Cell Membranes- Diffusion Flashcards
What is diffusion?
The net movement of molecules or ions from an area of higher concentration to an area of lower concentration
What way will molecules move?
Both ways but net movement will be to area of lower concentration and this continues until evenly distributed
What is the concentration gradient?
Path from an area of higher concentration to an area of lower concentration
Which way do particles move?
Down the concentration gradient
What kind of process is diffusion?
Passive so no energy is required
Can particles diffuse across cell membranes?
Yes, as long as they can move freely through the membrane
What is simple diffusion?
When molecules diffuse directly through a cell membrane
How do larger molecules diffuse through the phospholipid bilayer?
Extremely slowly because they’re so big
How do charged molecules diffuse through the phospholipid bilayer?
Slowly because they’re water soluble and the centre of the bilayer is hydrophobic
What does facilitated diffusion do?
Speeds up the diffusion of large molecules and charged molecules with carrier or channel proteins in the membrane
How is facilitated diffusion similar to simple diffusion?
Molecules move down a concentration gradient and it is a passive process
What do carrier proteins do?
Move large molecules across membranes down their concentration gradient
What do different carrier proteins do?
Facilitate the diffusion of different molecules
How do carrier proteins allow diffusion of large molecules?
- A large molecule attaches to a carrier protein
- Protein changes shape
- Molecules is released on opposite side of membrane
What do channel proteins do?
Form pores in the membrane for charged particles to diffuse through
What do different channel proteins do?
Facilitate the diffusion of different charged particles
What are the three factors that simple diffusion depends on?
Concentration gradient, thickness of exchange surface, surface area
How does concentration gradient affect the rate of diffusion?
The higher it is, the faster the rate of diffusion and as diffusion occurs, difference in concentration between both sides decreases until it reaches equilibrium so diffusion slows down over time
How does the thickness of the exchange surface affect the rate of diffusion?
The thinner the exchange surface, the faster the rate of diffusion
How does surface area affect the rate of diffusion?
The larger the surface area, the faster the rate of diffusion
What is the role of microvilli in diffusion?
Gives the cell a larger surface area so increases rate of diffusion
What are the two factors that facilitated diffusion depend on?
Concentration gradient and number of channel or carrier proteins
How does the concentration gradient affect facilitated diffusion?
Higher the concentration gradient, faster the rate of facilitated diffusion and when equilibrium is reach the rate of facilitated diffusion will level off
How does the number of channel or carrier proteins affect the rate of facilitated diffusion?
Once all proteins in the membrane are in use, facilitated diffusion can’t happen any faster so the greater the number of channel or carrier proteins in the cell membrane, the faster the rate of facilitated diffusion
