2.4.1 Diffusion

Question 1

What is diffusion

Answer 1

Diffusion is the movement of molecules from a region of its higher concentration to a region of its lower concentration

Question 2

Why do Molecules move down a concentration gradient

Answer 2

as a result of their random movement

Question 3

For living cells, the principle of the movement down a concentration gradient is the same, but the cell is surrounded by a, what?

Answer 3

cell membrane

Question 4

In living cells, the cell membrane can restrict what?

Answer 4

the free movement of the molecules

Question 5

What is the cell membrane

Answer 5

The cell membrane is a partially permeable membrane – this means it allows some molecules to cross easily, but others with difficulty or not at all

Question 6

Diffusion helps living organisms to:

Answer 6

Obtain many of their requirements
Get rid of many of their waste products
Carry out gas exchange for respiration

Question 7

Is a bigger cell’s surface area to volume ratio larger, or smaller

Answer 7

The bigger a cell or structure is, the smaller its surface area to volume ratio is, slowing down the rate at which substances can move across its surface

Question 8

Many cells which are adapted for diffusion have increased surface area in some way. name some

Answer 8

root hair cells in plants (which absorb water and mineral ions) and cells lining the ileum in animals (which absorb the products of digestion)

Question 9

The smaller distance molecules have to travel the:

Answer 9

the faster transport will occur

Question 10

why do blood capillaries and alveoli have walls which are only one cell thick?

Answer 10

ensure the rate of diffusion across them is as fast as possible

Question 11

The higher the temperature, the faster molecules, do what?

Answer 11

the faster molecules move as they have more energy

Question 12

Why do the higher temperature molecules move faster

Answer 12

results in more collisions against the cell membrane and therefore a faster rate of movement across them

Question 13

If the difference in concentration on either side of the membrane is greater, does movement happen faster or slower

Answer 13

the faster movement across it will occur

This is because on the side with the higher concentration, more random collisions against the membrane will occur

Question 14

How does the difference in concentration affect diffusion

Answer 14

The greater the difference in concentration between two regions

Question 15

How does temperature affect diffusion

Answer 15

The higher the temperature is, the more kenetic energy the particles of that substance will have. They will move/spread faster compared to when at a lower temperature when they have less kenetic energy

Question 16

How does a surface area of a membrane separating 2 regions affect diffusion

Answer 16

A membrane with a greater surface area will have a greater rate of diffusion across it.