membranes Flashcards
function of membranes
control exchange between body compartments (entry/exit of substances into cell)
What does the membrane consist of
Phospholipid bilayer, phospholipid head which is hydrophilic = on outside and fatty tail =hydrophobic= on inside
proteins embedded
What molecules can move through the membrane easily
small lipid soluble molecules
What do membrane proteins do
allow control of movement of molecules in/out of cell, by controlling protein synthesis you control access
What does the cell membrane of capillaries do
control exchange between the plasma and interstitial fluid
Is there more sodium inside or outside the cell
outside
Is there more calcium inside or outside of cell
outside ( and relatively low amount of both in/out compared to sodium)
More potassium inside or out of cell
inside (makes cell negative)
more chloride in/out of cell
outside (nacl)
define diffusion
substance move randomly down a concentration gradient until even (gas and liquids) due to energy in particles
define osmosis
movement of water through a semi-permeable membrane down a concentration gradient (water itself moves)
osmosis vs diffusion
both down a concentration gradient
both passive
diffusion is substance moving, osmosis is about solvent
osmosis is through a partially permeable membrane
define osmolarity
number of particles in a solution Osm/l (per litre) = solute osmotic concentration per volume solvent
define osmostic pressure
pressure needed to oppose osmosis = number of particles per unit volume of fluid
what is an aquaporin
membrane channel that transports water and controls water intake, only water not solutes
define osmolality
expression of solute osmotic concentration per mass solvent = Osm/kg
What is the rate of diffusion dependent on (4)
-membrane permeability to solute (lipid solubility or proteins present, size of molecule)
- diffusion distance (thickness of membrane)
-transmembrane gradients (ions= voltage gradient)
- membrane surface area (bigger=better)
iso/hyper/hypo osmotic
isosmotic = solutions both have same concentration of dissolved solutes (same osmotic pressure)
hyperosmotic= one solution has higher concentration of solutes , so has an increased osmotic pressure
hypoosmotic = one solution has lower concentration of dissolved solutes so has decreased osmotic pressure
what does tonicity depend on
osmolarity of solution and osmolality of cell, biological term relating to solution relative to living cells. tonicity has no units
osmolarity vs tonicity
osmolarity compares 2 solutions whereas tonicity compares solution and a cell , so has no units ( usually in reference to blood )
what happens if a red blood cell is in a hypertonic solution
water will leave the cell and cause it to shrivel up
how does transport of respiratory gases occur
simple diffusion as they are lipophilic
how does pneumonia affect gas exchange
pneumonia causes swelling of alveoli walls so membrane thickens so diffusion is harder = hypoxia
what can passive diffusion be divided into
simple and facilitated