Organisation Flashcards
(112 cards)
1
Q
What is Meant by Tissue, Organ and Organ System
A
Tissue- a group of cells with a similar function.
Organ- a group of tissues working together for a specific function.
Organ System- a collection of organs working together to carry out a function.
2
Q
Describe the Purpose of Digestion
A
-Food molecules such as carbohydrates, lipids and proteins are too large to be absorbed directly into the bloodstream.
-Because of this, they have to be digested.
-In digestion, enzymes are used to break down large food molecules into smaller soluble molecules.
-These smaller molecules can then be absorbed into the bloodstream
3
Q
List the Parts of the Digestive System
A
-Mouth
-Salivary Glands
-Oesophagus
-Liver
-Stomach
-Pancreas
-Small Intestine
-Large Intestine
-Appendix
-Anus
4
Q
Describe the Function of the Mouth and Salivary Glands in the Digestive System
A
-Food is chewed in the mouth and mixed with saliva.
-The enzymes in the saliva begin to digest starch into smaller sugar molecules.
5
Q
Describe the Function of the Oesophagus in the Digestive System
A
The oesophagus carries food from the mouth to the stomach.
6
Q
Describe the Function of the Stomach in the Digestive System
A
-In the stomach, the food is churned into a fluid. This increases the surface area for enzymes to digest, increasing the rate of digestion.
-In the stomach, hydrochloric acid helps the enzymes digest the proteins by providing the optimum pH.
-Protein molecules start their digestion in the stomach.
7
Q
Describe the Function of the Pancreas and Liver in the Digestive System
A
-The pancreas releases fluid into the small intestine.
-Pancreatic fluid contains enzymes which continue with the digestion of starch and proteins. The enzymes also start the digestion of lipids.
-The liver releases bile into the small intestine.
-Bile emulsifies lipids. It also neutralises the acid released from the stomach. This is important as the enzymes which operate in the small intestine work best under alkaline conditions.
8
Q
Describe the Function of the Small Intestine in the Digestive System
A
-The walls of the small intestine releases enzymes. These continue the digestion of proteins and lipids.
-In the small intestine, the products of digestion are absorbed into the bloodstream. This takes place by diffusion or by active transport.
9
Q
Describe the Function of the Large Intestine in the Digestive System
A
-The role of the large intestine is to absorb the water contained in the fluid passing through the digestive system.
-As the fluid passes through the large intestine, it turns into solid faeces.
10
Q
Describe what Happens to the Products of Digestion Once they are Absorbed into the Bloodstream
A
-Once the products of digestion are absorbed into the bloodstream, they are carried off to the body cells.
-Here the molecules are used to build new carbohydrates, lipids and proteins.
-Also, some of the glucose is used to release energy in respiration.
11
Q
What is an Enzyme
A
-Enzymes are biological catalysts that catalyse specific reaction in living organisms.
-They are large protein molecules.
12
Q
What is Meant by the Lock and Key Theory
A
-The lock and key theory states that enzymes are specific because the substrate must fit perfectly into the active site.
-If a substrate does not fit perfectly into the active site, then the enzyme will not be able to break it down.
13
Q
How do Enzymes Break Down Foods
A
-The substrate binds to the active site of the enzyme.
-This is because the shape of the active site and substrate are complementary
-Enzymes catalyse the breakdown of the substrate.
-The products are then released from the active site.
14
Q
Describe the Structure, Function and Products of Proteins
A
-Proteins build up cells and tissues. They are also the basis of all enzymes.
-They are long chains of amino acids.
-Proteins are broken down by protease (produced in the pancreas, stomach and small intestine) into amino acids.
-Once the amino acids have been absorbed into the bloodstream, they are carried to the body cells. The body cells join the amino acids back together in a different order to make human proteins.
15
Q
Describe the Structure, Function and Products of Carbohydrates
A
-Carbohydrates provide energy for cell respiration.
-A simple chain is two glucose molecules joined together. A complex chain is a long chain of simple carbohydrates joined together.
-Carbohydrates are broken down by carbohydrase (produced in the mouth pancreas and small intestine) into glucose or fructose.
16
Q
Describe the Structure, Function and Products of Lipids
A
-Lipids are an energy source. they are used in cell membranes and hormones.
-They are made up of three fatty acid molecules joined to a molecule of glycerol.
-Lipids are broken down by lipase (produced in the pancreas and small intestine) into glycerol and fatty acids.
17
Q
Describe the Purpose of Amylase as a Digestive Enzyme
A
-Amylase is made in the pancreas, small intestine and salivary glands.
-It works in the mouth, small intestine and stomach.
-It catalyses the chemical reaction breaking starch down into sugars.
18
Q
Describe the Purpose of Bile
A
-Bile is produced in the liver and is stored in the gall bladder. It increases the rate of lipid digestion.
-Bile emulsified lipids. This means that bile converts large lipid droplets into small lipid droplets. This increases the surface area for the enzyme lipase to act on which increases the rate of lipid breakdown.
