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B4 Blood- biology paper 1 Flashcards

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1
Q

What are the components of blood?

A

White blood cells, red blood cells, platelets and plasma.

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2
Q

What is the life span of a red blood cell?

A

3-4 months

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3
Q

Why do humans need transport systems?

A

Because we have a small surface area to volume ratio and we can’t rely on diffusion alone.

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4
Q

What is the plasma?

A

Yellowy liquid blood that transports red blood cells, white blood cells and platelets around the body.

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5
Q

What is the function of the plasma?

A

The plasma transports carbon dioxide, digested food molecules , urea and hormones around the body.

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6
Q

What is the function of red blood cells?

A

Red blood cells absorb oxygen in the lungs and release this oxygen to respiring cells.

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7
Q

What is the pigment inside red blood cells?

A

Haemoglobin.

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8
Q

What adaptations make red blood cells good at their job?

A
  • They are biconcave discs. Being concave (pushed in/curved on both sides) gives them an increased surface area to volume ratio for diffusion and oxygen absorption.
  • They are packed with haemoglobin, which binds to oxygen.
  • They have no nucleus so that there’s room for more haemoglobin.
  • They are small and flexible so that they can fit through narrow blood capillaries.
  • They are thin, so there is only a short distance for the oxygen to diffuse to reach the centre of the cell.
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9
Q

What percentage of the blood is plasma?

A

Plasma makes up 55% of the blood.

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10
Q

What percentage of the blood is made up of white blood cells, red blood cells and platelets?

A

45%

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11
Q

What is the function of white blood cells?

A

The white blood cells engulf and digest bacteria, make antibodies to stop bacteria and they also make antitoxins.

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12
Q

What are Phagocytes?

A

A type of white blood cell that engulf and destroy unwanted micro-organisms that enter the blood by the process of Phagocytosis. They are part of the body’s immune system.

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13
Q

What percentage of white blood cells are Phagocytes?

A

70%

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14
Q

What are Lymphocytes?

A

Lymphocytes are a type of white blood cell that are part of the immune system, they produce soluble proteins called antibodies when a foreign body such as a microorganism enters the body.

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15
Q

What percentage of white blood cells are Lymphocytes?

A

25%

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16
Q

Do platelets have a nucleus?

A

No

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17
Q

What are Platelets and what do they do?

A

Platelets are the remains of giant cells in the bone marrow and are involved in the blood clotting process. When the body is wounded, platelets accumulate and lead to the formation of a clot to prevent us from bleeding to death.

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18
Q

What is Haemophillia ?

A

A condition where your bloods ability to clot is severely reduced, which can cause easy bruising and bleeding to death if even mildly injured.

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19
Q

Which cell formed in the bone marrow are Platelets the remains of?

A

Platelets are the remains of the giant cell Megakaryocyte.

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20
Q

What are the 3 main types of blood vessels?

A

Arteries, veins and capillaries.

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21
Q

Where do arteries carry blood?

A

Arteries carry bright-red oxygenated blood away from our heart.

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22
Q

Describe an artery

A
  • Arteries have thick muscular and elastic walls to pump and accommodate blood
  • A narrow lumen
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23
Q

Is the blood in arteries under high or low pressure?

A

Under high pressure and so if the artery is cut, the blood will spurt out rapidly every time the heart beats.

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24
Q

Which artery is an exception and doesn’t carry oxygenated blood?

A

The Pulmonary artery, instead it carries de-oxygenated blood from the heart to the lungs.

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25
Q

Where do veins carry blood?

A

Veins carry blood away from our organs towards the heart.

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26
Q

Do veins carry de-oxygenated blood?

A

Yes

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27
Q

What vein is an exception?

A

The Pulmonary vein is an exception and instead, it carries oxygenated blood from the lungs back to the left atrium of the heart.

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28
Q

What colour is the blood that veins carry?

A

Usually a deep, purple-red color as the blood is low in oxygen.

