1
Q
ATP powered pumps
A
- Couples hydrolysis of ATP to transport of a molecule against its conc. gradient
2
Q
Channel proteins (ions)
A
- Transport ions down conc. gradient through hydrophillic pore in emmbrane protein. Can exist in an open or closed conformation & when open many ions can pass simultaneously
3
Q
Carrier Proteins (transporters)
A
- Bind water-soluble molecule on one side of the membrane & deliver them to the other side. involves a conformational change in the protein. Only bind over a few molecules at a time
4
Q
Uniports
A
- Work in passive diffusion & are selected for one type of molecule. They move molecules down their conc. gradients
- High rate of substance movement
- Partition coeffecient irrelevant
- No contact with hydrophobic lipid environment
- Limited by # of uniporters in membrane
- Specific transport
5
Q
GLUT1
A
- Main unporter for glucose in erythrocytes
6
Q
Symporter / Antiporter
A
- Use an existing electrochemical gradient rather than ATP hydrolysis to move 1 of the molecules against its conc. gradient & a second molecule down its gradient
- Secondary active transport
- Conformational change necessary to deliver the 2 molecules to other side of membrane only happens when both are bound to transporter
7
Q
P-class ATP powered pumps
A
- Heterotetramer with 2 subunits α α & β
- β phosphorylated during transport
8
Q
V-class ATP powered pumps
A
- Multiple subunits
- transports only protons against their gradient
- acidifies lysosome & vacuole
9
Q
F-class ATP powered pumps
A
- Multiple subunits
- related to V-class
- only member that generates ATP
- pumps only protons
- found in inner membrane of mitochondria, thylakoid, bacterial plasma membrane
10
Q
ABC superfamily
A
- More members than other classes
- Transport sugars, amino acids, phospholipids, proteins
- Responsible for multidrug resistance
11
Q
K+ / H+ ATPase
A
- Pareital cells of stomach
- Produces acidic environment
- Target of drugs like Prilosec, Nexium, Prevacid
- Acidity can also be centralised by basic anions found in over-the-counter medications
12
Q
Na+ / K+ ATPase
A
- Inhibited by the poison ouabain. By altering Na+ gradient, it indirectly affects Na+ / Ca2+ exchanger pumping Ca2+ out of cells, causing increased intracellular Ca2+. Affects heart contractions
13
Q
CFTR
A
- Cystic Fibrosis Transmembrane conductance Regulator
- Member of ABC superfamily
- Not a pump, but rather a transport of Cl- coupled to both ATP hydrolysis & ATP binding
- Epithelial cells of lung
- Allows water to flow out in response to outward movement of ions, hydrating mucous layer
- Layer captures bacteria & is easily washed away from airways
14
Q
∆F508
A
- Accounts for ~70% of CFTR mutations in the US
- Protein doesn’t fold at body T, but folds & is functional at lower T
15
Q
∆G551D
A
- Accounts for 4% of CFTR mutations
- Channel reaches cell surface but doesn’t open properly
- Kalydeco is an approved drug keeping channel open
16
Q
Voltage-gated ion channels
A
- Respond to changes in electric potential across membrane
- Found in all nerve cells, also found in muscle cells, egg cells & plants
- Opening of channel further changes membrane potential, can either activate / inactivate other voltage - gated channels
17
Q
Ligand-gated ion channels
A
- Respond to binding of a ligand e.g. a neurotransmitter or inward-rectifying potassium channels (Kir) that respond to the intracellular ligand PiP2
18
Q
Mechanically-gated ion channels
A
- Respond to mechanical force
- Auditory hair cells use this: Sound waves cause channel to open, causing ion flow that affects voltage-gated channels who transmit signal to brain
