Flashcards in MCB Lecture 9 Lipids and Bilayers Deck (42)
Describe lipid Bilayers' role in compartmentalisation
Lipid bilayer provides a physical barrier -> compartments
These compartments can have different properties and conditions
What are the three features of lipid Bilayers?
3. Variable fluidity
Describe how the lipid bilayer is amphipathic
The head is hydrophilic
The fatty acid tails are hydrophobic
Describe the structure of a phospholipid
Two fatty acid chains (hydrocarbons)
Draw the structure of cholesterol
Describe how lipid Bilayers have variable fluidity
2. Shorter chain fatty acids
3. Double bonds in fatty acids
Shorter chain fatty acids in the lipid bilayer lead to ... of ordered packing
Cholesterol lead to ... of ordered packing
Presence of double bonds in the fatty acid chains leads to ... of ordered packing
Reduction of ordered packing leads to ...
Membrane sets at a lower sptemp
Describe how the lipid bilayer is asymmetric
There is differential distribution of membrane proteins and another associated molecules/complexes
Glycolipids are almost always found ... ?
On the outside of the cell
Where is Phosphotidyl-Serine almost always found?
What is its charge?
What is important about phosphotidyl-inositols in the membrane?
These are important parts of signal transduction pathways
What is the structure of lipid rafts?
These are made up of sphingolipids which have long saturated fatty acid chains
What is the function of lipid rafts?
These provide regions for membrane proteins to reside and be localised
Lipid rafts are resistant to what?
Are lipid rafts dynamic or static?
Describe the structure of sterols in terms of polarity
Sterols have a tiny polar group (-OH)
Rigid steroid ring structure
Non polar aliphatic chain
What is a glycolipid?
Sugar associated with fatty acid chains
What is a sphingolipid? Where is it usually found?
Sphingolipids are usually found in lipid rafts
They are long, saturated, fatty acids
What type of molecule is a galactocerebroside?
What type of molecule is a ganglioside?
From what are all animal glycolipids a derived?
What are the two types of membrane proteins?
Integral and peripheral
What are the requirements for integral membrane proteins?
They must have some part attached or within the membrane
Need detergent to remove it
What are the two ways that helices can be embedded in a membrane?
Amphipathic: Hydrophobic stripe embedded (long ways)
Transmembrane, hydrophobic residues
What are peripheral proteins. For example...?
Peripheral protein are connected to the membrane only through interactions with other molecules
Where are the termini in transmembrane proteins (in general)?
What is the exception?
The N and C termini are usually on the cytosolic side.
The exception is
What are the two types of structure that can form transmembrane proteins?
Beta barrels - porins
What are the features of transmembrane helices?
How many residues span the bilayer?
How does the helix interact with lipids?
Hydrophobic side chains within the membrane
What are the features of transmembrane b-proteins?
How does the structure interact with the hydrophobic lipids?
These are beta sheets that are bent around to form channels through a membrane: porins
Hydrophobic residues protrude out into the lipids
Hydrophilic residues protrude into the channel
What are porins?
Describe their presence in prokaryotes and eukaryotes.
Porins are channels in the membrane
They are mostly found in prokaryotes.
In eukaryotes, they are seen in the inner mitochondrial membrane (bacterial origin)
What is special about the Translocase on the Outermitochondrial membrane?
What is its structure?
Translocase on outer mitochondrial membrane; a porin (beta barrel)
Why is there differential distribution of amino acids in transmembrane proteins?
Different amino acid residues have different properties, as does the membrane
Lipophilic, hydrophobic residues (ala, val, leu, ile, phenylalanine) are found within the membrane
Hydrophilic, polar residues are on the outside
Tryptophan and tyrosine are found at the interface between the two regions
Where are charged residues localised in the bilayer?
Where are non polar residues localised in the bilayer?
In the fatty acid chains
Which residues are often found at the polar/nonpolar interface?
Washing will remove what sort of proteins?
How do we remove the other ones?
Washing removes peripheral proteins
Detergents are required to remove integral proteins
Serine is the derivative of all what?
High cholesterol content makes the membrane more ...