B4

Question 1

when does diffusion happen

Answer 1

when there are unequal concentrations of molecules

Question 2

how does diffusion happen

Answer 2

particles move about and hit eachother

Question 3

how is diffusion important for plants

Answer 3

co2 enters plant leaf
and o2 leaves plant leaf

because there is more CO2 outside of plant and there is more O2 inside leaf

Question 4

how does co2 enter plants

Answer 4

through stomata

finds it’s way to photosynthesising cells where it’s used up

Question 5

what is an adaptation of a lung

Answer 5

lots of alveoli for increased surface area

Question 6

what is active transport

Answer 6

to go against concentration gradient

needs energy

from low concentration to high concentration

energy comes from respiration

Question 7

example of active transport

Answer 7

transport of mineral ions from soil into root hair cells

Question 8

what happens when air is breathed in

Answer 8

oxygen in air moves into capillaries

blood is deoxygenated to start with

so oxygen in lungs is at higher concentration

this means that the oxygen moves from lungs into the blood

now the blood is blood is oxygenated

Question 9

what happens when blood is received back into the lungs

Answer 9

when blood first reaches lungs it has a high level of co2 in the plasm

because co2 concentration is higher in blood it moves into lungs down it’s concentration gradient

Question 10

how much oxygen is absorbed by blood when respiring

Answer 10

about 4-5%

Question 11

why does mouth to mouth resuscitation work

Answer 11

you breath out more o2 than co2

Question 12

how does ventilation work

Answer 12

mechanical process

air at high pressure in one place moves to place with low pressure

space opens up in lungs - which reduces pressure - because:

rib cage moves upward and outward through muscle contractions
and diaphragm contracts and moves downwards

Question 13

what do living cells need for chemical reactions to take place

Answer 13

glucose oxygen water

Question 14

what is a partially permeable membrane

Answer 14

let’s smaller molecules pass through and not higher ones

all cell membranes are partially permeable

Question 15

what do root hair cells do

Answer 15

increase surface area

maximise water uptake

Question 16

why is it important for water to be moved from root as and into the rest of the plant

Answer 16

during osmosis movement stops when the concentration of water on either side of the cell membrane is the same

otherwise the plant could not gain anymore water

Question 17

what is the potato experiment

Answer 17

pieces of potatoes are weighed and left in a salt solution

left for a while

weighed again so change in mass can be recorded

this is because of osmosis

Question 18

why does the mass of a potato increase when left in water

Answer 18

because the water concentration is higher in the water in the beaker

than in the cytoplasm of the potato cells

even though water moves both waves across the membrane
- the net movement is into the potato cells so the mass goes up

Question 19

why does the mass of a potato decrease when in a very salty solution

Answer 19

because the very salty water has a lower water concentration than the cytoplasm inside the cells

the net movement of water is out the potato cells and into the solution in beaker

the cells shrink and the mass goes down

Question 20

how can a potatoes mass not change if it’s put in a salt solution

Answer 20

if the salt solution in the beaker has the same exact concentration of water molecules than inside the potatoes

no net movement

Question 21

what have a high surface to volume ratio

Answer 21

one cell because it only has one cell membrane to cross and it’s very efficient

Question 22

what had a low surface area to volume ratio

Answer 22

multi cellular animals

nutrients need to get into the cytoplasm of every single cell
and dispose of the waste products

very challenging because it’s a complex organism

Question 23

how do fish take up oxygen

Answer 23

through the gills

gills have many filaments and each has its own blood supply

this structure gives the gills a high surface area to volume ratio and ensures maximum effectiveness

Question 24

how do filaments work

Answer 24

oxygen diffuses from water into the bloodstream

carbon dioxide diffuses out of the blood and into the water

Question 25

how do animals get nutrients

Answer 25

in humans food is digested into small soluble molecules

that cross into the blood stream

across the wall of the small intestine

Question 26

how is the surface area of the small intestine increased

Answer 26

by villi (small projections of its surface)

villi have an extensive network of capillaries to absorb food molecules by diffusion and active transport

Question 27

why are water lily’s shaped the way they are

Answer 27

they need co2 to reach chloroplasts for photosynthesis

it’s leaves are large to maximise the surface area available for diffusion of carbon dioxide

it’s thin so the gas doesn’t have far to go to reach all the leafs cells

the have a high surface area to volume ratio

this ensures maximum efficiency

Question 28

why are organ systems specialised with the exchange of various materials

Answer 28

the effectiveness of a exchange surface is increased by having a large surface area and by being thin

this provides a short diffusion path

a large surface area to volume ratio maximises the efficiency of an exchange surface