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AQA A Level Biology > PAper 1B > Flashcards

PAper 1B Flashcards

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1
Q

why do single celled organisms use diffusion, and diffusion alone, to provide their nutrients ?

A

As the diffusion pathway is short

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2
Q

What do Multicellular organisms require to provide all of their cells with the nutrients they need??

A

transport systems and specialised exchange surfaces

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3
Q

Why do organisms with higher metabolic rates need an increased diffusion rate?

A

They exchange more mterials

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4
Q

What happens to the SA:V ratio as the object becomes bigger?

A

The ratio of surface area: volume ratio falls

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5
Q

Small organisms has a ____ SA:V ratio and exchange ____ with the _____

A

.Large.Directly.Surface

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6
Q

Larger organisms has a ____ SA:V, and they need _______ exchange surfaces to meet the organisms demands

A

.Smaller.Specialist

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7
Q

Give an example of a larger organisms specialist exchange surface

A

Mass transport system, to deliver and remove material

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8
Q

Sphere surface area formula

A

4 x Pi x r^2

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9
Q

Sphere volume formula

A

(4/3) x Pi x r^3

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10
Q

If a gas exchange surface is efficient at gas exchange, what else is it efficient at?

A

an efficient water loss surface

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11
Q

How do insects limit water loss?

A

.Rigid exoskeleton – chitin, waterproof cuticle.Small SA:V ratio – minimises water loss area.Spiracles – open and close to prevent water loss

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12
Q

What is the tracheal system?

A

The tracheal system is a system of tubes in insects that supply muscles with oxygen directly

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13
Q

Trachea divide into

A

tracheoles

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14
Q

Tracheoles branch throughout

A

the body tissues of the insect

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15
Q

What are spiracles and what do they do?

A

Spiracles are tiny pores at the end of the tracheaAllow respiratory gases in and out of the insectValves control the opening/closure of the spiracleWhen open, water can evaporate out of the spiracleClosed most of the timeOnly open to allow gas exchange

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16
Q

Limitations of the tracheal system?

A

.Relies on diffusion rather than a transport system.For diffusion to be adequate the diffusion distance must be short.This limits the size that insects can grow to

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17
Q

Describe and explain the diffusion gradients in the tracheal system

A

.During respiration, O2 is used.O2 at tracheole ends falls.Creates a diffusion gradient.O2 diffuses from atmosphere along the tracheas and tracheoles to the cells.CO2 is produced by respiring cells.Diffusion gradient in opposite direction.CO2 diffuses out of the tracheoles and into the atmosphere

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18
Q

Describe and explain muscle contractions in the tracheal system

A

.Abdominal pumping.Contraction of insect muscles.Trachea ‘squeezed’ and reduced in volume.Some air will be expelled from the trachea.Common in larger insects.Uses energy

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19
Q

Describe and explain water in the tracheoles

A

.Anaerobic respiration produces lactate.Lactate is water soluble so lowers water potential of muscles cells.Water moves into muscle cells from tracheoles.Volume in the tracheole ends decreases, drawing air in

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20
Q

What is a dicotyledonous?

A

.(dye coto lee denous).Flowering plants.The seed bears two cotyledons (seed leaves)

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21
Q

What gases are important in plants?

A

CO2 and O2

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22
Q

Photosynthesis equation

A

6CO2 + 6H2O  C6¬H12O6 + 6O2

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23
Q

Aerobic respiration equation

A

C6¬H12¬O6 + 6O2  6CO2 + 6H2O + ATP

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24
Q

Why do plants leaves have a large SA?

A

greater surface for diffusion to take place

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25
Q

Why are plants leaves thin?

A

Short diffusion pathway

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26
Q

Why are plants leaves membranes selectively permeable?

A

Control what goes in and out of the cell

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27
Q

Why do plants leaves have a large diffusion gradient?

A

Increased rate of diffusion

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28
Q

What reactions happen in a plant at night?

A

Respiration

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29
Q

\What reactions happen in a plant in the day?

A

Respiration and photosynthesis

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30
Q

What parts make up a plant leaf?

A
  1. Waxy cuticle2. Upper epidermis3. Palisade mesophyll cells4. Spongy mesophyll cells5. Sub-stomatal air space6. Lower epidermis cells7. Stomata8. Guard cells9. Sheath10. Phloem11. Xylem
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31
Q

How does a stomata facilitate efficient exchange?

A

Small pores, allow gases in and out, all cells are close to a stomatal pore therefore there is a short diffusion pathway

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32
Q

How do the air spaces facilitate efficient exchange?

A

Interconnected air spaces throughout the mesophyll layer so gases can move around mesophyll cells

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33
Q

How does the spongy mesophyll layer facilitate efficient exchange?

A

Large surface area of mesophyll cells allow for maximum diffusion

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34
Q

What happens to the stomata during the day? Why?

A

Open during the day, as photosynthesis is occurring it needs to allow the CO2 in and O2 out and water vapour out

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35
Q

What happens to the stomata during the night? Why?

A

Closed during the night, no photosynthesis so no need for CO2

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36
Q

Name the parts of a plant cell

A
  1. Nucleus2. RER3. Ribosomes4. Cell wall5. Golgi apparatus6. Chloroplast7. Mitochondria8. Cell membrane9. Vacuole10. Amyloplast (produces and stores starch)11. SER
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37
Q

Where are gills found?

A

Behind the fishes head

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38
Q

What are gills made up of?

A

Gill filaments

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39
Q

How are gill filaments arranged?

A

Stacked up in piles

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40
Q

What are perpendicular to the gill filaments?

A

Gill lamellae

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41
Q

What do gill lamellae do?

A

Increase gill SA

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42
Q

Describe the movement of water in a fishes gas exchange system

A

.Water is taken in through the mouth, forced over the gills, and out through the opening on each side of the body

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43
Q

What is countercurrent flow?

A

.The flow of water over the gill lamellae and the flow of blood within them are in opposite directions, this is known as countercurrent flow

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44
Q

Why is countercurrent flow important in fish?

A

.This means the maximum possible gas exchange can be achieved, if the water and blood flowed in the same direction, far less gas exchange would take place

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45
Q

How does countercurrent flow work?

A
  • Blood that is already well loaded with oxygen meets water which has its maximum concentration of oxygen, therefore diffusion of oxygen from the water to the blood takes place- Blood with little oxygen in it meets water which has had most, but not all, oxygen removed, so diffusion of oxygen from the water to the blood takes place
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46
Q

What does countercurrent exchange principle mean for the diffusion gradient?

