Cell Membranes - Gateway to Cells

Question 1

Cell Membrane

Answer 1

The function of the cell membrane is to provide a barrier that separates the contents of the cell from the exterior environment. However, cells require substances to move in and out of them.

The cell membrane is selectively permeable and performs the function of controlling the movement of substances into and out of the cell.

Question 2

Fluid Mosaic Model

Answer 2

This model describes the cell membrane as a double layer of lipids, a lipid bilayer, with the ability to flow and change shape, like a
two-dimensional fluid.

Specialised protein molecules are embedded in the lipid in various patterns like a mosaic.

Question 3

Lipid Component

Answer 3

The ‘fluid’ part of the cell membrane is composed of two layers of phospholipids forming a phospholipid bilayer.
Each phospholipid in these layers can be represented by a head and two tails.

A phosphate group on the head makes this end hydrophilic (able
to absorb water or dissolve in water).

The fatty acid tails are hydrophobic (water avoiding or unable to dissolve in water).

Question 4

Transport Protein

Answer 4

Passageways that allow specific substances to move across the membrane.

Membrane proteins are also involved in cellular communication.

Question 5

Receptor Proteins

Answer 5

Receptor proteins are different in different types of cells.

They cause the cells to respond only to certain signals from substances such as hormones that bind to them, giving them specific functions.

Question 6

Antigens

Answer 6

Identify the cell and are called antigens or marker molecules.

Allow the immune system to distinguish between foreign particles (‘non-self ’) and the body’s own (‘self ’) cells.

This ensures that the immune system will destroy only foreign particles that display ‘non-self ’ markers.