Membrane Bilayer Flashcards
Roughly what percentages of the membrane bilayer are protein, lipids?
Protein- 60%, lipid- 40%
What are unsaturated fatty acids?
Have a double bonded carbon in the card on tail
What are two other less common lipids?
Sphingomyelin and Glycolipids
What differentiates sphingomyelin from other lipids?
They have no glycerol backbone
What are the most common/predominant type of lipid in bilayers?
Phospholipids
Name two different types of Glycolipids and why they’re different?
Cerebroside (has 1 sugar attached) and ganglioside (has oligosaccharide attached)
What is the most common length of fatty acid tail for phospholipids?
14-24 carbons
List the functions of the membrane bilayer
Barrier, communication, signal generation in response to stimuli
What properties do lipids in membrane bilayers show?
Flexion, rotation, lateral diffusion, flip flop (rare)
What is lipid flip flop?
Where a phospholipid swaps lamellae. Very rare as its very thermodynamically unfavourable
In what way(s) does cholesterol affect membrane fluidity?
Forms H bonds with FA tails, TF less packing, TF ^ fluidity. Also decreases fluidity because less FA flexion can occur
What properties have cholesterol?
Polar head group, rigid, planar steroidal ring structure, non-polar tail
What movements can proteins in the membrane bilayer do?
Rotation, lateral diffusion, conformational change. NOT FLIP FLOP
In what ways can membrane proteins prevent motility/restrict movement?
Aggregation, tethering (to eg cytoskeleton), interaction (stabilises structure of tissues)
What differentiates peripheral and integral proteins?
Peripheral are bound to the surface not embedded in it, whereas integral ones are embedded in it or pass through it
What forces hold peripheral/extrinsic proteins in place? What can ‘break’ these?
H bonds, electrostatic forces, broken by changes in pH/ionic strength
What holds integral/intrinsic proteins in place? What breaks this?
Interaction with hydrophobic bits of bilayer, removed by agents that compete for non-polar interactions (eg detergent)
Why is flip flop so thermodynamically unfavourable?
It requires a hydrophilic head of the phospholipid to pass through a very strongly hydrophobic region to reach the other hydrophilic region.
What conformation are transmembrane proteins most commonly?
Alpha-helical
What makes up the cytoskeleton?
Spectrin, actin, Akyrin, Band 3 proteins. Band 3 protein bound to Akyrin bound to spectrin. Band 4.1(?) bound to actin bound to spectrin
What are two haemolytic anaemias? How are they treated?
Hereditary spherocytosis, hereditary elliptocytosis. Regular blood transfusions
What is hereditary spherocytosis? What causes it?
Mutation causes deficiency in Spectrin, RBC round up to spherical shape, less resistant to lysis, cleared by spleen TF RBC count drops
What is hereditary elliptocytosis? What causes it?
Defect in Spectrin TF cytoskeleton can’t assemble correctly, form ellipsoid cells, v fragile and lyse
Which is a defect in spectrin and which is a deficiency in spectrin?
Deficiency- hereditary spherocytosis. Defect- hereditary elliptocytosis
