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whats diffusion

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99 Terms

1

whats diffusion

the movement of particles from a higher to a lower concentration

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2

whats a concentration gradient

occurs when the concentration of particles is higher in one area than another- like a gradient/slope of concentration

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3

what does it mean when somethings against a concentration gradient

moving from an area of low concentration to an area of high concentration ( like going uphill)

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4

what does it mean when somethings going down a concentration gradient

moving from and area of high concentration to an area of low concentration (like going downhill)

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5

how does the concentration gradient affect the rate of diffusion

the bigger the concentration gradient, the faster the rate of diffusion

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6

in what substances does diffusion happen

in liquids and gases

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7

what are the 3 ways substances can move in and out of cells

  1. diffusion

  2. active transport

  3. osmosis

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8

whats active transport

movement of particles across a membrane from a lower to a higher concentration - against a concentration gradient (opposite of diffusion)

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9

what are the differences between active transport and diffusion

  • active transport requires energy, diffusion dosnt

  • active transport is against the concentration gradient whereas diffusion is down a concentration gradient

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10

whats a partially permeable membrane

a membrane with very small holes in it to allow small molecules through but larger molecules cant pass through

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11

whats osmosis

the movement of water molecules across a partially permanent membrane from an area of higher water concentration to an area of lower water concentration

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12

what kind of molecule can diffuse through cell membranes

  • small molecules e.g. glucose, amino acids water and oxygen

  • big molecules e.g. starch and proteins cant fit through the membrane

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13

whats water potential

the potential (likelihood) of water molecules to diffuse out or into a solution

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14

what does it mean of you have high water potential

you have a high concentration of water molecules

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15

true or false - water can pass both ways across a membrane during osmosis

true - water molecules move about randomly all the time

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16

what are turgid cells

cells full of water by the process of osmosis

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17

whats mitosis

when a cell reproduces itself by splitting to form two identical offspring

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18

what are the 4 stages in the cell cycle of mitosis

  1. gap phase 1

  2. synthesis

  3. gap phase 2

  4. mitosis

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19

what happens in gap phase 1 in the cell cycle

the cell grows and new cell protein and structures are made

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20

what happens in synthesis in the cell cycle

the cell replicates its DNA so when it splits during mitosis the two new cells will contain identical DNA

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21

how id DNA replicated during synthesis

  1. molecule of DNA splits

  2. bases on free floating nucleotide pair up with matching bases on the DNA

  3. cross ties link between the new and old DNA bases and so the new nucleotide join together so two new DNA molecules identical to the original one are formed

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22

whats the process of mitosis

  1. the cell has 2 copies of its dna all spread out in long strings

  2. before the cell divides, the dna forms x shaped chromosomes

  3. the chromosomes line up at the centre of the cell and the cell fibres pull them apart. the two arms of each chromosomes got to opposite ends of the cell

  4. membranes form around each of the sets of chromosomes. These become the nuclei of these new cells

  5. you now have two cells containing the same dna to each other and the parent cell

<ol><li><p>the cell has 2  copies of its dna all spread out in long strings</p></li><li><p>before the cell divides, the dna forms x shaped chromosomes</p></li><li><p>the chromosomes line up at the centre of the cell and the cell fibres pull them apart. the two arms of each chromosomes got to opposite ends of the cell</p></li><li><p>membranes form around each of the sets of chromosomes. These become the nuclei of these new cells</p></li><li><p>you now have two cells containing the same dna to each other and the parent cell</p></li></ol>
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23

what is cell differentiation

process by which a cell becomes specialised for its job

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24

why do cells become specialised

perform specific functions / allow organisms to work efficiently

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25

how is a sperm cell specialised

sperms have long tails ans stream lined heads to help them swim. They also have lots of mitichondria to provide them with lots of energy.

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26

how is a structure of a red blood cell specialised

  • biconcave shape for large surface area to absorb+ release oxygen

  • dont have a nucleus so can carry more oxygen

  • small and flexible so can pass easily through capillaries

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27

what are stem cells

undifferentiated cells which can divide by mitosis to become new cells which can then differentiate

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28

where are stem cells present

  • embryos

  • adult animals

  • meristems in plants

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29

what are embryonic stem cells

found in human embryos and have potential to turn into any type of cell

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30

where are adult stem cells found

bone marrow and embryos

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31

whats the difference between adult and embryonic stem cells

adult are found in bone marrow and arent as versatile as embyonic as can only develop into a limited number of cell types.

