Biology: The Cell Membrane

Overview of Cell Structure

• Cells have three main structures: cytoplasm, plasma membrane, and genetic material.

The Plasma Membrane

• Defines the cell, separating its internal environment from the external surroundings.
• Also known as the phospholipid bilayer, consisting of two layers of phospholipids.

Phospholipid Bilayer Components

• Bilayer: "Bi" means two, referring to the two layers of phospholipids.
• Phospho: Refers to the phosphate group present.
• Lipid: Indicates that these molecules are fats.

Characteristics of Phospholipids

• Hydrophilic Head: Contains choline and phosphate; interacts with water.
• Hydrophobic Tail: Composed of fatty acid chains; avoids contact with water.

Function of the Bilayer

• The arrangement creates a barrier regulating the movement of substances in and out of the cell.

Fluid Mosaic Model

• Describes the cell membrane as flexible (Fluid) and structured with various components (Mosaic).
• Proteins within the bilayer are not fixed and can move freely.

Types of Membrane Components

• Glycolipids: Lipids with carbohydrate groups; serve as cell surface markers.
• Transmembrane Proteins: Span the lipid bilayer, facilitating transport of substances and communication.
• Interior Protein Network: Provides structural support and maintains the shape of the membrane.
• Cell Surface Markers: Include glycoproteins and glycolipids, crucial for self-recognition and identity.
• Transporters: Selectively allow specific substances to cross the membrane.