-The enzyme lipase works best in alkaline conditions. However, the stomach releases acidic fluid directly into the small intestine.
-Because bile is alkaline, it neutralises the stomach acid, allowing the lipase in the small intestine to work effectively.
19
Q
Explain why it is Difficult to Digest Fat When the Gall Bladder is Blocked
A
-Less bile reaches the small intestine so there is less emulsification of fat.
-This means there is a smaller surface area for lipase to break down fat.
-The pH of the small intestine is also not neutralised so lipase is not at its optimum pH to break down fat.
20
Q
Describe the Effect of Temperature on Enzymes
A
-As the temperature increases, the reaction gets faster as the activity of the enzyme increases. At higher temperatures, the enzyme and substrate are moving faster.
-This means that there are more collisions per second between the substrate and the active site.
-At the optimum temperature, the enzyme is working at its fastest rate and there are the maximum frequency of collisions between the substrate and the active site.
-At high temperatures the enzyme molecules vibrate and the active site changes shape. Scientists say that the enzyme is denatured.
-Now the substrate no longer fits perfectly into the active site so the reaction stops.
21
Q
Describe the Effect of pH on Enzymes
A
-If the pH is more acidic or more alkaline than the optimum pH for an enzyme, then it interferes with the bonds holding the enzyme together.
-This changes the shape of the active site and at extreme pH values, the enzyme may become denatured
-Because the active site has changed shape, it no longer fits the substrate perfectly so the enzyme does not work e.g. amylase can longer digest starch so the rate of digestion decreases.
-Stomach enzymes often work better in acidic conditions whereas enzymes in the small intestine work better in alkaline conditions.
22
Q
Why are Safety Goggles an Essential in the Food Tests Required Practical
A
-This required practical uses a number of chemicals which are hazardous e.g. Benedict’s solution and iodine which are irritant.
-Therefore we need to wear safety goggles to protect our eyes from splashes.
23
Q
Describe a Method to Prepare a Food Sample in the Food Tests Required Practical
A
-First, grind the food sample into a paste using a pestle and mortar and a small amount of distilled water.
-Transfer the paste to a beaker. Add more distilled water and stir. Stir the sample to ensure that the molecules present in the food dissolve in the distilled water.
-Next, pass the solution through a filter to remove any undissolved food particles. These could make the sample cloudy and make any colour changes difficult to see.
-At this point, the solution can be tested for the the chemicals present in the sample.
24
Q
Describe a Method to Test for Starch in the Food Tests Required Practical
A
-First, place a small volume of the food solution into a test tube.
-Then, add several drops of iodine solution.
-If starch is present in the food sample, the iodine would turn from an orange colour to a blue-black colour.
25
Describe a Method to Test for Reducing Sugars (Glucose) in the Food Tests Required Practical
-First, add several drops of Benedict's solution to the food solution.
-Now, place the test tube into a beaker and half fill the beaker with hot water from kettle. Leave the test tube in the hot water for five minutes.
-If reducing sugars are present in the food sample, the Benedict's solution would turn from a blue colour to:
-green if only a small amount of sugar is present
- yellow if more sugar is present
-brick red if there is a lot of sugar present
26
Describe a Method to Test for Proteins in the Food Tests Required Practical
-First, place a small volume of the food solution into a test tube.
-Then, add several drops of Biuret solution to the food solution.
-If proteins are present in the food sample, the Biuret solution would turn from a blue colour to a lilac colour.
27
Describe a Method to Test for Lipids in the Food Tests Required Practical
-When preparing the food sample for lipids, do not filter the food solution. This is because any lipids present will be
absorbed onto the filter paper.
-To test for lipids, add a small amount of ethanol and a small amount of distilled water to the food solution.
-Then, shake the test tube.
-If lipids are present in the food sample, a white cloudy suspension forms.
28
Describe a Method for the Effect of pH on Amylase Required Practical
-Placer one drop of iodine into each well of a spotting tile.
-Now, set up 3 test tubes, one with 2cm^3 starch solution, one with 2cm^3 amylase solution and one with 2cm^3 pH 5 buffer solution. Leave the test tubes in a water bath for 10 minutes.
-Combine the three solutions into one test tube and mix with a stirring rod. Return the solution to a water bath and start a stop watch. The amylase will start to break down the starch.
-After thirty seconds, transfer one drop of the solution to the first well in the spotting tile containing iodine solution.
-Continue taking samples every thirty seconds, moving onto the next well in the spotting tile until there is no more starch present. This is when the iodine remains orange and does not turn blue-black.
-Record the the well number where the iodine first remained brown then repeat the experiment with different pH buffers.
29
What is Meant by a Buffer Solution
-A buffer solution has a set pH which is decided when it is made.
-Buffer solutions are used in biology to control the pH.
30
Why is it Important to Leave the Test Tubes in a Water Bath for 10 Minutes in the Effect of pH on Amylase Required Practical
-By leaving our test tubes in the water bath for ten minutes, we make certain that the solutions in the test tubes reach the same temperature as the water bath.
