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organisation Flashcards

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1
Q

What are cells?

A
  • the basic building blocks of all living organisms
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2
Q

What are tissues?

A
  • a group of specialised cells with a similar structure and function
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3
Q

What are organs?

A
  • a number of different of tissues working together to perform a specific function
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4
Q

Describe the relationship between organs, organ systems and organisms

A

*organs are organised into organ systems,
* they work together to peform a specific function
* and to form organisms

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5
Q

What is the digestive system?

A
  • an example of an organ system
  • several organs work together to digest and absorb food
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6
Q

What are the products of digestion used for?

A
  • building new carbohydrates, lipids and proteins; some glucose is used in respiration
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7
Q

What happens during the first stage of the digestive system (mouth)?

A
  • mechanical digestion takes place by chewing in the mouth
  • salivary glands secrete amylase - begins catalysing the digestion of starch
  • breaks it down into simple sugars like glucose and maltose
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8
Q

Describe the path of food in the body

A
  • mouth -> oesophagus -> stomach -> small intestine -> bloodstream (soluble molecules only) -> large intestine -> rectum
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9
Q

What is the function of the stomach? What are the adaptations of the stomach?

A
  • has a muscular wall which contracts and churns the food, mixing it to form a liquid, increasing surface area for enzymes to work on
  • secretes pepsin (a type of protease enzyme) which breaks down proteins into amino acids
  • produces hydrochloric acid which both kills harmful microorganisms in the food and provides optimal pH conditions for the pepsin to work
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10
Q

What is the role of the pancreas in digestion?

A
  • secretes lipase, protease and carbohydrase enzymes into the small intestine to digest the food and the small intestine itself produces all of these enzymes in smaller amounts
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11
Q

What is the role of the small intestine in digestion?

A
  • where soluble molecules are absorbed into the blood
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12
Q

What is the role of the large intestine in digestion?

A
  • absorbs water from undigested food to produce faeces
  • passes out of your body through the rectum and anus
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13
Q

Where is bile made and stored?

A
  • made in the liver
  • stored in the gall bladder
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14
Q

Where does bile get released into and why?

A
  • the small intestine
  • neutralises the hydrochloric acid from the stomach to provide optimal alkaline pH conditions for the pancreatic enzymes to work
  • emulsifies fats to form small droplets which increases the surface area for lipase enzymes to work on and digest more quickly
  • the alkaline conditions and large surface area increase the rate of fat breakdown by lipase
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15
Q

What happens once the molecules are broken down into smaller, soluble ones e.g. amino acids, fatty acids, glycerol and simple sugars?

A
  • they’re absorbed across the lining of the small intestine and into the bloodstream via diffusion and active transport
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16
Q

What do digestive enzymes do? e.g. lipase

A
  • convert food into small soluble molecules that can be absorbed into the bloodstream and used by cells
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17
Q

What happens to the remaining material that isn’t absorbed into the bloodstream?

A
  • passes into the large intestine where excess water is absorbed back into the blood and faeces remain which are then stored in the rectum and excreted
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18
Q

What is an enzyme?

A
  • enzymes are known as biological catalysts; they increase the rate of reaction without being used up
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19
Q

What is the function of an enzyme?

A
  • can break up large molecules and join small ones
  • protein molecules and the shape of the enzyme is vital to its function
  • this is because each enzyme has its own uniquely shaped active site where the substrate binds
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20
Q

What do carbohydrase enzymes help break down, where are they made and what do they work in?

A
  • help break down carbohydrates into simple sugars, like glucose and maltose
    e.g. analyse - starch into maltose
  • made in the salivary glands, pancreas and small intestine
  • work in the mouth and small intestine
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21
Q

What do protease enzymes help break down, where are they made and what do they work in?

A
  • help break down proteins into amino acids
  • made in the stomach, pancreas and small intestine
  • work in the stomach and small intestine
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22
Q

What do lipase enzymes help break down, where are they made and what do they work in?

A
  • help break down lipids into glycerol and 3 fatty acid molecules
  • made in the pancreas and small intestine
  • work in the small intestine
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23
Q

Why does rate of enzyme activity increase as temperature increases initially?

