Membrane Lipids Flashcards
What are cell membranes needed for
Partitions cells and organelles from outside environment
Needed for energy generation e.g in mitochondrial
Cell to cell communication
Contains membrane bound enzymes
What is the structure of the plasma membrane
What is the structure of phospholipids
What are the names of the major phospholipids
What is the structure of phosphotidylethanolamine and its net charge
What is the structure of phosphotidylserine and its net charge
What is the structure of phosphotidylcholine and its net charge
What is the structure of sphingomyelin and its net charge
Net charge of 0
What is the structure of sphingosine and its net charge
Net charge +1
What is sphingomyelin and what is its properties
What are the different sterols present in different organisms
What is the structure of cholesterol
How does the structure of cholesterol relate to its function
What are glycolipids
They’re lipids modified with sugars
Why is packing of hydrophobic molecules favourable
Organised water forms around hydrophobic molecules as they can’t form H bonds with water
Why does a bilayer form
Why are cells spherical
So is due to ampipathic nature and shape of lipids
What are the properties of membranes
What is used to study the properties of membranes
Liposomes- these are artificial phospholipid membranes
How are liposomes studied
The lipid molecules are tagged with a green fluorescent protein - it emits green fluorescence when exposed to blue light
How does photo bleaching of liposomes work
Why cant movement of lipids from one side of the membrane (one mono layer) move to the other side of the membrane occur
This is because the polar head groups would have to move through the hydrophobic core of the membrane which is energetically unfavourable
How does movement of lipid molecules within the bilayer occur
What does the fluidity of the membrane depend on
How does cholesterol affect phase transition of the membrane
How is semi permeability of the plasma membrane investigated
What are lipid rafts made up of
What is the distribution of different phospholipids in the membrane
Distribution of lipids is asymmetrical
What is the role of phosphotidylserine
How does modification of lipid head groups allow for a cell to respond to an extra cellular signal
Receptor binds extracellular signal
Receptor dimerises which then activates the receptor protein and becomes pholsphorylated
When the receptor becomes phosphorylated it causes activation of PI 3-kinase
PI 3-kinase then phosphorylates inositol phospholipid
The phosphorylated inositol phospholipid can then bind to an intracellular signal
What are the key features of membrane proteins
What is the general composition of cell membranes
What is an integral membrane protein
Integrated fully into the membrane
Formed by alpha helices or beta strand
Hydrophobic region anchors the protein into the membrane
The part that sticks out is the functional region of the protein
What is a single pass transmembrane protein
Is an integral protein
One hydrophobic region in membrane
Only formed from alpha helix
What is a multi pass protein
Many transmembrane domains
Is an integral protein
What is a beta barrel
Has interconnecting loop regions which is hydrophilic so sticks out above and below the membrane
Is formed from curved beta strands
Beta strand region sits in the membrane
What are peripheral membrane proteins
Proteins that only associate with one mono layer of the I layer of the plasma membrane
Some form a complex with integral proteins
Can be on the cytosolic or extracellular side of the membrane
Some can have a lipid modification which anchors them to the mono layer of the membrane
What is a monotopic membrane protein
Has an ampipathic helix
The hydrophobic region of the protein is embedded within the membrane
What is a GPI anchor protein
Has a lipid modification which anchors the protein the the extracellular side of the membrane
What are the 2 major classes of integral membrane proteins
What is the structure of alpha helices in transmembrane proteins
Structure maximised H bonds
All H bonds are intrahelical
Regular arrangement of polypeptide chain
Structure stabilised by H bonds between c=o group of residue n and -NH group 4 residues down
Which amino acids are most likely to be in a TM domain of a TM protein
How can you predict the number of TM domains
Hydrophobic it’s analysis
No of bright regions corresponds to the number of TM domains within the bilayer there may be- these domains contain hydrophobic amino acids
A certain no. Of alpha helices are required to make a TM domain
What are the characteristics of beta barrel integral proteins
Beta barrel forms a trimer in membrane- three barrels put together= structure of porin
Name the different types of OMPs and their functions
What is meant by topology
Orientation of a protein relative to membrane/ environment
How do G coupled protein receptors work
It does 2 different things on different sides of the membrane
What can be used to study membrane proteins
Detergents - this is because a lipid environment is essential for the structure and function of a membrane protein so detergents maintain the structure and function
The protein is taken out of the plasma membrane and is in solution so it can be analysed
How are detergents used to study membrane proteins