A

a diffusion gradient for oxygen uptake is maintained across the entire width of the gill lamellae

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47
Q

In countercurrent flow, how much oxygen from the water is absorbed into the blood of the fish?

A

about 80% of the oxygen available in the water is absorbed into the blood of the fish

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48
Q

What would happen if there was parallel flow in fish?

A

.If the flow of water and blood had been the same in the same direction (parallel flow), the diffusion gradient would only be maintained across part of the length of the gill lamellae and only 50% of the available oxygen would be absorbed by the blood

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49
Q

Why are gills good exchange surfaces?

A

.High SA.Good blood supply.countercurrent flow

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50
Q

Why do plants rely on the transpiration stream? How is it made?

A

.Plants rely on the transpiration stream to transport water from their roots to their leaves.The transpiration stream is created as water is evaporated from the surface of the leaf

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51
Q

What are xerophytes?

A

Plants adapted to living in areas with a short supply of water

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52
Q

How do plants prevent water loss?

A

A thick cuticle, rolled up leaves, sunken stomata, hairs on leaves, reduced SA:V ration

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53
Q

How does a a thick cuticle prevent water loss?

A

Waxy cuticle acts as a waterproof barrier

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54
Q

How do rolled up leaves prevent water loss?

A

Stomata on lower epidermis protected/trap still air Traps water vapour so high water potential No water potential gradient between plant and air

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55
Q

How does a sunken stomata prevent water loss?

A

Traps still, moist air next to the lead surface Lower water potential gradient

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56
Q

How does having hairs on leaves prevent water loss?

A

Traps still, moist air next to leaf surface Lower water potential gradient

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57
Q

How does having a reduced SA:V ratio prevent water loss?

A

Slower rate of diffusion Still able to photosynthesise

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58
Q

Respiration equation

A

C6H12O6 + O2  CO2 + H2O + ATP

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59
Q

Name components of the lungs

A
  1. Lung2. Nasal cavity3. Bronchiole4. Alveoli5. Intercostal muscles6. Ribs7. Diaphragm8. Lung9. Bronchus10. Trachea11. Bronchus
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60
Q

Features of lungs

A

Lobed structures

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61
Q

Features of trachea

A

Flexible airway supported by cartilage rings.Muscular walls lined with ciliated epithelium and goblet cells

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62
Q

Features of bronchi

A

Trachea splits into two bronchi.Large bronchi are supported by cartilage rings.Lined with ciliated epithelium and goblet cells

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63
Q

Features of bronchioles

A

.Subdivisions of bronchi.Muscular walls lined with epithelium cells.Can constrict to control air flow

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64
Q

Where are alveoli and what are they?

A

Alveoli are located at the end of bronchioles. They are the site of gas exchange in mammals. Tiny air sacs (100-300 um).

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65
Q

Why are lungs on the inside?

A

If they were on the outside they would dry out and get damaged

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66
Q

How many alveoli do we have?

A

300 mil

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67
Q

How much SA does the alveoli have?

A

70m^2

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68
Q

What are alveoli lined with?

A

epithelial cells

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69
Q

Why are alveoli good surfaces for gas exchange?

A
  1. Short diffusion pathway (one cell thick), large SA, constant concentration gradient maintained through good blood supply, red blood cells slowed down and flattened against capillary wall
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70
Q

What is breathing/ventilation?

A

the constant movement of air into and out of the lungs

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71
Q

What is respiration?

A

the chemical process of using glucose and oxygen to produce carbon dioxide and ATP while releasing energy

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72
Q

Define inspiration

A

pressure outside the lungs is greater than inside, air moves in

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73
Q

Define expiration

A

pressure inside the lungs is greater than outside, air forced out

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74
Q

Muscles involved in ventilation/breathing?

A
  • Internal intercostal muscles- External intercostal muscles- Diaphragm
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75
Q

How does a bell jar work?

A

.The rubber sheet moves down, the volume in the bell jar increases so the pressure in the bell jar decreases, the pressure inside the bell jar is greater than outside, air moves in via the balloons and inflates them

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76
Q

Explain how inspiration works?

A

.External intercostal muscles contract, internal intercostal muscles relax.Rib cage pulled up and out.Increases volume of thorax.Diaphragm muscles contract and diaphragm moves down.Increases volume in thorax further and reduces pressure inside.Atmospheric pressure is now greater than pulmonary pressure.Air is forced into lungs

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77
Q

Explain how expiration works?

A

.External intercostal muscles relax, internal intercostal muscles contract.Rib cage pushed down and in.Decreased volume of thorax.Diaphragm muscles relax and diaphragm moves up.Decreases volume in thorax further and increases pressure inside.Atmospheric pressure is now less than pulmonary pressure.Air is forced out of the lungs

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78
Q

Is inspiration passive or active?

A

Active

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79
Q

Is expiration passive or active?

A

Passive

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80
Q

Define tidal volume

A

The volume of air inhaled and exhaled in normal breath

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81
Q

Define expiatory reserve volume

A

Volume of a maximum exhalation after normal exhalation

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82
Q

Define residual volume

A

Volume remaining in the lune after maximum exhalation

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83
Q

Define inspiratory reserve volume

A

Additional volume that can be inhaled after inhalation of tidal volume

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84
Q

Define vital capacity

A

maximum volume of exhalation after lungs are maximally filled

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85
Q

Pulmonary ventilation rate equation with units

A

Pulmonary ventilation rate (dm3min-1) = tidal volume (dm3) x breathing rate (min-1)

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86
Q

Name the 4 main lung diseases we need to know about

A

Pulmonary fibrosis, tuberculosis, asthma, emphysema

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87
Q

Describe pulmonary fibrosis

A

.Scaring forms on the epithelium lining of the lungs.This causes the lining to thicken.This reduces the amount of oxygen able to diffuse across the membrane and into the bloodalso.The volume of air entering the lungs is also reduced.A healthy lung is elastic allowing it to spring back into shape, expelling air.Fibrosis reduces the elasticity of the lungs, making it more difficult to breathe out.This inhibits ventilation

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88
Q

Symptoms of pulmonary fibrosis

A

Shortness of breath, especially when exercising Chronic, dry cough Pain and discomfort in the chest Weakness and fatigue

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89
Q

How does pulmonary fibrosis cause shortness of breath, especially when exersizing?

A

.Fibrosis tissue occupies space in the lung.This reduces the air space available.less air=less oxygen.oxygen in high demand during exercise, breathing more, but can’t get the oxygen needed

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90
Q

How does pulmonary fibrosis cause a chronic, dry cough?

