Components of cell membrane

What is the function fluid mosaic model?

To describe the structure of the cell membrane

What is the fluid in the fluid mosaic model?

Phospholipids form a bilateral in which the phospholipid molecules are constantly moving

What is the mosaic in the fluid mosaic model?

There are proteins of different sizes and shapes embedded in the phospholipid bilayer (so it looks a bit like a mosaic)

What are the 5 key components of the cell membranes?

• phospholipid bilayer

• cholesterol

• proteins

• glycoproteins

• glycolipids

Describe the function of the phospholipid bilayer in the cell membrane.

• made up of phospholipids, each is made with hydrophilic heads and hydrophobic tails

• causes phospholipids to arrange themselves to arrange themselves into a bilayer so that the hydrophilic heads are facing out (toward water) and hydrophobic tails are facing in (away from water)

• this arrangement creates a hydrophobic centre in bilayer so water-soluble substances cannot pass through

• fat-soluble substances can dissolve in bilayer and pass directly through cell membrane

Describe the function of cholesterol in cell membranes

• To provide stability

• Cholesterol molecules contain hydrophobic and hydrophilic regions

• Hydrophobic regions bind to phospholipid fatty acid tails, pack closely together

• Reduces fluidity of cell membrane

What are the 2 types of proteins in the cell membrane?

Extrinsic (integral) and Intrinsic (peripheral) proteins

Explain intrinsic proteins.

• intrinsic (or integral) proteins are embedded through both sides of the phospholipid bilayer

• Include channel and carrier proteins- transport large molecules and ions across the membrane

Explain extrinsic proteins

• extrinsic (or peripheral) proteins are only present in one side of phospholipid bilayer

• these proteins provide support to membrane or may be involved in cell signalling

What is the role of glycoproteins and glycolipids?

• Glycoproteins consist of intrinsic proteins attached to carbohydrates, but glycolipids consist of lipids attached to carbohydrates

What are glycolipids and glycoproteins involved in?

• cell adhesion- attachment of cells to one another

• cell recognition- allows cells to recognise one another

• cell signalling- communication between cells

What are the 2 types of cell membrane?

1. Cell-surface membranes - surround cells to act as a barrier between cell and its environment, controlling which substances enter & leave the cell. 

2. Membranes around organelles - These surround organelles to act as a barrier between the organelle cytoplasm, dividing cell into different compartments (compartmentalisation). 

What are the different factors affecting the permeability of the cell membrane?

Temperature and Solvents

How does temperature affect the permeability of the cell membrane?

Changes in temperature affect the movement of phospholipids and the structure of proteins in the cell membrane.

How do solvents affect the permeability of the cell membrane?

Solvents are liquids that have the ability to dissolve substances

• when cells are placed in a solvent eg ethanol, phospholipids dissolve, causes membrane to become more fluid

• disrupts the structure of the cell membrane to make it more permeable

• increasing the concentration of solvent further increases permeability of cell membrane