-This means that all solutions are the same temperature.
31
Why will the Iodine Initially Turn Blue-Black in the Effect of pH on Amylase Required Practical
-Initially the colour of the iodine solution will turn blue / black.
-This is because the amylase will not have had time to break the starch down.
-Because our solution still contains a high level of starch, this will turn the iodine blue / black.
32
Why is Taking Sample Every Thirty Seconds a Problem in the Effect of pH on Amylase Required Practical
-Because we are taking samples every thirty seconds, it is only possible to state when the starch was all broken down to the nearest thirty seconds.
-This makes our experiment inaccurate.
-A way to address this is to take samples more frequently, for example every ten seconds.
33
Why is Observing when the Reaction has Finished a Problem in the Effect of pH on Amylase Required Practical
-It can be difficult to see when the reaction has finished as the blue / black colour of the iodine solution tends to show a gradual change.
-There is no clear cut-off point where the iodine solution stays orange showing that the starch has all been broken down.
-A way to address this problem is by asking several people to look at the spotting tile and decide when the reaction has completed. A mean can be taken of their answers.
34
Why is it Important that the Small Intestine is Long
-The length of the small intestine in humans is 5 metres.
-Because the human small intestine is so long, this provides a very large surface area for absorption of the small soluble molecules produced in digestion.
-Also, it takes several hours for the molecules to make
their way down the small intestine.
-This means that there is plenty of time for the molecules to be absorbed into the bloodstream.
35
Describe how the Small Intestines are Adapted as an Effective Exchange Surface
-Villi and microvilli massively increase the surface area for the absorption of the products of digestion.
-The good blood supply rapidly takes away the molecules that are absorbed into the bloodstream. This makes the concentration gradient very steep, which makes diffusion faster.
-The thin membrane on the villi make the pathway for diffusion very short. This increases the rate of diffusion.
36
Why do the Cells Lining the Surface of the Villi Have a Large Number of Mitochondria.
-The cells lining the surface of the villi have a large number of mitochondria.
-This is because they use active transport to move certain molecules from the small intestine into the bloodstream.
-Active transport requires energy from respiration. The large number of mitochondria ensure that there is always a large
amount of energy available for active transport.
37
Describe the Key Structures in the Lungs and Their Functions
Trachea- carries air down the throat
Rings of Cartilage- prevent the trachea from collapsing when inhaling
Bronchi- one bronchus carries air down into each lung
Bronchioles- these tiny tubes carry air down to the alveoli
Alveoli- these are where gases diffuse in and out of the bloodstream
38
Describe how the Lungs are Adapted as an Effective Exchange Surface
-Each lung contains millions of alveoli: This means that there is a huge surface area to volume ratio for diffusion of gases in and out of the blood so the rate of diffusion is high.
-Alveoli have very thin walls. This makes the diffusion pathway very short, which increases the rate of diffusion.
-Alveoli have a very efficient blood supply. This ensures that once oxygen diffuses into the blood, it is rapidly removed. This means that the concentration gradient for oxygen is very steep, which keeps the rate of diffusion high.
-The same applies to carbon dioxide. By constantly providing more carbon dioxide, thisex ensures the maximum rate of diffusion from the bloodstream into the air.
39
Describe the Exchange of Gases when Breathing
-When breathing in, oxygen-rich air moves into the lungs. This maintains a steep concentration gradient with the blood.
-Oxygen continually diffuses into the bloodstream though the gas exchange surfaces on the alveoli.
-When breathing out, carbon dioxide-rich air is removed from the lungs.
-This maintains the concentration gradient so that carbon dioxide continually diffuses out of the bloodstream into the air of the lungs.
40
Describe how the Lungs Take in Air
-When breathing in, the intercostal muscles contract. As this happens, the ribs move up and down, the diaphragm contracts and the volume of the chest increases.
-The increased volume means there is lower pressure in the chest.
-Air outside the chest is now at a higher pressure than inside so air is drawn into the lungs.
41
Describe how the Lungs Remove Air
-When breathing out, the intercostal muscles relax. As this happens, the ribs fall, the diaphragm relaxes and the volume of the chest decreases.
-The decreased volume means there is higher pressure in the chest.
-Air inside the chest is now at a higher pressure than outside so air is forced out of the lungs.
42
What is Meant by a Single Circulatory System
-Fish have a single circulatory system.
-This is because the blood only passes through the heart once per cycle before going to the gills to collect oxygen and then on to the body organs.
43
Describe what Happens to Blood when it Passes Through the Gills and Organs of a Fish
-When the blood passes through the gills, the red blood cells collect oxygen. The blood is now oxygenated.
-When the blood passes through the organs, the red blood cells give up their oxygen.
-The oxygen diffuses from the blood to the cells of the organs where it is used for respiration. This means that the blood becomes deoxygenated.
44
Describe the Disadvantage of a Single Circulatory System
-The main disadvantage of the single circulatory system is that the blood loses pressure as it passes through the gills.