A
  • enzymes have more kinetic energy so are moving more quickly
  • therefore there are more frequent, successful collisions with substrates, so more enzyme-substrate complexes form per second, increasing rate of catalysation
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24
Q

Describe what happens at 37ºC in terms of enzyme activity

A
  • at 37ºC, the rate of enzyme activity reaches a maximum (the optimum temperature) where the rate of activity is at its highest
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25
Q

Describe what happens past the optimum temperature in terms of enzyme activity

A
  • the rate of enzyme activity rapidly decreases to 0 the more you increase the temperature
  • this is because temperatures that are too high affect the bonds that hold the enzyme together, causing the active site to change shape
  • the enzyme becomes denatured because the substrate can no longer fit into the active site, so the enzyme can no longer catalyse the reaction
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26
Q

How is the rate of enzyme activity affected by pH?

A
  • if the pH falls too low or too high above the optimum pH (7), the bonds holding the enzyme in its specific folded shape will begin to dissolve
  • causing the active site to distort so the substrate molecule no longer fits and the enzyme can no longer catalyse the reaction
  • so the enzyme becomes denatured and rate of enzyme activity decreases
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27
Q

Explain the lock and key model

A
  • enzymes have an active site on their surface which is complementary to the substrate molecule (the reactant)
  • the substrate must fit perfectly and be complementary to the shape of the active site in order to bind to it and form an enzyme-substrate complex
  • the substrate is then broken down into the products of the reaction
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28
Q

Why are enzymes very specific in the chemical reactions that they catalyse?

A
  • the active has a specific shape and the substrate must fit perfectly and be complementary to the active site in order to form an enzyme-substrate complex
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29
Q

What is the main function of the circulatory system?

A
  • to get nutrients and oxygen to every cell in the body and take waste products like carbon dioxide and urea to where they can be removed from the body
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30
Q

How does a single circulatory system works?

A
  • deoxygenated blood travels from the heart to the gills, for example, where it is oxygenated and then returns back to the heart after it gives oxygen to the cells
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31
Q

What are the problems with a single circulatory system?

A
  • the blood loses a lot of pressure as it only goes to the heart once, so it travels to organs slowly, so cannot deliver lots of oxygen
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32
Q

How does a double circulatory system work?

A
  • deoxygenated blood flows into the right atrium and then into the right ventricle and travels from the heart to the lungs to undergo gaseous exchange
  • oxygenated blood flows into the left atrium and then into the left ventricle which pumps it all around the body (organs) and then returns back to the heart
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33
Q

What are the advantages of a double circulatory system?

A
  • maintains a relatively high blood pressure throughout so that it can travel quickly around the body and deliver oxygen more efficiently
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34
Q

What is the function of the heart?

A
  • an organ consisting mainly of muscle tissue that pumps blood around the body in a double circulatory system
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35
Q

Describe the structure of the heart

A
  • muscular walls to provide a strong heartbeat
  • muscular wall of left ventricle is thicker because blood needs to be pumped all around the body rather than just to the lung
  • 4 chambers that separate oxygenated blood from deoxygenated
  • valves to make sure blood does not flow backwards
  • coronary arteries cover the heart to provide its own oxygenated blood supply
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36
Q

Explain the process of the heart

A
  • blood flows into right atrium through vena cava, and left atrium through pulmonary vein
  • atria contract forcing the blood into the ventricles
  • ventricles then contract, pushing blood in the right ventricle into pulmonary artery to be taken to the lungs, and the blood in the left ventricle to the aorta to be taken around the body
  • as this happens, valves close to make sure the blood does not flow backwards
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37
Q

What is the function of the aorta?

A
  • the main artery which carries oxygenated blood from the left ventricle of the heart to the rest of the body
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38
Q

What is the function of the vena cava?

A
  • a vein that brings deoxygenated blood from the body into the right atrium of the heart
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39
Q

What is the function of the pulmonary artery?

A
  • an artery that takes deoxygenated blood from the right ventricle of the heart to the lungs for oxygenation
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40
Q

What is the function of the pulmonary vein?

