4.1 - Structure of the cell membrane

Question 1

Types of cell membranes (2 types - expand, and what are the two membranes common point)

Answer 1

1. cell surface membranes - surround cells to act as a barrier between the cell and its environment, controlling the entry and exit of the cells
2. membranes around organelles - divides the cells into different compartments
   * both types of membranes are partially permeable - let some molecules pass through

Question 2

Purpose of glycoproteins and glycolipids

Answer 2

1. cell adhesion - attachment of cells to one another
2. cell recognition - recognise one another
3. cell signalling - communication between cells

Question 3

Glycoproteins and glycolipids (what does it contain)

Answer 3

• glycoproteins consist of proteins attached to a carbohydrate
• glycolipids consist of lipids to carbohydrates

Question 4

Extrinsic proteins (aka, where is it present and what is its purpose)

Answer 4

• peripheral proteins - present on only one side of the bilayer
• provide support to the membrane or in cell signalling

Question 5

Intrinsic proteins (aka, where are tehy embedded and what type of proteins do they include)

Answer 5

• integral proteins and are embedded through both sides of the phospholipid bilayer
• include channel and carrier proteins - transport large molecules and ions across the membrane

Question 6

Cholesterol (purpose, what does it contain and what do they bind to, what does it reduce)

Answer 6

• provides stability to cell membranes
• consists of a hydrophilic and hydrophobic region
• reduces fluidity

Question 7

what’s in the phospholipid bilayer? (what is it made up of, how is it arranged and what does this cause, and what can dissolve within the layer)

Answer 7

each phospholipid molecule is made up of a hydrophulic head and two hydrophobic tails
* causes phopsholipids to arrange themselves into a bilayer so that the hydrophilic ehads are facing out towards the water and the hydrophobic tails are facing in away from the water

arrangement causes a hydrophobic centre - water soluble substances can’t pass through

lipid-soluble substances can dissolve in the bilayer and pass directly through the cell membrane

Question 8

Structure of the membrane (5 features)

Answer 8

phospholipid bilayer;
* made up of phospholipids with hydrophilic heads and hydrophobic tails

cholesterol
* adds stability

proteins
* may be intrinsic/extrinsic proteins

Glycoproteins;
* proteins attached to a carbohydrate

Glycolipids
* lipids attached to a carbohydrate

Question 9

What is the fluid mosaic model? (why is it a fluid/mosaic)

Answer 9

• fluid - phospholipids form a bilayer in which the phospholipid molecules are constantly moving
• mosaic - there are proteins of different sizes and shapes embedded in the phospholipid bilayer (mosaic shape)