A

.The fibrosis tissue causes an obstruction in the lung.The body attempt to remove it by coughing, but it won’t move.So you are always coughing

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91
Q

How does pulmonary fibrosis cause pain and discomfort in the chest?

A

The mass of fibrosis tissue causes pressure, leading to pain.Discomfort leads to more coughing which causes more scaring

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92
Q

How does pulmonary fibrosis cause weakness and fatigue?

A

.Respiration reduced due to lack of oxygen

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93
Q

Describe tuberculosis?

A

.Formation of small hard lumps called tubercles in lungs.Stimulation of the white blood cells to fight these results in scar tissue.Can lay dormant

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94
Q

Cause of tuberculosis

A

A bacteria

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95
Q

Symptoms of tuberculosis

A

Persistent coughFatigueLoss of appetiteHigh temperatureChest painsFeverCoughing up blood

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96
Q

Describe asthma

A

The cells of the epithelial lining secrete larger quantities of mucus than normalThe muscles surrounding the bronchioles contract and so constricts the airways

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97
Q

How many people does asthma affect?

A

10% of world populationKills 2000 people in the UK each year

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98
Q

Cause of asthma

A

Localised allergic reactionCommon allergens include:.Pollen.Animal fur.Faeces of house dust mitesAllergens stimulate WBC found in the lining of the bronchi and bronchioles to release histamineHistamine causes:.InflammationLining of airways becomes inflamed

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99
Q

Symptoms of asthma

A

Difficulty breathingWheezingTightness in chestCoughing

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100
Q

Describe emphysema

A

Loss of elasticity preventing expansion and contractionCommon in smokersThe lungs have been permanently stretchedSo no longer able to expel all of the air from the alveoliSome alveoli burst, the surface area of alveoli reduced, little gas exchange occurs

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101
Q

Cause of emphysema

A

smoking

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102
Q

symptoms of emphysema

A

Shortness of breathChronic coughBluish skin

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103
Q

Name the parts of the digestive system

A
  1. Tongue2. Salivary gland3. Lobe of liver4. Gall bladder5. Traverse limb of the large intestine6. Ascending limb of the large intestine7. Salivary gland8. Oesophagus9. Stomach10. Pancreas11. Small intestine12. Descending limb of the large intestine13. Rectum14. Anus
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104
Q

What is digestion?

A

Digestion is the process in which large molecules are hydrolysed by enzymes into small molecules which can be absorbed and assimilated.

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105
Q

What does the oesophagus do?

A

The oesophagus carries food from the mouth to the stomach

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106
Q

What is the stomach?

A

a muscular sac with an inner layer that produces enzymes

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107
Q

What is the role of the stomach?

A

to store and digest food, especially proteins. It has glands that produce enzymes which digest proteins

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108
Q

What is the ileum?

A

a long muscular tube

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109
Q

What happens in the ileum?

A

Food is further digested in the ileum by enzymes that are produced by its walls and by glands that pour their secretions into

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110
Q

How is the ileum adapted for its purpose of absorbing the products of digestion into the blood stream?

A

The inner walls of the ileum are folded into villi, which gives them a large surface area. The surface area of these villi is further increased by millions of tiny projections, called microvilli, on the epithelial cells of each villus.

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111
Q

What does the large intestine do?

A

Absorb waterMost of the water that is absorbed is water from the secretions of the many digestive glands

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112
Q

What happens in the rectum?

A

rectum is the final section of the intestines. The faeces are stored here before periodically being removed via the anus in a process called egestion

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113
Q

Where are the salivary glands?

A

Near the mouth

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114
Q

What does the salivary glands do?

A

They pass their secretions via a duct into the mouth. These secretions contain the enzymes amylase, which hydrolyses starch into maltose

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115
Q

What is the pancreas?

A

a large gland situated below the stomach

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116
Q

What does the pancreas do?

A

The secretion contains proteases to hydrolyse proteins, lipase to hydrolyse lipids and amylase to hydrolyse starch

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117
Q

What are the two stages of digestion in humans?

A
  1. Physical breakdown2. Chemical digestion
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118
Q

What is physical breakdown and why does it happen?

A

If food is large it is broken down by means of structures like the teeth into smaller pieces. This not only makes it possible to ingest the food but also provides a large surface area for chemical digestion. Food is churned by the muscles in the stomach wall and this also physically breaks it up.

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119
Q

What happens in chemical digestion?

A

Hydrolyses large insoluble molecules into smaller soluble ones

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120
Q

What carries out chemical digestion?

A

Enzymes

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121
Q

How do all enzymes function?

A

Hydrolysis

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122
Q

What is hydrolysis

A

the splitting up of molecules by adding water to the chemical bonds that hold them together

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123
Q

How does one molecules hydrolysis from enzymes usually work?

A

Usually one enzyme hydrolyses a large molecule into sections, and these sections are then hydrolysed into smaller molecules by one or more additional enzymes

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124
Q

What are the different types of digestive enzymes and their reactions?

A
  1. Carbohydrase’s hydrolyse carbohydrates to monosaccharides2. Lipases hydrolyse lipids (fats and oils) into glycerol and fatty acids3. Proteases hydrolyse proteins to amino acids
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125
Q

Where is the enzyme amylase produced?

A

The mouth and pancreas

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126
Q

What does amylase do?

A

Amylase hydrolyses the alternate glyosidic bonds of the starch molecules to produce the disaccharide maltose

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127
Q

What does the disaccharade maltase do?

A

maltose is in turn hydrolysed into the monosaccharide a-glucose by it

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128
Q

What is maltase produced by?

A

The lining of the ileum

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129
Q

What is the full process of carbohydrate digestion in humans?

A
  • Saliva enters the mouth from the salivary glands and is thoroughly mixed with food when chewing- Saliva contains salivary amylase, this starts hydrolysing any starch in the food to maltose. It also contains mineral salts which help to maintain the pH at around neutral. - The food is swallowed and enters the stomach, where the conditions are acidic, this acid denatures the amylase and prevents further hydrolysis of the starch- After a time the food is passed into the small intestine, where it mixes with the secretion from the pancreas called the pancreatic juice- The pancreatic juice contains pancreatic amylase, this continues the hydrolysis of any remaining starch to maltose, alkaline salts are produced by both the pancreas and intestinal wall to maintain the pH at around neutral so that the amylase can function- Muscles in the intestine wall push the food along the ileum, its epithelial lining produces the disaccharide maltase, the maltase hydrolyses the maltose from starch breakdown into a-glucose.
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130
Q

What is the optimum pH for amylase?

