Transport

Question 1

What is diffusion?

Answer 1

Diffusion is the movement of particles from an area of high concentration to that of a low concentration.

This is passive as it requires no energy.

Question 2

What is osmosis?

Answer 2

The diffusion of water across a semi-permeable membrane to balance the concentrations of solution inside and outside a cell.

Water must move, as larger molecules cannot fit through the holes. Water moves IN if the concentration is higher OUTSIDE.

Question 3

Osmosis practical

Answer 3

1) Weigh, and place identical cylinders from same vegetable in sugar solutions of varying concentrations.

2) After set time, remove excess water and reweigh , calculate %change in mass = final mass - initial mass / initial mass × 100.

3) Plot % change in mass against concentration. Using the LOBF, the concentration at 0% change in mass is the same as inside the vegetable.

Question 4

What is active transport?

Answer 4

Active transport is the movement of particles through a membrane via carrier proteins. This requires energy, and so can move them against the concentration gradient.