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29
Q

Do veins carry a pulse?

A

No, because veins are under low pressure and so you won’t be able to feel anything.

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30
Q

Are veins under high or low pressure?

A

Veins are under low pressure.

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31
Q

Why do veins have valves?

A

To prevent the back-flow of blood

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32
Q

Describe a vein

A
  • Have a wide lumen

- Have thin walls, and much less muscular tissue than arteries

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33
Q

Why do veins have a wide lumen?

A

To compensate for the low pressure, slow moving blood, a wider lumen allows more space for de-oxygenated blood to travel through.

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34
Q

What is the role of the capillaries?

A

The site of the exchange of substances

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35
Q

How thick are the walls of the capillaries?

A

One cell thick

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36
Q

Why are the walls of capillaries one cell thick?

A

The thin walls enables substances , such as oxygen and glucose, to diffuse easily out of the blood and into our cells.

Substances produces in our cells, like carbon dioxide, can also pass easily into the blood through the walls of our capillaries.

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37
Q

Why do the capillaries have a narrow lumen?

A

Because capillaries are where the exchange of oxygen, nutrients and waste products occur and so the capillaries have evolved to have the greatest surface area to volume ratio.

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38
Q

How is oxygen exchanged across the capillaries?

A

Oxygen diffuses through the capillary wall, into the tissue fluid, and the cells.

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39
Q

How is carbon dioxide exchanged across the capillaries?

A

Carbon dioxide diffuses from the cells into the tissue fluid, then across the capillary walls into the blood plasma.

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40
Q

How is glucose exchanged across the capillaries?

A

Glucose diffuses from the blood plasma, across the capillary walls to the tissue fluid, and then to the cells.

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41
Q

How is waste product urea exchanged across the capillaries?

A

The waste product urea diffuses from the cells of the liver, to the tissue fluid, and then across the capillary walls into the blood plasma.

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42
Q

What is meant by humans having a double circulatory system?

A

The heart pumps the blood through 2 circuits:
- The Pulmonary circulation , which transports de oxygenated blood from our heart to the lungs and then back to the heart.

  • The Systemic circulation, which transports oxygen and nutrients to the body tissues, and carries away de-oxygenated blood containing carbon dioxide and other waste materials.
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43
Q

Are capillaries under low or high pressure?

A

Low pressure

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44
Q

What is the wall of the heart mostly made out of?

A

Muscular tissue

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45
Q

What separates the left and right side of the heart?

A

A septum.

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46
Q

Why does the left side of the heart have thicker walls?

A

Because it’s put under higher pressure than the right side.

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47
Q

Where does blood enter the heart?

A

Through the top chambers, called the Atria.

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48
Q

What does the Pulmonary artery do?

A

Takes deoxygenated blood to the lungs.

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49
Q

What does the Vena Cava do?

A

Brings de-oxygenated blood into the heart.

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50
Q

What do the ventricles do?

A

The ventricles contract and force blood out of the heart.

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51
Q

What does the Right Ventricle do?

A

Forces de-oxygenated blood to the lungs through the pulmonary artery.

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52
Q

What does the left ventricle do?

A

The left ventricle pumps oxygenated blood around the body though the big artery called the aorta.

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53
Q

What does the pulmonary vein do?

A

The pulmonary vein brings oxygenated blood from the lungs.

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54
Q

What does the Aorta do?

A

The Aorta carries oxygenated blood around the body.

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55
Q

How many chambers does the heart have?

A

Four : the right ventricle, the left ventricle, the right atrium, the left atrium.

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56
Q

In simple terms, how does the circulatory system work?

A

De-oxygenated blood is pumped from the heart to the lungs where it then collects oxygen. Afterwards, the now oxygenated blood returns to the heart and this is then pumped around the whole body where it delivers the oxygen to the body cells.

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57
Q

Why do capillaries have very thin walls?

A

So that the diffusion path is short.

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58
Q

Why do veins contain valves?

