The Cell Membrane

Cell Membrane Function

• The cell's plasma membrane acts as a barrier that selectively controls what enters and exits the cell.

Cell Membrane Composition

• The cell membrane is composed primarily of a phospholipid bilayer.
• The bilayer consists of two layers of phospholipids, with their hydrophilic (water-loving) heads facing the outside and inside of the cell, and their hydrophobic (water-fearing) tails facing each other in the middle.

Phospholipid Arrangement

• The phospholipids in the cell membrane are arranged in a bilayer structure.
• The hydrophilic heads of the phospholipids face the watery environment both inside and outside the cell.
• The hydrophobic tails of the phospholipids face each other in the middle of the membrane.

Embedded Proteins

• Proteins are embedded within the phospholipid bilayer.
• These proteins have various functions, including transporting molecules across the membrane, acting as receptors for signaling molecules, and providing structural support.

Permeability

• Small, nonpolar molecules (like oxygen and carbon dioxide) can easily pass through the cell membrane.
• Larger, polar molecules (like glucose and ions) need help from transport proteins to cross the membrane.