L4- Electrochemical gradients Flashcards
Molecules that punch holes in membranes are said to what?
Facilitate diffusion. As ions can now diffuse across
Why are molecules in liquids in constant motion?
Thermal agitation
What did Fick show?
Diffusion across an interphase is proportional to:
-area of interface
- conc. gradient
(and negatively to distance across)
Which dimension has fastest diffusion?
3D. Lower chance of molecules bumping into each other.
In which dimension do molecules bump into each other more?
2D (or 1d)
This is what catalysts provide- surface where they can bump into each other.
What is the formula for the electrochemical gradient?
ec gradient= (gradient caused by diffusion) - (gradient caused by electrophoretic movement)
What would make a strong electrochemical gradient for example?
A negative electrode on the opposite side from a high conc. of Na+. They would follow electrophoretic and concentration gradients.
Which charge do cells have inside?
Negative
What does the rate at which ions move across the membrane depend on?
- size of elecctrochemical gradient
- nature of the ion
- number of open ion channels
- properties of the ion channel
What is current?
The flow of ions
What is voltage?
Potential difference. Can’t get current if there’s no voltage. More ions on one side than the other.
What is Ohm’s law?
Current (I) = Volts (v) x conductance
or
Current=voltage/ resistance
(resistance is inverse of conductance)
What does selectivity of an ion channel do?
Means only one type of ion can get through, e.g. Na+ can but K+ can’t in a sodium selective channel.
WHat does permeability of an ion channel do?
If it’s more permeable, more ions can get through faster
What in the nature of an ion channel affects rate of ion flow?
- selectivity
- permeability