A

Because the blood in valves is under low pressure and so the valves prevent the blood from flowing backwards.

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59
Q

What happens when blood starts to flow backwards?

A

The valves shut to prevent back-flow.

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60
Q

What happens to the valves when blood is flowing in the right direction?

A

The valves open to allow the blood to flow through.

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61
Q

What happens to the coronary arteries in coronary heart disiease?

A

The coronary arteries that supply blood to the heart muscle become narrow

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62
Q

What can cause coronary heart disiese?

A

a diet high in saturated fat, which can lead to a build up of fatty material on the lining of the vessels.

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63
Q

What blocks the coronary arteries in coronary heart disiese?

A

A build up of fatty plaques containing cholesterol.

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64
Q

What happens when a coronary artery gets blocked?

A

The blood supply to part of the heart muscle is cut off. That part of the heart cannot continue to contract, causing a heart attack.

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65
Q

How can stress cause coronary heart disease?

A

Because it raises blood pressure and increases our blood’s ability to clot.

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66
Q

What is needed for the muscles of the heart to work?

A

A good supply of oxygen and glucose, which is provided by the coronary arteries.

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67
Q

How can doctors solve the problem of coronary heart disiese?

A

A stent can be placed in the blocked artery and a tiny balloon is inflated to open up the blood vessel and the stent at the same time. The balloon is deflated and removed but the stet remains in place, holding the blood vessel open. As soon as this is done, the blood in the coronary arteries flows frrely.

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68
Q

When a stent is inserted in a coronary artery, is general anaesthetic required?

A

No

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69
Q

What is the problem with using stents in the body?

A

They cause blood clotting and so anticoagulant drugs will need to be used, which may cause internal bleeding or bruising.

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70
Q

What is bypass surgery ?

A

Another type of surgery which can be performed that replaces narrow or blocked arteries with bits of veins from other parts of the body.

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71
Q

When will bypass surgery need to be used over the inserting of a stent?

A

When arteries are so badly blocked that stents can’t help .

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72
Q

What are some dis-advantages of bypass surgery ?

A
  • Surgery is expensive

- Involves the risks involved with general anaesthetic.

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73
Q

What are Statins?

A

Drugs that help lower the cholesterol in the blood and help slow down the rate at which fatty materials are deposited in the coronary arteries.

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74
Q

What is the main vein in our body?

A

The vena cava

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75
Q

What is the main artery in our body?

A

The aorta

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76
Q

What is angina?

A

When the arteries become narrower and the heart has to work harder to pump blood around the body.

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77
Q

What is the resting rhythm of a healthy heart?

A

70 beats a minute

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78
Q

What controls the basic rhythm of our heart?

A

The pacemaker

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79
Q

What controls the natural pacemaker?

A

The natural pacemaker is controlled by a group of specialised cells in our right atrium , which generate electrical signals that make the heart contract independently in the nervous system.

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80
Q

What may happen if the natural pacemaker stops working properly?

A

The heart may beat too slowly and you may not get enough oxygen or the heart may beat too fast and blood can’t be pumped properly [tachycardia].

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81
Q

What are the different types of arrhythmia a person can suffer from?

A

Tachycardia, where the heart beats too fast, bradycardia, where your heart beats too slow and atrial fibrillation, an irregular and fast heartbeat.

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82
Q

What is arrhythmia?

A

An abnormal heart rhythm.

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83
Q

What can be done to solve the problem of a disrupted natural pacemaker?

A

An artificial pacemaker can be installed. This mechanical device sends strong, regular signals to your heart to stimulate it to beat properly.

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84
Q

How much do artificial pacemakers usually weigh and why?

A

20 - 50 g so that they’re small and convenient.

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85
Q

Can modern pacemakers speed up during exercise?

A

Yes

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86
Q

What problems may occur to our heart valves over time?

A

They may start to leak or become stiff, making the heart less efficient.

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87
Q

What are mechanical heart valves usually made of?