A

Neutral

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131
Q

Why is maltase referred to as a membrane bound disaccharidase?

A

It is not released into the lumen of the ileum but is a part of the cell surface membranes of the epithelial cells that line the ileum

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132
Q

Where is sucrose found?

A

in many natural foods, especially fruits.

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133
Q

Where is lactose found?

A

in milk and hence any milk products

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134
Q

What does sucrase do?

A

hydrolyses the single glyosidic bond in the sucrose molecule, this hydrolyses produces the two monosaccharides glucose and fructose.

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135
Q

What does lactase do?

A

hydrolyses the single glyosidic bond in the lactose molecule, this hydrolysis produces the two monosaccharides glucose and galactose.

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136
Q

What are lipids hydrolysed by?

A

Enzymes called lipases

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137
Q

What are lipases?

A

enzymes produced in the pancreas that hydrolyse the ester bond found in triglycerides to form fatty acids and monoglycerides

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138
Q

What is a monoglyceride?

A

a glycerol molecule with single fatty acid molecule attached

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139
Q

What is emulsification and why does it happen?

A

Lipids (fats and oils) are firstly split up into tiny droplets called micelles by bile salts, which are produced by the liver.This process is called emulsification and increases the surface area of the lipids so that the action of lipases is sped up

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140
Q

What are proteins hydrolysed by?

A

a group of enzymes called peptidases (proteases)

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141
Q

What do endopeptidases do?

A

hydrolyse the peptide bonds between amino acids in the central region of the peptide molecule forming a series of peptide molecules

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142
Q

What do exdopeptidases do?

A

hydrolyse the peptide bonds on the terminal amino acids of the peptide molecules formed by the endopeptidases. In this way they progressively release dipeptides and single amino acids

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143
Q

What do dipeptidases do?

A

hydrolyse the bond between the two amino acids of a dipeptide. Dipeptidases are membrane bound, being part of the cell surface membrane of the epithelial cells lining the ileum

144
Q

What helps maintain the neutral pH for amylase?

A

Saliva contains mineral salts that maintain the neutral pH for amylase

145
Q

How is protease kept at the right pH?

A

Stomach produces hydrochloric acid which provides an acidic pH for protease

146
Q

What allows amylase to function after the stomach, how?

A

Alkaline salts are produced by the pancreas and intestinal wall to neutralise stomach acid and allow amylase to function.Bile salts produced by the liver and released/stored in the gall bladder also helps as it is alkaline

147
Q

Describe the structure of bile salts

A

.One end is soluble in fat (lipophilic) but not in water (hydrophobic).The other side is insoluble in fat (lipophobic) but soluble in water (hydrophilic)

148
Q

Describe the process of the absorption of triglycerides

A

.Lipid mixed with bile salts.This forms micelles.Monoglycerides and fatty acids releases.Monoglycerides and fatty acids are absorbed through the membrane of the ileum.Monoglycerides and fatty acids are converted back to triglycerides in the endoplasmic reticulum.Triglycerides are packaged into chylomicrons.Chylomicrons released by exocytosis.Chylomicrons go into lymphatic vessels and then into the blood stream

149
Q

What are chlymicrons?

A

Small milky globules.A small fat globule composed of proteins (1-2%) and lipid.They transport fat from the intestines to the liver and to adipose (fat) tissue.After a fatty meal, the blood is so full of chylomicrons that it looks milky.The chylomicrons are synthesised in the mucosa (the lining) of the intestine

150
Q

Define mass transport

A

the bulk movement of materials from exchange surfaces to the cells throughout the organism

151
Q

What do efficient transport systems have?

A
  • A suitable transport mediumo Normally liquid but can be a gaso Materials (oxygen, waste) can dissolve- Closed system of tubular vesselso Contains or holds the mediumo Forms branching to all parts of the organismo Ensures medium is close to cells- Mechanisms for movement of tissue fluido Generates pressureo Enables the medium to move
152
Q

What is the circulatory systems transport medium, tubular vessels and mechanisms for movement of tissue fluid?

A

Blood, veins/arteries/capillaries and heart

153
Q

What type of muscle is the heart?

A

A cardiac muscle

154
Q

What is the heart?

A

An organ in the circulatory system

155
Q

The heart is myogenic, what does this mean?

A

It naturally contracts and relaxes

156
Q

Describe our circulatory system

A

Double

157
Q

How is the heart apart of a double circulatory system?

A

Blood passes the heart twice, through two different circuits

158
Q

In the circulatory system, what is circuit one?

A

links the heart and the rest of the body

159
Q

In the circulatory system, what is circuit two?

A

links the heart with the lungs

160
Q

Name the parts of the heart

A
  1. Right atrium2. Right ventricle3. Left atrium4. Left ventricle5. Pulmonary artery6. Aorta7. Superior vena cava8. Inferior vena cava9. Pulmonary vein10. Septum11. SAN node
161
Q

What is the SAN node

A

the hearts pace maker, initiates an electrical wave of electricity

162
Q

How do the coronary arteries maximise mass transport?

A
  1. Coronary arteries supply the heart with the oxygen it requires, the oxygen is needed so that the heart can contract and pump blood around the bod
163
Q

How does the wall thickness of the heart maximise mass transport?

A

left ventricle wall is much thicker to produce necessary pressure, since it is thicker it can contract much stronger, this increases the pressure so the blood can travel around the entire body

164
Q

How do the valves of the heart maximise mass transport?

A

open and close between atriums and ventricles as well as ventricles and vessels to help produce necessary pressure and prevent backflow. This also generally builds pressure in the blood

165
Q

What are the 3 heart valves and where are they?

A
  • Semi-lunar valves (between ventricle and vessel)- Left atrioventricular valve (tricuspid valve) between left atrium and left ventricle- Right atrioventricular valve (bicuspid valve) between right atrium and right ventricle
166
Q

Describe the opening and closing of valves?

A
  • Pressure is higher where concave (as ventricle fills with blood)- Pushes the flexible, fibrous tissues together- Tissues form a tight fit with no gap- Prevents the backflow of blood (back into the atrium)- Pressure is higher above the valve- Pushes the flexible fibrous tissues apart- Causes opening for blood to travel (from high to low pressure) into the ventricle
167
Q

What causes the hearts beat sound?

A

The opening and closing of valves

168
Q

Advantages of biological valve replacements

A

Cows are in high supplyFairly well testedFewer long term issues

169
Q

Disadvantages of biological valve replacements

A

Unethical to use cowsNot suitable for allCan need replacing

170
Q

What is systole?

A

contraction

171
Q

What is diastole?

