ICPP 3 Flashcards
What is a semi-permeable membrane?
A layer through which only allowed substances can pass
What does passive transport rely on?
permeability and concentration gradient
What important roles do transport processes play?
Maintaining ionic composition
Maintaining pH
Regulating cell volume
Ion gradients for excitability of nerve and muscle
What are 2 examples of ligand gated ion channels, and the benefit of this transport?
- nACh receptors, Na+ influx
- ATP sensitive K+ channels , close when ATP binds.
This mechanism is FAST.
What does the movement of charged molecules (ion) depend on?
Concentration gradient AND electrochemical gradient.
Will follow concentration gradient first but if equal concentration, a positive ion will want to move to the negative side and vice versa.
What is the difference between a primary active transporter and a secondary active transporter?
Both transporters require energy, however primary active transports utilise ATP directly, whereas secondary transporters use existing concentration gradients. E.g NCX uses Na+ gradient to move calcium.
PMCA= primary transporter, uses ATP hydrolysis.
What is the free ion distrubution across the membrane of Ca2+,Na+,K+ and Cl-?
Calcium: EC = 1mM, IC= 100nM
Na+: EC = 140mM, IC=14mM
K+: EC=6mM, IC= 160mM
Cl-: EC= 120mM, IC= 4mM
Give an example of a unitransporter.
PMCA.
Proton pump.
What is the different between a symporter and an antiporter?
Both are mechanisms for cotransport.
Symporter moves both molecules the same way.
Antiporter moves molecules in opposite directions.
What are the functions of the Na+K+ ATPase?
- Forms cellular concentration gradient of Na+ and K+.
2. Drives secondary active transport.
Give 2 examples of secondary active transport.
Na+/H+ exchanger
Na+ glucose symporter in SI
Which calcium transporter has a high affinity but a low capacity?
PMCA
Wich calcium transporter has a low affinity but a high capacity?
NCX
Reversal of the NCX has a possible role in ____.
Ischaemia. K+/Na+ ATPase stops functioning due to no ATP, intracellular Na+ rises and reverses the NCX.
What are 2 acid extruder transporters?
Na+/H+ exchanger
Cl-/HCo3- transporter
Both alkalinase the cell
What is an example of a base extruder?
Cl-/HCO3- exchanger
What is amiloride?
A potassium sparing diuretic which inhibits the Na+/H+ exchanger
Transport of _______ is key in cell volume regulation.
Osmotically active ions
What transporter moves glucose from the gut lumen to the epithelial cells?
SGLT-1-Na+ dependent glucose symport
Once in the epithelial cell, how does glucose then move into the blood?
GLUT transporters (GLUT 2 here). Facilitated transport down its concentration gradient
What ensures that there is always a low concentration of glucose?
Rapid conversion to Glucose - 6-phosphate on entering the cell by hexokinase in liver and glucokinase in other cells.
How does insulin stimulate the rate of uptake of glucose into adipose tissue and skeletal muscle?
Recruits Glut-4 transporters from the internal vesicular membranes to the plasma membrane to increase the transport capacity.
What is the MOA of fluoxetine?
Outward flow of K+ leads to uptake of serotonin through SERT in synaptic cleft.
Fluoxetine inhibits SERT.
What is the structure of the Na+/K+ ATPase?
Alpha and beta subunit.
Beta subunit directs pump to the surface
Alpha subunit has binding sites
Why is the Na+/K+ ATPase ‘p-type’?
It phosphorylates aspartate
