Cell Membranes Diffusion

Question 1

What is diffusion?

Answer 1

the net movement of particles from an area of high concentration to an area of low concentration.

Question 2

At which point will diffusion stop?

Answer 2

Diffusion will stop when particles are evenly distributed through a liquid or a gas.

Question 3

In which direction do particles move when diffusion occurs?

Answer 3

down the concentration gradient , the move from areas of high concentration to areas of low concentration.

Question 4

Is any energy required for the process of diffusion to occur?

Answer 4

No energy is needed for diffusion to occur , diffusion is a passive process.

Question 5

Name the two types of diffusion

Answer 5

simple diffusion and facilitated diffusion

Question 6

Explain simple diffusion

Answer 6

occurs when molecules diffuse directly through the cell membrane (phospholipid bilayer)

Question 7

Which molecules can pass through a cell membrane by simple diffusion and why is this the case?

Answer 7

Oxygen and carbon dioxide can pass through the plasma membrane by simple diffusion , this is the case as oxygen and carbon dioxide molecules are small and hence can pass through between spaces between the phospholipids , carbon dioxide and oxygen are also non polar , hence they are soluble in lipids and can dissolve in the hydrophobic part of the bilayer.

Question 8

Which 3 factors affect the rate of simple diffusion?

Answer 8

The concentration gradient
The thickness of the exchange surface
The surface area

Question 9

How does an increase in the concentration gradient affect the rate of diffusion?

Answer 9

The higher the concentration gradient the greater the rate of diffusion.

Question 10

How does the thickness of the exchange surface affect the rate of diffusion?

Answer 10

As the thickness of the exchange surface decreases the rate of diffusion increases.

Question 11

How does an increase in cell surface area affect the rate of diffusion?

Answer 11

As the surface area increases the rate of diffusion also increases.

Question 12

How is facilitated diffusion different from simple diffusion?

Answer 12

Facilitated diffusion utilises carrier and channel proteins in order to help charged or large particles diffuse across the CSM.

Question 13

In facilitated diffusion in which way do particles move?

Answer 13

In facilitated diffusion particles diffuse down the concentration gradient from areas go high concentration to areas of low concentration.

Question 14

Is facilitated diffusion a passive process?

Answer 14

Facilitated diffusion is a passive process it does not use energy.

Question 15

Name the two types of proteins that can facilitate the diffusion of large or charged particles across a CSM:

Answer 15

Carrier proteins
Channel proteins

Question 16

Which type of molecules do carrier proteins help cross the membrane?

Answer 16

Carrier proteins facilitate the movement or large molecules across the membrane.

Question 17

Explain how carrier proteins facilitate the movement of large particles:

Answer 17

First, a large molecule attaches to a carrier protein in the membrane. Then, the protein changes shape.
This releases the molecule on the opposite side of the membrane

Question 18

Carrier proteins and channel proteins can be referred to collectively as ?

Answer 18

Transport proteins

Question 19

Which type of molecules do channel proteins facilitate the diffusion of?

Answer 19

Charged particles

Question 20

Which factors affect the rate of facilitated diffusion?

Answer 20

The concentration gradient and the number of channel or carrier proteins

Question 21

How does the concentration gradient affect the rate of facilitated diffusion?

Answer 21

The higher the concentration gradient, the faster the rate of facilitated diffusion. As equilibrium is reached, the rate of facilitated diffusion will level off.

Question 22

How does the abundance of channel and carrier proteins affect the rate of facilitated diffusion?

Answer 22

once all the proteins in a membrane are in use, facilitated diffusion can’t happen any faster, even if you increase the concentration gradient. So the greater the number of channel or carrier proteins in the cell membrane, the faster the rate of facilitated diffusion.

Question 23

How do you work out the rate of diffusion?

Answer 23

For a straight line graph, this means finding the gradient of the line. For a curved graph, it means drawing a tangent and finding the gradient of the tangent.