-This means that the blood travels relatively slowly from the gills to the organs.
-Because of this, the blood cannot deliver oxygen rapidly to the organs.
45
What is Meant by a Double Circulatory System
-Humans have a double circulatory system as the blood passes through the heart twice per cycle.
-Blood is pumped to the lungs by the right side of the heart
and blood is pumped to the body by the left.
46
Describe the Human Double Circulatory System
-First deoxygenated blood passes from the heart to the lungs, where it collects oxygen. The oxygenated blood
now passes from the lungs back to the heart.
-The heart now pumps the oxygenated blood to the organs,
where the blood loses its oxygen.
-Finally the deoxygenated blood passes back to the heart from the organs to begin the cycle.
47
Describe the Advantage of a Double Circulatory System
-The advantage of the double circulatory system is that the blood passes through the heart twice per cycle.
-First the blood is pumped from the heart to the lungs. In the lungs, the blood loses pressure and slows down.
-Now the blood returns to the heart where it is pumped to the organs.
-This means that the blood is now travelling with a higher pressure and is able to deliver oxygen rapidly to the organs.
48
Describe the Function of Each Blood Vessel in the Heart
Vena Cava- receives deoxygenated blood from the body
Pulmonary Artery- carries deoxygenated blood to the lungs
Pulmonary Vein- receives oxygenated blood from the lungs
Aorta- carries oxygenated blood to the body
49
Describe the Pathway of Blood Through the Heart
-Blood first enters the left atrium and right atrium. The right atrium receives deoxygenated blood from the body and the left atrium receives oxygenated blood from the lungs.
-The atria now contract, forcing blood into the ventricles.
-The ventricles now contract, forcing blood out of the heart. Blood travels from the right side of the heart to the lungs and from the left side of the heart to the body.
-This is why the left ventricle has a thicker muscular wall
than the right ventricle since the left ventricle pumps blood around the entire body.
50
Describe the Role of Valves Between the Atria and the Ventricles
-When the atria contract, the valves are forced open, allowing blood to pass down to the ventricles.
-When the ventricles contract, the valves shut.
-This means that the blood passes out of the ventricles (to either the lungs or the body), without the blood passing back up into the atria.
51
Describe the Role of the Coronary Artery
-The coronary artery runs directly from the aorta and passes through the heart muscle.
-The job of the coronary artery is to provide the heart's muscle tissue with oxygen.
-The oxygen is used by the muscle cells to carry out respiration. This releases the energy needed for the heart to contract.
52
Describe the Role of Pacemakers and Artificial Pacemakers
-The pacemaker is a collection of cells in the right atrium. This controls the natural resting heart rate.
-Sometimes, the pacemaker does not work correctly. This can cause the heart rate to become irregular. In this case, doctors can implant an artificial pacemaker into the patient.
-An artificial pacemaker senses when the heart rate is irregular and sends electrical signals to the heart muscle to trigger it to beat in a regular pattern.
53
Describe the Function and Adaptations of Arteries
-Arteries carry oxygenated blood away from the heart.
-The heart pumps blood at a high pressure so arteries have strong walls and elastic fibres to withstand this.
-The walls are thick compared to the lumen.
-Arteries contain thick layers of muscle to make them strong and elastic fibres allow them to stretch and spring back.
54
Describe the Function and Adaptations of Capillaries
-Capillaries link arteries and veins together. They are tiny vessels with narrow lumens.
-They carry the blood really close to every cell to exchange substances with them.
-They have permeable walls so substances can diffuse in and out. They supply food and oxygen and remove waste such as carbon dioxide.
-Their walls are extremely thin (usually one cell thick). This increases the rate of diffusion by decreasing the distance over which it occurs.
55
Describe the Function and Adaptations of Veins
-Veins carry deoxygenated blood from the organs back to the heart.
-Veins have thin walls because the blood flowing through the veins is travelling slowly and at low pressure. Despite the low pressure, they have large lumens to help the blood flow.
-Because the blood flowing through veins moves slowly and at low pressure, there is the risk that the blood stops flowing and starts moving backwards.
-Valves in the veins prevent this from happening. When the blood starts to flow backwards, the valves close to stop this.
56
Describe the Purpose of Plasma in Blood
-The blood plasma is the liquid part of the blood. The purpose of blood plasma is to transport dissolved substances around the body.
-Molecules produced during digestion are transported from the small intestine to body cells. This includes glucose which is produced when starch is digested.
-Carbon dioxide is also transported in blood plasma. Carbon dioxide is produced by cells when they carry out aerobic respiration. The carbon dioxide is carried to the lungs where it is breathed out.
-Finally, blood plasma carries the waste product urea. This is produced by the liver and transported in the plasma to the kidneys to be excreted in urine.
57
Describe the Function and Adaptations of Red Blood Cells
-Red blood cells carry oxygen from the lungs to cells in the body.
-Red blood cells have no nucleus. This means that they have more room for haemoglobin (they can carry more oxygen).
