Biology 34 - Diffusion

What is diffusion?

The gradual movement of particles from areas with many of them to areas with fewer of them. Just the natural tendency for stuff to spread out.

Define diffusion in technical terms.

Spreading of particles from area of high concentration to an area of low concentration.

Where and WHY does diffusion happen?

In both Liquids and Gases. This is because these substances are free to move around randomly .

What happens when different gases diffuse?

It's like the smell of perfume spreading in a room.

What affects the diffusion rate?

Concentration gradient and temperature.

How does the concentration gradient affect diffusion rate?

The bigger the concentration gradient, the faster the diffusion rate.

How does temperature influence the diffusion rate?

A higher temperature speeds up diffusion because particles have more energy.

What is a primary function of cell membranes?

Hold cells together and let substances in and out.

What special capability do cell membranes have regarding substances?

They let stuff in and out of the cell.

Are cell membranes selective in what they let in and out?

Yes, they are semi-permeable, allowing certain substances to pass while blocking others

which types of cells can diffuse through cell membranes?

Only very small molecules such as Oxygen, Glucose, Amino Acids and Water

Can big molecules easily pass through cell membranes?

No, big molecules like starch and proteins can't fit.

How do particles move through cell membranes?

Just like diffucsion in air, particles mmove From areas of high concentration to low, but they move randomly.

What affects the diffusion rate through cell membranes?

Surface area of the membrane, Larger the surface area of the membrane the faster the diffusion rate.

How do dissolved substances move in and out of cells?

By diffusion.

Q1: A student adds a drop of ink to a glass of cold water.

• What might the student observe to happen to the drop of ink? Explain your answer. [2 marks]

• How might the observation differ if the ink was added to a glass of warm water? [1 mar