Topic 2 - Organisation Flashcards
1
Q
What is a cell?
A
Cells are the basic building blocks of all living organisms.
2
Q
What is a tissue?
A
A tissue is a group of cells with a similar structure and function.
3
Q
What is an organ?
A
Organs are aggregations of tissues performing specific functions.
4
Q
What are organ systems?
A
Organs are organised into organ systems, which work together to form organisms.
5
Q
What is the digestive system? (2)
A
- The digestive system is the organ system that breaks down food in humans and other mammals.
- It’s also an exchange system - exchanges materials with the environment by taking in nutrients and releasing substances such as bile.
6
Q
What organs is the digestive system made up of + what do they do? (5)
A
- Glands (e.g, the pancreas and salivary glands), which produce digestive juices.
- The stomach, where food is digested.
- The liver, which produces bile.
- The small intestine, where food is digested and soluble food molecules are absorbed.
- The large intestine, where water is absorbed from undigested food, leaving faeces.
7
Q
What are digestive juices?
A
Secretions from the digestive system that help to break down food. They contain enzymes.
8
Q
What are enzymes?
A
Biological catalysts. All large proteins
9
Q
What is a catalyst?
A
A catalyst is a substance which increases the speed of a reaction, without being changed or used up in that reactions.
10
Q
What do enzymes do? (3)
A
- Enzymes catalyse specific reactions in living organisms due to the shape of their active site.
- This is because, for the enzyme to work, the substrate has to fit into the enzymes active site.
- If the substrate doesn’t match the enzyme’s active site, then the reaction won’t be catalysed.
11
Q
What is an active site?
A
Every enzyme has an active site with a unique shape that fits onto the substance involved in a reaction.
12
Q
What is the ‘lock and key theory’?
A
A simplified model to explain enzyme action.
13
Q
What is the ‘induced fit’ model of enzyme action?
A
The idea that the active site changes shape a little as the substrate binds to it to get a tighter fit.
14
Q
What must temperature be like to have optimum conditions for enzyme action? (4)
A
- A higher temperature increases the rate of reaction at first.
- But if it gets too hot, some of the bonds holding the enzyme together break.
- This changes the shape of the enzymes active site, so the substrate won’t fit anymore => enzyme is said to be denatured.
- Enzymes in the human body have an optimum temperature (temp at which they work best) of around 37 degrees celsius.
15
Q
What must pH be like to have optimum conditions for enzyme action? (4)
A
- If pH is too high, or too low, it interferes with the bonds holding the enzyme together.
- This changes the shape of the active site and denatures the enzyme.
- All enzymes have an optimum pH, but its different depending on where the enzymes work.
- For many enzymes the pH is neutral/7, but not always.
16
Q
What is pepsin and what is its optimum pH?
A
Pepsin is an enzyme used to break down proteins in the stomach. It works best at pH 2, which means its well suited the acidic conditions in the stomach.
17
Q
In what 2 ways is food broken down?
A
- Mechanically - this includes our teeth grinding down food, and our stomach churning up food.
- Chemically - where enzymes help to break down food.
18
Q
What do digestive enzymes do?
A
Digestive enzymes convert food into small soluble molecules that can be absorbed into the bloodstream.
19
Q
What are the products of digestion used for?
A
The products of digestion are used to build new carbohydrates, lipids and proteins. Some glucose is used in respiration.
20
Q
What do carbohydrases do?
A
Carbohydrases break down carbohydrates to simple sugars
21
Q
What does amylase do? Where is it made + where does it work?
A
- Amylase helps to break down starch into maltose (and other sugars, e.g, dextrins).
- Made in the salivary gland, pancreas + small intestine.
- Works in the mouth and small intestine.
22
Q
What do proteases do? Where are they made + where do they work?
A
- Proteases help to break down proteins into amino acids.
- Made in the stomach, pancreas + small intestine.
- Work in the stomach + small intestine.
23
Q
What do lipases do? Where are they made + where do they work?
A
- Lipases help to break down lipids into fatty acids and glycerol.