A
  • a vein that carries oxygenated blood from the lungs to the left atrium of the heart
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41
Q

What is the function of the coronary arteries?

A
  • arteries that branch out of the aorta and spread around the heart muscle, in order to provide oxygen to the muscle cells of the heart – this allows heart muscles to respire and release energy needed for muscular contraction
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42
Q

What is the function of the right ventricle?

A
  • a heart chamber that pumps blood to the lungs where gas exchange takes place
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43
Q

What is the function of the left ventricle

A
  • a heart chamber that pumps blood around the rest of the body
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44
Q

Why does the left ventricle have a thicker muscular wall than the right?

A
  • in order to provide enough force to provide a high blood pressure to pump the blood long distances all around the body
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45
Q

What is the natural resting heart rate controlled by?

A
  • a group of cells located in the right atrium called pacemaker cells that send electrical impulses, which stimulate the heart muscles to contract rhythmically
  • without this, the heart would not pump fast enough to deliver the required amount of oxygen to the whole body
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46
Q

What happens if the pacemaker cells stop working?

A
  • an artificial pacemaker can be implanted, which is an electrical device that corrects irregularities in the heart rate
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47
Q

What are the three different types of blood vessel?

A
  • arteries
  • veins
  • capillaries
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48
Q

What is the function of the arteries?

A
  • they carry very high-pressure blood from the heart to the organs in the body
  • AWAY from the heart
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49
Q

What are the adaptations of the arteries?

A
  • have very thick muscular walls to withstand the high blood pressure within them
  • have a layer of elastic fibres which help them to stretch when surges of blood pass through, and recoil in between surges, keeping the blood flowing correctly and preventing artery damage due to the high pressure of the blood
  • have narrow lumens to maintain the high blood pressure needed to carry blood from heart to organs
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50
Q

What is the function of the veins?

A
  • carry low pressure blood from the body to the heart
  • TOWARDS the heart
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51
Q

What are the adaptations of the veins?

A
  • as blood is low pressure and travelling slowly, the blood could move backwards; the veins therefore contain valves to prevent the backflow of low-pressure blood
  • they have thin walls; the walls do not need to be thick as the blood is low pressure
  • they have a large lumen because they transport blood at low pressure
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52
Q

What is the function of the capillaries?

A
  • very narrow thin blood vessels that connect branches of arteries to veins
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53
Q

What are the adaptations of the capillaries?

A
  • very thin walls (one cell thick) to allow for a short diffusion path, increasing rate of diffusion and exchanging of substances
  • their walls are very permeable to allow high rates of diffusion and exchange of substances
  • very small lumen to increase the SA:Vol ratio; this facilitates better exchange of oxygen, nutrients and other toxins to and from the blood and tissues.
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54
Q

How would you calculate rate of blood flow?

A
  • volume of blood / number of minutes
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55
Q

Where are the lungs found?

A
  • thorax (top part of body) and protected by ribcage
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56
Q

What is the function of the lungs?

A
  • the organ where gas exchange occurs
  • supply oxygen to blood and remove carbon dioxide
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57
Q

What is the function of the trachea?

A
  • it brings air into the lungs and is supported by rings of cartilage which prevent it collapsing
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58
Q

What is the function of the bronchi?

A
  • branches off the trachea to bring air into the lungs; also supported by rings of cartilage
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59
Q

What is the function of the bronchioles?

A
  • branches off the bronchi which carry air to the alveoli
60
Q

What is the function of the alveoli?

A
  • site of gaseous exchange
61
Q

What is the function of the diaphragm?

A
  • separates the lungs from the digestive organs, moves down causing inhalation
62
Q

What is the function of the intercostal muscles?

A
  • contract and relax to ventilate the lungs
63
Q

Explain how ventilation works

A
  • The ribcage moves up and out and the diaphragm moves down causing the volume of the chest to increase
  • Increase volume results in lower pressure
  • Air is drawn into the chest as air moves from areas high pressure (the environment) to low pressure (the lungs)
  • opposite happens when exhaling
64
Q

Explain how gas exchange works

A
  • Inhalation causes the alveoli to fill with oxygen
  • Blood in capillaries surrounding alveoli is deoxygenated - lots of CO2 as its a product of respiration
  • Oxygen diffuses down conc gradient into capillary bloodstream - low conc of oxygen
  • CO2 diffuses down its conc gradient from blood to alveoli
65
Q

How are alveoli adapted for their function?