A

Titanium and polymer.

88
Q

What is one issue with replacing a damaged valve with a mechanical valve?

A

anticoagulant drugs will need to be used to prevent blood clots , which may cause internal bleeding or bruising.

89
Q

Which lasts longer, a mechanical heart valve or a biological heart valve?

A

A mechanical, a biological heart valve lasts for only 12 - 15 years.

90
Q

Where do we get biological heart valves from?

A

Pig, cattle and even human donors.

91
Q

When are artificial hearts used?

A

When a heart has failed but a donor is not yet available.

92
Q

What is a disadvantage of artificial hearts?

A

Anticoagulant drugs need to be taken, which prevent the blood from clotting.

93
Q

Are biological heart valves rejected by our immune system

A

Yes and so immunosuppressant drugs may need to be taken .

94
Q

What are the issues associated with immunosuppressant drugs?

A

Immunosuppressants can lead to a higher risk of cancer because they may suppress a person’s immune system and leave them vulnerable to infection and attacks.

95
Q

Why do many people die before getting the chance to have a heart transplant?

A

Because people have to wait a long time for a heart donor with a tissue and blood match , to reduce the chances of their body rejecting the heart.

96
Q

By 2015, how many people worldwide had been fitted with a completely artificial heart?

A

1,500

97
Q

How much does artificial heart surgery cost?

A

£150,000 +

98
Q

What is the problem with artificial hearts being battery operated?

A

Patients always need to be near a charging point.

99
Q

Do all artificial hearts fit in the chest cavity?

A

No so this is also an issue

100
Q

Why should patients with pacemakers avoid electromagnetic fields?

A

Because electromagnetic fields can disrupt pacemakers and prevent them from working properly , as pacemakers are constantly sending out electrical signals.

101
Q

Why are immunosuppressant drugs used?

A

So that when a heart is transplanted, the body doesn’t reject it.

102
Q

What protects our lungs?

A

The ribcage.

103
Q

What separates our lungs from our abdomen?

A

The diaphragm

104
Q

What is the job of our lungs?

A

To transfer oxygen to the blood and to remove waste carbon dioxide from it.

105
Q

What is ventilation?

A

Breathing in and out.

106
Q

What is respiration?

A

The use of oxygen to release glucose from the mitochondria in our cells, in order to release energy.

107
Q

Where is the breathing system found?

A

In our thorax.

108
Q

What is the diaphragm?

A

The sheet of muscle that separates the lungs from our digestive organs.

109
Q

What does the abdomen contain?

A

Our digestive organs.

110
Q

What happens to the diaphragm when we breathe in and out.

A

When we breathe in, the diaphragm contracts and when we breathe out, the diaphragm relaxes.

111
Q

What happens to the air pressure in our lungs when we breathe in?

A

Decreases

112
Q

What happens to the air pressure in our lungs when we breathe out?

A

Increases

113
Q

What happens to the intercostal muscles when we breathe in?

A

They contract

114
Q

What happens to the intercostal muscles when we breathe out?

A

They relax.

115
Q

What happens to the lung volume when we breathe in?

A

Increases

116
Q

What happens to the lung volume when we breathe out?

A

Decreases.

117
Q

How does air pass into the lungs?

A

Through a tube called the trachea

118
Q

What prevents the trachea from collapsing during inhalation?

A

Rings of cartilage

119
Q

What happens after air passes through the bronchi?

A

The trachea splits into 2 smaller tubes called the bronchi, with one passing to each lung.

120
Q

What does the bronchi subdivide into?

A

Smaller tubes called bronchioles, which split into smaller alveoli.

121
Q

What happens in the alveoli?

A

Gases diffuse in and out of the bloodstream.[gas exchange]

122
Q

What are the adaptations of the alveoli that speed up gas exchange?

A
  • The millions of alveoli mean that the lungs have a large surface area.
  • The alveoli have very thin walls so the diffusion path is short
  • The alveoli have a very good blood supply, as they are surrounded by capillaries.
123
Q

What is the surface area of alveoli?

