7 Membrane Structure and Function Flashcards
What is the key feature of the plasma membrane?
It is selectively permeable.
What is the key feature of the plasma membrane?
It is selectively permeable.
What are the physical properties of a phospholipid
It has a hydrophilic head and hydrophobic tail (it is amphipathic)
What does ‘amphipathic’ mean?
It has a hydrophilic and a hydrophobic region?
A phospholipid has both a hydrophilic and hydrophobic section. What does this mean it is?
Amphipathic.
What model describes how a phospholipid membrane is arranged?
The phospholipids and proteins are arranged according to the ‘fluid mosaic model’
How does the fluid mosaic model describe the phospholipid membrane?
It is bilayer of phospholipids interspersed with proteins. This layer is fluid i.e. dynamic.
Where are the proteins of the phospholipid membrane located?
These proteins are also amphipathic so they go all the way through the membrane.
How is the lipid bilayer held together?
By the hydrophobic tails of the phospholipids as they exert an attractive force ad thus prevent the layers form separating.
In what was is a phospholipid membrane dynamic?
It has fluidity in which adjacent phospholipids with places as do the occasional opposite phospholipids.
What can cause a decrease in membrane fluidity?
A decreased temperature.
How can the components of the phospholipid membrane affect its fluidity?
If the phospholipids have unsaturated hydrocarbon tails they will be kinked which prevents packing and thus makes it more fluid.
Alternately cholesterol can be added to adjust fluidity.
How does integrating cholesterol into a membrane affect membrane fluidity?
At moderate temperatures it reduces fluidity by reducing phospholipid movement.
However at low temperatures it prevents solidification by preventing packing.
Thus it acts as a buffer to cause intermediate fluidity.
Why is membrane fluidity important?
It allows the enzymes and other membrane proteins to more easily collide with their substrates etc.
What are the basic functions of transmembrane proteins?
Transport, Enzymes, Signal Transduction, Cell-Cell recognition, Joining adjacent cells; and attaching to the cytoskeleton and ECM.
What are the basic functions of transmembrane proteins?
Transport, Enzymes, Signal Transduction, Cell-Cell recognition, Joining adjacent cells; and attaching to the cytoskeleton and ECM
What are the physical properties of a phospholipid
It has a hydrophilic head and hydrophobic tail (it is amphipathic)
What does ‘amphipathic’ mean?
It has a hydrophilic and a hydrophobic region?
A phospholipid has both a hydrophilic and hydrophobic section. What does this mean it is?
Amphipathic.
What model describes how a phospholipid membrane is arranged?
The phospholipids and proteins are arranged according to the ‘fluid mosaic model’
How does the fluid mosaic model describe the phospholipid membrane?
It is bilayer of phospholipids interspersed with proteins. This layer is fluid i.e. dynamic.
Where are the proteins of the phospholipid membrane located?
These proteins are also amphipathic so they go all the way through the membrane.
In what way and where a membrane proteins and lipids modified?
The ER adds carbohydrates to some transmembrane proteins to make them glycoproteins.
However only in Golgi are carbohydrates added to lipids to form glycolipids. In the Golgi the carbohydrates of some glycoproteins are also modified.
In what was is a phospholipid membrane dynamic?
It has fluidity in which adjacent phospholipids with places as do the occasional opposite phospholipids.
What can cause a decrease in membrane fluidity?
A decreased temperature.
How can the components of the phospholipid membrane affect its fluidity?
If the phospholipids have unsaturated hydrocarbon tails they will be kinked which prevents packing and thus makes it more fluid.
Alternately cholesterol can be added to adjust fluidity.
How does integrating cholesterol into a membrane affect membrane fluidity?
At moderate temperatures it reduces fluidity by reducing phospholipid movement.
However at low temperatures it prevents solidification by preventing packing.
Thus it acts as a buffer to cause intermediate fluidity.
Why is membrane fluidity important?
It allows the enzymes and other membrane proteins to more easily collide with their substrates etc.
When might organism need special adaptions to maintain membrane fluidity?
If they are extremophiles i.e. living in especially hot or cold climates.
What are the basic functions of transmembrane proteins?
Transport, Enzymes, Signal Transduction, Cell-Cell recognition, Joining adjacent cells; and attaching to the cytoskeleton and ECM
What are the types of membrane protein?
Integral and Peripheral.
What are integral membrane proteins?
Proteins which penetrate into the hydrophobic interior of the phospholipid membrane.
Some are classed as ‘transmembrane proteins’ as they cross all the way through the membrane and out the other side.
What are peripheral membrane proteins?
Proteins which simply bond onto the surface of the membrane, often by attracting to integral proteins/
What is the typical composition of an integral membrane protein?
They have a hydrophobic region consisting of non polar amino acids. coiled into a-helices.
How can cell recognise each other?
Different species have different glycolipids (carbs+lipid) and different glycoproteins (carbs+proteins.)
These ‘membrane carbohydrates’ can be detected by receptors in the membranes of other cells allow them to distinguish each other?
How do red blood cells from different blood groups differ?
The ‘membrane carbohydrate’ glycoproteins in their plasma membranes have different carbohydrate parts and thus are recognised differently.
Where are membrane proteins and lipids manufactured?
In the ER.
In what way and where a membrane proteins and lipids modified?
The ER adds carbohydrates to some transmembrane proteins to make them glycoproteins.
However only in Golgi are carbohydrates added to lipids to form glycolipids. In the Golgi the carbohydrates of some glycoproteins are also modified.
How are transmembrane proteins embedded in the correct place of the phospholipid membrane?
As transmembrane proteins move through the Golgi they are constantly embedded in the membrane. Therefore when the vesicle buds off at the trans face they cross the membrane of the vesicle. Therefore when the vesicle fuses with the plasma membrane the protein is transmembrane.
How are non-transmembrane proteins embedded in the correct place?
When the vesicle buds off from the trans Golgi proteins etc. to go on the outside of the plasma membrane are placed in the centre of the vesicle whereas those to go on the intracellular side go on the outside.
Therefore when the vesicle fuses with the plasma membrane the proteins end up in the correct place.