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32

what are the uses of embryonic stem cells

  • can grow into any type of cell found in the body

  • all tissues and organs can be potentially regrown

  • however transplanted tissues and organs may be rejected by the patients immune system

  • difficult to obtain and store embryonic stem cells

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33

what are the uses of adult stem cells

  • Adult stem cells are found only in specific areas of the body and can only develop into a limited number of cell types e.g. bone marrow, breasts and intestines.

  • however as from the same body, would not reject their own cells

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34

why are stem cells so important

because they have the potential to develop into different types of cells in the body which can be used for development, growth and repair

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35

what are meristems

only plant cells which divide by mitosis found in the roots and shoots.

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36

whats the disadvantage of specialised cells

once theyre specialised, theyre onlt adapted to carry out 1 job

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37

what factors affect the rate of diffusion

distance - if diffusion distance is small, it will happen faster

surface area - larger surface area, higher number of particles able to move in given time

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38

what are the 3 main factors affecting the movement of substances

  1. surface to volume ratio

  2. temperature

  3. concentration gradient

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39

how does the surface to volume ratio affect the movement of substances

rate of diffusion,osmosis or active transport is higher in cells with larger surface area to volume ratio

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40

how does the temperature affect the movement of substances

as the temperature increases, particles move in and out of cells faster as they have more energy

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41

how does the concentration gradient affect the movement of substances

  • substances move in and out of the cell faster if theres a big difference in concentration between the inside and outside of the cell

  • of there are more particles on one side, there are more there to move across

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42

why is diffusion quicker in a single celled organism

  • substances can diffuse straight into and out across the membrane as they only have to travel a short distance

  • they have a relativity large surface area to volume ratio which means they are able to exchange enough substance across the cell membrane to supply the volume of the cell

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43

why is it more difficult to diffuse substances in multicellular organisms

  • its too slow as some cells are deep inside the organism meaning its a long way from them to the outer environment

  • larger organism have a low surface area to volume ratio meaning you cant supply enough substances through the small outer surface for the large volume organism

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44

how do multicellular organisms exchnange substances

they cant do it through their outer membrane so have to use specialised exchange surfaces

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45

whats a transport system

an efficient system to transport substances from organs to the cells that use them.

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46

what are some examples of transport systems in animals

circulatory system and the digestive system

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47

what are examples of transport systems in plants

xylem and phloem

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48

how are exchange surfaces in specialised exchange organs adapted to maximise effectiveness

  • walls are thin so only have short distance to travel

  • large surface exchange area

  • in animals have lots of blood vessels to get stuff in and out of the blood quickly

  • permeable membranes

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49

how are the lungs adapted for gas exchange

the alveoli where the gas exchange takes place have a large surface area, thin walls, a good blood supply and a moist lining for dissolving gases

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50

how are villi adapted to exchange nutrients

  • small intestine contains villi dissolve food molecules are absorbed quicker into the blood

  • they have a single layer of surface cells whihc increase surface area

  • have a very good blood supply to assist quick absorption

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51

explain how the structure of a leaf allows gases to diffuse in and out of cells

  • leaves are broad so have a large surface area for diffusion

  • they’re thin which means gases only have to travel a short distance

  • air spaces inside the leaf lets gases move easily between the cells and increases the surface area increasing the chance of oxygen to get into cells

  • underneath of leaf covered in stomata through which carbon dioxide diffuses into leaf and water vapour diffuses out

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52

describe the transport of water and mineral ions into a root hair cell

  • water is drawn into root hair cell by osmosis as there is usually a higher concentration of water in the soil than inside the plant

  • mineral ions move into the root hair cell by active transport since the concentration of minerals is usually higher in the root hair cells than the soil (otherwise minerals would diffuse out of the root hair cells)