A

75m^2 of a humans.

124
Q

Why is their a steep concentration gradient during gas exchange?

A

Because once the oxygen diffuses into the blood, it is rapidly removed.

125
Q

If all the alveoli in our lungs were layed out flat, what would their surface area be equivalent to?

A

10 - 15 table tennis tables

126
Q

Why is it good that the alveoli are a spherical shape?

A

This shape means that each alveolus gives a relatively large surface area for diffusion.

127
Q

What moves air in and out of the alveoli?

A

Ventilation, which helps maintain a steep diffusion gradient.

128
Q

What happens to our thorax when we breathe in?

A

Intercostal muscles contract, the volume of he thorax increases, the pressure in the lungs decreases and air enters our lungs.

129
Q

What happens to our thorax when we breathe out?

A

Intercostal muscles relax, the volume of the thorax decreases, pressure increases in our lungs and we breathe out.

130
Q

What happens to our diaphragm when we breathe in?

A

When we breathe in, our diaphragm moves down to allow our lungs to fill with air.

131
Q

What happens to our diaphragm when we breathe out?

A

When we breathe out, our diaphragm rises up to force air [carbon dioxide] out of our lungs.

132
Q

What is an organ?

A

A group of tissues working together to perform a task.

133
Q

What are the organs of plants?

A
  • Stem
  • Roots
  • Leaves
134
Q

What is the job of the roots?

A

The roots anchor the plant into the ground so that. it doesn’t fall over and also absorbs water and mineral ions from the soil

135
Q

What is the job of the stem?

A
  • The stem transports water, mineral ions and nutrients, such as sugar, around the plant.
  • The stem holds up the flower where reproduction takes place.
  • The stem holds the leaves towards the sunlight so that photosynthesis can occur.
136
Q

What is photosynthesis?

A

The process in which plants use sunlight to covert carbon dioxide and water into oxygen and glucose.

137
Q

What is glucose?

A

Stored chemical energy

138
Q

What is respiration?

A

A chemical reaction where oxygen and glucose react in a cell to form carbon dioxide and water. Energy is also released.

139
Q

Where in the cell does respiration take place?

A

In the mitochondria

140
Q

What are the different tissues in a plant arranged in?

A

Layers

141
Q

What are the tissues of a leaf called?

A

The upper epidermis, the palisade mesophyll, the spongy mesophyll, the lower epidermis.

142
Q

What does the leaf do?

A

Carries out photosynthesis.

143
Q

What are the biggest land based organ systems in the world?

A

Plant organ systems

144
Q

What is the first tissue of a leaf on its upper surface?

A

The upper epidermis

145
Q

Why are the upper epidermal cells in a leaf usually transparent?

A

Because they lack chloroplasts.

146
Q

What protects the surface of the leaf?

A

Epidermal tissues

147
Q

How does epidermal tissue protect the surface of the leaf?

A

Secretes a waxy substance and this waterproofs the surface of the leaf.

148
Q

What is the second layer of a leaf?

A

The palisade mesophyll

149
Q

Why is the palisade mesophyll adapted to photosynthesis

A

Because the tissue contains loads of chloroplasts , which carry out photosynthesis.

150
Q

Where does most photosynthesis occur in a leaf?

A

At the palisade mesophyll layer.

151
Q

What cells are the palisade mesophyll layer made up of?

A

Pallisade cells

152
Q

What are palisade cells?

A

long cells arranged vertically in the layer that are also tightly packed together.

153
Q

What is in the palisade cells that maximises photosynthesis

A

Loads of chloroplasts

154
Q

How thick is the palisade mesophyll layer?

A

Between one and five cells thick

155
Q

What layer is beneath the palisade mesophyll layer?

A

The spongy mesophyll layer

156
Q

What shape are the cells in the spongy mesophyll layer?