- Made in the pancreas + small intestine.
- Work in the small intestine.
24
Q
Where is bile made and stored?
A
Bile is made in the liver and stored in the gall bladder.
25
What are the features of bile and why? (3)
* It is alkaline to neutralise hydrochloric acid from the stomach, because the hydrochloric acid from the stomach makes the pH too acidic for enzymes in the small intestine to work properly. The enzymes in the small intestine work best in these alkaline conditions.
* It also emulsifies fat to form small droplets which increases the surface area for the enzyme lipase to work on - makes its digestion faster.
* The alkaline conditions and large surface area increase the rate of fat breakdown by lipase.
26
What is the method to prepare a food sample? (4 steps)
1. Get a piece of your food and break it up using a pestle and mortar.
2. Transfer the ground up food to a beaker and add some distilled water.
3. Give the mixture a good stir with a glass rod to dissolve some of the food.
4. Filter the solution using a funnel lined with filter paper. This will get rid of all the solid bits of food.
27
How do you test for reducing sugars in food? (5)
* Benedict’s test
1. Prepare a food sample and transfer 5 cm(3) to a test tube.
2. Prepare a water bath so that it's set to 75 °C.
3. Add some Benedict's solution to the test tube (about 10 drops) using a pipette.
4. Place the test tube in the water bath using a test tube holder and leave it in there for 5 minutes. Make sure the tube is pointing away from you.
5. During this time, if the food sample contains a reducing sugar, the solution in the test tube will change from the normal blue colour to green, yellow or brick-red - it all depends on how much sugar is in the food.
28
How do you test for starch in food? (2)
* Iodine test
1. Make a food sample and transfer 5 cm(3) of your sample to a test tube.
2. Then add a few drops of iodine solution and gently shake the tube to mix the contents. If the sample contains starch, the colour of the solution will change from browny-orange to black or blue-black.
29
How do you test for proteins in food? (3)
* Biuret test
1. Prepare a sample of your food and transfer 2 cm(3) of your sample to a test tube.
2. Add 2 cm(3) of biuret solution to the sample and mix the contents of the tube by gently shaking it.
3. If the food sample contains protein, the solution will change from blue to purple. If no protein is present, the solution will stay blue.
30
How do you test for Lipids in food? (3)
* Sudan III stain solution
1. Prepare a sample of the food you're testing. Transfer about 5 cm(3) into a test tube.
2. Use a pipette to add 3 drops of Sudan III stain solution to the test tube and gently shake the tube.
3. Sudan Ill stain solution stains lipids. If the food sample contains lipids, the mixture will separate out into two layers. The top layer will be bright red. If no lipids are present, no separate red layer will form at the top of the liquid.
31
What is the 8 step method to investigate how pH affects amylase activity? - required practical 4
1. Put a drop of iodine solution into every well of a spotting tile.
2. Place a Bunsen burner on a heat-proof mat, and a tripod and gauze over the Bunsen burner. Put a beaker of water on top of the tripod and heat the water until it is 35 °C (use a thermometer to measure the temperature). Try to keep the temperature of the water constant throughout the experiment.
3. Use a syringe to add 1 cm(3) of amylase solution and 1 cm(3) of a buffer solution with a pH of 5 to a boiling tube. Using test tube holders, put the boiling tube into the beaker of water and wait for five minutes.
4. Next, use a different syringe to add 5 cm(3) of a starch solution to the boiling tube.
5. Immediately mix the contents of the boiling tube and start a stop clock.
6. Use continuous sampling to record how long it takes for the amylase to break down all of the starch. To do this, use a dropping pipette to take a fresh sample from the boiling tube every thirty seconds and put a drop into a well. When the iodine solution remains browny-orange, starch is no longer present.
7. Repeat the whole experiment with buffer solutions of different pH values to see how pH affects the time taken for the starch to be broken down.
8. Remember to control any variables each time (e.g. concentration and volume of amylase solution) to make it a fair test.
32
How do you calculate the rate of reaction for required practical 4 - effect of pH on amylase?
