Movement Across Membranes

Question 1

Diffusion

Answer 1

Diffusion is a random movement of molecules from an area of high concentration to an area of lower concentration

Question 2

What is equilibrium ?

Answer 2

Overtime the particles will be equally distributed this is called equilibrium this does not mean the particles stop moving

Question 3

What are the four factors affecting rate of diffusion ?

Answer 3

• temperature
• concentration gradient
• surface area
• volume

Question 4

How does temperature affect the rate of diffusion ?

Answer 4

At higher temperatures, molecules have more kinetic energy and so move faster. Therefore diffusion occurs faster

Question 5

How does concentration gradient affect the rate of diffusion?

Answer 5

If there is a very large difference in concentration between two areas, molecules with a diffuse from the higher to the lower concentration quickly. If the concentration gradient small, diffusion will happen more slowly.

Question 6

How does the surface area affect the rate of diffusion?

Answer 6

A larger surface area speeds up the rate of diffusion.

Question 7

How does the volume affect the rate of diffusion ?

Answer 7

Diffusion takes longer if it has to fill a larger volume.

Question 8

Osmosis

Answer 8

Is the net movement of free water particles from an area of high water potential to an area of low water potential over semipermeable membrane

Question 9

What does net movement mean?

Answer 9

It means there is nothing to stop particles randomly moving against a concentration gradient but in general they will follow the gradient

Question 10

What is water potential?

Answer 10

It is a measure of the concentration of free water molecules in a solution, pure water has a water potential of zero

Question 11

What is an isotonic solution?

Answer 11

The solution outside the cell has the same water potential is inside the cell-(no net movement)

Question 12

What is hypotonic solution?

Answer 12

This solution outside the cell has a higher water potential than inside the cell - (net movement of free particles into the cell)

Question 13

What happens to cells in dilute solution ?

Answer 13

They become turgid - (full of water)

Question 14

What is hypertonic solution ?

Answer 14

The solution outside the cell has a lower water potential inside the cell -(net movement of free water particles out of the cell)

Question 15

What happens to a cell in hypertonic solution ?

Answer 15

It becomes flaccid

Question 16

What is plasmolysed ?

Answer 16

When a plant loses a lot of water and it cannot be replaced via its roots , the cells of the plant will slowly becoming plasmolysed

Question 17

Why does a plant wilt ?

Answer 17

Because the cells become plasmolysed and as this happens, tugor pressure inside the cell falls and so cannot support the plants weight

Question 18

Active transport

Answer 18

Is the movement of molecules from an area of low concentration to an area of high concentration using energy

Question 19

What is the protein called that is used in active transport ?

Answer 19

Carrier molecule or carrier protein

Question 20

What does the energy in active transport do ?

Answer 20

Pump the substance using energy across the membrane against the concentration gradient