Diffusion, Osmosis, Active Transport

Question 1

What is diffusion?

Answer 1

The spreading out of particles resulting in a net movement from a high concentration to a low concentration

Question 2

Why is diffusion a passive process?

Answer 2

Doesn’t require energy to take place

Question 3

What is equilibrium?

Answer 3

A stable state where the numbers of particles are balanced

Question 4

What four factors affect the rate of diffusion?

Answer 4

Temperature
Surface area
The difference between concentrations

Question 5

What diffuses in and out of a cell?

Answer 5

In - food (nutrients), oxygen

Out - carbon dioxide, waste

Question 6

What diffuses into and out of the lungs?

Answer 6

O2 diffuses out of the alveoli and into the blood supply

CO2 diffuses out of the blood and into the alveoli to be exhaled

Question 7

What are the four features of lungs for diffusion?

Answer 7

• many alveoil -> increase surface area
• thin membrane -> decrease distances gases must diffuse
• circulation/breathing -> maintain concentration gradients
• blood supply close to the alveoli -> reduces distance gases must diffuse

Question 8

What is diffuses in the kidneys?

Answer 8

Urea diffuses into the blood plasma and travels to the kidneys

Question 9

What diffuses in the small intestine?

Answer 9

Products of digestion diffuse across the membrane of the small intestine and into the blood so they can be used by the body

Question 10

What 3 features does the small intestine have for diffusion?

Answer 10

1) . Very long and folded - ensure that there is enough time for nutrients to be absorbed as food passes through
2) . Inner layer of tissue folded into finger like projections - increases surface area over which diffusion occurs
3) . Each finger has blood vessels - nutrients only need to diffuse a short distance to rwach the blood ie speeds it up

Question 11

What are fish gills made up of?

Answer 11

Folded, layered tissue

Question 12

What do the fish have for gas exchange

Answer 12

• A good blood supply close by
• A thin membrane
• gill fillaments with tiny lamellae increase SA

Question 13

What is counter current flow - fish? What does it explain?

Answer 13

The bloood supply flows in the opposite direction to the water.
Explains why there is always a lower concentration of oxygen in the blood than the water

Question 14

What does counter current flow ensure?

Answer 14

Oxygen continually diffuses into the blood

Question 15

What do leaves diffuse?

Answer 15

O2 for photosynthesis, CO2 diffuses out as a waste product

Question 16

What are the four features leaves have for diffusion?

Answer 16

1) . Many leaves- increases surface area
2) . Think membrane- shorter distances for gases
3) . Guard cells - control whether the stoma are open or closed
4) . Spongey mesophyll layer - full of air pockets which allows gas to diffuse quickly

Question 17

What is surface area to volume ratio?

Answer 17

How close the internal parts of the object are to the surface

Question 18

What is Osmosis?

Answer 18

Diffusion of water from a high concentration (a dilute solution) to a low water concentration (a concentrated solution) through a partially permeable membrane

Question 19

Is osmosis a passive process?

Answer 19

Yes it doesnt require energy

Question 20

What is a partially permeable membrane?

Answer 20

Like the cell membrane it doesnt let all types of particles through

Question 21

What does a partially permeable membrane have?

Answer 21

Pores/gaps within it which control the movement of particles from one side to another

Question 22

What happens to cells in a solution with a higher water concentration than them?

Answer 22

They will burst and it is a Hypotonic solution

Question 23

What happens to cells in a solution with the same water concentration than them? What is the solution called?

Answer 23

They will remain the same

Isotonic solution

Question 24

What happens to cells in a solution with a lower water concentration than them? What is the solution called?

Answer 24

The cell shrivels up and is a Hypertonic solution

Question 25

What 3 ways does a athelets body change while exercising?

Answer 25

• uses up much of the glucose in their body during respiration
• athelete generates heat as they respire more
• they sweat more to try to cool themselves down (results in loss of water and mineral ions)

Question 26

What is Active Transport?

Answer 26

Moves substances from a more dilute solution to a more concentrated solution, against a concentration gradient. It requires energy from respiration.

Question 27

What are the 5 steps in the process of active transport?

Answer 27

• needs special carrier proteins in a cell membrane
• particle to be transported gravbed by the carrier protein
• carrier protein given energy from a molecule (ATP)
• carrier protein rotates and releases the particle to the other side
• carrier protein rotates back and can transport another

Question 28

How can the effectiveness of an exchange surface be increased?

Answer 28

1) . Having a large surface area
2) . A membrane that is thin, to provide a short diffusion path
3) . (In animals) having a efficient blood supply
4) . (In animals) for gaseous exchange being ventilated

Question 29

What does active transport allow?

Answer 29

Mineral ions to be absorbed into plant root hairs from very dilute solutions in the soil, as it requires ions for healthy growth

Question 30

What does active transport allow sugar molecules to do?

Answer 30

To be absorbed from lower concentrations in the gut into the blood which has a higher sugar concentration, sugar molecules are used for cell respiration

Question 31

what sort of molecules can’t fit through cell membranes

Answer 31

starch and proteins

Question 32

what does it mean if there is a larger surface area of a membrane?

Answer 32

• the faster the diffusion rate as more particles can pass through at once

Question 33

what happens when there is a lower concentration of nutrients in the gut than in the blood?

Answer 33

active transport allows nutrients to be taken into the blood despite the conc gradient being the wrong way round, glucose can therefore be taken into the bloodstream when its concentration in the blood is higher in the gut

Question 34

how are alveoli adapted to exchange substances?

Answer 34

• an enormous surface area
• a moist lining for dissolving gases
• very thin walls
• a good blood supply

Question 35

What are the size of stomata controlled by?

Answer 35

Guard cells - they close the stomata if the plant is losing water faster than its being replaced, without guard cells the plant would wilt