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53

how are root hair cells adapted to take in water and mineral ions

  • cells on plant roots grow into long hairs which stick out into soil

  • each branch of root covered in these microscopic hairs

  • gives plant big surface area for absorbing water and mineral ions from soil

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54

how do you find the surface area of an object

the sum of all the areas of the faces

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55

how do you find the surface area to volume ratio

you find the surface area and divide it by the volume

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56

whats the double circulatory system

Two circuits carrying the blood from the heart to the lungs and back and from the heart to around the body and back

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57

what are the advantages to mammals having a double circulatory system

  • returning blood to the heart after its picked up oxygen at the lungs means it can be pumped out around the body at a higher pressure

  • this increases rate of blood flow at the tissues (blood can be pumped around body faster) so more oxygen is delivered to the cells

  • important for mammals ad take up a lot of oxygen maintaining body temp

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58

describe the route that of blood in a double circulatory system

  • blood flows into two atria from vena cava and pulmonary vein

  • atria contracts pushing blood into the ventricles

  • the ventricles contract forcing blood into pulmonary artery and the aorta and out the heart

  • blood then flows into organs through arteries and returns through veins

  • the atria fills up again and the cycle starts over

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59

what are the 3cdifferent types of blood vessels found in the circulatory system

  1. arteries

  2. capillaries

  3. veins

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60

what do arteries do

carry blood away from heart

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61

how are arteries adapted to their function

  • heart pumps blood out at high pressure so the artery walls are strong and elastic

  • walls are thick compared to size of lumen

  • contain thick layers of muscle to make them strong and elastic fibres to make them stretch and spring back

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62

what do cappilaries do

are involved with the exchange of materials at the tissues

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63

how are capillaries adapted to their function

  • carry the blood really close to every cell in the body so can exchange substances with them

  • permeable walls so substances can diffuse in and out

  • supply food and oxygen and take away waste (co2)

  • walls one cell thick - increases rate of diffusion

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64

what do veins do

carry blood to heart

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65

how are veins adapted to their function

  • blood is at low pressure so walls dont need to be as thick

  • bigger lumen than arteries to help blood flow

  • valves to keep blood flowing in right direction

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66

if an animal has a small surface area to volume ratio what does this mean

their volume is large compared to their surface area

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67

why is the left ventricular wall thicker than the right ventricular wall

has to pump blood further around the body compared to the right side

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68

what side of the heart pumps deoxygenated blood to the lungs

the right side of the heart

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69

whats the functions of valves in the heart

valves stop the blood from flowing backwards

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70

how is cardiac muscle adapted to its function

cardiac muscle contains lots of mitochondria to provide the cells with ATP so the cardiac muscle can contract

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71

what does blood consist of

plasma, platlets, red blood cells, white blood cells

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72

what do red blood cells do

transport oxygen from the lungs to all the cells in the body

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73

what is plasma

liquid that carries everything in blood

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74

what are 2 waste products carried away in plasma

  1. carbon dioxide ( carried from body cells to the lungs to be breathed out)

  2. urea ( carried from liver to the kidneys where its removed in urine)

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75

how is plasma adapted to its function

Plasma is clear and watery. This makes it suitable to transport molecules as many of them are soluble in water.

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76

what is the function of red blood cells

to transport oxygen from the lungs to all the cells in the body

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77

how are red blood cells adapted to their function

  • small and biconcave disc shape to give large surface area to volume ratio for absorbing + releasing oxygen

  • dont have a nucleus - frees up space for more haemoglobin so they can carry more oxygen

  • small and flexible so can pass through capillaries

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78

whats the importance of haemoglobin in red blood cells

  • enables red blood cells to carry oxygen around the body

  • in the lungs, haemoglobin binds to oxygen to become oxyhaemoglobin

  • in body tissues oxyhaemoglobin splits up to release oxygen to the cells

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79

what are the minerals that plants take up and why

  • magnesium for making chlorophyll

  • phospherous to make dna and cell membranes

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80

what do phloem tubes do

transport food both up and down the stem to storage tissues.

