CELLS: Diffusion Flashcards
What is diffusion?
The net movement of molecules or ions from a region where they are more highly concentrated to a region where their concentration is lower until they are evenly distributed.
In diffusion, can particles diffuse both ways?
Yes, but the net movement will be to the area of lower concentration.
What is the concentration gradient?
The path from an area of higher concentration to an area of lower concentration.
In diffusion, how do particles diffuse across the concentration gradient?
They diffuse down the concentration gradient.
Can particles diffuse across cell membranes?
Give an example.
Yes, as long as they can move freely through the membrane.
- Eg. oxygen and carbon dioxide can diffuse easily through cell membranes because they’re small, so they can pass through spaces between the phospholipids.*
- Also, they are non-polar so are soluble in lipids, so can dissolve in hydrophobic bilayer.*
When molecules diffuse directly through a cell membrane.
Simple diffusion.
Simple diffusion.
When molecules diffuse directly through a cell membrane.
Why is diffusion considered passive?
It does not rely on energy from an external source, for example ATP.
Instead energy comes from the natural, inbuilt motion of the particles.
What molecules might find it harder to diffuse through the phospholipid bilayer?
Charged particles and larger molecules.
Why might some molecules find it harder to diffuse through the phospholipid bilayer?
How might these molecules diffuse instead?
Larger molcules = due to size would diffuse extremely slowly.
Charged particles = would diffuse slowly, as thye are water soluble and the centre of the bilayer is hydrophobic.
They might diffuse through carrier protiens or channel proteins in a process known as facilitated diffusion.
What are the similarities and differences between simple diffusion and facilitated diffusion?
Similarities:
- Passive process - does not rely on external source like ATP.
- Moves particles down concentration gradient.
Differences:
- Facilitated diffusion uses carrier proteins and channel proteins.
What is the role of carrier proteins in facilitated diffusion?
To move large molecules across membranes.
Different carrier proteins faciliatate diffusion of different molecules.
What are the two proteins involved in facilitated diffusion?
Carrier proteins and channel proteins.
Explain the mechanisms involved in large molecules diffusing across the cell membrane:
- Large molecule attaches to carrier protein in membrane.
- Protein changes shape.
- This releases molecule on the opposite side of the membrane.
Explain the mechanisms involved with diffusing charged particles across the cell membrane:
- Channel proteins form pores in cell membrane.
- Charged particle diffuses though this.
