Diffusion

Question 1

give the definition of diffusion

Answer 1

Diffusion is the net movement of particles (molecules or ions) from an area of higher concentration to an area of lower concentration.

Question 2

will molecules diffuse both ways ?

Answer 2

Molecules will diffuse both ways, but the net movement will be to the area of lower concentration.

Question 3

explain the concentration gradient

Answer 3

The concentration gradient is the path from an area of higher concentration to an area of lower concentration. Particles diffuse down a concentration gradient.

Question 4

how long does diffusion continue ?

Answer 4

This continues until particles are evenly distributed throughout the liquid or gas.

Question 5

What type of process is diffusion ?

Answer 5

passive as no energy is needed for it to happen

Question 6

what type of molecules is simple diffusion for ?

Answer 6

small ,uncharged particles

Question 7

what is simple diffusion ?

Answer 7

Movement of particles from high to low concentration without a protein .WHen particles move directly across a membrane

Question 8

give an example of simple diffusion ?

Answer 8

Example:Oxygen and carbon dioxide can diffuse easily through cell membranes because they’re small, so they can pass through spaces between the phospholipids. They’re also non-polar, which makes them soluble in lipids, so they can dissolve in the hydrophobic bilayer.

Question 9

what happens with larger molecules when dfffusing across cell membranes ?

Answer 9

they go extremely slowly

Question 10

what happens with charged particle when diffusing ?

Answer 10

Charged particles, e.g. ions and polar molecules, would also diffuse slowly because they’re water soluble, and the centre of the bilayer is hydrophobic .particles diffuse through carrier proteins or channel proteins in the cell membrane instead .This is facilitated diffusion

Question 11

what are carrier and channel proteins called ?

Answer 11

transport proteins

Question 12

what do carrier proteins do ?

Answer 12

Carrier proteins move large molecules across the membrane, down their concentration gradient.

Question 13

do all carrier proteins do all molecules ?

Answer 13

Different carrier proteins facilitate the diffusion of different molecules.

Question 14

how do carrier proteins work ?

Answer 14

First, a large molecule attaches to a carrier protein in the membrane. ƒ Then, the protein changes shape. ƒ This releases the molecule on the opposite side of the membrane .

Question 15

what do channel proteins do ?

Answer 15

transport charged particles across the membrane

Question 16

what are the factors affecting the rate of diffusion?

Answer 16

the concentration gradient
the amount of carrier and channel proteins

Question 17

how does the concentration gradient affect the rate of diffusion?

Answer 17

the higher the concentration gradient, the faster the rate of facilitated diffusion .As equilibrium is reached, the rate of facilitated diffusion will level off.

Question 18

how does the amount of carrier and channel proteins affect diffusion ?

Answer 18

once all the proteins in a membrane are in use, facilitated diffusion can’t happen any faster, even if you increase the concentration gradient.

Question 19

how do you calculate the rate of diffusion ?

Answer 19

For a straight line graph, this means finding the gradient of the line.
For a curved graph, it means drawing a tangent and finding the gradient of the tangent.
change in y/change in X

Question 20

what are aquaporins ?

Answer 20

special channel proteins that allow the facilitated diffusion of water through cell membranes. Some kidney cells are adapted to have lots of aquaporins. The aquaporins allow the cells to reabsorb a lot of the water that would otherwise be excreted by the body