-Red blood cells have a biconcave disc shape. This increases their surface area, which means that oxygen can diffuse in and out faster.
-In the lungs, haemoglobin binds to oxygen to become oxyhaemoglobin. In body tissues, oxyhaemoglobin splits up into haemoglobin and oxygen to release oxygen to the cells.
58
Describe the Function and Adaptations of White Blood Cells
-White blood cells form part of the immune system (defend against disease). For example, certain white blood cells produce antibodies (lymphocytes) while others ingest microbes (phagocytes).
-Unlike red blood cells, they do have a nucleus. The nucleus contains the cell's DNA. This encodes the instructions that the white blood cells need to do their job (eg make antibodies).
59
Describe the Purpose of Platelets in Blood
-Platelets are small fragments of cells. They have no nucleus.
-They help the blood to clot at a wound to prevent blood pouring out and microorganisms getting in.
-A lack of platelets can cause excessive bleeding and bruising.
60
Give Uses of Blood and Blood Products in Medicine
-Blood transfusions to replace blood lost during an injury (or an operation).
-Platelets can be extracted from donated blood and given to patients whose blood may not clot effectively.
-Proteins (such as antibodies) can be extracted from blood and given to patients who require them.
61
What are the Risks when Using Blood or Blood Products
-The first risk is with blood transfusions. Every person has a blood type. This means that any donated blood has to be matched so that it is not incompatible with that person's blood type.
-If the blood is incompatible, the transfusion will be rejected by the person's immune system and that can be fatal.
-The second risk is that blood-borne infections can be passed to patients who receive a blood transfusion or a blood product. However, donated blood is screened in the UK to prevent infections.
62
Describe what Happens in Coronary Heart Disease and its Effect on the Heart Muscle
-Coronary heart disease is when the coronary arteries that supply blood to the muscle of the heart get blocked up by fatty material building up.
-This causes the arteries to become narrow, so blood flow is restricted and there is a lack of oxygen to the heart muscle.
-This can result in a heart attack.
63
Describe how a Stent Works to Help Those With Coronary Heart Disease
-Stents are a way of lowering the risk of a heart attack in those with coronary heart disease.
-They are tubes that are inserted inside arteries. They keep them open, making sure blood can flow normally through to the heart muscle.
64
Give the Advantages and Disadvantages of Stents
Advantages:
-Stents are effective for a long time and recovery from the surgery is relatively quick.
Disadvantages:
-There is a risk of complications or infection during surgery.
-Patients may develop a blood clot near the stent.
-Stents do not treat the underlying causes of coronary heart disease so a person who has been fitted with a stent can still have narrowing of other regions of the coronary arteries.
65
Describe how Statins Reduce Cholesterol in the Blood
-Cholesterol is an essential lipid that the body produces and needs to function properly. However, too much of a certain type of cholesterol (LDL) can cause health problems.
-Having too much LDL cholesterol in the bloodstream can cause fatty deposits to build up in arteries which can lead to coronary heart disease.
-Statins are drugs that can reduce the amount of LDL cholesterol present in the bloodstream. This slows down the rate of fatty deposits forming.
66
State the Advantages of Statins
-By reducing the amount of LDL cholesterol in the blood, statins reduce the chance of coronary heart disease. and heart attacks.
-Statins can also increase the amount of a beneficial cholesterol (HDL) in the bloodstream. HDL cholesterol can remove LDL cholesterol from the blood.
-Some studies suggest that statins may also prevent some other diseases.
67
State the Disadvantages of Statins
-Statins are a long term drug that must be taken regularly. There is the risk that someone could forget to take them.
-Statins can sometimes cause negative side effects such as headaches. Some of these side effects can be serious such as kidney failure.
-The effect of statins isn't instant. It takes time for their effect to kick in.
68
Describe the Effect on Patients with Faulty Heart Valves
-Heart valves do not fully open when the atria contract. In this case, the heart has to work extra hard to force the blood out of the atria and into the ventricles. This can make the heart become enlarged.
-Heart valves that leak blood when the ventricles contract. In this case, oxygenated blood is not pumped effectively to the body. Because of this, the patient may feel weak and tired.
69
Compare the Use of Mechanical and Biological Valves
Mechanical Valves:
-These can last a lifetime.
-Risk of blood clotting. Patient needs to take anti-clotting drugs for rest of life.
Biological Valves:
-Do not last as long and may need to be replaced.
-Patients are not required to take drugs with this type of valve
70
What is the Problem with the Heart in the Case of Heart Failure
In the case of heart failure, the heart cannot pump enough blood around the body.
71
State the Problems with Heart Transplants
-The surgery can lead to bleeding and infection.
-There are not enough donated hearts so there is a long waiting list.
-The patient must take drugs to stop the donated heart from being rejected by the body's immune system. These drugs must be taken for the rest of the patient's life.
72
Evaluate the Use of Artificial Hearts
-Artificial hearts are less likely to be rejected by the body's immune system than a donor heart.
-This is because they are made of metals/plastics so the body does not see them as 'foreign' and attack it in the same way as living tissue.
