The principal components of the plasma membrane are lipids (phospholipids and cholesterol), proteins, and carbohydrates. The plasma membrane protects intracellular components from the extracellular environment. The plasma membrane mediates cellular processes by regulating the materials that enter and exit the cell.
Members of the Shudra caste, for example, are relegated to performing hard physical work regardless of their skill, intelligence, or ambition. Those born into the Brahman caste must attend university or become a member of the clergy, even though they may show no interest or aptitude toward that end.
The caste system in India is an important part of ancient Hindu tradition and dates back to 1200 BCE. The term caste was first used by Portuguese travelers who came to India in the 16th century. Caste comes from the Spanish and Portuguese word casta which means race, breed, or lineage. Many Indians use the term jati.