2-Active Transport (11 Oct) (2-pump vs carriers: (both are carrier…
2-Active Transport (11 Oct)
1-primary active transport= pump
1- def: a carrier based protein which a motor connected to it- we can power that motor to operate against the conce. grad.
structures are similar in nature to the carriers
but they have fuel source that:
allows utilisation of ATP to power conformational change and drive transport of solutes against their concentration gradient
phosphorylation of particular protein
that triggers the conformational change and
changes the binding affinity for that solute
2-pump vs carriers:
facilitated diffu uses carriers
active transport uses pumps
both are carrier mediated transport
both are called transporters
binding the solute and transporting them across the memb.
pumps: ATPase enzyme that are also carriers
hydrolyse ATP to ADP and phosphate which drives the pumping process
3- Sodium potassium pump=Na+/K+pump
present in every cell in the body :all
nerve cells use the movement of ions Na and K across membrane
function of that pump is sugg. to be 2/3 of the energy devoted for the function of the cell
pumps Na and K ions in sequence
remov. Na ion in one
remov. K + in another direction
trasp. 3 Na+ out of the cell
2 K+ into the c.
by operating the pump
not only changing the conc, of solute. in either side of the memb.
but also in separation of charge and contributing in the establishment of the membrane potentials
keeping the intra cellular conc. of Na+ low :black_flag:
becau. of pumps 3 Na+ out
keeping the intra cellular conc. of K+ high :red_flag:
becau. pumping K+ into the cell against its conc. grad.
2 +ve charge coming in and 3+ve charge going out of the cell
adds an additional negative charge to the inside the cell: each time it operates
Na+ /K+ pump is electrogenic :star:
net movement of charge
def: the actual operation of the pump generates a separation of charge from the inside and outside of the cell
contributes to the resting memb. potentials:
inside is more negative with respect to the outside of the cell
establishing or contributing to the membrane potentials= the electro potentials of the cell
being able to establish electrical gradients across epithelial cells and across different tissues within the body
example: how can actually influence the charge and movement of solutes across the apethilial cells
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maintains intra- & extracellular Na+ & K+ concentrations
4- diagram of Na+/K+ pump sequence
E1 form + ATP+
3Na+ + hydralysis of ATP + phosphorylation of protein
cause conformational change>>E1p (occludes Na+)
spontaneous change of conformation:>>E2P
opening of the extra cellular site
Na + diffuse out to the extracellular site
E2-P form empty: opens up the availability
of binding site for potassium
dephosphorylation of protein>>E2 occludes K
binding of ATP changes the conformation>> E1
and release the K+ inside the cell
we can block the Na+/K+ pump
with E2-P conformation
has a binding side
inactivates the Na+/K+ pump
problematic when you consider
this pump is present in all cells of the body
if we want to inhibit it that can have
significant effect on cell function
5- how Na-K pump influence the charge and movement
of solute across epithelial cell
independantly of direct transfer of Na and K
on the apical site of epithelial cell :question:
presence of certain channels: a Na channel
allows the diffu. of Na ino the cell
increasing the intracellular concentration of Na
this is specific expression of ion channel on the apical side of the memb.
on the basolateral site we have expression of different type of ion channels
the distinction of ion channel expression on the apical side vs. basolateral side is very important aspect involved with the transfer of solutes across epithelial cell=transcellular transport of these solutes
on the basolateral side we have
Na-K pump and K channel
if we have Na comming in from apical memb.
increasing Na conc.
Na-K pump binds to 3 Na ions
pumps it out of the cell
brings 2 K ions into the cell
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6- Na-K pump help maintain cell volume
bec. it regulates the conc. of ion across membrane
regulating the osmolarity of
the cell or the cytoplasm inside the cell
helps to maintain the water balance
the osmotic gradient across the cells influence the movement of water
once the Na-K pump is operating appropriately
the ion concentration grad. is constant
conc. of the osmolarity inside
the cell is the same as the outside
NO real net movement of water ino or out of the cell
if we block the sodium potassium pump using Ouabain
stop the functioning of that channel
run down the concentration grad.
we have the net mov. of 3 Na+ into the cell
and 2K+ out of the cell
the changes in the conc. grad.
because of the block of the pump
increase the osmolarity in the cell
diffu. of w into the c.
thru osmosis down its conc. grad.
cell swelling and potential lysis of the cell
7- Na-K pump benefits
helps maintain the conc. grad.
helps influence the electrical properties of the c.
and interstitial spaces
helps to maintain the osmolarity
volume of the c.