Membranes and membrane transport Flashcards
wk 4
what are the four types of membranes?
nuclear, plasma, mitochondrial and endoplasmic reticulum
What is the basic structure of the phospholipid bilayer
Hydrophilic head, hydrophobic fatty acid chains with intergral and perhipheral proteins and carbohydrates
describe carbohydrates in phospholid membrane.
associated with membrane, attached to lipid and proteins and recognises specific molecules
what effects the fluidity of the phospholipid membrane?
temperature, fatty acid chain length, bonding and presence of cholestrol
what varies in membrane composition?
amount of proteins, cholestrol, carbohydrates and lipids.
If the membrane gets more heat….
it becomes more fluid as lipids move around
if the membrane gets more cold….
less fluid as the chains pack tightly together and are laterally organised.
What is the effect of fatty acids on phospholipid protein?
Long chain = more stiff, shorter chain = less stiff
What is the impact of double bonds in the phospholipid membrane?
makes the fatty acids un-saturated which makes the membrane more stiff.
What is the effect of cholestrol in a low temperature?
increases fluidity of the membrane
what is the impact of cholestrol in a high temperature?
decreases fluidity.
Where are proteins in the phospholipid membrane?
freely migrating or anchored to a specific region.
what is an example of a protein that is bound to cell wall?
Neuronal transmitter protein in plasma membrane of muscle cell. it recognises a chemical signal from a neuron.
what is the ECM made up of?
collagen, fibronectin and heparin
what do membrane proteins bind to?
the ECM
What is the role of integrins ?
maintains structure as it binds to ECM and filaments
what is the importance of cholesterol in membrane proteins?
membrane integrity, source of production for hormones, vitmian D and bile and regulate s fluidity
Is the outside of the cell more postive or negative when compared to the inside? Why
Positive. More posotive ions (Ca, K and Na)
What is hypertonic (on the outside)?
solutes concentrated on the outside of the cell
What is isotonic?
solute concentration is equal on each side of the cell
what is hypotonic (on the outside)?
Less solute on the outside of the cell.
what is a clinical example of osmosis?
Red blood cells.
What happnes when red blood cells are hypotonic on the outside
not enough solute on the outside, cell takes in water and bursts = poor kidney function
What are three types of passive transport?
Simple diffusion, facilitated diffusion and osmosis.
What can move through simple diffusion?
CO2, O2 and lipid soluble subtnaces (steroids)
How does simple diffussion occur?
The molecules engage in random collisions with like molecules.
What is an example of faciliated channel?
Aquaporin (in red blood cells and kidney) where water goes through hydrophilic channel
How does facilated diffusion with a carrier protein work?
molecule binds to specfic carrier –> it chnages shape –> allows to come in
what are the two classes of carrier proteins?
Symporters and antiporters
what are symporters?
Simultaneously transports sugar and ion
what is an example of symporter carrier protein?
Na and Glucose.
What are antiporters?
Where one solute moves in ONE direction whilst the second moves in ANOTHER.
What is an example of a antiporter carrier protein?
Na and Ca in cardiac muscles
What is primary active transport?
When molecules move against the concentration gradient using energy from ATP.
How does the Na/K ATPase (primary active) function?
3 Na+ bind to protein pump INSIDE cell –> ATP breaks into ADP –> protein pump changes shape –> Na is expelled from the cell –> K binds to protein pump (now open to outside) –> K enters the cell.
What is secondary active transport?
The energy from the primary transport creates a ion gradient which is used to transport another compound.
What is an example of secondary active transport?
Na+ gradient using Na symporter
How does the Na symporter work?
Na moves down concetration gradient –> allows for uphill transport of glucose (cotransportred substate)
What is a clinical example of Primary Active transport?
Heart disease- Digoxin is a treatment for heart disease as it increases foce of hear contraction. It inhibits Na/K ATPase. This lowers Na gradient = less Ca exported = stronger muscle contractions
What are the three processes in which macromolecules move?
Phagocytosis, pinocytosis and receptor-mediated endocytosis.
How does phagocytosis occur?
partcile binds to cell surface –> polymerisation and depolumerisation of actin microfilaments –> vacuole forms –> fuses with lyosomes –> digested by enzymes
What are the two roles of receptor- mediated endocytosis?
1- uptake of nutrition
2. Waste disposal
Describe the mechanism of action for receptor-mediated endocytosis.
Plasma membrane folds inwards –> folds into a small pocket around materials –> pocket deepens forming a vesicle –> vesicle separates from plasma and migrates contents to centre
What are the main differences between carrier and channel?
Binding (carrier binds), speed (channel is faster) and make up (channel= tunnel/pore, Carrier= conformational change)
What is the difference between peripheral and integral proteins?
Peripheral = surface whilst intergal is all the way through.
What is the role of intergrin and how?
ntegrins: bind ECM and to actin filaments (part of cytoskeleton) on inside
