Lipids in Cell Membranes Flashcards
What are some examples of lipids?
1- Phospholipids
2- Fats
3- Sterols
4- Some vitamins
What is the solubility of lipids in water?
Very low
What are the roles of lipids?
1- Sources of energy
2- Forming membranes
3- Participating in cell signalling
Describe the structure of fatty acids.
1- Carboxyl group with a long hydrocarbon chain
2- CH3(CH2)4-24COOH (CH2 anywhere between 2 to 24)
3- All naturally occuring fatty acids have an even number of carbons
How are fatty acids acquired into the body?
1- Short and medium chains are absorbed into the blood stream
2- Long chains cannot be absorbed so they are synthesised
In respect to the ratio of carbon bonds to double bonds, what are the three types of fatty acids?
1- Saturated (16:0)
2- Unsaturated (18:1)
3- Polyunsaturated (20:4)
What are examples of sterols?
1- Bile acids
2- Steroid hormones
3- Vitamins
4- Cell membranes
What type of lipid is cholesterol?
Sterol
What is Gaucher’s disease?
1- Inherited disorder
2- Affects lipid pathways
3- Accumulation of glucocerebrocide
How do disorders which affect the lipid pathway affect the body?
1- Lipid accumulation 2- Affect neurological system 3- Enlarged liver and spleen 4- Enlarged bone marrow cavities 5- Failure to thrive
Which three groups of lipids are found in the membrane?
1- Phospholipids
2- Glycolipids
3- Sterols
Describe the structure of a phospholipid.
1- Polar head group
2- Glycerol backbone
3- Fatty acid chains (usually two)
What are five examples of phospholipids?
1- Choline 2- Ethanolamine 3- Serine 4- Glyerol 5- Inositol
Describe the structure of a glycolipid.
1- Sphingosine backbone
2- Fatty acid chain
3- Attached to CH R group
What is an amphipathic compound?
A molecule with a hydrophilic head and a hydrophobic tail
Describe the lipid bilayer.
1- Biylayer of phospholipids
2- Hydrophilic heads point outwards and are attracted to water
3- Hydrophobic tails point inwards and seek to aggregate with other, hydrophobic molecules
4- Contain lipids which help contribute to membrane strength and stability
Why are membranes important?
1- Compartmentalisation, separating cell from outside
2- Compartmentalisation, separating organelles
3- Have highly selective barriers to control entry and exit
4- Have sensors which respond to internal and external conditions to help the cell act accordingly
What are the two classes of proteins in the membrane?
1- Peripheral (extrinsic) proteins
2- Integral (intrinsic) proteins
In what ways can phospholipids move within the membrane?
Membrane is extremely fluid
1- Lateral movement: very frequent, 10^7 per second
2- Flip-flop: very rare, may happen ~once per month
What is the difference of the structure of phospholipids between fluid and viscous membranes?
1- Fluid membranes have phosphilipids with unsaturated hydrocarbon tails with kinks
2- Viscous membranes have phospholipids with saturated hydrocarbon tails with no kinks
Describe the structure of cholesterol.
1- Polar head group
2- Rigid, planar steroid ring structure
3- Nonpolar hydrocarbon tail
How does the cholesterol molecule fit in the phospholipid membrane?
1- Polar head next to hydrophobic phospholipid heads
2- Rigid, planar steroid ring structure next to proximal tail to stiffen the region
3- Nonpolar hydrocarbon tail next to distal tail, more fluid than proximal tail
Where does membrane synthesis take place?
Endoplasmic reticulum
How is new membrane transported to other parts of the cell?
1- Vesicle trafficking
2- Bits of membrane pinch off from the ER to form vesicles
3- These travel in the cytosol and fuse with other membranes, releasing their content
How is asymmetry generated in the membrane?
1- Newly synthesised phospholipids are released into the outer leaflet of the ER bilayer
2- Lipids are transferred to other side by flippases
3- This created asymmetry
What are lipid rafts?
1- Subdomain of membranes 2- Organising centre 3- Contain high concentrations of cholesterol and glycophingolipids 4- Regulate vesicle trafficking 5- Responsible for cell signalling
In regards to their position in the membrane, what are the four types of membrane proteins?
1- Transmembrane
2- Membrane-associated
3- Lipid-linked
4- Protein-attached
How are transmembrane proteins positioned in relation to phospholipids?
Transmembrane proteins have hydrophobic amino acid side chains, which interact with the hydrophobic tails
How are membrane-associated proteins positioned in relation to phospholipids?
1- Attached to only one side of the membrane and not across
2- Contain domains that selectively bind to phospholipids
How are lipid-linked proteins attached to the phospholipid membrane?
1- Attached via GPI anchors
2- GPI: glycosylphosphatidylinositol
