Questions: What is the plasma membrane composed of? Nucleic acids and lipids Cholesterol and carbohydrates Cholesterol and nucleic acids Carbohydrates and proteins Lipids (phospholipids and cholesterol) and proteins

The answer is the last one: Lipids (phospholipids and cholesterol) and proteins.

Explanation for each option:

1. Nucleic acids and lipids: Incorrect. Nucleic acids are not a component of the plasma membrane. The primary nucleic acids, DNA and RNA, are found in the nucleus and cytoplasm, not in the membrane structure.

2. Cholesterol and carbohydrates: Incorrect. While cholesterol is a component of the plasma membrane, carbohydrates are not a primary structural component. Carbohydrates are often attached to proteins and lipids on the extracellular surface of the membrane, but they do not form the membrane's main structure.

3. Cholesterol and nucleic acids: Incorrect. As mentioned, nucleic acids are not part of the plasma membrane structure.

4. Carbohydrates and proteins: Incorrect. Proteins are indeed a major component of the plasma membrane, but carbohydrates are not a primary structural component. They are present as glycoproteins and glycolipids on the surface.

5. Lipids (phospholipids and cholesterol) and proteins: Correct. The plasma membrane is primarily composed of a phospholipid bilayer with embedded proteins. Cholesterol is interspersed within the bilayer, providing fluidity and stability to the membrane.

In summary, the plasma membrane is mainly composed of lipids (phospholipids and cholesterol) and proteins, which together form a dynamic and functional barrier for the cell.