A
  • small and arranged in clusters, creating a large surface area for diffusion
  • capillaries provide a large blood supply, maintaining the conc gradient
  • thin walls means short diffusion path
66
Q

What is the blood?

A
  • a tissue consisting of plasma, in which the red blood cells, white blood cells and platelets are suspended
67
Q

What is the function of plasma in blood?

A
  • transports nutrients, hormones and proteins to parts of the body that need it; removes waste products in the blood
  • carries the components in the blood
68
Q

What is the function of the atria?

A
  • they contact, pushing blood into the ventricles
69
Q

What is the function of red blood cells in blood?

A
  • they transport oxygen from the lungs to other tissues and cells in the body
70
Q

What is the function of white blood cells?

A
  • part of the immune system, which is the body’s defence against pathogens
71
Q

What are the three types of WBC and what do they do?

A
  1. produce antibodies (small proteins that clump them together) against microorganisms
  2. engulf and digest pathogens
  3. produce antitoxins to neutralise toxins produced by microrganisms
72
Q

What is the function of platelets?

A
  • they help the blood to clot at a wound and stop microorganisms entering at the wound
  • clot dries and hardens to form a scab which allows new skin to grow underneath while preventing microorganisms from entering
73
Q

What are the adaptations of platelets?

A
  • no nucleus
  • small fragments of cells

they have proteins on their surface that enable them to stick to breaks in a blood vessel and clump together
they secrete proteins that result in a series of chemical reactions that make blood clot, which plugs a wound

74
Q

What can a lack of platelets cause?

A
  • excessive bleeding and bruising
75
Q

What are the adaptations of red blood cells?

A
  • biconcave disc shape which increases SA:Vol ratio to maximise the absorption of oxygen
  • no nucleus to allow more room to carry oxygen
    contains lots of haemoglobin which binds to the oxygen in the lungs (to form oxyhaemoglobin) and releases it in body tissues
  • very small diameter to allow them to fit through narrow blood vessels and flexible
  • thin short diffusion patn
76
Q

What are the adaptations of white blood cells?

A
  • some have cytoplasm which can flow, making it possible for the cell to change shape, in order to surround and engulf bacteria
77
Q

Why does someone with CHD lack oxygen in their heart?

A
  • layers of fatty material build up inside the coronary arteries, narrowing them. this reduces the flow of blood through the coronary arteries, resulting in a lack of oxygen for the heart muscle
78
Q

How can CHD be treated?

A
  • stents and statins
79
Q

What are stents and how do they work?

A
  • wire meshes that are inflated and physically widen the artery and keep it open to allow more blood to flow through them
80
Q

What are statins and how do they work?

A
  • drugs that reduce the level of LDL cholesterol in the blood, which slows down the rate at which fatty material builds up in the coronary artery walls
81
Q

What are the pros of stents?

A
  • blood can flow normally through the coronary artery, reducing the risk of heart attacks; hence they’re very effective
  • effective for long periods of time and the recovery time from surgery is relatively quick
82
Q

What are the cons of stents?

A
  • the stent will not prevent any other regions of coronary arteries from narrowing, because it does not treat the underlying cause of the disease
  • a surgery is required, meaning the patient is more at risk of developing blood clots and infections
83
Q

What are the pros of statins?

A
  • they are proven to be effective in reducing the risk of CHD, strokes and heart attacks
  • they increase the amount of HDL cholesterol which is good
84
Q

What are the cons of statins?

A
  • statins have unwanted and harmful side-effects e.g. liver problems, kidney failure and memory loss
  • statins are not instant; they take a while to begin to work
    -*the patient could forget to take them
85
Q

What are the consequence of heart valves becoming faulty (too stiff)?

A
  • this leads to muscle fatigue of the heart, as it has to work much harder to pump the same amount of blood, which can lead to enlargement of the heart
86
Q

What are the consequences of heart valves developing a leak?

