Cell membrane Flashcards
What is a lipid
Large a varied group of organic compounds e.g. fats and oils
What are the 3 components of a lipid
A lipid is similar to a Carbohydrate it contains:
- carbon
- hydrogen
- oxygen
However the proportion of oxygen is less than carbohydrates
What determines the properties of any particular lipid
- They glycerol molecule in a lipid always stays the same
- The fatty acids determine the properties of the lipid
What is the test for fats and oils
Emulsion test
What is a fatty acid
An organic acid with a carboxyl (COOH) group at one end, which has a long hydrocarbon tail (R group) attached
What is the general formula of a fatty acid
RCOOH
What are the two types of fatty acids
- Saturated fatty acids
- Unsaturated fatty acids
How do the fatty acids in a lipid vary
- Length of the hydrocarbon tail
- HOw saturated the R group is
What is the difference between saturated and unsaturated fatty acids
- Saturated fatty acid
- Single carbon to cabon bonds (C-C)
- Unsaturated fatty acids
- Double carbon to carbon bonds (C=C)
How thick is the cell surface membrane
7nm
What type of microscope allows you to investigate the detailed structure of a cell membrane
A light microscope
An electron microscope
Electron microscope
Compare an electron microscope to a light mircroscope
Jamie we need to do this.
What is the structure of a cell membrane?
The structure of a cell membrane is composed of…
- 75% Phospholipids, the remainder being
- Proteins, cholesterol and polysaccharides
phospholipid, protein, cholesterol, polysaccharide
Which is the key element of the cell surface membrane
- Phospholipid
What is the structure of a phospholipid
A Phospholipid has
- 2 fatty acid chains and a phosphate group
- The Phosphate end of the phospholipid molecule is polar and therefore attracts other polar molecules e.g. water (Hydrophilic)
- The Lipid end of the phospholipid molecule is non polar, and therefore does not attract water (Hydrophobic)
What happens when a phospho lipid comes into contact with water
- Hydrophilic heads are attracted to water and dip into it
- The hydrophobic tails move away from the water
- This forms a mono layer
What 2 things happen if you shake up this mono layer
- Phospholipids would form tiny spherical structures called micelles
- The hydrophobic tails turn inwards and are protected by the hydrophilic head
With respect the cell membrane…what 3 things can phospholipids form
- Monolayers
- Miceles
- More importantly bi layers
Why are Bi layers important
It forms the basis of the structure for the cell surface and other membranes
What does a phospholipid by layer look like?
What are the 5 reasons why phospholipids form the basis of cell membrane structure
- Phospholipids can form bi layers
- The inner phospholipid layer
- Has its hydrophilic head pointing inwards towards the centre of the cell and interacts with the water in the cytoplasm
- The outer phospholipid layer
- Has its hydrophilic head pointing outwards interacting with the water surrounding the cell
- The hydrophobic tails of the two phospholipid layers point towards each, other towards the centre of the membrane
- The phospholipid component of a membrane allows lipid soluable molecules accross, but excludes water soluable molecules
What are the two ways proteins are embedded into the phospholipid bylayer
- Extrinsic proteins
- Intrinsic proteins
What is an extrinsic protein?
- Extrinsic proteins can be found on each side of the phospholipid bi-layer
- Their function is to provide structural support and form recognition sites by identifying cells and receptor sites for hormone attachment
What is an intrinsic protein?
- Intrinsic proteins can be found accross both of the phospholipid bi-layers
- Some of the intrinsic proteins are carriers, transporting water soluable substances accross the cell membrane
- Other intrinsic proteins allow active transport of ions accross the membrane by forming channels
Label the cell membrane
Label cell membrane answers