Rate = 1000/time and units are s(-1)
33
If an experiment measures how much something changes over time, how can you measure the rate of reaction?
Rate = change / time
Change could be something like amount of product formed
34
What is the purpose of the lungs? (4)
* You need to get oxygen from the air into your bloodstream so that it can get into your cells for respiration.
* You also need to get rid of the carbon dioxide in your blood.
* This exchange of gases all happens inside your lungs.
* Air is forced in and out of your lungs by the act of breathing.
35
How do you calculate someone's breathing rate?
Breaths per minute = number of breaths / number of minutes
36
What is the thorax?
The top part of your body.
37
How is the thorax separated from the lower part of the body (the abdomen)?
By a muscle called the diaphragm.
38
What surrounds the lungs?
The lungs are like big pink sponges and are protected by the ribcage. They're surrounded by the pleural membranes.
39
What is in the thorax (organs, tissues, bones etc.)? (11)
* Oesophagus (food pipe)
* Trachea (windpipe)
* Bronchiole
* Bronchus
* Alveoli
* Diaphragm
* Pleural membranes
* Ribcage
* Heart
* Intercostal muscle
* Lungs
40
How does air go through the body for gas exchange? (4)
* The air that you breathe in goes through the trachea.
* This splits into 2 tubes called bronchi, one going to each lung.
* The bronchi split into progressively smaller tubes called bronchioles (which are within the lungs).
* The bronchioles finally end at small bags called alveoli where the gas exchange takes place by diffusion.
41
What are alveoli?
The lungs contain millions of little air sacs called alveoli, which are surrounded by a network of blood capillaries. This is where gas exchange happens.
42
How does gas exchange work in the alveoli? (3)
* The blood passing next to the alveoli has returned to the lungs from the rest of the body, so it contains lots of carbon dioxide and very little oxygen.
* Oxygen diffuses out of the alveolus (high concentration) into the blood (low concentration).
* Carbon diffuses out of the blood (high concentration) into the alveolus (low concentration) to be breathed out.
43
How does the oxygen which is in the blood, enter the body cells, and how does carbon dioxide leave the body cells?
* When the blood reaches body cells, oxygen is released from the red blood cells (high concentration) and diffuses into the body cells (low concentration).
* At the same time, carbon dioxide diffuses out of body cells (high concentration) into the blood (low concentration). It's then carried back to the lungs.
44
What is the function of the circulatory system? (2)
* The circulatory system's main function is to get food and oxygen to every cell in the body.
* As well as being a delivery service, it's also a waste collection service - it carries waste products like carbon dioxide and urea, to where they can be removed.
45
What does the circulatory system include? (3)
* The heart
* Blood vessels
* The Blood
46
What kind of circulatory system do humans have? (2)
* A closed circulatory system - means our blood flows in vessels.
* A double circulatory system where the blood travels through the heart twice for each complete circuit of the body.
47
What is the Pulmonary circulation?
The right ventricle pumps deoxygenated blood to the lungs, to take in oxygen. The blood then returns to the heart.
48
What is the Systemic circulation?
The left ventricle pumps oxygenated blood all around the other organs of the body. The blood gives up its oxygen at the body cells and the deoxygenated blood returns to the heart to be pumped out to the lungs again.
49
What is the heart?
The heart is an organ that continuously pumps blood around the body in a double circulatory system.
50
What do the walls of the heart do?
They are made up of muscle tissue, and contract to pump the blood.
51
What are the 4 chambers of the heart?
* Right atrium
* Right ventricle
* Left atrium
* Left ventricle
52
What are the 4 main blood vessels leading in and out of the heart's main chambers?
* Vena cava
* Pulmonary artery
* Aorta
* Pulmonary vein
53
Why does the heart have valves?
To make sure blood goes in the right direction.
54
What are coronary arteries?
Coronary arteries branch off the aorta and surround the heart making sure it gets the oxygenated blood it needs.
55
Go to camera roll and look at labelled diagram of heart - try to recall labels from memory.
Rate based on how well you remember the labels.