-Blood doesn't flow through artificial hearts as smoothly which can lead to blood clots and strokes.
-The patients has to take drugs to thin their blood to make sure this doesn't happen. However, this can cause problems with bleeding if they are hurt in an accident.
-The surgery to fit an artificial heart can lead to bleeding and infection.
73
Describe what is Meant By a Tumour
-Cancer is caused by uncontrolled cell growth and division. This uncontrolled growth and division is a result of changes to the cells.
-A tumour is an uncontrolled growth of cells. This forms a mass (or lump) of tissue.
74
Describe the Similarities Between Benign and Malignant Tumours
-They both result from changes in the cell / genes.
-They grow by uncontrollable cell division.
-They are made up of abnormal cells and can form a lump of cells.
75
Describe the Differences Between Benign and Malignant Tumours
-Benign tumours do not spread to other parts of the body. This means that generally a benign tumour is less likely to be harmful than a malignant tumour (since they spread).
-Benign tumours can be relatively harmless and so are not classed as cancers. Malignant tumours on the other hand are potentially very harmful so these are classes as cancers.
-Benign tumours are surrounded by a membrane. The membrane means that benign tumours remain in one location.
-A secondary tumour is when a malignant tumour has spread from its original location to a new location. The tumour at the new location is called the secondary tumour.
76
Describe how Secondary Tumours can be Formed
-Malignant tumours can spread around the body, invading neighbouring healthy tissues.
-Cells may break up and enter the blood stream. The cells can then move through the walls of the capillary and into the tissue of an organ near by.
-They can then lodge into another organ and form a secondary tumour. They live longer and divide faster, disrupting the organ's functions.
77
What Does it Mean that Some Cancers are Linked to Genetics
With cancers that are linked to genetics, we inherit an increased risk of developing these cancers from the genes that we receive from our parents.
78
Explain how radon Increases the Risk of Developing Cancer
-Atoms of radon release ionising radiation. Ionising radiation can damage the DNA in our cells. If certain genes are damaged, this can cause the cells to undergo uncontrolled cell division by mitosis and this can lead to cancer.
-Radon is a radioactive gas that we breathe into our lungs. Because radon leads to DNA damage in our lung cells, it increases the risk of lung cancer.
-However, the DNA in other cells is not damaged as a result of radon so radon does not increase the risk of other types of cancer.
79
State Different Lifestyle Factors that can Increase the Risk of Developing Cancer
Smoking- smoking has been directly linked to lung cancer, However, it is suggested that it is also linked to bowel, stomach and cervical cancer.
Obesity- obesity is the second biggest preventable cause of cancer after smoking. It is linked to bowel, liver and kidney cancer.
UV Exposure- UV radiation from the sun increases the risk of skin cancer. People in sunnier climates, who go outside often and who use tanning beds are at greater risk of the disease.
80
Describe the Different Methods of Treating Cancer
Chemotherapy- chemicals used to stop cells dividing.
Surgery- cancerous tumour is cut out to stop it invading other organs.
Radiotherapy- cancer cells destroyed by radiation. This stops mitosis in cancerous cells.
81
Explain how Cancer may Cause a Person to Lose Weight
-Cancer causes organs to reduce enzyme production.
-This mean that food is not fully broken down so not fully digested. As a result:
-Fewer fatty acids are absorbed so fewer fatty acids are available so less fat is stored in the body.
-Fewer amino acids are absorbed so fewer amino acids are available for making new proteins for growth and repair.
-Less glucose is absorbed so less glucose available for respiration so more fat is used up in metabolism and respiration
82
Describe the Different Factors Affecting Health
-Good health involves a state of both physical and mental well being. Poor health can be caused by both communicable and non-communicable diseases.
-Communicable diseases can be passed from person to person via pathogens such as bacteria or viruses. A good example of a communicable disease is measles.
-Non-communicable diseases cannot be spread from person to person. A good example of a non-communicable disease is coronary heart disease.
-Poor health can also be caused by stress, a poor diet or other factors e.g. pollution.
83
List Examples of Communicable and Non-communicable Diseases
Communicable:
-Measles, HIV, Tuberculosis, HPV
Non-communicable:
-Cervical cancer, Asthma, Depression, Arthritis, Dermatitis, Coronary heart disease
84
How Does HIV Increase the Chance of Catching TB
-Most people who are exposed to the TB bacterium do not catch TB. That's because their immune system can fight off the bacterium before it can cause tuberculosis.
-People who have HIV can have a weakened immune system. This means that they are less able to fight off the TB bacterium if they are exposed to it.
-Because of this, TB can be a serious infection in people who have HIV.
85
How do Some Viruses Trigger the Development of Cancer
-Some types of cancer can be triggered by infection by certain viruses.
-Infection with some types of hepatitis virus can cause long term infections in the liver where the virus lives in the cells. This can lead to an increased chance of developing liver cancer.
-HPV is a relatively harmless communicable disease caused by a virus. In women, infection with HPV can increase the risk of developing cancer of the cervix.