A
  • causes blood to flow in the wrong direction, causing pumping blood to be less efficient; this makes the patient feel weak and tired, as their blood pressure drops
87
Q

How can faulty heart valves be replaced?

A

using a mechanical metal valve or using a biological valve from an animal e.g. pig

88
Q

What are the pros of mechanical heart valves?

A
  • they can last a lifetime
89
Q

What are the cons of mechanical heart valves?

A
  • they require anti-clotting drugs; the patient could forget to take them
  • they have a tendency to form blood clots which could be fatal
90
Q

What are the pros of biological heart valves?

A
  • patients do not need to take drugs
91
Q

What are the cons of biological heart valves?

A
  • they don’t last as long as mechanical heart valves
  • because they don’t last as long, the patient has to have surgeries more frequently, which exposes the patient to a higher risk of infection and blood clots
  • some people may ethically or religiously object to having a biological valve implant because the animal cannot consent
92
Q

How can heart failure be treated?

A
  • getting an artificial hearts or getting a heart (or heart-and-lung) transplant
93
Q

What are the pros of artificial hearts?

A
  • they can be used as a temporary solution until a donor is found or to allow their damaged heart to rest
  • they are less likely to be rejected by the immune system because they’re not biological material
94
Q

What are the cons of artificial hearts?

A
  • they increase the risk of blood clotting and strokes; the patient can take blood-thinners to solve this, but this will affect their daily life, e.g., cuts will not heal as quickly
  • artificial hearts are not a long-term solution to heart failure
95
Q

What are the pros of heart transplant?

A
  • heart transplants are proven to lead to a longer, better quality of life for most patients
  • most patients say they have extra energy and feel more able to cope with everyday activities
96
Q

What are the cons of heart transplant?

A
  • there are not enough heart donors to treat every patient, so there will be long waitlist; some patients may die before even getting a donor heart
  • higher risk of immune rejection
  • due to higher risk, the patient must take immunosuppressants to stop donated heart from being rejected by the body’s immune system; puts patient at higher risk of severe symptoms and frequent infections because their immune system is weakened
97
Q

How can extreme blood loss be treated?

A
  • artificial blood
98
Q

What are the pros and cons of artificial blood?

A
  • patient has more time to produce new blood cells
  • however, can only be used for short periods of time - then a blood transfusion has to take place
99
Q

Define health

A
  • the state of physical and mental well-being
100
Q

What are communicable diseases?

A
  • diseases that can be spread from person to person and are spread by pathogens like bacteria and viruses
101
Q

What are non-communicable diseases?

A
  • diseases that cannot be passed from person to person (e.g., coronary heart disease)
102
Q

major factor + other factors of diseases (communicable + non-communicable)

A

MAJOR: ill-health

OTHER:
- poor diet (undernutrition or obesity)
- high levels of stress
- life situations

103
Q

the ways different types of disease may interact

A

defects in the immune system mean that an individual is more likely to suffer from infectious diseases; e.g. people with HIV/AIDS have a defective immune system, increasing their risk of developing diseases like the influenza and tuberculosis
viruses living in cells can be the trigger for cancers; e.g. HPV increases the risk of cervical cancer
immune reactions caused by a pathogen can trigger allergic reactions; e.g. skin rashes (dermatitis) and worsen symptoms for asthma sufferers
severe physical ill health can lead to depression and other mental illness; e.g. a disease that has caused paralysis causing depression

104
Q

What are non-communicable diseases caused by?

A
  • risk factors
105
Q

Define a risk factor

A
  • something that is linked to an increase in the probability of developing a certain non-communicable disease in their lifetime – they do not guarantee that someone will get the disease
106
Q

What can risk factors either be

A
  • aspects of a person’s lifestyle e.g. exercise
  • substances in the person’s body or environment e.g. air pollution
107
Q

Define a causal mechanism

A
  • correlation does not mean evidence for cause; it simply suggests that they may be linked
108
Q

many diseases are caused by the interaction of one factor (T/F)

A

F!
they’re mainly caused by a number of factors

109
Q

How would you investigate whether a disease is linked to a diet?