A

relaxation

172
Q

What happens in ventricular systole?

A

ventricle completely full, forces tricuspid and bicuspid valves to close, forces semi-lunar valve to open, pushes blood out of the heart

173
Q

What happens in atrial systole?

A

pushes last bit of blood into ventricle, ventricular diastole occurs in this stage

174
Q

What happens in ventricular and atrial diastole?

A

They relax, makes up the majority of the cycle, blood movement is aided by gravity

175
Q

What is haemoglobin

A

A respiratory pigment used to transport oxygen

176
Q

What type of molecule is haemoglobin?

A

A protein

177
Q

Why is haemoglobin needed?

A

as oxygen has a low solubility in water

178
Q

Describe the structure of haemoglobin

A

Each haemoglobin has beta polypeptides, alpha polypeptides and four haem groups (1 per polypeptide chain) which contain a ferrous ion (Fe2+)Each haem group carries one O2 molecule

179
Q

What is haemoglobin called when it is combined with oxygen?

A

oxyhaemoglobin

180
Q

What must haemoglobin do to be efficient?

A
  1. Readily associate with oxygen at the exchange surface2. Readily dissociate with oxygen at the tissues
181
Q

Define affinity

A

the attractive force binding atoms in molecules, chemical attraction

182
Q

What is high affinity with haemoglobin?

A

high attractive force, readily associates with O2

183
Q

What is low affinity with haemoglobin?

A

take up less O2 (lower association) but release more readily (easily disassociation)

184
Q

In the body, where is oxygen affinity high and low?

A

High in exchange surfaces (lungs) and low in respiring tissues (muscles)

185
Q

How does affinity change?

A
  1. The environment:.How much oxygen is available.Partial pressure of oxygen2. Metabolic rate:.How much oxygen is required by the organism
186
Q

What is partial pressure of oxygen?

A

.The amount of gas present in a mixture of gases .Measured in kilopascals (kPa)

187
Q

If the environment has a low concentration (partial pressure) of oxygen:

A
  • Need haemoglobin to hold onto oxygen- High affinity for oxygen- Hold onto oxygen tightlyBUT- Means oxygen will not be used up as readily- Organisms have a low metabolic rate
188
Q

If the environment has a high concentration (partial pressure) of oxygen:

A
  • Oxygen is readily available- Do not need to hold on to oxygen - Low affinity for oxygenSO- Oxygen dissociates easily
189
Q

How does partial pressure differ throughout the body?

A

.High at exchange surfaces.Low at muscles, where it has been used to respire

190
Q

How does haemoglobin change how it works in different pO2 levels?

A

Low pO2, difficult to attach the first O2Medium pO2, changed shape means it can easily associate (disrupt bonds in the structure)High pO2, fewer binding sites so difficult to fully saturate

191
Q

What is an oxygen dissociation curve

A

Relationship between the saturation of haemoglobin with oxygen and the partial pressure of oxygen

192
Q

Drawn an oxygen dissociation curve

A

IDK Chec your notes

193
Q

Describe oxygen dissociation curve

A

The higher the pO2 the more saturation of haemoglobin with oxygen. At low pO2, the rate of increase of saturation of haemoglobin with oxygen is low, then it speeds up as pO2 increases, before again slowing as pO2 reaches large values.

194
Q

Explain oxygen dissociation curve

A

At low pO2, the rate of increase of saturation of haemoglobin with oxygen is low as it is initially difficult to attach the first O2. The rate of increase of saturation of haemoglobin with oxygen increases as the changed shape of the haemoglobin means it can easily associate (disrupt bonds in the structure). The rate of increase of saturation of haemoglobin with oxygen slows again as pO2 reaches large values, because the fewer binding sites make it difficult to fully saturate.

195
Q

What does a shift to the left on an oxygen dissociation curve mean?

A

NAME?

196
Q

What does a shift to the right on an oxygen dissociation curve mean?

A

NAME?

197
Q

What is the Bohr Effect?

A

Haemoglobin has a reduced affinity for oxygen in the presence of carbon dioxide. The greater the concentration of carbon dioxide, the more readily the haemoglobin releases it

198
Q

Why does the behaviour of haemoglobin change in different regions of the body?

A

The Bohr Effect

199
Q

Describe and explain the behaviour of haemoglobin at the gas exchange substance (lungs)?

A
  • At the gas exchange surface (lungs), the level of carbon dioxide is low because it diffuses across the exchange surface and is expelled from the organism. The affinity of haemoglobin for oxygen is increased, which, coupled with the high concentration of oxygen in the lungs, means that oxygen is readily loaded by haemoglobin. The reduced carbon dioxide level has shifted the oxygen dissociation curve to the left.
200
Q

Describe and explain the behaviour of haemoglobin at rapidly respiring tissues (muscles)?

A
  • In rapidly respiring tissues (muscles), the level of carbon dioxide is high. The affinity of haemoglobin for oxygen is reduced, which, coupled with the low concentration of oxygen in the muscles, means that oxygen is readily unloaded from the haemoglobin into the muscle cells. The increased carbon dioxide level has shifted the oxygen dissociation curve to the right.
201
Q

Why is it that the greater the concentration of carbon dioxide, the more readily haemoglobin releases its oxygen?

A

Because dissolved carbon dioxide is acidic and the low pH causes haemoglobin to change shape.

202
Q

Describe and explain the loading, transporting and unloading of oxygen

A
  • At the gas exchange surface carbon dioxide is constantly being removed- The pH is raised due to the low level of carbon dioxide- The higher pH changes the shape of haemoglobin into one that enables it to load oxygen readily- This shape also increases the affinity of haemoglobin for oxygen, so it is not released while being transported in the blood to the tissues- In the tissues, carbon dioxide is produced by respiring cells- Carbon dioxide is acidic in solution, so the pH of the blood within the tissues is lowered- The lower pH changes the shape of haemoglobin into one with a lower affinity for oxygen- Haemoglobin releases its oxygen into the respiring tissues
203
Q

Explain the statement, ‘The more active a tissue, the more oxygen is unloaded’

A

The higher rate of respiration  the more carbon dioxide the tissues produce - the lower pH  the greater the haemoglobin shape change  the more readily oxygen is unloaded  the more oxygen is available for respiration

204
Q

Why is the loading, transporting and unloading of oxygen important?

A

This means that there is a flexible way of ensuring that there is always sufficient oxygen for respiring tissues.

205
Q

Why is the blood returning to the lungs usually only 75% saturated?

