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Biology Unit 2 Module 2
Transcript of Biology Unit 2 Module 2
Biology Unit 2 Module 2
Why Do We Eat?
Our nutrition comes from what we eat. It is important to ensure that you have a balanced diet. Good nutrition will provide better health, strengthen the immune system, help to learn more efficiently, make you stronger, and more productive.
What's in a Balanced Diet?
There are 7 components of a balanced diet:
1. Carbohydrates for energy
2. Proteins for growth and repair
3. Fats for energy, cell membranes, and insulation
4. Vitamins to aid enzymes
5. Minerals to help body functions
6. Water for transport
7. Fibre for digestion
How Much of Each Component do we Need?
The required amount for each individual varies. Energy intake is very important. People have differing levels of activity, so there aren't accurate guidelines on energy intake. In general:
50% should be from carbohydrates
30% from fats
13% from protein
If you gain weight, you are consuming too much energy-containing food. If you lose weight, you aren't getting enough. Malnutrition is caused by an unbalanced diet, in both ways. Obesity is caused by consuming too much energy, which is deposited as fat in the adipose tissues. This impairs health, giving someone a BMI of >30, 20% above the recommended weight (for your height)
BMI = mass in kg
height in m
18.5 - 25
Over 30 - 35
Over 35 - 40
Obese (class 1)
Obese (class 2)
Morbidly obese (class 3)
The location of fat deposit is also important
Extra fat around the middle (apple shaped) is worse than excess fat around the hips and thighs (pear shaped)
Diet and Coronary Heart Disease
Obesity - Health Risks
Up to 30,000 deaths a year in the UK are obesity related. It is a large contributor to the chances of getting cancer, a cardiovascular disease, type 2 diabetes, gallstones, osteoarthritis, and hypertension.
Other Diet Components
Overall energy intake must be balanced with energy use. Coronary Heart Disease is when fatty substances are deposited on the arterial walls. This is called atherosclerosis.
This decreases the water potential of the blood, so more water is held in the plasma, which increases blood pressure. Hypertension is when blood pressure is too high during diastole, which can damage the inner linings of the arteries.
These are an essential part of the diet. There are 2 types of fats - saturated and unsaturated. Animal fats tend to be saturated, and plants unsaturated. Saturated fats are more harmful. Poly and monounsaturated fats like the ones found in olive oils, are particularly beneficial to health.
This is not a triglyceride, although it has similar properties. It is made in the liver from saturated fats. High blood cholesterol concentrations are linked to 45-47% of CHD deaths. Concentration should be below 5.2 mmoldm-3
Why is Cholesterol in the Blood?
It is essential to normal functioning of the body. It is found in cell membranes, steroid sex hormones, and bile. It is insoluble in water. It is transported as soluble lipoprotein, tiny balls of fat and protein. There are high density lipoproteins and low density lipoproteins.
These are a mixture of unsaturated fats, proteins, and cholesterol. These tend to carry cholesterol from the body tissues, back to the liver. The liver has receptor sites that allow HDLs to bind to their plasma membranes. In the liver, cholesterol is used in cell metabolism to make bile, or is broken down. Therefore, high levels of HDLs can reduce blood cholesterol levels. They reduce the effects of atherosclerosis, and may even go as far as removing any fatty deposits.
These are made up of saturated fats, protein, and cholesterol. These carry cholesterol from the liver to the tissues. Tissue cells have receptor sites that allow LDLs to bind to their plasma membranes. If too much saturated fat is consumed, the concentration of LDLs rises. This can cause atherosclerosis.
Diet and Lipoproteins
We do not eat lipoproteins; our body makes them. Overall, it is best to keep to a diet which will maintain low LDL concentrations. The HDL:LDL ratio is very important. HDLs reduce atherosclerosis, caused by LDLs. Eating a lot of unsaturated fats, having a low fat diet, and low proportions of saturated fats are all beneficial to health, and the effects of lipoproteins.
Improving Food Production
Plants as Food
Plants carry out photosynthesis. Most plants store energy as starch. They also absorb minerals, such as nitrates, from the soils, and make a range of biological molecules. Herbivores make use of these molecules. Humans are omnivores. We gain nutrition directly from eating plants, and indirectly from eating herbivores. By making the food chain more efficient, we can increase food production
How Can We Make It More Efficient?
In plants, we can improve the growth rate of crops, increase yield, reduce loses from disease and pests, make harvesting easier, and improve responses to fertilisers. In animals, we can improve the rate of growth, increase productivity, and increase resistance to disease.
