Lecture 6: How molecules pass the plasma membrane Flashcards
What is diffusion?
the movement of molecules from one area to another.
FROM HIGH CONCENTRATION TO LOW CONCENTRATION
What is typically the Net movement for diffusion
0
What does the steady-state/equilibrium entail?
NO net change (not necessarily no movement but overall no change)
What is a concentration gradient?
it is the difference (delta) in concentration between two sides
Do charges affect the movement of ions? why or why not?
- YES they do
- like charges repel each other
- opposite charges attract each other
What is an electrical gradient?
it is the difference in charges, the total positive on one side vs another
How does passive diffusion work with the plasma membrane?
- no energy is required
- uses a concentration gradient to move molecules from high concentration to low concentration
- reaches a steady state
What is an example of passive diffusion across the plasma membrane
oxygen transports across the lung membrane
What is Fick’s Law of diffusion?
the influences of factors on the rate of net diffusion of a substance across a membrane
Which factors increase the rate of diffusion according to Ficks law?
- the concentration gradient of the substance
- the surface area of the membrane
- lipid solubility
How many factors affect the rate at which molecules cross the membrane according Fick’s Law
5
Which factors decrease the rate of diffusion according to Ficks law?
- the molecular weight of the substance
- distance (thickness)
What is passive diffusion of ions?
- charged properties
- their movement is based on the concentration gradient AND their chemical charge
What is the gradient that is caused by passive diffusion of ions?
electrochemical gradient
What is osmosis?
the diffusion of water molecules
