L17 - Introduction to cell membranes (2) Flashcards
What is an example of a peripheral protein?
RED blood cells that can be viewed by scanning microscopy.
Describe the nature of the cytoskeleton of red blood cells as an example of peripheral proteins.
The cytoskeleton is linked to the plasma membrane.
Red blood cells as an example: Mutations in spectrin cause certain types of hemolytic anemia.
Why is membrane aysymmetry important?
- COAGULATION - clot formation as provides the nucleation site for the coagulation cascade.
- CELL RECOGNITION AND CLEARANCE - identification of dead cells for e.g.
What are the blood group substances?
ABO system - A,B,O or AB
O is the universal donor
AB is the universal acceptor
The blood group is determined by the structure of the ogliosaccharides attached to sphingomyelin and proteins in the red blood cell membrane and to proteins in plasma and other body fluids.
What is the function of membrane proteins?
Membrane proteins each transport a particular solute. They are all multi-pass integral membrane proteins. They allow the solute to pass through the membrane so it does not come into contact with the membranes hydrophobic core.
What is passive transport and what is active transport?
Passive transport: solute moves down its concentration gradient (channels and carriers).
Molecules move with the concentration gradient
Through carriers or channels
The movement through a channel can be regulated by the channel opening and closing - by ions, voltage changes or ligand binding – called Gating
Active transport: solute moves against its concentration gradient so requires energy
(only carriers).
Molecules move against concentration gradients through the action of carriers
Energy dependent process. The energy can come from the electrochemical gradient, ATP or light.
What is an electrochemical gradient?
A gradient that is established by ionic differences on either side of the membrane (produced by the action of ion channels and carriers/pumps)
Do channels or carriers transport solute more rapidly?
Channels transport solute more rapidly than carriers.
Carrier proteins directly bind to the solute, whereas channels proteins only interact very weakly with the solute, so can transport solutes quicker.
Carrier-mediated diffusion enhances the rate of transport. What are the 3 types of carrier-mediated transport?
Uniport, Symport and Antiport
Glucose uptake is driven by an electrochemical gradient. What are the 3 carriers involved?
Glucose transports across epithelial cells and involved the combined action of 3 epithelial cells.
Glucose/sodium ion symporter at the apical surface
Sodium/Potassium pump at the basal surface
Glucose carrier at the basal surface