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81

what do xylem tubes do

carry water and minerals from the roots up the shoot to the leaves in the transpiration stream

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82

whats translocation

the movement of sugar to all other parts of the plant

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83

whats transpiration

the loss of water from the plant through the evaporation and diffusion of water from a plants surface

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84

whats the transpiration stream

the movement of water through the xylem tissue

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85

why is the transpiration stream constant in a plant

  • evaporation and diffusion of water from the leaves create a shortage of water in the leaves

  • means more water is drawn up from the rest of the plant through the xylem vessels to replace it

  • causes more water to be drawn up through the roots

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86

whats the 4 benefits of the transpiration stream in a plant

  1. constant stream of water from ground helps keep plant cool

  2. provides plant with constant supply of water for photosynthesis

  3. water creates turgor pressure in the plant cells to help support the plant and stop it wilting

  4. minerals needed by the plant can be bought in from soil along with the water

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87

how are phloem adapted to their function

  • cells are arranged end to end to form phloem tubes with sieve plates inbetween them to allow movement of substances through the plant

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88

how are xylem adapted to their function

thick side walls strengthened by lignin which allows plant to withstand pressure of water moving through the plant

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89

whats a transpiration stream

the flow of water through a plant, from the roots to the leaves, via the xylem vessels.

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90

whats a stomata

Stomata are tiny holes found in the underside of leaves. They control water loss and gas exchange by opening and closing

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91

whats the 3 things transpiration rate affected by

  1. increase in light intensity

  2. increase in temperature

  3. increase in air movement

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92

how is the transpiration rate affected by an increase in light intensity

  • brighter the light, greater the transpiration rate

  • increases the rate of photosynthesis causing stomata to open and let c02 in

  • stomata close when dark as photosynthesis cant happen in the dark

  • when stomata are closed water cant escape

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93

how is the transpiration rate affected by an increase in tenperature

  • the warmer it gets , faster transpiration happens

  • when warm, water particles have more energy to evaporate an diffuse out of stomata

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94

how is the transpiration rate affected by an increase in air movement

  • lots if air movement (wind) around leaf transpiration happens faster

  • if air around leaf is still water vapour surrounds leaf and dosnt move away

  • means high concentration of water particles outside of leaf as well as inside it so diffusion dosnt happen as quickly

  • if windy, water vapour is swept away maintaining low concentration of water in the air outside leaf

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95

what are some adaptations plants have to reduce water loss from their leaves

  • waxy cuticle to make it waterproof

  • more stomata on lower side of leaf to slow diffusion as its more protected from the wind and cooloer

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96

a shrub lives in a dry desert. Its stomata are small and located on the lower surface of its leaves. How does this help the shrub survive in the desert

  • having stomata on lower surface of leaf slows diffusion ad its more protected from wind and cooler

  • small stomata helps reduce water loss which helps it survive as low availability if water means it needs to conserve as much water as it can

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97

what does a potometer measure

rate of water uptake

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98

how do you use a potometer

1.Cut a shoot at a slant underwater.

  1. Assemble the potometer in water and insert the shoot underwater.

  2. Remove the apparatus from the water but keep the end of the capillary tube submerged in a beaker of water.

  3. Check that the apparatus is water and air tight.

  4. Dry the leaves and allow the shoot time to acclimatise and then shut the tap.

  5. Remove the end of the capillary tube from the beaker of the water until one air bubble has formed, then put the end back into the water.

7. Record the starting position of the air bubble.

8. Start the stopwatch and record the distance moved by the bubble per unit time, the rate of air bubble movement is an estimate of the transpiration rate.

<p>1.Cut a shoot at a slant underwater.</p><ol start="2"><li><p>Assemble the potometer in water and insert the shoot underwater.</p></li><li><p>Remove the apparatus from the water but keep the end of the capillary tube submerged in a beaker of water.</p></li><li><p>Check that the apparatus is water and air tight.</p></li><li><p>Dry the leaves and allow the shoot time to acclimatise and then shut the tap.</p></li><li><p>Remove the end of the capillary tube from the beaker of the water until one air bubble has formed, then put the end back into the water.</p></li></ol><p>7. Record the starting position of the air bubble.</p><p>8. Start the stopwatch and record the distance moved by the bubble per unit time, the rate of air bubble movement is an estimate of the transpiration rate.</p>
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99

how do you calculate the rate of transpiration using a potometer

divide distance the bubble moved by time taken

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