Question

Which of the following is an incorrect statement ?

• A. Mature sieve tube elements possess a conspicuous nucleus and usual cytoplasmic organelles.
• B. Microbodies are present both in plant and animal cells.
• C. The perinuclear space forms a barrier between the materials present inside the nucleus and that of the cytoplasm.
• D. Nuclear pores act as passages for proteins and RNA molecules in both directions between nucleus and cytoplasm.

Answer 1

The Correct Option is A

To determine which statement is incorrect, let's analyze each option based on biological knowledge regarding cellular structures and functions:

1. Mature sieve tube elements possess a conspicuous nucleus and usual cytoplasmic organelles.
   Sieve tube elements are specialized cells found in the phloem of vascular plants. They are responsible for the transport of nutrients, primarily carbohydrates, throughout the plant. A key characteristic of mature sieve tube elements is that they lack a nucleus and most cytoplasmic organelles. They retain only a thin peripheral layer of cytoplasm and are largely empty to facilitate transport. Therefore, this statement is incorrect.
2. Microbodies are present both in plant and animal cells.
   Microbodies, such as peroxisomes, are small organelles that contain enzymes for specific metabolic pathways. They are found in both plant and animal cells, performing various functions like detoxification, breakdown of fatty acids, and involvement in photorespiration in plants. This statement is correct.
3. The perinuclear space forms a barrier between the materials present inside the nucleus and that of the cytoplasm.
   The perinuclear space is the gap between the two membranes of the nuclear envelope. It does indeed help contain and separate nuclear contents from the cytoplasm, acting as part of a selective barrier along with nuclear pores. Thus, this statement is correct.
4. Nuclear pores act as passages for proteins and RNA molecules in both directions between nucleus and cytoplasm.
   Nuclear pores are large protein complexes that span the nuclear envelope, allowing the transport of molecules like RNA and proteins between the nucleus and the cytoplasm. This bidirectional passage is essential for cellular functions such as protein synthesis and the wearing of genetic information. Thus, this statement is correct.

In conclusion, the statement that "Mature sieve tube elements possess a conspicuous nucleus and usual cytoplasmic organelles" is incorrect because mature sieve tube elements lack a nucleus and most organelles, adapting them for their role in transport.