56
How does blood flow through the heart? (6)
* Deoxygenated blood enters the heart via the vena cava, emptying into the right atrium.
* Blood flows down through a set of atrioventricular valves into the right ventricle.
* When the ventricles contract, blood travels up through the pulmonary artery to the nearby lungs where gas exchange occurs (and the blood becomes oxygenated).
* Oxygenated blood returns to the heart via the pulmonary vein, emptying into the left atrium.
* Blood flows down through a set of atrioventricular valves into the left ventricle.
* When the ventricles contract, blood travels up through the aorta, and to the rest of the body.
57
What is the natural resting heart rate controlled by?
The natural resting heart rate is controlled by a group of cells located in the right atrium that act as a pacemaker. These cells produce a small electric impulse which spreads to the surrounding muscle cells, causing them to contract.
58
Why would an artificial pacemaker be used, and how do they work?
* An artificial pacemaker is often used to control heartbeats if the natural pacemaker cells don't work properly.
* It's a little device that's implanted under the skin and has a wire going to the heart. It produces an electric current to correct irregularities in the heart rate.
59
What are arteries?
Arteries are blood vessels which carry blood away from the heart towards the organs.
60
What are the features of arteries and why? (3)
* The heart pumps blood out at a high pressure, so the artery walls are strong and elastic.
* They contain thick layers of muscle to make them strong and elastic fibres to allow them to stretch and spring back.
* The walls are thick compared to the hole down the middle - the lumen.
61
What are capillaries and what do they do? (3)
* Arteries branch into capillaries.
* Capillaries are involved in the exchange of materials at the tissues => carry blood really close to every cell in the body to exchange substances with them.
* They supply food and oxygen to the cells, and take away waste products like carbon dioxide and urea.
62
What are the features of capillaries and why? (4)
* They are really tiny and have permeable walls, so substances being exchanged with the cells can diffuse in and out.
* Their walls are usually only 1 cell thick.
* It increases the rate of diffusion by decreasing the diffusion pathway (distance over which diffusion occurs).
* Very narrow => gives them a larger SA:Vol which also increases rate of diffusion.
63
What are veins?
Capillaries join up to form veins, which carry blood to the heart.
64
What are the features of veins and why? (3)
* Blood is at a lower pressure in the veins, so the walls don't need to be as thick as artery walls.
* Veins have a bigger lumen than arteries to help the blood flow despite the low pressure.
* They also have valves to keep the blood flowing in the right direction.
65
How do you calculate the rate of blood flow?
Rate of blood flow (ml/min) = Volume of blood (ml) / Number of minutes (min)
66
What is blood?
Blood is a tissue consisting of plasma, in which the red blood cells, white blood cells and platelets are suspended.
67
What is the role of red blood cells?
To transport oxygen around the body.
68
How are red blood cells adapted to carry more oxygen? (5)
* Oxygen absorbed by the red blood cells combines with haemoglobin in the red blood cell to form oxyhaemoglobin.
* No nucleus so it can absorb more oxygen.
* Bioconcaved shaped => increases SA so more oxygen can be absorbed.
* Thin cell membranes to allow efficient oxygen absorption.
* Small in size so they can pass through very small blood vessels.
69
What happens to haemoglobin in the lungs and body tissues?
* In the lungs, oxygen diffuses into the blood. The oxygen combines with haemoglobin in red blood cells to become oxyhaemoglobin.
* In body tissues, oxyhaemoglobin in red blood cells splits up into haemoglobin and oxygen to release oxygen to the cells.
70
What are platelets and what do they do?
* Small bits of cells that don't have a nucleus.
* Help to from clots (a scab) when there is a wound => stops too much blood being lost and also prevents infection getting into the wound.
71
What happened if you don't have platelets in your blood?
Then blood cannot clot, as a result you can bruise and bleed very easily.
72
What is plasma?
A liquid that carries substances around the body.
