The mammalian cell & membrane transport (lectures 6 & 7) Flashcards
what are the 2 body fluid compartments?
ICF - intracellular fluid
ECF - extracellular fluid
• plasma
• interstitial fluid
ECF has a very different composition to the ICF
why are body fluid compartments in a state of chemical disequilibrium?
ionic compositions are very different
due to:
• active transport of solutes
• membranes act as barriers to prevent solutes diffusing to alleviate the disequilibrium
why are body fluid compartments in osmotic equilibrium?
water is the only molecule that can freely move between compartments
what is osmolarity?
the number of particles per unit volume
how are concentration and osmolarity different?
concentration is based on particle weight
osmolarity is based on particle number
why are organic solutes a problem in maintaining intracellular osmolarity?
they are relatively large and some are highly charged
this attracts many counter ions which significantly contribute to osmolarity
cell in danger of being perpetually hyperosmotic to ECF and possible rupture due to continual osmosis
answer:
cells actively pump inorganic ions out
what are the 2 types of membrane transport proteins?
CARRIER PROTEINS
bind solute on one side of the membrane and deliver it the other by a conformational change in protein
CHANNEL PROTEINS
form hydrophilic pores in the membrane through which many solutes can diffuse
what is passive transport?
downhill transport
from high to low concentration
no energy input
simple diffusion
facilitated diffusion
what is primary active transport?
uphill transport coupled directly to ATP hydrolysis
what is secondary active transport?
when a generated solute gradient is used by a cotransporter protein to drive uphill transport of a second molecule
coupling uphill transport to downhill transport
exploits the downhill gradient
what is a uniport?
carrier that only transports one substance
what is a antiport?
transported molecules are in opposite directions
what is a symport?
both transported molecules are in the same direction
what is the sodium potassium pump an example of?
primary active antiport transport
3Na+ out and 2K+ in
what is the pumping cycle of the sodium potassium pump?
1) 3 Na+ bind to cytosolic binding sites
2) hydrolysis of ATP
3) conformational change of protein and Na+ released outside
4) 2 K+ bind to extracellular binding site
5) dephophorylation
6) protein returns to original shape and K+ released inside the cell