86
Describe how Allergies can be Triggered by the Immune System
-Allergies can sometimes be triggered when we are exposed to a pathogen.
-The immune system fights off the pathogen, but in the process the person can develop an allergy for example to harmless dust particles.
87
Describe how Arthritis can Lead to Depression
-A mental illness affects the mind rather than the body.
-People who develop the physical illness arthritis can sometimes go on to develop depression. That is because arthritis can make movement extremely painful.
-This can make it difficult for people with arthritis to lead a normal life, for example going out to meet friends or family. Because of this, they can feel isolated which can lead to depression.
88
Describe the Casual Mechanism Between Smoking and Lung Cancer
-A causal mechanism is a scientific explanation of how one factor could cause another.
-Cigarette smoke contains a number of chemicals that damage DNA.
-Damaging DNA can lead to uncontrolled cell division by mitosis (increasing the risk of cancer).
89
Explain the Problem with Biased Sampling and Attempts to Overcome This
-Epidemiology is looking at patterns of disease to attempt to narrow down risk factors. In epidemiology, we would ideally look at everyone but that's not possible.
-Instead we take a sample population and look at them. This sample population must represent the whole population as closely as possible but that can be difficult to achieve.
-If we take a small sample, we might find that we've selected people who are not typical. The same applies if we take a sample from a small area. In both of these cases, the sample population may be biased.
-To reduce the risk of bias, the ideal sample is very large and random. The aim would be to take a very diverse cross-section of people from lots of different places.
90
What is Meant by a Positive and Negative Correlation
-With a positive correlation, as one factor increases, another factor also increases.
-With a negative correlation, as one factor increases another factor decreases.
-However, a correlation does not prove a cause.
91
Describe the Harmful Substances Found in Cigarettes
-Tar is a carcinogen (causes cancer). It coats the lining of the alveoli which makes it harder to take in oxygen (emphysema).
-It also damages ciliated cells. Healthy cilia located in the trachea and bronchi sweep mucus out of the lungs.
-Carbon monoxide is a poisonous gas that binds to red blood cells so they cannot carry oxygen. This causes breathlessness when exercising.
-Nicotine is as addictive drug which creates a sensation of calm. It causes high blood pressure which can lead to a stroke.
92
Describe the Effects of Smoking on Different Parts of the Body
Lungs- tar in the lungs increases the chance of cancer and respiratory infections such as bronchitis or COPD.
Heart- nicotine makes the heart beat faster and increases blood pressure, increasing the chance of a heart attack or stroke.
Alveoli- tar in cigarettes' smoke damages the alveoli, making it harder for oxygen to get into the blood (emphysema).
Red blood cells- carbon monoxide means red blood cells can;t carry enough oxygen around the body.
93
State Possible Effects of Smoking While Pregnant
-Increased risk of miscarriage.
-Increased risk of premature birth.
-Increased risk of the baby being born with a low body-mass.
94
Explain how Different Diets Increase the Risk of Cardiovascular Diseases
-If you consume a diet which is high in fat and low in vegetables, this increases the levels of certain types of cholesterol in the bloodstream.
-The effect of this is to increase the rate that fatty materials build up in the arteries, leading to coronary heart disease.
-A diet which is high in salt can cause blood pressure to increase. High blood pressure is a major risk factor for cardiovascular diseases.
95
State Benefits of Exercise to Health
-Exercise relieves stress and releases endorphins
-Lowers LDL cholesterol and burns off excess calories
-Increases size of lung and heart capacity
-Increases the ratio of muscle to fat- higher metabolic rate so less likely to be overweight
96
State some Effects of Alcohol on Adults
-Increased risk of liver cirrhosis. In liver cirrhosis, healthy liver tissue is gradually replaced with scar tissue. Over time, liver function is reduced and eventually the liver can die.
-Increased risk of liver cancer.
-Effects on the brain including memory loss and addiction.
97
Describe the Effect of Alcohol While Pregnant
-Drinking alcohol when pregnant can lead to the foetus developing foetal alcohol syndrome.
-When a child is born with foetal alcohol syndrome, they have learning difficulties and other mental or physical problems.
98
What is Type 2 Diabetes
-Type 2 diabetes is non-communicable disease when body cells become resistant to insulin.
-It mainly occurs in overweight adults but can be controlled by diet.
99
Describe how Excessive Alcohol Consumption can Indirectly Lead to Type 2 Diabetes
-People who consume excessive alcohol can become obese.
-As obesity is a major risk factor for type 2 diabetes, excessive alcohol consumption can lead to type 2 diabetes.
100
Describe the Function and Adaptations of the Epidermal Tissue
-The epidermal tissue protects the upper and lower surfaces of the leaf.
-The upper epidermis is transparent. This is because light passes through the upper epidermis, to the palisade mesophyll where it is used in photosynthesis.
-The upper epidermis is covered by a waterproof waxy cuticle. This reduces the loss of water by evaporation from the upper surface of the leaf.
