ICPP 2 Membrane Permeability: Transport Of Ions And Small Molecules Flashcards
What is a semi permeable membrane?
A layer through which only allowed substances can pass
What is passive transport independent on?
Permeability
Concentration gradient
What is the net rate of transport given by?
Fick’s law
What is Fick’s law?
J = P(C1-C2) given in exam
P- permeability coefficient
C- concentration gradient on either side
Define passive transport
Solutes move by diffusion down conc. or electrical gradient
No energy required
Define active transport
Solute moves against concentration gradient
Energy required
Example of a non gated pore
Na+/K+ leak channels
Example of ligand gated ion channel
Nicotinic ACh receptor in neuromuscular junction
Why do patients with cystic fibrosis have thick mucus and find it hard to breathe?
- Mutation in cystic fibrosis transmembrane conductance regulator
- Stops Cl- form leaving (and taking 5 H2O with it)
Explain the cystic fibrosis transmembrane conductance regulator
1- transports Cl- out of epithelial lung cells
2- takes 5 H2O out with it per Cl-
3- Moistens surroundings
What impact does vibrio cholera infection have on the cystic fibrosis transmembrane conductance regulator?
What does this cause?
1- toxin produced
2- produces protein kinase A
3- phosphorylates cystic fibrosis transmembrane conductance regulator
4- CFTCR remains permanently open
5- Cl- and H2O leaves
6- diarrhoea
How does cholera cause diarrhoea
1- toxin produced
2- produces protein kinase A
3- phosphorylates cystic fibrosis transmembrane conductance regulator
4- CFTCR remains permanently open
5- Cl- and H2O leaves
6- diarrhoea
Types of carrier proteins
Uniport - one substance
Co transport- 2+ substances
- symport - same direction
- antiport - opposite direction
Symport co-transporter
Transport of 2+ substances in the same direction
Antiport co-transporters
Transports 2+ substances in opposite directions
Examples of 4 co-transporters
- Na+/K+ ATPase
- Na+/Ca+ exchanger NCX
- Na/H+ exchanger NHE
- Na+/glucose co-transporter
What type of active transport is in Na+/K+ ATPase?
Primary active transport
What type of protein is Na+/K+ ATPase?
Antiport co transporter
Na in
K out
What type of active transport is in Na+/Ca2+ ATPase?
Secondary active transport
What type of active transport is in Na+/H+ ATPase?
Secondary active transport
What type of protein is Na+/Ca2+ ATPase?
Antiport co-transporter
Na in
Ca out
What type of protein is Na+/H+ ATPase?
Antiport co-transporters
Na in
H out »_space; cel alkalisation
What type of protein is Na+/glucose ATPase?
Symport co-transporter
Both in
Physiological roles of transport processes
- Maintenance of ionic composition
- Maintenance of intracellular pH
- Regulation of cell volume
- Concentration metabolic fuel + building blocks
- Expulsion of metabolic waste + toxic substances urea
- Generation of ion gradients necessary for electrical excitability of nerve + muscle
What type of molecules can permeate a lipid bilayer?
Examples
- Hydrophobic molecules - O2, CO2, N2, benzene
- Small uncharged polar molecules - H2O, urea, glycerol
What type of molecules can’t permeate a lipid bilayer?
Examples
- Large uncharged polar molecules - glucose, sucrose
- Ions - H+ Cl- etc.
