M&R Session 2- Membranes As Permeability Barriers Flashcards
What is passive transport?
Movement of ions/molecules down a concentration gradient.
Doesn’t require energy.
What is active transport?
Movement of ions/molecules against unfavourable electrical and chemical gradients.
Requires energy.
Define uniport.
When a solute molecule is transported from one side to the other side of a membrane.
Define symport.
When the transfer of one molecule depends on the transfer of a 2nd molecule in the same direction.
Define antiport.
When the transport of one molecule depends on the transfer of a 2nd in the opposite direction.
Which two groups can freely move through the bilayer?
- hydrophobic molecules e.g oxygen, carbon dioxide, nitrogen and benzene
- small, uncharged, polar molecules e.g water, urea and glycerol.
Which two groups of molecules cannot freely pass through the bilayer?
- ions e.g sodium, chloride, potassium, magnesium, calcium etc
- large, uncharged, polar molecules e.g glucose and sucrose
What is secondary active transport?
When the transport of one substance is linked to the concentration gradient of another substance.
What does secondary active transport require?
A co-transporter
What is the rate of passive transport proportional to?
The concentration gradient.
What are the two methods of facilitated diffusion?
- ping-pong
- protein channels
Why is facilitated diffusion saturable?
Because each protein transporter can only interact with a few ions/molecules therefore as the concentration gradient increases, eventually, all receptor spaces will be filled and the rate will reach a maximum.
What is the direction of movement of sodium ions (give concentrations)?
From out to in.
145mM to 12mM
What is the direction of movement of potassium ions?
In to out
155mM to 4mM
What is the direction of movement of chloride ions?
Out to in
123mM to 4.2mM