A

ideally, have to carry out census for entire population, monitoring what they eat and linking it to risk of developing disease
not practically possible so scientists use sampling of small group to represent entire population
PROBLEM; sample may not be representative for entire population of country
assume that they are the average but this may not be the case – hence we cannot use results to draw conclusions about whole country
to avoid bias, we need to take as large a sample as possible and must be as random as possible

110
Q

What are the risk factors for cardiovascular diseases?

A

diet is a major risk factor for CHD; diet high in fat and low in vegetables increases levels of LDL cholesterol in blood, increasing the rate at which fatty material deposits in the walls of the coronary arteries
diet high in salt can increase blood pressure, increasing risk of developing certain cardiovascular diseases
risk for cardiovascular diseases is also massively increased by smoking, but risk is decreased in people who exercise regularly

111
Q

What are the risk factors for type 2 diabetes?

A

obesity is a major risk factor for developing t2diabetes; risk factors can interact – e.g., drinking excess alcohol can lead to obesity which can increase the risk of type 2 diabetes

112
Q

What are the risk factors for liver and brain function?

A

excessive drinking increases the risk of liver cirrhosis and liver cancer, as well as affecting the brain, leading to addiction and memory loss

113
Q

What are the risk factors for lung disease and lung cancer?

A

smoking is a major risk factor for lung disease and lung cancer because cigarette smoke contains carcinogens

114
Q

What are the risk factors for unborn babies?

A

smoking when pregnant increases the risk of miscarriage, stillbirth and premature birth
drinking alcohol can also affect an unborn baby, as it can cause foetal alcohol syndrome, leading to learning difficulties and mental or physical problems

115
Q

What are the risk factors for cancer?

A

carcinogens increase the risk of cancer, including exposure to ionising radiation (emitted from things like radon gas)

116
Q

Define cancer

A
  • the result of changes in cells that lead to uncontrolled growth and division (this is how tumours form)
117
Q

What are benign tumours?

A
  • growths of abnormal cells which are contained in one area, usually within a membrane. they do not invade other parts of the body
118
Q

What are malignant tumours?

A
  • growths of abnormal cells which invade neighbouring tissues and spread to different parts of the body in the blood, where they form secondary tumours
119
Q

What is the function of epidermal tissues?

A
  • they protect the surface of the leaf
120
Q

What are the adaptations of upper epidermis?

A
  • it is transparent, to allow light to pass through to the photosynthetic palisade cells below it
121
Q

What is the function of palisade mesophyll?

A
  • photosynthetic cells packed full of chloroplasts that contain chlorophyll, absorbing the light energy needed for photosynthesis to take place
122
Q

What is the function of waxy cuticle?

A
  • covers the upper epidermis, and is a thin layer of oily material which helps to reduce water loss by evaporation
123
Q

What are the adaptations of lower epidermis?

A
  • has pores in it called stomata to allow gas exchange to take place; also controls amount of water vapour leaving the leaf
124
Q

What is the function of spongy mesophyll?

A

*a tissue full of air spaces to allow oxygen and carbon dioxide to diffuse through it easily

125
Q

What is the function of xylem?

A
  • tissue that transports water from the roots to the leaves, providing the water needed for photosynthesis and other reactions to take place; they also transport dissolved mineral ions including magnesium, which is used to make chlorophyll, and nitrate ions, which are used to make proteins
126
Q

What is the function of phloem?

A
  • a tissue that transports sugars like glucose from the leaves to the rest of the plant, in order to carry out respiration to release energy; or the sugars can be stored as starch
127
Q

What is the function of meristem tissue and where is it found?

A
  • found at the growing tips of shoots and roots, and contain stem cells which can differentiate into different types of specialised plant tissue
128
Q

Define translocation

A
  • the movement of sugars and other molecules through phloem tissue
129
Q

Describe how water enters and leaves the plants

A

enters through root hair cells
water constantly evaporating from surfaces of leaves (transpiration)
transpiration starts with evaporation of water from palisade cells inside leaf
the water vapour then diffuses through the air spaces in spongy mesophyll and out of leaf via pores in lower epidermis called stomata
as water is lost, more water is absorbed by the roots + passes into leaf via xylem in order to replace water that has been lost

130
Q

Define transpiration

A
  • evaporating from the leaves
131
Q

What is the transpiration stream?

