Transport Across Cell Membranes

Question 1

What is diffusion

Answer 1

Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration.

Molecules will diffuse both ways, but the net movement will be to the area of lower concentration. This continues until particles are evenly distributed throughout the liquid or gas.

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

Diffusion is a passive process,
no energy is needed for it to happen.

Question 2

Small, non-polar molecules diffuse through cell membranes :

Answer 2

Small, non-polar molecules such as oxygen and carbon dioxide are able to diffuse easily through spaces between phospholipids.

Question 3

What is osmosis

Answer 3

Water is also small enough to fit between phospholipids, so it’s able to diffuse across plasma membranes even though it’s polar. The diffusion of water molecules like this is called osmosis.

Question 4

Factors that affect rate of diffusion

Answer 4

• The concentration gradient,
the higher it is the faster the rate of diffusion

•the thickened of the exchange surface,
the thinner the exchange surface
(Shorter the distance have to travel)
the faster the rate of diffusion

•The surface area,
Larger the surface area,
faster the rate of diffusion

•the temperature,
warmer it is, the faster the rate of diffusion because the particles have more kinetic energy so they move faster