73
What substances does plasma carry around the body? (7)
* Carbon dioxide - waste product from respiration
* Waste products like urea
* Nutrients that are needed by the body, such as glucose for respiration
* Hormones
* Proteins
* Red blood cells, white blood cells + platelets
* Antibodies and antitoxins produced by white blood cells
74
What are the features of white blood cells and what do they do? (3)
* Biggest type of blood cell and has a nucleus
* Help to protect the body from infection
* Can squeeze through very small blood vessels to get to any invading pathogens
75
What 3 ways do white blood cells kill pathogens?
* They engulf (ingest) and digest pathogens that enter the body => phagocytosis.
* Produce antitoxins to neutralise toxins produced by the pathogens.
* Produce antibodies to kill pathogens.
76
What is health?
Health is the state of physical and mental well-being.
77
What are some major causes of ill health?
Diseases, both communicable and non-communicable, are major causes of ill health.
78
What are communicable diseases?
Diseases that can spread from person to person or between animals and people. They're sometimes described as infectious or contagious diseases.
79
What can communicable diseases be caused by?
Bacteria, viruses, parasites and fungi.
80
What are some examples of communicable diseases?
Measles and malaria.
81
What are non-communicable diseases?
Diseases that cannot be spread between people or animals and people. They generally last for a long time and get slowly worse.
82
What are some examples of non-communicable diseases?
Asthma, cancer and coronary heart disease.
83
How might different types of diseases interact? (4)
* Defects in the immune system mean that an individual is more likely to suffer from infectious diseases, as their body is less likely to be able to defend itself against the pathogen that causes the disease.
* Viruses living in cells can be the trigger for cancers. E.g, infection with HPV (human papilloma virus) can cause cervical cancer in women.
* Immune reactions initially caused by a pathogen can trigger allergies such as skin rashes and asthma.
* Severe physical ill health can lead to depression and other mental illness, particularly if the physical illness has an impact on the persons ability to carry out everyday activities or if it affects their life expectancy.
84
What factors other than disease, can affect your health? (3)
* Whether or not you have a good, balanced diet that provides your body with everything it needs and in the right amounts. A poor diet can affect your physical and mental health.
* The stress you are under - being constantly under lots of stress can lead to health issues.
* Your life situation - e.g, whether you have easy access to medicines to treat illness, or whether you have access to things that can prevent you from getting ill in the first place like healthy foods, or condoms to prevent STDs.
85
Why is sampling often used when collecting data related to patterns in diseases (epidemiological data)?
Because it would take too long and cost too much to collect data from the entire population.
86
What are cardiovascular diseases?
Cardiovascular disease is a term used to describe diseases of the heart or blood vessels.
87
What is coronary heart disease?
In coronary heart disease 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.
88
What are stents and what do they do? (4)
* Stents are wire mesh tubes that can be inserted inside arteries to widen them and keep them open.
* They are particularly useful in people with coronary heart disease.
* Stents keep the coronary arteries open, making sure blood can pass through to the heart muscles.
* This keeps the person's heart beating and the person alive.
89
What are the advantages of stents? (3)
* Stents are a way of lowering the risk of a heart attack in people with coronary heart disease.
* They are effective for a long time
* The recovery time from the surgery is relatively quick.
90
What are the disadvantages of stents? (3)
* There is a risk of complications during the operation (e.g, heart attack).
* Also a risk of infection from surgery.
* Risk of patients developing a blood clot near the stent => thrombosis.
91
What are statins and what do they do?
* Statins are drugs that can reduce the amount of 'bad' cholesterol present in the blood stream.
* Taking statins slows down the rate of fatty deposits forming.
92
What is cholesterol and how can it be 'bad'? (3)
* Cholesterol is an essential lipid that your body produces and needs to function properly.
* However, too much of a certain type of cholesterol ('bad' / LDL cholesterol) can cause health problems.
* Having too much of this 'bad' cholesterol in the bloodstream can cause fatty deposits to form inside arteries, which can lead to coronary heart disease.
93
What are the advantages of statins? (3)
* Can reduce risk of strokes, coronary heart disease and heart attacks.
