Transport of Molecules Across Membranes Flashcards
What types of molecules are able to cross a pure lipid bilayer? By what mechanism do they cross?
- Gases & small polar / uncharged molecules
- Passive diffusion
What types of molecules are NOT able to cross a pure lipid bilayer?
- Ions
- Charged molecules
- Large uncharged / polar molecules
What TWO factors influence the movement of charged molecules across a membrane?
- Concentration gradient (chemical)
- Electrical Potential (voltage)
What does the Electrochemical gradient determine?
The energetically favourable direction of movement of a molecule
What equation gives the equilibrium potential for two solutions separated by a membrane that is permeable only for a given ion (X+/-)?
Nernst Equation
(don’t need to know the equation)
TRUE OR FALSE:
When ΔG is negative, there is net movement of a molecule INTO the cell?
True
What are the THREE broad classes of transport proteins?
- ATP-powered Pumps
- Transporters /Carriers
- Ion Channels
What type of transport do ATP-powered Pumps facilitate?
Active Transport
What type of transport do Transporters / Carriers facilitate?
- Facilitated Diffusion
OR - Coupled Transport / Secondary Active Transport
What type of transport do Ion Channels facilitate?
Facilitated Diffusion
What are the THREE classes of ATP-powered Pumps?
- P class
- V class
- ABC superfamily
What are the THREE classes of Ion Channels?
- Voltage gated
- Ligand gated
- Non-gated (resting)
What are the THREE classes of Transporters / Carriers?
- Uniporters
- Symporters
- Antiporters
What reaction powers ATP-powered Pumps?
ATP hydrolysis
* ATP –> ADP + Pi
TRUE OR FALSE:
ATP-powered Pumps transport molecules WITH their electrochemical gradient?
False.
They transport AGAINST the gradient
What is Active Transport?
Coupling of ATP hydrolysis and “uphill” transport of ions or small molecules
Does Active Transport provide high or low rates of transport?
Low