is incorrect. Hence the correct choice is (B). Final Answer: \[ \boxed{\text{(B) (ii) is correct; (iii) is incorrect}} \]