Selective permeability and the Fluid Mosaic Model

Define selective permeability.

The property of membranes allowing only certain molecules to pass.

Why is simple diffusion not selective?

It depends only on size and polarity of molecules.

Which transport processes can be selective?

Facilitated diffusion and active transport.

Define glycosylation.

The attachment of carbohydrate chains to phospholipids or proteins.

What is a glycolipid?

A phospholipid with an attached carbohydrate chain.

What is a glycoprotein?

A membrane protein with an attached carbohydrate chain.

Where are carbohydrate chains located on membranes?

On the extracellular side.

What are the functions of glycolipids and glycoproteins?

Cell adhesion and cell recognition.

Give an example of a glycoprotein function.

Desmosomes binding skin cells together.

Why are desmosomes important?

They form a physical barrier against pathogens.

Give an example of a glycolipid.

ABO blood group antigens on red blood cells.

Explain the fluid mosaic model of membranes.

A flexible membrane with diverse embedded molecules.

Why is the membrane described as fluid?

Phospholipids move within the bilayer.

Why is the membrane described as a mosaic?

It contains many different molecules.

How does membrane fluidity help cells?

Allows vesicle formation and protein movement.

Which molecule helps regulate membrane fluidity?

Cholesterol.

Name two processes enabled by membrane fluidity.

Endocytosis and exocytosis.

What structures must be labelled when drawing a membrane?

Phospholipids, proteins, cholesterol, glycoproteins, and glycolipids.