This is where humans select the individual organisms that are allowed to breed, according to their chosen characteristics. This exaggerates small differences (Charles Darwin). There are 3 stages to selective breeding: Isolation, artificial selection, and inbreeding/line breeding. Humans apply the selection pressure in these cases.
Fertilisers replace minerals in the soil, which may have been removed by previous crops e.g. NPK fertiliser. Pesticides kill organisms that spread disease in crops. Some crops are sprayed with fungicide to reduce the growth of fungus. Infected animals can be treated with antibiotics. These reduce the spread of disease, especially in animals which remain at a close proximity with each other e.g. battery farmed hens.
Microorganisms and Food
Microorganisms and Food Spoilage
There are 4 main ways that microbes can spoil our food:
Visible growth e.g. colonies of moulds often grow on bread
Microbes release enzymes onto food to absorb nutrients. When this happens, food often smalls sweet as sugars are released from carbohydrates. The food is eventually reduced to a mulch
The bacterium 'Clostridium botulinium' produces the botulin toxin. This causes botulism. It is incredibly toxic - 1μg can kill a person
Microbes can also cause infection e.g. Salmonella attacks the lining of the stomach and the digestive system
Many microorganisms gain nutrition by digesting organic matter. They then leave behind waste materials. Food is spoilt once we can see the effects.
How Do We Prevent Spoilage?
Cooking denatures enzymes, killing microbes. Pasteurising involves heating to 72°C for 15 seconds, then rapidly cooling.
Drying and salting cause water loss due to osmosis
Smoking; this contain anti-bacterial chemicals
Picking; acid pH denatures enzymes and proteins
Irradiation kills/disrupts the DNA of microbes
Cooling/freezing sows down enzymes, restricting growth and reproduction. Also incl. canning and vacuum wrapping
Using Microorganisms to Make Food
Many traditional foods are made by the aid of microorganisms.
In yoghurt, 'Lactobacillus' bacteria use lactose to make lactic acid, which makes milk easier to digest
Cheese is made from curdled milk. Curds are affected by Lactobacillus. Extra flavour i.e. in blue cheese comes from 'Penicillium' fungi
Yeast is a fungus which respires aerobically to release carbon dioxide, which causes bread to rise
Alcohol is made through anaerobic respiration of yeast. Yeast respires sugar in grapes.
Single cell protein (SCP) is used to make Quorn, a mycoprotein (made by fungus). It was first made in the early 1980s. It is marketed as a meat substitute for vegetarians. It contains no animal fat or cholesterol. Microorganisms such as Candida, Kluyveromyces, and Scytalidium can produce a protein with a similar amino acid profile to animal and plant protein. They can grow on almost any organic substrate, incl paper and whey.
Mycoprotein production can be many times faster than animal or plant protein
Production can be increased or decreased due to demand
There are no animal welfare issues
They are a good source of protein for vegetarians.
Lots of people won't eat a protein that is grown on waste
Isolation is needed; the protein is grown in huge fermenters, and needs to be isolated from the material it grows on
Protein has to be purified to ensure it is uncontaminated
The conditions for making them are ideal for harmful microbes
It does not have the taste or texture of normal protein
Organisms That Cause Disease
Health and Disease
To be healthy means to be in a state of physical, mental, and social wellbeing. When you are healthy, you are:
Disease is a departure from good health due to a malfunction of the body or mind. Symptoms may be social, mental, or physical.
Parasites and Pathogens
Parasites are organisms that live in or on another organism. This is called a host. They may harm the host by taking their nutrition. There are internal and external parasites. They often go unnoticed, which is better for the parasite, as the host will not try to remove it. Parasites may cause damage that allows other organisms to invade and cause secondary illnesses.
The human body is a good habitat in which microorganisms can live. Many cause no harm, or are beneficial. Pathogens are organisms that cause diseases. They take nutrition from the host, but also cause damage/harm.
Organisms That Cause Infectious Disease
Bacteria, fungi, protoctists, and viruses can all cause disease.
These belong to the Prokaryote kingdom. They are very small, but reproduce rapidly. Some can do so every 20 mins or so in the right conditions. They can cause disease by damaging cells, or releasing toxins. Cholera is caused by 'Vibrio cholerae'. TB is caused by 'Mycobacterium tuberculosis' or 'M. Bovis'.
Athlete's Foot and Ringworm are caused by a fungus called 'Tinea'. The fungus lives in the skin. When it sends out reproductive hyphae, they grow on the surface of the skin to release spores. These cause redness and severe irritation.
