What Is the Cell Membrane?

• The cell membrane is the outer covering of the cell.

• It protects the cell and controls what enters and exits.

• It is found in all cells – both animal and plant cells.

• It is selectively permeable, which means it allows some substances to pass through but blocks others.

What Is the Cell Membrane Made Of?

1. Phospholipid Bilayer

• The main part of the membrane is a double layer of phospholipids.

• Each phospholipid has a water-loving head and water-hating tails.

• The heads face the water inside and outside the cell, the tails hide inside, away from water.

• This structure gives the membrane its flexibility and makes it a good barrier.

2. Proteins

• Integral proteins go across the membrane.

                  They form channels or transporters to move substances in and out.

• Peripheral proteins are on the surface of the membrane.

                  They help the cell communicate and support its structure.

• Some proteins act as receptors, which receive signals from outside the cell.

Integral Proteins

• Found inside the membrane, often going all the way through.

• Help with transport of substances and act as receptors for signals.

Peripheral Proteins

• Found on the surface of the membrane, not inside it.

• Help with cell shape, support, and communication.

3. Cholesterol

• Found in animal cell membranes (not plant cells).

• It makes the membrane stronger and less fluid, helping it stay stable in different temperatures.

4. Carbohydrates

• Attached to proteins (glycoproteins) or lipids (glycolipids).

• These are used for cell recognition, cell signaling, and helping cells stick to one another.

What Does the Cell Membrane Do?

• Protects the cell and holds its shape.

• Controls what enters and leaves (nutrients, water, waste, gases).

• Allows communication with other cells using receptors.

• Helps the cell respond to changes in its surroundings.

• Supports cell attachment to other cells or surfaces.

Note/summary- These are the 5 things inside a cell membrane:

1. Phospholipids – form the basic double layer (bilayer).

2. Integral Proteins – go through the membrane; help with transport and signals.

3. Peripheral Proteins – sit on the surface; help with structure and communication.

4. Cholesterol – adds strength and flexibility (in animal cells).

5. Carbohydrates – attached to proteins or lipids; help with cell recognition.