* Can increase amount of 'good' / HDL cholesterol in the bloodstream, which can remove 'bad' cholesterol as well.
* Some studies suggest they also help to prevent other diseases as well.
94
What are the disadvantages of statins? (3)
* Long-term drug that must be taken regularly + risk someone could forget to take them.
* Can sometimes cause negative side effects, e.g, headaches, but some can be very serious, e.g, kidney failure, liver damage and memory loss.
* It doesn't take effect instantly - takes time to kick in.
95
What can doctors do if a patient has a heart failure? (2)
* Doctors may perform a heart transplant (or heart and lungs transplant if lungs are also diseased) using donor organs from people who have recently died.
* However, if donor organs aren't available right away or if they're not the best option, doctors may fit an artificial heart.
96
What are artificial hearts and what are they used for?
* Artificial hearts are mechanical devices that pump blood for a person whose own heart has failed.
* They're usually used as a temporary fix, to keep someone alive until a donor heart can be found, or to help a person recover by allowing the heart to rest and heal.
* In some cases, they're used as a permanent fix, which reduces the need for a donor heart.
97
What are the advantages of an artificial heart? (2)
* They're less likely to be rejected by the body's immune system than a donor heart.
* This is because they're made from metals or plastics, so the body doesn't recognise them as 'foreign' in the same way it does with living tissue.
98
What are the disadvantages of an artificial heart? (5)
* Surgery to fit an artificial heart + transplant surgery can lead to bleeding and infection.
* Artificial hearts don't work as well as healthy natural ones - parts of the heart could wear out and the electrical motor could fail.
* Blood doesn't flow through artificial hearts as smoothly as through natural hearts, which can cause blood clots and lead to strokes.
* A patient with an artificial heart has to take drugs to thin their blood and make sure blood clots don't occur => can cause problems with bleeding if they're hurt in an accident because their blood can't clot normally to heal the wounds.
* May be uncomfortable for the patient.
99
How can heart valves be damaged/ weakened and what can that cause? (3)
* By heart attacks, or old age.
* The damage may cause the valve tissue to stiffen, so it won't open properly.
* Or a valve may become leaky, allowing blood to flow in both directions rather than just forwards => means blood doesn't circulate as effectively as normal.
100
How can severe valve damage be treated? (5)
* By replacing the valve.
* Replacement valves can be ones taken from humans or other mammals - biological valves.
* Can be man-made - mechanical valves.
* Replacing a valve is a much less drastic procedure than a whole heart transplant.
* But fitting artificial valves is still major surgery and there can still be problems with blood clots.
101
What happens if someone loses a lot of blood, e.g, in an accident?
Their heart can still pump the remaining red blood cells around as long as the volume of their blood can be topped up.
102
What is artificial blood and what is it used for? (4)
* A blood substitute, e.g, a salt solution (saline), which is used to replace the lost volume of blood.
* It's safe (if no air bubbles get into the blood) and can keep people alive even if they lose 2/3 of their red blood cells.
* This may give the patient enough time to produce new blood cells. If not, the patient will need a blood transfusion.
* Ideally, an artificial blood product would replace the function of lost red blood cells, so that there's no need for a blood transfusion => scientists are currently working on products that can do this.
103
What are risk factors - in terms of health and disease?
Things that are linked to an increase in the likelihood that a person will develop a certain disease in their lifetime. They don't guarantee that someone will get the disease.
104
What can risk factors be (examples) - in terms of health and disease?
They can be:
* Aspects of a person’s lifestyle e.g, exercise.
* Substances in the person’s body, e.g, asbestos fibres, or environment, e.g, air pollution.
105
How can smoking be a risk factor that causes disease? (2)
* Smoking is a direct cause of cardiovascular disease, lung disease and lung cancer. Damages artery walls and cells in lining of lungs.
* Smoking when pregnant reduces amount of oxygen the baby receives in the womb and can cause lots of health problems for the unborn baby.
