Question

Which of the following statement is not true for chloroplast?

• A. It contains DNA as its genetic material
• B. It produces ATP
• C. It has an electron transport chain
• D. It contains transcriptional but no translational apparatus

Hint:

Chloroplasts have 70S ribosomes (similar to bacterial ribosomes), which are inhibited by chloramphenicol but not by cycloheximide, confirming their endosymbiotic prokaryotic origin.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Chloroplasts are semi-autonomous organelles of endosymbiotic origin. They contain their own genetic material and the necessary components to express their genes.

Step 2: Detailed Explanation:
Let us evaluate each statement:
- Statement (A) is true: Chloroplasts contain their own double-stranded circular DNA (cpDNA), which encodes several essential proteins.
- Statement (B) is true: They produce ATP during the light reactions of photosynthesis via photophosphorylation.
- Statement (C) is true: They contain an electron transport chain (ETC) located in the thylakoid membrane, consisting of Photosystem II, plastoquinone, cytochrome $b_6f$, plastocyanin, and Photosystem I.
- Statement (D) is false (not true): Because chloroplasts are semi-autonomous, they contain both a transcriptional apparatus (RNA polymerase) and a complete translational apparatus (70S ribosomes, tRNAs, and translation factors) to synthesize proteins encoded by their own DNA. Stating that they have no translational apparatus is incorrect.

Step 3: Final Answer:
The incorrect statement is (D).