A

More rounded

157
Q

What do the cells in the spongy mesophyll layer lack?

A

Chloroplasts

158
Q

What allows carbon dioxide and oxygen to circulate freely through the spongy mesophyll layer?

A

The gaps between the cells

159
Q

Why does the spongy mesophyll cells have a large surface area?

A

To make the diffusion of gases easier and quicker

160
Q

What tissue is on the under side of a leaf?

A

The lower epidermis

161
Q

Why doe the lower epidermis tissue have stomata?

A

To allow gases to enter and leave the leaf.

162
Q

What does the stomata do?

A

Controls gas exchange

163
Q

What are stomata?

A

Tiny holes that allow gas exchange to occur in a leaf

164
Q

What do the guard cells on the lower epidermis tissue do?

A

Controls the opening and closing of the stomata

165
Q

What does a plants vascular tissue contain?

A

Veins

166
Q

What 2 transport systems does a plant have?

A

The phloem and the xylem

167
Q

What does the phloem do?

A

The phloem transports sugars [glucose] made my photosynthesis from the leaves to the rest of the plant.

168
Q

What processes does phloem need to transport food for?

A
  • Growing parts of the plant for immediate access
  • Storage organs such as bulbs and tubers.
  • Developing seeds
169
Q

What is a bulb?

A

An underground food store able to grow into a new plant. A natural method of asexual reproduction in plants.

170
Q

What is active transport/

A

The transport of molecules against their concentration gradient from a region of low concentration to a region of high concentration.

171
Q

What are companion cells?

A

Cells that help the phloem to transport substances by providing energy.

172
Q

What is the transport of substances up and down the phloem called?

A

Translocation

173
Q

What is translocation?

A

The transport of dissolved material within a plant.

174
Q

What is transpiration?

A

The loss of water from leaves by evaporation through the stomata.

175
Q

What is a tuber?

A

A swollen, fleshy underground stem of a plant, such as the potato, bearing buds from which new plant shoots arise.

176
Q

What is the meaning of turgid?

A

Enlarged and swollen with water. Having turgor. Description of a plant cell in which the vacuole has swollen due to water gain by osmosis.

177
Q

How are the cells that make up phloem adapted to their functions?

A
  • Sieve tubes : specialised for transport and have no nuclei. Each sieve tube has a perforated end so its cytoplasm connects one cell to the next.
  • Companion cells ; transport of substances in the phloem requires energy. One or more companion cells attached to each sieve tube provide this energy. A sieve tube is completely dependent on its companion cell(s).
178
Q

What is the meaning of perforated?

A

a hole or break in the containing walls or membranes of an organ or structure of the body

179
Q

Are the phloem cells alive?

A

Yes

180
Q

What plant pests push their teeth right into the phloem to feed on the sugary phloem?

A

Greenfly and other aphids (small sap-sucking insects)

181
Q

What does the xylem transport?

A

water and minerals from the roots up the plant stem and into the leaves.

182
Q

In a mature flowering plant or tree, what specialised cell make up the majority of the xylem

A

Vessels

183
Q

Are the cells of the xylem alive?

A

No

184
Q

What strengthens the xylem’s vessels and why?

A

Lignin because the cells are no longer alive and so this chemical gives strength and support to the plant

185
Q

What are lignified cells called?

A

Wood

186
Q

Does transport in the xylem require energy?

A

No so it’s a physical process

187
Q

What does xylem transport and in which direction?

A

Transports water and minerals upwards (from roots to leaves)

188
Q

What are vascular bundles?

A

Groups of xylem and phloem tissue in a plant.

189
Q

In short, what are xylem vessels?

A

Narrow, hollow, dead tubes with lignin, responsible for the transport of water and minerals in plants.

190
Q

What is hydrogen bonding?

A

The strongest type of van der Waals force that arises through a dipole-dipole attraction when hydrogen atoms are covalently bonded to highly electronegative nitrogen, oxygen or fluorine atoms.