A

In humans, haemoglobin normally becomes saturated with oxygen as it passes through the lungs. In other words, most of the haemoglobin molecules are loaded with their maximum four oxygen molecules. When this haemoglobin reaches a tissue with a low respiratory rate, only one of these molecules will normally be released. The blood returning to the lungs will therefore contain haemoglobin that is still 75% saturated with oxygen.

206
Q

If a tissue is very active (an exercising muscle) then how many oxygen molecules are usually unloaded from each haemoglobin?

A

3 oxygen molecules are usually unloaded from each haemoglobin molecules.

207
Q

What do veins do?

A

carry blood towards the heart

208
Q

What do Venules do?

A

control blood flow from capillaries to veins

209
Q

What do capillaries do?

A

Link arterioles to veins

210
Q

What do Arteries do?

A

carry blood away from the heart

211
Q

What do Arterioles do?

A

control blood flow from arteries to capillaries

212
Q

Why is the tough layer of blood vessels important?

A

resist pressure changes from both within and outside

213
Q

Why is the muscle layer of vessels importan?

A

contract to control flow of blood

214
Q

Why is the elastic layer of vessels important?

A

stretches and recoils, helps to maintain pressure

215
Q

Why is the lumen of vessels important?

A

a passage for the blood to travel through

216
Q

Order of thickness muscle layer of blood vessels (thick to thin)

A

Ateriole, artery, vein, capillary

217
Q

Order of thickness of elastic layer of blood vessels (thick to thin)

A

Artery, arteriole, vein, capillary

218
Q

Order of lumen size of blood vessels (thick to thin)

A

Vein, arteriole, artery, capillary

219
Q

Which blood vessels have high pressure?

A

Artery

220
Q

Which blood vessels have valves present?

A

Vein

221
Q

The artery elastic layer is much thicker than veins so …

A

it keeps the blood pressure high, stretching at systole and springing back during diastole

222
Q

The arteries have no valves but the veins do as …

A

blood is constantly under high pressure in arteries but much lower pressure in veins so back flow is more likely

223
Q

Veins have thinner muscle layers as …

A

they are carrying blood away from tissue therefore construction and dilation does not control flow to tissues

224
Q

There are spaces between the lining cells of capillaries as …

A

this gives them an increased rate of diffusion, short diffusion pathway, and an increased surface area/coverage to cells

225
Q

Why are thick elastic tissue good?

A

Stretches under pressure, when heart beatsSprings backEvens out pressure/flow

226
Q

Why are thick muscle tissue good?

A

Muscle contractsReduces diameter of lumenChanges flow/pressure

227
Q

Why is a smooth epithelium good in vessels?

A

Smooth, so reduces friction, lessens possible blood clots, and provides less resistance

228
Q

What does the SAN do?

A

sends an electrical wave the septum (base), via the atrium

229
Q

What is the SAN?

A

the hearts pace maker, initiates an electrical wave of activity

230
Q

What is the AVN?

A

the second node for contraction, initiates an electrical wave down the septum

231
Q

Atrial systole is a weaker contraction than …

A

ventricular systole

232
Q

Equation for cardiac output (with units)

A

Cardiac output (dm3min-1) = heart rate (bpm) x stroke volume (dm3)

233
Q

Heart rate is …

A

how many times the heart beats per minute

234
Q

Stroke volume is …

A

volume of blood pumped at each beat

235
Q

What is a cardiovascular disease?

A

A degenerative disease of the heart and circulatory system

236
Q

4 examples of cardiovascular disease

A
  • Strokes- Angina- Heart failure/attacks- Atherosclerosis
237
Q

A risk factor is …

A

any characteristic or exposure of an individual that increases the likelihood of developing a disease or injury (not causes)

238
Q

A correlation is …

A

a change in one or two variables that is reflected by a change in the other

239
Q

Are risk factors correlations?

A

Yes

240
Q

Name 4 risk factors for cardiovascular disase

A

SmokingHigh Blood PressureCholesterolDiet/Lifestyle

241
Q

How is smoking a risk factor for cardiovascular disease?

A

Smoking cigarettes makes the walls of your arteries sticky from the chemicals, so fatty material can stick to them. If the arteries that carry blood to your heart get damaged and clogged, it can lead to a heart attack. If this happens in the arteries that carry blood to your brain it can lead to a stroke. The build-up of plaque is called atherosclerosis.

242
Q

How is high blood pressure a risk factor for cardiovascular disease?

A

If your blood pressure is consistently too high this means that your heart has to work harder to pump blood around your body. It also makes the walls of your arteries less stretchy, causing a build-up of fat which can lead to a heart attack or stroke. The build-up of plaque is called atherosclerosis.

243
Q

How is cholesterol a risk factor for cardiovascular disease?

A

Cholesterol joins with proteins to form lipoproteins, non-high density lipoproteins can build up fatty deposits which narrow your arteries, leading to heart attacks or strokes. The build-up of plaque is called atherosclerosis.

244
Q

How is diet/lifestyle a risk factor for cardiovascular disease?

A

Eating unhealthy and not exercising can cause high cholesterol and a weak heart, this can lead to a heart attack or stroke. The build-up of plaque is called atherosclerosis.

245
Q

What is tissue fluid?

A

a watery liquid that bathes all of the tissues in our body

246
Q

What does tissue fluid do?

A

Allows the exchange of substances between the blood and cells

247
Q

What does tissue fluid contain?

A

Molecules required:- Glucose, amino acids, fatty acids, ions and oxygenWaste produced:- Carbon dioxide, urea and water

248
Q

Unlike the blood, what does tissue fluid not contain?

A

it does not contain large products like red blood cells and plasma proteins

249
Q

What is the formation of tissue fluid dependent on?

A

NAME?

250
Q

What is hydrostatic pressure caused by and what does it do?

A

.Result of heart pumping.Forces small molecules out.Prevents movement of liquid in

251
Q

How is tissue fluid formed?

A
  1. The hydrostatic pressure is greater than the osmotic pressure (water potential) at the arterial end (where it is narrow), which forces the fluid out of the capillary, along with some molecules, but not large molecules like proteins. This is called ultra-filtration and it lowers the water potential of the capillary. At the venous end (where it is wider), the hydrostatic pressure is lower than the osmotic pressure so fluid moves into the capillary, bringing waste products with it
252
Q

What is ultra-filtration?

A

When hydrostatic pressure forces smaller molecules out of the capillaries, but leaves the big molecules there

253
Q

What is it like at the arteriole end?

A

.Higher hydrostatic pressure.Lower osmotic pressure.Net loss of water/fluid out.Tissue fluid is formed

254
Q

What is it like at the venular end?

