Membranes Flashcards
What causes cystic fibrosis?
Defects in a chloride channel. This is caused by issues with endoplasmic reticulum due to incorrect folding.
What are 3 uses of epigenetic gene editing selection of new crop varieties?
- increased photosynthesis efficiency
- crop yield
- resistance to pests and disease
What is the benefit of sub-cellular molecules being compartmentalisation?
Allows for areas to be optimised for a particular function.
What type of cells allow for electrical insulation (think axon)?
Shwann cell
What disease can defects with myelination lead to?
Multiple sclerosis
What is the role of plasma membrane?
Provides cell boundary & prevent movement of materials in to & out of the cell
What is the role of organelle membrane?
Divide cytoplasm into compartment
What are the fundamental properties of membranes?
- barrier
- flexible
- selectively permeable
- only certain molecules can pass into & out of cells
What are the main components of the membrane?
- lipids
- proteins
- carbohydrates
What are the 2 types of movements that phospholipids carry out?
- rotate
- exchange
What type of movement rarely happens in phospholipids?
Flip-flop
Why is the flip flop movement rarely adopted by phospholipids?
As its not energetically favourable
Describe the amphipathic parts of a phospholipid
- Polar head-group
- Hydrophobic tail
Why would there be a kink in the phospholipid?
If there was an unsaturated double bond
Why does an unsaturated double bond cause a kink in phospholipids?
because it changes the bond angle
Are unsaturated double bonds usually cis or trans?
Cis
What is the difference between cis and trans phospholipid bonding?
Trans - Hydrogen bond to carbon on opposite sizes
Cis -Hydrogen bond to carbon on the same sizes
How does the number of double bonds in the fatty acid chain of phospholipids determine fluidity?
the greater the number of double bonds, the less tightly packed the molecules are, and therefore the greater the fluidity.
Do cold-blooded or warm blooded have more double bonds?
Cold-blooded animal membrane
What are the 4 types of major membrane phospholipids?
- Phosphatidyl ethanolamine
- Phosphatidyl serine
- Phosphatidyl choline
- Phosphatidyl myelin
Why is Phosphatidyl serine different to the other phospholipid membranes?
it is negatively charged
What are the 3 parts of cholesterol?
- polar head
- rigid steroid ring structure
- non-polar hydrocarbon tail
What is the purpose of cholesterol?
Prevent the membrane from becoming crystalline. Regulates fluidity
What is a micelle?
Another formation/different type of packing of lipid molecules
What is a bilayer?
More biologically relevant - fatty acid tails points inwards away from the aqueous environment.
Why is the fact that phospholipids form a spherical shape due to their chemical makeup biologically useful?
If the cell is broken the membrane wants to repair itself
What is the purpose of membrane proteins?
Provide functional units (the orientation of a protein is always the same in the membrane)
What Fluorescence recovery after photobleaching (FRAP)?
Areas of a tissue is photobleached, before a laser removes the fluorescence from the area. Diffusion occurs which then makes the area bleached again, as fluorophores diffuse into the area.
Describe transmembrane domains’ structure?
Alpha helical
What do peripheral membrane proteins do?
Associate with integral membrane proteins or directly bind lipids
What can cholesterol form if there are lots of cholesterol molecules?
Microdomains
What type of junction prevents proteins from moving?
Tight junction
What does membranes having tight junctions allow to happen?
Allows the apical & basal lamina to have different domains, as proteins can move between the 2 surfaces.
What 2 molecules determine the properties of a membrane?
The protein & lipid composition
What are the roles of the lipid & proteins in the membrane?
Lipids = provide the overall structure of the membrane.
Proteins = perform specific function
What is the advantage of red blood cells having a biconcave?
- allows more effective absorption of oxygen
- need to change shape to fit though capillaries
What protein forms dimers beneath the membrane by connecting integral proteins?
Spectrin
Do membranes tend to be symmetrical?
membranes tend to be asymmetrical
What are the possible blood groups you could be?
O, A, B, AB
What determines your blood group?
The structure of the oligosaccharide attached to the sphingomyelim and proteins in the red blood cell membrane.
What are 2 events where membrane asymmetry is important?
- coagulation (clot formation)
- cell recognition & clearance
Why is membrane asymmetry important in coagulation?
Phosphatidyl serine on platelets & other cell membranes provide the nuclear ion site for the coagulation cascade
Why is membrane asymmetry important in cell recognition?
The macrophage plasma membrane contains receptors, which recognise aminophospholipids. These are transferred to the outer leaflet of the plasma membrane of apoptosis cells.
What type of molecules are lipid bilayers highly impermeable to?
Polar molecules and ions
What is a liposome used for?
DNA/RNA/drug delivery, cosmetics
What is cystinuria?
Crystals of cystine form, due to genetic defect in transporter. Rare condition in which stones made from an amino acid called cysteine form in the kidney, ureter & bladder
Describe the transport molecules involved in passive transport
Channels & carriers
Describe the transport molecules involved in active transport
Carriers
What are other names given to carrier proteins?
Pump, permease, transporter
What 2 factors contribute to electrochemical gradient?
Membrane potential
Concentration gradient
What transports solutes faster - channels or carriers?
Channels
Why are channels faster than carriers?
Channel proteins only interact very weakly with solute, while carrier protein directly bind to the solute.
What do ion channels do?
Allows transport of different ions, which are specific to that channel. This occurs by forming narrow hydrophilic pores through membranes. This allows rapid movement of ions down the concentration gradient of electrochemical gradient.
What 2 things can regulate ion channels?
- changes in voltage
- binding of small molecules (ligands)
What 3 things can mediate active transport?
- coupled carrier
- ATP-driven pump
- light-driven pump (harnessing of light)
What are the 3 types of carrier-mediated transport?
- uniport
- symport
- antiport
What does it mean if carrier-mediated transport is uniport?
Transport one solute
What does it mean if carrier-mediated transport is symport?
Both move in same direction
What does it mean if carrier-mediated transport is antiport?
Move in opposite direction
What is a benefit of carrier mediated processes?
Enhance concentration of solutes that are found in low concentrations
What is mammalian plasma membrane transport driven by?
Na+ gradients
What is bacteria, yeast, intracellular membranes transport driven by?
H+ gradients
What 3 carriers are needed to transport glucose across epithelial cells?
- glucose/sodium symporter (apical surface)
- sodium/potassium pump (basal surface)
- glucose carrier (basal surface)
What 2 types of proteins make up the erythrocyte cytoskeleton?
- integral proteins
- peripheral membrane proteins
