Found in cell membranes are phospholipids, cholesterol, proteins (integral and peripheral), and carbohydrate groups as glycoproteins and glycolipids; nucleic acids are not components of the membrane.
Explanation
The cell membrane is the phospholipid bilayer that forms a flexible barrier around the cell. Phospholipids have hydrophilic heads facing outward and hydrophobic tails inward, creating a bilayer that is fluid and selectively permeable. Cholesterol molecules insert between phospholipids, modulating membrane fluidity and stability. Proteins interact with the bilayer in two main ways: integral (transmembrane) proteins span the membrane, while peripheral proteins associate with the surface. Carbohydrate groups are often attached to lipids (glycolipids) or proteins (glycoproteins) on the extracellular surface, forming the glycocalyx. The membrane is a dynamic mosaic, with components asymmetrically distributed between the inner and outer leaflets and capable of reorganizing in response to signals. Nucleic acids are not components of the membrane; they reside in the nucleus or cytoplasm as genetic material.
Key Points
- 1, The membrane is mainly a phospholipid bilayer with cholesterol that modulates fluidity.
- 2, Proteins (integral and peripheral) and carbohydrate structures (glycolipids/glycoproteins) perform transport, signaling, and recognition.
- 3, The membrane is not composed of nucleic acids; its components form a selective barrier and signaling platform.