191
Q

Where is the phloem found in trees?

A

Just underneath the bark

192
Q

Phloem…

A

Transports food (sugar)

193
Q

Xylem…

A

Transports water

194
Q

Why is transport so important in plants?

A

Because it’s vital to move the food made by photosynthesis around a plant, as all the cells need sugars for respiration as well as for providing materials for growth.

The movement of water and dissolved mineral ions in the roots is equally important as the mineral ions are needed for the production of proteins and other molecules within the cells.

195
Q

Why does a plant need water to hold itself upright?

A

Because when a cell has plenty of water inside it, the water presses the vacuole against the cytoplasm, which presses against the cell walls. This pressure gives support and structure to plants and leaves.

196
Q

What are the small openings all over a leaf called ?

A

The stomata

197
Q

When does the stomata open?

A

When the plant needs to allow air into the leaves.

198
Q

What happens to the water vapour in plants when the stomata opens and what is this known as?

A

The water vapour is lost when the stomata opens. The water vapour evaporates from the cells lining the air spaces and then passes out of the leaf through the stomata by diffusion. This loss of water vapour is known as transpiration.

199
Q

What happens as water evaporates from the surface of the leaves?

A

More water is pulled up through the xylem to take its place. This constant movement of water molecules through the xylem from the roots to the leaves is known as the transpiration stream.

200
Q

What is the transpiration stream driven by?

A

The evaporation of water from the leaves

201
Q

Where in a plants is most water vapour lost from?

A

The leaves

202
Q

Why is it important that plants close their stomata?

A

To limit the loss of water vapour.

203
Q

Why do the stomata open?

A

To let in carbon dioxide for photosynthesis.

204
Q

How do you find the mean?

A

You add together all your data sets and then divide by the number of samples you have taken.

205
Q

What is estimation?

A

A calculated guess

206
Q

What factors affect the rate of transpiration?

A

temperature, humidity, the amount of air movement and light intensity.

207
Q

How does a high temperature increase the rates of transpiration?

A

Increases molecular movement so that: more water molecules evaporate from cell surfaces and the rate of transpiration is increased

208
Q

How does air movement increase the rates of transpiration?

A

Removes water vapour from leaf surfaces so more water diffuses from the leaf

209
Q

How does light intensity increase the rates of diffusion?

A

Increases the rate of photosynthesis, stomata open to let in carbon dioxide and then water vapour diffuses out of the leaf

210
Q

Why will anything that increases the rate of photosynthesis increase the rate of transpiration?

A

Because more stomata open to let in carbon dioxide and when they open, the rate at which water is lot by evaporation and diffusion increases.

211
Q

Why does humidity increase the rates of transpiration?

A

Because hot, dry and windy conditions mean that more water evaporates from the cells and diffusion happens quicker. Water vapour diffuses more rapidly into humid air because the concentration gradient is steeper.

212
Q

What adaptation do leaves have that allows them to photosynthesise as much as possible while losing as little water as possible.

A

Most plants have a waterproof, waxy layer ( the cuticle) to prevent uncontrolled water loss. In very hot environments, the cuticle may be very thick and shiny.

Also , most of the stomata are found on the underside of leaves to protect them from direct light and the energy of the sun.

213
Q

If a plant begins to lose water faster than it’s replaced by the roots, what may happen?

A
  • The whole plant may wilt. Wilting is a protection mechanism against further water loss . The leaves all collapse and hang down , which greatly reduces the surface area available for water loss by evaporation. [transpiration]
  • Stomata close , which stops photosynthesis and risks overheating. However, this prevents most water loss and any further wilting.
214
Q

What will stop a plant from wilting?

A

A temperature drop, the sun going in or rain

215
Q

What apparatus is used to investigate the effect of different factors on the rate of transpiration in plants.

A

A potometer

216
Q

What is a potometer used to show?

A

The water uptake of a plant under different conditions.

Science (31 decks)

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