Intro To Cell Membranes Flashcards
What does the appearance of biological membranes differ on?
They differ depending on location and function
What do plasma membranes do ?
They provide cell boundary and prevents movement of materials in to and out of the cells
What do organelle membranes do ?
Divide cytoplasm into compartments
What are the fundamental properties of membranes?
- Barrier
- Flexible, self-repairing, continuous
- Selectively permeable
Can phospholipids move about in the bilayer?
Phospholipids can rotate or exchange in the lateral plane of the membrane - but normally move very slowly from one leaflet to the other
What determines the fluidity of the lipid bilayer?
Its composition. The greater the number of double bonds, the shorter the acyl chains, the less tightly packed the molecules are = greater the fluidity
What does amphipathic mean?
It is a molecule which has a polar and non polar region.
What determines the fluidity of lipid bilayer?
No. of double bonds and No. of C atoms in the fatty acid chains of the phospholipids.
How are phospholipids Amphipathic?
Polar Headgroup and hydrophobic tail.
What state of matter are membranes at the temperature of the organism?
Fluids (liquid)
Describe the composition of a cell membrane in a cold - blooded animal.
More double bonds and/or shorter acyl chains than membranes of warm blooded animals
What is the net charge of Phosphatidyl serine?
-1
What effects does cholesterol have on the cell membrane?
Makes the membrane less permeable.
Packs between phospholipids and makes the membrane less deformable at the surface. It does not make the overall membrane more rigid
What does high concentrations of cholesterol do to the membrane ?
Prevents the membrane from becoming crystalline
What is crystalline?
Solidification of membranes.
What are formed by lipids in aqueous solutions?
Micelles or bilayers.
What do lipid bilayers preferably form?
Sealed compartments.
What are integral membrane proteins?
They are proteins that directly insert in the membrane by a hydrophobic domain.
What are peripheral membrane proteins?
Peripheral membrane proteins are extrinsic membrane proteins temporarily bound with membranes which helps in cell signalling.
What two ways can peripheral membrane proteins associate with the membrane?
- Associate with integral membrane proteins or directly bind lipids
- Covalently bound lipids which insert into the membrane
What are micro domains?
micro domains refer to small, specialized regions within the cell membrane.
What do membrane lipids form?
Clusters or microdomain
What forms rafts?
Cholesterol and sphingolipids can form micro domains called rafts.
Membrane (raft) is slightly thicker in the microdomain
Where do tight junctions prevent movement?
They prevent movement between apical and baseolateral membranes
What does the cytoskeleton do to RBC?
Flexible cytoskeleton gives red blood cells its flexibility and rigidity
What do optical tweezers show us about the red blood cell membranes?
Shows us the tensile strength of red blood cell membranes
What happens when red blood cells are placed in hypotonic solutions?
Hypotonic solutions can cause red blood cells to swell and potentially burst due to the influx of water through osmosis.
What are red blood cell ghosts?
Predominantly plasma membrane (check)
What happens when red blood cells are placed in hypertonic solutions?
When red blood cells are placed in a hypertonic solution, they will lose water and shrink.
What do mutations in spectrin cause?
Mutations in spectrin causes certain types of hemolytic anemia
Integral proteins acts as anchor within the cytoskeleton (check)
Are membranes symmetric?
No they are asymmetric
When is membrane asymmetry important?
Coagulation
Cell recognition and clearance
Why is O antigen a universal blood donor?
The structure of the O antigen will be recognised in A and B antigens
What is coagulation?
Coagulation is the process by which blood changes from a liquid to a gel, forming a blood clot.
It’s a vital mechanism that helps stop bleeding when a blood vessel is injured.
Is AB a universal blood acceptor or donor?
Universal acceptor
Why do channels transport solute more rapidly than carriers?
Carrier proteins directly bind to the solute whereas channel proteins only interact very weakly with the solute
(Channels can transport 100 million ions per second)
Suggest 3 features for the ion channels
Form narrow hydrophilic pores through the membranes
Are specific for different ions - e.g. potassium channel, sodium channel
Allow rapid movement of ions down the conc gradient or electrochemical gradient
How many different types of channel are there ?
Over 100 different types of channel with different properties
What does the mutation of voltage-gates sodium channel SCN9A cause?
It causes congenital insensitivity to pain
What are the 3 types of carrier - mediated transport ?
Uniport
Symport
Antiport
The mammalian plasma membrane is transport driven by __?
Sodium gradients
Bacteria, yeast, intracellular membranes are transport driven by __?
Proton gradients
Bacteria, yeast, intracellular membranes are transport driven by __?
Hydrogen gradients
Glucose uptake is driven by ___?
An electrochemical gradient
Describe the 3 types of transport of glucose at a transcellular level
Glucose/sodium ion symporter at the apical surface
Sodium/Potassium pump at the basal surface
Glucose carrier at the basal surface
