Question

Nissl bodies are mainly composed of

• A. Proteins and lipids
• B. Nucleic acids and SER
• C. DNA and RNA
• D. Free ribosomes and RER

Answer 1

The Correct Option is D

Nissl bodies, also known as Nissl substance, are a prominent feature observed in the neuron cell body, particularly under a microscope when stained with certain dyes. These structures are crucial for the production of proteins within the neuron.

Let's analyze the options to understand what Nissl bodies are made of:

1. Proteins and lipids: While proteins are produced in neurons, Nissl bodies are not primarily composed of lipids alongside proteins. Lipids are generally part of cell membranes and do not form Nissl bodies.
2. Nucleic acids and SER: Nucleic acids, such as DNA and RNA, are key components of the genetic material within the cell. SER (Smooth Endoplasmic Reticulum) is involved in lipid synthesis and detoxification, not directly associated with Nissl bodies.
3. DNA and RNA: DNA is located in the nucleus and not part of Nissl bodies. Although RNA is involved in protein synthesis, the combination of DNA and RNA alone does not constitute Nissl bodies.
4. Free ribosomes and RER: This is the correct answer. Nissl bodies consist of rough endoplasmic reticulum (RER) and free ribosomes. The ribosomes are responsible for protein synthesis, which is vital for the neuron's function.

The rough endoplasmic reticulum, characterized by the presence of ribosomes on its surface, contributes to the synthesis of membrane proteins and secreted proteins. Therefore, the presence of abundant rough ER in neurons forms the Nissl bodies, which are evident under the microscope as basophilic granules.

Thus, the correct answer is Free ribosomes and RER.