106
How can alcohol be a risk factor that causes disease? (3)
* Drinking too much alcohol can be a direct cause of liver disease. Liver breaks down alcohol, but the reaction can damage its cells. Liver cells may also be damaged when toxic chemicals leak from the gut due to intestine damage which is caused by alcohol.
* Too much alcohol can damage brain function => damages nerve cells in the brain causing brain to lose volume.
* Drinking alcohol when pregnant can damage the baby's cells, affecting its development and causing a wide range of health issues.
107
How can obesity be a risk factor that causes disease?
Obesity can directly cause Type 2 diabetes by making the body less sensitive or resistant to insulin, meaning it struggles to control glucose concentration in the blood.
108
What are carcinogens and how can they be a risk factor that causes disease? (4)
* Cancer can be directly caused by exposure to certain substances or radiation.
* Things that cause cancer are known as carcinogens. Carcinogens work in different ways.
* E.g, some damage a cell's DNA in a way that makes the cell more likely to divide uncontrollably.
* Ionising radiation is an example of a carcinogen.
109
What is an example of risk factors that can't cause a disease, but are related to other risk factors that can?
A lack of exercise and a high fat diet are heavily linked to an increased chance of cardiovascular disease, but they can't cause the disease directly. It's the resulting high blood pressure and high 'bad' cholesterol levels that can actually cause it.
110
What are the human costs of non-communicable diseases? (3)
* Tens of millions of people around the world die from non-communicable diseases every year.
* People with these diseases may have a lower quality of life or a shorter life span.
* Affects the person themself, and loved ones.
111
What are the financial costs of non-communicable diseases? (4)
* Cost to NHS of researching and treating these diseases is huge - its the same for other health services + organisations around the world.
* Families may have to move or adapt their home to help a family member with a disease - can be costly.
* If the family member with the disease has to give up work or dies, the family's income will be reduced.
* A reduction in number of people able to wok can affect a country's economy.
112
How is cancer caused?
By uncontrolled cell growth and division. This uncontrolled growth and division is a result of changes that occur to the cells and results in the formation of a tumour.
113
What is a tumour?
A growth of abnormal cells. Not all tumours are cancerous - can be benign or malignant.
114
What is a Benign tumour?
Where the tumour grows until there's no more room. Benign tumours are growths of abnormal cells which are contained in one area, usually within a membrane. They do not invade other parts of the body, and usually aren't dangerous or cancerous.
115
What are Malignant tumours?
They invade neighbouring healthy tissues. Cells can break off and spread to other parts of the body by travelling in the bloodstream. The malignant cells then invade healthy tissues elsewhere in the body and form secondary tumours. Malignant tumour cells are dangerous and can be fatal - they are cancers.
116
Who can develop cancer?
Anyone.
117
Why have cancer survival rates increased?
Due to medical advances such as improved treatment, being able to diagnose cancer earlier, and increased screening for the disease.
118
What are 4 lifestyle risk factors that can increase the risk of developing cancer?
* Smoking - linked to lung, mouth, bowel, stomach and cervical cancer. Biggest preventable cause of cancer.
* Obesity - linked to bowel, liver and kidney cancer. 2nd biggest preventable cause of cancer.
* UV exposure - people who are often exposed to UV radiation from sun have an increased risk of developing skin cancer. People who live in sunny climate and those who spend a lot of time outside = at a higher risk. People who frequently use sun bed are also at a higher risk.
* Viral infection - e.g, infection with hepatitis B and hepatitis C viruses can increase risk of developing liver cancer. Likelihood of becoming infected with these viruses can depend on lifestyle, e.g, can spread through unprotected sex or sharing needles.
119
What is a genetic risk factor with example?
* Sometimes you can inherit family genes that make you more susceptible to cancer.
* Mutations in the BRCA genes have been linked to an increased likelihood of developing breast and ovarian cancer.
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What order are the plant tissues in from the top to the bottom of the leaf? (5)
* Waxy cuticle - not a tissue but still included
* Epidermal tissue
* Palisade mesophyll tissue
* Spongy mesophyll tissue
* Epidermal tissue
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What is the waxy cuticle?
