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Question 1

What is diffusion?

Answer 1

The net movement of particles from a region of higher concentration to a region of lower concentration, which then spread out uniformly.

Question 2

What is a concentration gradient?

Answer 2

A difference between 2 concentrations. The bigger the difference between concentrations, the steeper the concentration gradient and the faster diffusion occurs.

Check Biology page 24.

Question 3

What is a partially permeable or semi-permeable membrane?

Answer 3

A membrane that allows some molecules through it and not others.

Question 4

What is osmosis?

Answer 4

The diffusion of small molecules of a solvent through a semi-permeable membrane. The overall movement of solvent molecules will stop when the concentration of solutes is the same on both sides of a membrane.

Question 5

How do you find the percentage change in mass?

Answer 5

(Final mass - initial mass)
__________________________ x100
Initial mass

Question 6

What is active transport?

Answer 6

Transporting molecules against a concentration gradient or transporting molecules that are too big to diffuse through the cell membrane.

Question 7

How is active transport carried out?

Answer 7

Using transport proteins in cell membrane. The transport proteins capture certain molecules and carry them across the cell membrane. This is an active process and so requires energy.

Check Biology book page 25.

Question 8

Which type of processes are osmosis and diffusion?

Answer 8

They are passive processes, so they don’t require an input of energy.

Question 9

How do we carry out the experiment for osmosis in potato slices?

Answer 9

1. Cut potato into small cubes of equal size (e.g. 2cm diameter).
2. Blot the potato cubes gently with tissue paper to remove excess water.
3. Measure the initial mass of each cube.
4. Place the cubes in sucrose solutions of different concentrations (1%, 2% etc.)
5. Blot with tissue paper again and record new mass.
6. Find difference in mass (end mass - start mass) and use the percentage change equation to calculate percentage gain or loss of mass.

Question 10

What happens during the potato slice experiment?

Answer 10

Water is moving by osmosis from a more dilute solution (in the potato) to a more concentrated solution (the sucrose solution) across a selectively permeable membrane (the cell membranes of all the potato cells holding water).