A

.Lower hydrostatic pressure.Higher osmotic pressure.Net movement in.Removal of waste

255
Q

What percentage of tissue fluid returns via the lymphatic system instead of the capillaries?

A

10%

256
Q

What is the lymphatic system and what does it do?

A
  • Is separate to the circulatory system- Made up of lymph capillaries- Contains accumulated tissue fluid (lymph)- Drains back into the blood via two ducts that join veins close to the heart
257
Q

Draw a diagram of the lymphaic system, both

A

check notes

258
Q

What is lymph moved by?

A
  • Hydrostatic pressure of the tissue fluid- Contraction of body muscles squeezes lymph vessels
259
Q

Fluid in the blood is called

A

plasma

260
Q

Fluid surrounding the cells is called

A

tissue fluid

261
Q

Fluid in the lymphatic system is called

A

lymph

262
Q

Define Gene

A

a short section of DNA that codes for a polypeptide or functional RNA

263
Q

Define allele

A

a version of a gene

264
Q

Define locus

A

a position on a chromosome

265
Q

Define homologous

A

the structural features and pattern of genes are the same

266
Q

For maternal and paternal chromosomes where are same genes found

A

in the same positions on the chromosomes

267
Q

The genetic code is:

A
  • Non overlapping- A triplet code- Universal
268
Q

What is meant by a triplet code?

A

every 3 base pairs (nucleotides) codes for 1 amino acid

269
Q

What is meant by universal?

A

the code is the same in all species, ATA codes for the same thing in every species

270
Q

What is meant by non overlapping?

A

Each base is discrete (123456 is 123, 456 and NOT 123, 234, 345, 456) so that the bases don’t get mixed up when they are being read, meaning the wrong amino acid is formed

271
Q

How many possible triplet codes are there?

A

64

272
Q

How many possible amino acids are there?

A

20

273
Q

The genetic code is degenerate, what does this mean?

A

Some amino acids are coded by more than one triplet, e.g. tyrosine is TAT or TAC

274
Q

What do some triplet codes act as?

A

Some triplet codes act as punctuation marksSome indicate start and stop points for start/end of an amino acid chain:- A start codon is ATG

275
Q

What is transcription?

A

formation of pre mRNA in the nucleus

276
Q

What is translation?

A

formation of polypeptides in the ribosomes

277
Q

How does transcription work?

A

.Parental DNA has its hydrogen bonds broken by DNA helicase, leaving a template strand.Free RNA nucleotides are attracted to it and form weak hydrogen bonds with the DNA nucleotides that are complementary to their bases.RNA polymerase comes along and resynthesizes the sugar phosphate backbone along the RNA nucleotides and breaks the hydrogen bonds, making a strand of pre mRNA.The pre mRNA is then spliced, which removes introns and joins together exons, turning into mRNA (no longer pre)

278
Q

What are introns?

A

non-coding DNA

279
Q

What are exons?

A

coding DNA

280
Q

What is translation?

A

The process by which mRNA is used to make a specific protein

281
Q

Describe how translation happens

A

Translation is the process by which mRNA is used to make a specific protein, after mRNA has been produced through transcription and splicing it then moves through the cytoplasm to a ribosome and enters between the two sub units and attaches to it. Here a start codon (AUG) tells the ribosome to start reading the RNA on it. Each triplet of bases is called a codon, and after the initial start codon tells the ribosome to read it the ribosome then moves along the mRNA and reads the codons, attaches (with temporary hydrogen bonds) tRNA with a complementary anticodon to the mRNA’s codon. Each tRNA has a specific amino acid attached, as one tRNA binds to the mRNA so does another one next to it, then their amino acids form polypeptide bonds to join them together and the first tRNA leaves and another one joins as the ribosome moves along the mRNA and forms a polypeptide bond in a condensation reaction with the amino acid there. This continues till a stop codon is reached which has no complementary anticodon so the chain stops and the polypeptide chain formed leaves the ribosome and coils up into an amino acid which join using energy from ATP.

282
Q

What does tRNA do?

A

.Transport specific amino acids

283
Q

How many different tRNA’s are there?

A

20

284
Q

Do all tRNA’s have the same structure?

A

Yes

285
Q

What is a tRNA made up of?

A

codon, anti codon, hydrogen bonds, ester bonds, amino acids

286
Q

Describe the structure of tRNA

A

.Each consists of a single polynucleotide strand of RNA.Folded to form a clover arrangement.Held in place by hydrogen bonds between complementary base pairs.One end acts as an attachment site for the amino acid.The other end is called the anti-codon

287
Q

What is a mutation?

A

Any change in one or more nucleotide base or a change in the sequence of the bases in DNA

288
Q

Characteristic of mutations

A

.Random.Spontaneous.Natural.Positive or negative

289
Q

Three types of mutations

A

.Insertion.Deletion.Substitution

290
Q

Define insertion

A

A nucleotide is added to the DNA sequence

291
Q

Define deletion

A

A nucleotide is lost from the DNA sequence

292
Q

Define subsitution

A

One nucleotide is replaced by another nucleotide with a different base

293
Q

What is a frame shift?

A

every amino acid after the insertion or deletion will move one place

294
Q

What will substitution affect?

A

Only one triplet code

295
Q

What will deletion and insertion affect?

A

the whole amino acid sequence, by causing a frame shift

296
Q

What is a mutagen?

A

A physical or chemical agent that changes the genetic material of an organism

297
Q

What do mutagenic agents do?

A

increase the frequency of a mutation occurring above the natural

298
Q

Name 4 things that act as mutagenic agents

A

Caffeine, x-rays, mustard gas and UV radiation

299
Q

What are chromosomal mutations?

A

Changes in the structure or number of whole chromosomes

300
Q

What are the two types of chromosomal mutations?

A

.Polyploidy.Nondisjunction

301
Q

What is polyploidy?

A

.Changes in whole sets of chromosomes.Cells have multiple sets of chromosomes

302
Q

What form of polyploidy is very common in plants?

A

.3n = triploid

303
Q

What is non-disjunction?

A

.Homologous pairs fail to separate.Changes in number of individual chromosomes per cell

304
Q

What is down’s syndrome caused by?

A

extra chromosome 21

305
Q

Define meiosis

A

the process by which a diploid nucleus (2n) divides to produce four haploid daughter nuclei (n)

306
Q

Name the phases in meiosis

A

Interphase, prophase I, Metaphase I, Anaphase I, Telophase I, cytokinesis, Prophase II, Metaphase II, Anaphase II, telophase II and cytokinesis

307
Q

What is a homogolous pair?

