Flashcards in Forces across membranes Deck (31):
if a molecule is hydrophilic it is also.....
lipophobic (and vice versa)
describe the general structure of membranes?
- embedded with glycoproteins
- embedded with glycolipids
- phospholipds contain hydrophilic phosphate heads and hydrophobic lipid tails
- cholesterol molecules stabilise membrane
what are the function of glycoplipids in membranes?
used in self recognition (antigens) and the immune response
what is the function of receptor proteins?
are intergral with allows communication between the ECF and ICF
what is the function of peripheral membrane proteins?
- anchor membrane to cytoskeleton
- performs siganlling functions
- attch cell to exctracellular matrix
which membranes have the lowest protein content?
myelin (18% protein)
which membranes have the highest protein content?
membarens involved in energy transduction e.g inner membranes of mitochondria (~75%)
what is the protein content of plasma membranes?
what are electrochemical gradients?
gradients resulting from the difference between electrical charge and concentration
what are the concentrations of ions in the fluid compartments?
ECF: high Na+, low K+
ICF: Low Na+, high K+
describe the process of endocytosis
invagination of cell membrane creates a vesicle which transports macromolecules inside cells
what is the function of the cell membrane? (4)
- act as a selectively permeable barrier
- maintain concentration gradients
- provide site for receptors
- allows the transport of molecules
what properties do molecules need to pass through the bilayer easily?
- uncharged (non polar)
what type of channels allow passage of water
describe the structure of open channels
form water filled pores thta allow the passage of water soluble molecules
what two general types of channel proteins are there?
closed ion or open ion
what two types of gated chennels are there?
voltage gated and ligand gated
what is diffusion?
a process by which substances move between two compartments allowing the substance to spread across the whole volume giving equal concentrations
how do carrier proteins function?
have binding sites for solutes, the binding of the solute causes a conformtaional change
- can only be open to ECF or ICF but not both at the same time
what is movement through a carrier protein with the concentration gradient called?
what is movement through a carrier protein against a concentration gradient called?
active transport (requires ATP)
how does the Na+/K+ ATP pump work?
is an electrogenic pump
- 3 Na+ out for every 2 K+ in
how much of the bodeis resting energy used to power Na+/K+ pump?
what is osmosis?
the net movement of water from an area of high water concentration to an area of low water concentration
what is the osmotic pressure?
the force required to oppose the increase in volume resulting form osmosis
what is osmolarity?
the number of solute PARTICLES in solution
what is osmolarity measured in?
what is the osmolarity of plasma
285 millisomoles (300)
what is tonicity?
the number of NON-PENETRATING particles in soltution
what terms can be used to describe solutions?