Diffusion And Osmosis

Question 1

Define diffusion

Answer 1

This is the net movement of molecules or ions down a concentration gradient form an area of higher concentration to an area of lower concentration

Question 2

What kind of process is diffusion

Answer 2

A passive process

Question 3

What kind of particles can diffuse across the phospholipid bilayer

Answer 3

• small
•non polar molecules
•Lipid soluble molecules
(E.g oxygen and carbon dioxide)

Question 4

What kind of substances CANT diffuse through the phospholipid bilayer

Answer 4

• Large
• polar molecules
Except water

Question 5

Why can water diffuse through the phospholipid bilayer even though it is polar

Answer 5

Because it is a very small molecule

Question 6

List and explain the factors affecting rate of diffusion

Answer 6

• Concentration gradient —
The higher the concentration gradient the faster the rate of diffusion

• Thickness of the exchange surfaces —
The thinner the exchange surface the faster the rate of diffusion (shorter distance particles travel)

• The surface area—
The larger the surface area (the phospholipid bilayer) the faster the rate of diffusion

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

Question 7

What is osmosis

Answer 7

This is the diffusion of water molecules down a water potential gradient form an area of higher water potential to an area of lower water potential across a partially permeable membrane

Question 8

What is the water potential of pure water

Answer 8

Zero

Question 9

Water potential of any solution (mixture of solute and solution) is

Answer 9

Always negative

Question 10

What is water potential

Answer 10

This is the potential of water molecules to diffuse in or out of a solution

Question 11

What is an isotonic solution

Answer 11

This is a solution where the is no difference in water potential in the cell and in the solution surrounding the cell

Or here is no net movement of water molecules because there is no difference in water potentials between the cell and the surrounding

Question 12

What happens when an animal cell is placed in isotonic solution

Answer 12

It stays the same because of no net movement of water

Question 13

What happens when an plant cell is placed in isotonic solution

Answer 13

It stays the same because of no net no of water

Question 14

What is a HYPOTONIC solution

Answer 14

Solution with a higher water potential outside the cell compared to inside the cell

There is net movement of water into the cell from the solution

Question 15

What happens when ANIMAL cell is placed in hypotonic solution

Answer 15

Water in the surrounding cell will move into the cell by osmosis.
Animal cell swells and could eventually burst

Question 16

What happens when PLANT cell is placed in hypotonic solution

Answer 16

Water will move into the cell by osmosis
Vacuole will swell
Contents of the vacuole and cytoplasm will push against the cell wall
Cell becomes more turgid (swollen)

Question 17

Will the plant cell burst and why?

Answer 17

No

The in-elastic cell wall is able to withstand the pressure

Question 18

What is Hypertonic solution

Answer 18

This a solution with a lower water potential compared to inside the cell

There is net movement of water, out of the cell

Question 19

What happens will if an Animal cell is placed in a hypertonic solution

Answer 19

Water will move out of the cell by osmosis
The cell then will shrink

Question 20

What happens when an Plant cell is placed in Hypertonic solution

Answer 20

Water will move out of the cell by osmosis into the solution

Cytoplasm and plasma membrane will pull away from from the cell wall (called plasmolysis)

The cell becomes flaccid (limp)