-Stomata on the lower epidermis allow carbon dioxide gas to diffuse into the leaf, where it is used in photosynthesis. Oxygen can also diffuse out of the leaf through the stomata.
101
Describe the Function and Adaptations of the Palisade Mesophyll
-The palisade mesophyll is where most of the photosynthesis takes place in the leaf.
-These cells are found in the top of the leaf. This is because the top of the leaf receives the most light energy and is the main site of photosynthesis.
-Palisade mesophyll cells are packed full of chloroplasts. Chloroplasts contain chlorophyll, which is used to trap light energy for photosynthesis.
-The chloroplasts tend to be found in the upper part of the palisade mesophyll cell. This is the part of the cell that receives the most light.
102
Describe the Function and Adaptation of Spongy Mesophyll
-The function of the spongy mesophyll is to allow carbon dioxide to diffuse from the stomata to the palisade mesophyll cells (for photosynthesis) and to allow oxygen to diffuse from the palisade mesophyll cells to the stomata.
-To allow this to happen, the spongy mesophyll contains large air spaces. These large air spaces increase the rate of diffusion of gases.
103
Describe the Function and Adaptations of Phloem
-Phloem transport dissolved food substances (mainly sugars) made in the leaf to the rest of the plant. This is called translocation.
-Some of the sugars carried in the phloem are used to release energy in respiration (for example glucose). Some of the sugars can be stored as starch and then used later.
-The transport goes in both directions.
-Phloem are made of columns of elongated living cells with small pores in the end walls to allow cells sap to flow through.
104
Describe the Function and Adaptations of Xylem
-Xylem transport water and mineral ions from the roots to the stem and leaves.
-One dissolved mineral transported in the xylem is the magnesium ion Mg2+. Magnesium is used to make chlorophyll.
-Xylem are made of dead cells joined end to end with no end walls between them and a hole down the middle. They are strengthened with a material called lignin.
105
Describe what is Meant by Transpiration
Transpiration is when water vapour evaporates from a leaf and diffuses out through stomata.
106
Describe what is Meant by the Transpiration Stream
-The transpiration stream describes how water moves from the soil, into the root hair cells, into the xylem, up the xylem to the leaves, then evaporates from the surface of cells in the leaves and then diffuses out of the stomata.
107
Describe the Stages in Transpiration
-Water is constantly lost from the leaves. This occurs due to evaporation due to heat and water loss from the stomata.
-This produces a concentration gradient. There is more water in the roots than in the leaves. Water moves via osmosis from a high concentration to a lower one in the roots.
-As water moves from the roots to the leaves, more water is drawn up from the soil into the root hair cells. This occurs because the concentration of the water is greater than in the roots.
-In turn, water moves into the roots via osmosis.
108
Describe the Main Roles of Transpiration in the Plant
-The transpiration stream brings water to the leaf. This is needed for the process of photosynthesis.
-The water contains dissolved mineral ions such as magnesium. Magnesium ions are used by the plant to make chlorophyll.
-Finally, transpiration plays an important role in cooling the plant. When the water vapour evaporates from the leaf, this carries away energy, which reduces the plant's temperature.
-This is especially important in conditions where the weather is warm.
109
Describe how Different Conditions Affect the Rate of Transpiration
-Evaporation is faster at higher temperatures. This increases the rate of transpiration as more water evaporates from the surface of cells in a given time.
-In dry conditions, the air is not humid (ie the air does not contain a large amount of water vapour). This also increases the rate of evaporation, increasing the rate of transpiration.
-Windy conditions increase the rate of transpiration. This is because the wind carries away any water vapour from the surface of the leaf. This allows more to evaporate.
-In high light intensity, plants open their stomata to allow carbon dioxide to diffuse into the leaf (for photosynthesis). However, this also allows water vapour to diffuse out of the leaf, increasing the rate of transpiration.
110
Explain how Guard Cells are Adapted to Their Function
-They have a kidney shape which opens and closes the stomata. Thin outer walls and thickened inner walls make the opening and closing work.
-When the plant has lots of water, the guard cells fill with it and go plump and turgid. This makes the stomata open so gases can be exchanged for photosynthesis.
-When the plant is short of water, the guard cells lose water and become flaccid, making the stomata close. This helps to stop too much water escaping.
-They are sensitive to light so close at night to save water. They are also mostly found on the underside of the leaf as it is shaded and cooler so less water is lost.
111
Explain why Stomata Close in Hot Conditions
-In hot conditions, a large amount of water vapour can diffuse out of the stomata. This could be dangerous for a plant.
-To reduce this, plants close many of their stomata to reduce the rate of transpiration.
-However, the problem now is that carbon dioxide gas cannot diffuse into the plant fast enough for photosynthesis to take place.
112
Explain why Plants in Hotter Climates Have Less Stomata than Other Plants
-Plants are at risk of losing a great deal of water by transpiration in the hot and dry conditions of the desert.
-To reduce this, desert plants often have fewer stomata than other plants.