A

one chromatid of mum and one chromatid of dad

308
Q

What are sister chromatids?

A

identical chromatids together

309
Q

What two forms of genetic variation are there?

A

Crossing over and independent segregation

310
Q

What is crossing over?

A

Crossing over is the exchange of alleles

311
Q

What is independent segregation?

A

Independent segregation is the random arrangement of chromosomes

312
Q

State what happens in each phase of meiosis.

A

Interphase – The cell is synthesising DNA and checking it (2 chromatid per chromosome)Prophase I – The chromosomes thicken and get bigger, shorten and condense, the nuclear membrane breaks downMetaphase I – The chromosomes line up along the equator and attach the spindle fibres from the poles to their centromeresAnaphase I – The pair of chromosomes are split as each is pulled to opposite poles in the cell by the spindle fibres contracting – the homologous chromosomes are separated from each other but the chromosome stays tgtherTelophase I & Cytokinesis – The cells form two nucleus, one for each set of new chromosomes, and pull apart while forming a membrane to produce two daughter cellsProphase II – The chromosomes thicken and get bigger, shorten and condense, the nuclear membrane breaks downMetaphase II – The chromosomes line up along the equator and attach the spindle fibres from the poles to their centromeresAnaphase II – The sister chromatids are split as each chromatid is pulled to opposite poles in the cell by the spindle fibresTelophase II & cytokinesis – The cells form two nucleus, one for each set of new chromatids, and pull apart while forming a membrane to produce two more daughter cells each (4 cells now altogether)

313
Q

What is a genotype?

A

The genetic makeup of an organism, the genes and alleles that they have

314
Q

What is a phenotype?

A

Observable characteristics, genotype + environment = phenotype

315
Q

What are the causes of genetic variation?

A

.Mutations, sexual reproduction, meiosis

316
Q

How does crossing over work?

A

Homologous pairs line up, chromatids of each pair become twisted, section of chromatid breaks off and re-joins chromatid of the other homologous chromosome, sections have different alleles, new combination of linked alleles

317
Q

With crossing over, what happends to the amount of possible versions of allele combinations?

A

No crossing over = 2 versionsWith crossing over = 4 possible versions

318
Q

Who discovered independent segregation? When?

A

.Gregor Mendel (19th Century)

319
Q

What is independent segregation?

A

the random segregation of chromosomes during anaphase

320
Q

What did Gregor Mendel say about independent segregation?

A

.Genes are inherited independently of one another.BUT genes close together have a high likelihood of being inherited together

321
Q

Independent segregation key points

A

.Homologous pairs line up along the equator randomly.Combination of chromosomes pulled to each pole is random.Daughter cells produced are genetically different

322
Q

The formula for the number of combinations of genes after independent segregation

A

2^n

323
Q

The formula for the number of combinations of genes after fertilisation after independent segregation

A

(2^n)^2

324
Q

Why does the formula (2^n)^2 not work for crossing over?

A

Crossing over is completely random

325
Q

What is the ‘n’ in the formula (2^n)^2?

A

number of chromosomes

326
Q

What is the first ‘2’ in the formula (2^n)^2?

A

possible number of routes the chromosomes could go to (pulled to two poles)

327
Q

What does RNA stand for?

A

Ribonucleic Acid

328
Q

What is RNA made of?

A

A polymer of nucleotides

329
Q

Nucleotide composition in RNA

A

.Phosphate .Nitrogenous Base .Pentose sugar (ribose sugar)

330
Q

RNA size in comparison to DNA

A

Shorter

331
Q

What are the 4 bases in RNA

A

A, U, C and G – Uracil replaces Thymine

332
Q

Sugar present in DNA

A

Deoxyribose (pentose sugar)

333
Q

Sugar present in RNA

A

Ribose (pentose sugar)

334
Q

Structure of DNA

A

DOuble helix

335
Q

Structure of RNA

A

Single strand

336
Q

Base pairing in DNA

A

A to T, C to G

337
Q

Base pairing in RNA

A

A to U, C to G

338
Q

Length of DNA

A

Long as two times the bases in RNA

339
Q

Length of RNA

A

Short, less bases than DNA

340
Q

Is DNA and RNA a polymer or monomer?

A

Both polymers of nucleotides

341
Q

What type of base pairing is in DNA??

A

Complementary

342
Q

Type of base pairing in RNA

A

No base pairing

343
Q

Can you predict the percentage of other bases from one base percentage in DNA?

A

Yes

344
Q

Can you predict the percentage of other bases from one base percentage in RNA?

A

No

345
Q

Name the 3 types of RNA

A

mRNArRNAtRNA

346
Q

What is mRNA?

A

messenger RNA, copies of the DNA sequence which leaves the nucleus through membrane pores and give instructions to the ribosomes to make proteins

347
Q

What is rRNA?

A

ribosomal RNA, combines with protein to make up the ribosomes structure

348
Q

What is tRNA?

A

transfer RNA, carries specific amino acids during the process of protein synthesis (called translation)

349
Q

How do all the RNA’s work together in protein synthesis?

A

.The mRNA gives the instructions to make the proteins and brings it to the ribosome, the rRNA makes up the ribosome to make the protein and the tRNA reads the mRNA and interact to make the protein

350
Q

What is DNA replication vital for?

A

.Growth .Development/specialisation.Reproduction

351
Q

What are the 3 proposed methods of DNA replication?

A

Conservative replicationDispersive replicationSemi-conservative replication

352
Q

What is conservative replication?

A

.One DNA molecule contains both parental DNA strands.The other molecule contains only newly-synthesised DNA

353
Q

What is dispersive replication?

A

.Parental DNA is interspersed between the two molecules.Both new strands have some new and some original DNA

354
Q

What is semi-conservative replication?

A

.BOTH DNA double helices, consist of one parental and one new DNA strand

355
Q

What are the 5 key requirements of semi-conservative replication?

A

.DNA template.Free nucleotides.DNA helicase.DNA polymerase.Energy

356
Q

Describe the process of semi-conservative replication (6 marks)

A

The parental DNA is gets broken apart by the enzyme DNA helicase V, which breaks the hydrogen bonds between bases. These open bases attract free nucleotides V which come and loosely attach to the complementary bases (A to T and C to G) on the original (template V) strand of parental DNA. Hydrogen bonds V form between the nitrogenous bases. DNA polymerase V helps form the sugar-phosphate backbone of the DNA which gives the new strand structure and support, it holds it in place. This has now formed a daughter DNA’s double helix. V 6/6

AQA A Level Biology (19 decks)

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