Flashcards in Membrane lipids and proteins Deck (65):
Describe the membrane?
Two-dimensional sea of mobile lipid in which proteins diffuse.
At what scale do the lipids move?
Nano meter scale.
What two things does the cell membrane include?
> Plasma membrane.
> Internal membranes (eg. ER, Golgi)
What 3 things does the membrane contain?
>Carbohydrate (glyco-proteins, -lipids)
Ratio between lipids and proteins depends on?
What would be the ratio of lipids:proteins for a myelin?
The function is for insulation. Therefore, the lipid composition ratio is higher than protein.
What is the major responsibility for the membrane lipids?
Name the 4 types of the major membrane lipids?
Polar head group charge.
Fatty acid chain vary in length with a degree of unsaturation.
Cholesterol and its esters.
Amphipathic but relatively large CH portion
Have hydrophilic and hydrophobic portion.
Glycerides- a fatty acid ester of glycerol
Minor includes some antigens
eg. A, B
What is the fatty acid chain length?
C12 to C22
What does each C=C bond introduce to the phospholipids?
Introduces a rigid kink in the R tail.
What does polar mean?
What happens to phospholipids when in aqueous solution?
Hydrophobic interactions cause tails to aggregate and exclude water from a "core".
How is the membrane stabilised?
By tail-tail and head-head interactions
Name the 2 types of membrane proteins?
Integral membrane protein?
One of more regions embedded in lipid bilayer.
Most are transmembrane proteins.
Peripheral membrane protein?
Attached to membrane through integral membrane proteins or membrane lipids.
How are transmembrane proteins arranged in the membrane?
When is orientation established?
Name the 3 types of how the span membrane?
Multimeric protein complexes
What would the single span function as?
What would the multiple spans function as?
May form an aqueous "pore" in the membrane.
What would the multimeric protein complexes function as?
Bacterial lactose permease?
The most abused protein on the planet.
Know the function of every amino acid.
How many transmembrane domains does bacterial lactose permease have?
12 Transmembrane domains
What two parts of this bacterial lactose permease allows it to function as a permease?
Glu325 and His322
What are the 3 different net charges that amino acid residues in proteins have?
Describe neutral net charge?
Polar- depending on side groups (ie. OH or CO)
The charge in the atom is not symmetrically.
Hydrophilic ( bond with water).
The atoms attraction to water.
ie. hydrophilic or hydrophobic
What does the hydropathy index tell us about the amino acids side chain?
What is the electrical charge distribution along a protein? and what does it depend on?
Varies and depends upon primary structure.
How would you describe regions of high charge density (along a protein) as being?
How would you describe regions of low charge density (along a protein) as being?
What type of plot would thou use to predict the protein structure?
Describe the hydropathy plot?
The more positive value, the more hydrophilic the amino acids are in that particular region.
Name the 5 transmembrane domain regions that are likely to be rich in hydrophobic residues?
What anchors the regions within a protein?
How many residues form alpha helix?
20-25 AA residues
What do domains outwit membrane tend to be? and form?
Tend to be charged.
Form beta sheets
Name the important functions that occasionally charged residues within transmembrane domains have to do?
Stabilising structures, binding substrates and charge transfer.
Name the 2 residues that are found in domains outwith the membrane?
Gly and Pro
What does polar peptide linkage form?
Shielded H-bonds within the helix
Name the 4 methods used as evidence for the structure of the fluid mosaic model?
1) lipid area
2) X-ray and neutron diffraction
3) Transmission electron microscopy
Describe how the lipid area can be used as evidence for the structure of the fluid mosaic model?
2 x membrane area
Describe how the x-ray and neutron diffraction can be used as evidence for the structure of the fluid mosaic model?
There is a regular variation in density.
Describe how the transmission electron microscopy can be used as evidence for the structure of the fluid mosaic model?
Uses electrons instead of light allows a much higher resolution.
Describe how the freeze-etching can be used as evidence for the structure of the fluid mosaic model?
reveals embedded proteins in fracture faces.
Subliming a layer of ice crystals from the fractured plane to expose the natural surfaces.
Name the 3 methods used as evidence for the dynamics of the fluid mosaic model?
1) Electron spin resonance
Describe how electron spin resonance can be used as evidence for the dynamics of the fluid mosaic model?
Use of spin-labelled phospholipids
Describe how phase-transition can be used as evidence for the dynamics of the fluid mosaic model?
As the temp increase, the membrane starts to melt from a gel like structure to a fluid one. Therefore, shows that it is very dynamic.
Describe how protein-tagging can be used as evidence for the dynamics of the fluid mosaic model?
Used to observe specific protein movement.
Describe the difference between x-ray and neutron diffraction when being used as evidence for the structure of the fluid mosaic model?
X-ray identifies the phosphate and cholesterol.
Neutron identifies the ester and cholesterol.
Why are some proteins immobile within the membrane?
They are anchored by the actin skeleton
What is the barrier and exchange surface between the cell and the environment?
The cell membrane.
Name the 3 mechanisms by which substances cross the membrane?
2) Osmosis (net water movement)
3) Transport (facilitative or active)
Can be through the bilayer or the use of a channel.
Region of high to low
Describe facilitative transport?
Use of a protein to travel across the membrane (ie. useful to large molecules)
Use of the gradient (high to low)
Describe primary active transport?
Use of a protein to go through the membrane.
Directly uses ATP as energy to transport these molecules against their gradient (low to high)
Describe secondary active transport?
Whats its other name?
Uses a protein as a means to travel across the membrane.
Allows 2 molecules to travel: one with its gradient and one against.
Uses the energy given by the molecules going with its gradient to transport the one against.
What does it mean by solvent?
The bulk of liquid that the solute is dissolved in.