Major constitute of nerve cell membrane:
**Core Concept**
The nerve cell membrane, also known as the plasma membrane, is a complex structure composed of various lipids and proteins. It serves as a selective barrier that regulates the movement of substances in and out of the cell while maintaining cellular homeostasis.
**Why the Correct Answer is Right**
The major constituent of the nerve cell membrane is phospholipids, specifically phosphatidylcholine and phosphatidylethanolamine. These phospholipids are arranged in a bilayer structure, with their hydrophilic (water-loving) heads facing outwards and their hydrophobic (water-fearing) tails facing inwards. This unique arrangement allows the membrane to maintain its structural integrity and function as a selective barrier.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the type of lipid that is the major constituent of the nerve cell membrane.
**Option B:** This option is incorrect because cholesterol, although present in the membrane, is not the major constituent.
**Option C:** This option is incorrect because proteins, although essential for membrane function, do not constitute the majority of the membrane.
**Clinical Pearl / High-Yield Fact**
The phospholipid bilayer structure of the nerve cell membrane is crucial for maintaining cellular homeostasis and regulating the movement of substances in and out of the cell. This structure is essential for various cellular functions, including signal transduction and neurotransmitter release.
**Correct Answer: B. Cholesterol.