A protective layer that reduces water loss from the leaf while still allowing light through.
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What is palisade mesophyll?
Has lots of chloroplasts - means they're near the top of the leaf where they can get the most light => where photosynthesis takes place.
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What is the epidermal?
Covers whole plant, covered in waxy cuticle. Transparent so light can penetrate the leaf.
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What is spongy mesophyll?
Contains big air spaces to allow gases to diffuse in and out of the cell. Carbon dioxide in and oxygen out.
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What are the stomata?
Small pores gas diffuses into/out of. When open, water is lost by the process of transpiration - controls water lost.
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What are guard cells?
Changes shape to open and close the stomata.
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What is the meristem?
Found at the growing tips of shoots and roots. Have the ability to divide. Make unspecialised cells that have the potential to become any type of specialised cell (stem cells). Also found between xylem and phloem.
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What are the characteristics/features of xylem cells? (3)
* Made up of dead cells joined together end to end.
* The walls are strengthened with lignin.
* The dead cells have no end walls between them, so there is a hole down the middle of the tissue - creating a hollow tube.
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What is transpiration / the transpiration stream? (3)
* Water and mineral ions travel through the xylem tubes from the root to the stems and leaves - only in this direction => called the transpiration stream.
* Transpiration through the stomata in the leaves, pulls water up through the plant due to cohesion between water molecules.
* Transport in the xylem = a physical process and requires no energy.
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How does transpiration work? (8)
* Most transpiration occurs at the leaves.
* Transpiration is caused by evaporation and diffusion of water from the surface of the leaf / spongy mesophyll cells.
* Water diffuses through the stomata to the surrounding air down the concentration gradient.
* Water then evaporates.
* This decreased the concentration of water in the leaf.
* Water is drawn up from other areas of the plant through the xylem to replace the water lost from the leaf.
* This results in more water being drawn up from the roots.
* This causes a constant transpiration stream of water.
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What are the purposes of transpiration? (4)
* Provides the water for photosynthesis
* Transports mineral ions
* Cools the leaf as water evaporates
* Provides water that keeps the cells turgid, which supports herbaceous plants
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What are the features/characteristics and functions of phloem cells? (6)
* Companion cells support the phloem tissue as the phloem cells have lost most of their organelles and pushed their cytoplasm to the side.
* Phloem is made up of columns of elongated living cells.
* The cells have small pores in the end walls (sieve plates) to allow dissolved sugars to flow through
* This means dissolved sugars made in leaves can travel to the rest of the plant for storage or immediate usage
* Phloem can transport dissolved sugars in both directions in the tissue.
* This process is called translocation and does require energy from companion cells.
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What are the 4 main factors that affect transpiration rate?
* Light intensity
* Temperature
* Air flow
* Humidity
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How is light intensity a factor that affects the rate of transpiration? (2)
* The brighter the light, the greater the transpiration rate.
* Stomata begins to close the darker it gets as photosynthesis can't happened in the dark so they don't need to be open to let CO2 in => means very little water can escape.
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How is temperature a factor that affects the rate of transpiration?
* The warmer it is, the faster transpiration happens.
* When it's warm, the water particles have more energy to evaporate and diffuse out of the stomata.
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How is air flow a factor that affects the rate of transpiration? (3)
* Windy conditions increase the rate of transpiration.
* If it isn't windy, water vapour surrounds the leaf and doesn't move away => means there's a high concentration of water particles outside the leaf as well as inside so diffusion doesn't happen as quickly.
* If air flow is good, the water vapour is swept away, maintaining a steep concentration gradient between the plant and the outside.
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How is humidity a factor that affects the rate of transpiration? (2)
* The drier the air, the faster the transpiration rate.
* Diffusion happens faster when there is a larger contrast between the water inside and outside the leaf - when it isn't humid.
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How does transpiration link to photosynthesis?
Transpiration is an unavoidable consequence of photosynthesis - only 5% of water taken up by the plant is used for photosynthesis.
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Look at picture in camera roll of labelled diagram of investigating transpiration rate.
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