A
  • the constant stream of water loss and replacement; it is driven by the transpiration (evaporation of water) in the leaves
132
Q

Why is transpiration important

A
  • it brings water to the leaf, which is required for photosynthesis; the transpiration stream also transports dissolved mineral ions like magnesium into the leaf
    transpiration also cools the leaf down, especially in warm weather, allowing cells to function optimally
133
Q

What are the factors that effect transpiration and how

A

1) temperature - greater temperature, greater rate of transpiration
2) wind intensity - as wind intensity increases, rate of transpiration increases; more wind removes water vapour quickly once it has diffused out of the leaf. makes a greater concentration gradient between water vapour inside the leaf and water vapour outside the leaf, leading to an increased rate of diffusion and transpiration outside the leaf
3) humidity - the greater the humidity, the slower the rate of transpiration; if the air is more humid, there is a less steep concentration gradient, so reduced rate of diffusion and transpiration
4) light intensity - the greater the light intensity, the greater the rate of transpiration; as light intensity increases, so does the rate of photosynthesis

134
Q

How do guard cells function in light vs in dark

A
  • more light means more photosynthesis takes place; this means more water is produced and lost, and, to allow more carbon dioxide in, the guard cells open to widen the stomata, increasing rate of transpiration
    when it is dark, stomata close, as less CO2 is needed due to lack of photosynthesis
135
Q

What happens to the plant in hot conditions?

A
  • the plant closes its stomata to reduce water loss by transpiration, but the plant cannot photosynthesise
136
Q

What happens to the plant during high light intensity?

A

*the guard cells swell and change their shape as they become turgid, causing stomata to open to allow carbon dioxide to ender the leaf

137
Q

What happens to the plant when there is lots of water available?

A
  • water will move into the guard cells via osmosis from dilute to concentrated solution, causing it to swell, become turgid and open the stomata to allow more carbon dioxide to diffuse into the leaf
138
Q

What happens to the plant when there is little water?

A
  • guard cells become flaccid (limp), as water moves out of the guard cells via osmosis from the dilute solution inside to the concentrated solution, closing stomata to reduce water loss but the plant will be unable to photosynthesise due to a lack of carbon dioxide
139
Q

Why do guard cells have thin outer walls and thick inner walls?

A
  • to make the opening and closing work, so that when turgid, they open, and when flaccid, they close
140
Q

Why are guard cells sensitive to light and why do they close at night?

A
  • to save water without losing out on photosynthesis
141
Q

Why are more stomata found on the lower epidermis

A
  • because the lower surface is shaded and cooler, so less water is lost by transpiration than if they were on the upper epidermis – guard cells are thus adapted for gas exchange and controlling water loss
142
Q

How do we investigate distribution of stomata and guard cells?

A

1) either peel epidermal tissue off the leaf and place it on slide with water and cover slip OR apply varnish to underside, allow it to dry, then use piece of tape to remove varnish
2) once in slide with large water droplet, view slide using a microscope
3) draw and clearly label. estimate total number of stomata on surface by counting sample of them in your field of vision
4) count in several different fields of vision and calculate mean; use this and total area of leaf to estimate how many stomata there are in total
5) compare distribution of stomata in different areas of leaf or between different leaves

143
Q

Why can you estimate the rate of transpiration by measuring the uptake of water?

A
  • because you can assume that water uptake but the plant is directly related to water loss by the leaves
144
Q

How do you investigate rate of transpiration?

A

1) set up apparatus
2) record starting position of air bubble
3) start stopwatch and record distance moved by the bubble per unit time
4) keep conditions constant throughout e.g. temperature, air humidity

145
Q

What are root hair cells adapted for?

A
  • the efficient uptake of water by osmosis, and mineral ions by active transport
146
Q

What is the role of stomata and guard cells?

A

to control gas exchange and water loss

ZZ Biology P1 (4 decks)

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