Topic B1 - Cell Biology

Question 1

Diffusion

Answer 1

Simple definition - Diffusion is the gradual movement of particles from places where there are lots of them to places where there are fewer of them.

Fancy definition - Diffusion is the spreading out of particles from an area of higher concentration to an area of lower concentration.

Question 2

Where diffusion happens

Answer 2

Diffusion happens in both solutions and gases. This is because the particles in these substances are free to move about randomly.

The simplest type of diffusion is when different gasses diffuse through each-other. An example of this would be when perfume particles diffuse through air.

Question 3

Facts about diffusion

Answer 3

• the bigger the concentration gradient (the difference in concentration), the faster the diffusion rate.
• a higher temperature will also give a faster diffusion rate because the particles have more energy, so they move around faster.

Question 4

What is osmosis?

Answer 4

Osmosis is the movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower concentration.

Question 5

What is a partially permeable membrane?

Answer 5

A partially permeable membrane is just one with small holes in it. So small that only tiny molecules (like water) can pass through them and bigger molecules like sucrose can’t.

Question 6

Simple definition of osmosis is…

Answer 6

It is just the diffusion of water molecules.