These include the common cold, influenza, and HIV/AIDS. Viruses invade cells and take over the genetic material and organelles. They then use the cell to manufacture new copies of the virus, so that the host cell eventually bursts, releasing the viruses.
These are similar to animal e.g. Amoeboid dysentry and Malaria. They cause harm by entering host cells and feeding on contents as they grow. The malarial Plasmodium has immature forms which feed the contents of red blood cells.
Transmission of Diseases
In order to cause a disease, a pathogen must be able to travel from host to host, get into the host's tissues, reproduce, and cause damage. Pathogens first need to get past any primary defences.
Transmission of Malaria
Malaria is caused by the eukaryotic organism Plasmodium. Plasmodium Falciparum is the most widespread, however there is also P. vivax, ovale, and malariae. Malaria is spread via a vector; the female Anopheles mosquito. This carries the Plasmodium from an infected person to an uninfected person. Their probiscus penetrates a blood vessel to withdraw blood. Malarial parasites live in the red blood cells of the human host, and feed on haemoglobin.
The malarial parasite can also be transmitted by careless and unhygenic medical practices, aka unscreened blood transfusions, and the use of unsterilised needles. It can also pass across the placenta to an unborn child.
Transmission of HIV/AIDS
This is caused by the Human Immunodeficiency Virus. When you are infected by this, you are HIV positive. Once the virus is active, it attacks and destroys T-helper cells in the immune system. This reduces your ability to fight infections. This makes you unable to fight off any other diseases. and so you may contract a range of opportunistic infections. This is what eventually kills someone. AIDS is Acquired Immune Deficiency Syndrome.
Transmission of Tuberculosis
This is caused by Mycobacterium TB and M. bovis. These can infect many parts of the body, but are usually found in the lungs. TB is transmitted through droplet infection. Apparently, up to 30% of people may be infected by TB, however in most cases it is inactive, or controlled by the immune system. The bacteria is contained in tiny droplets which are passed on through coughs and sneezes, laughing, or just talking.
Responses to Diseases
These are any defences which prevent pathogens from entering the body.
The outer layer of the skin is called the epidermis, and is made up of layers of cells. Most of these are called keratinocytes, and are produced by mitosis at the base of the epidermis. They then migrate out to the surface of the skin, and dry out as they do so. Their cytoplasm is replaced by keratin. This is called keratinisation, and takes approx. 30 days. By the time they reach the surface, they are no longer living, and so act as a barrier to pathogens.
Certain substances must enter our blood, which reduces the barrier between our blood and environment, so that it is more vulnerable to pathogens. Areas such as our airways, lungs, and digestive system are all vulnerable. These areas are protected by mucous membranes. The epithelial layer contains goblet cells. These membranes are found in the gut, genital areas, anus, ears, and nose. Eyes are protected by antibodies in the tear fluid.
The Worldwide Importance of Certain Diseases
Why Are Diseases Important?
The World Health Organisation (WHO) says that good health is a basic human right. Poor health causes a lot of suffering and economic costs, due to a loss of productivity. Contributors to poor health may be poverty, lack of proper shelter, unclean water, poor nutrition, hygiene, lack of government investment, inadequate health services, inadequate education, and civil unrest.
Malaria kills approx. 3 million people each year. Approx. 300 million are affected worldwide, and increasing. Malaria is restricted to areas with the Anopheles mosquito, around tropical regions. Global warming may cause it to be able to survive further north. It can be controlled by nets, drugs to stop the spread of Plasmodium in the body, and insecticides.
This is still spreading in pandemic proportions. It has been spreading rapidly in China, Russia, and other Eastern European countries. Can be controlled by antibiotics, volunteer supervised medications, and BCGs (although this is no longer thought of as effective.
The WHO declared TB as a public health emergency in 1993. Approx. 1% of the world's population is newly infected each year. 10-15% of these go on to develop the disease. 30% of the world's population may be infected with mycobacterium. It is particulary common in SE Asia and Sub-Saharan Africa, and rising in Eastern Europe. There is an increasing threat from new strains which are resistant to most existing TB drugs. To control, use condoms, educate people, trace people to see who is likely to be infected, screen blood donations, heat donations, and set up needle exchange schemes.
Phagocytes - A Secondary Defence
Many trapped pathogens aren't killed by the body. These must be killed before they can reproduce and cause symptoms of disease. There are 2 types of phagocyte:
The most common are neutrophils, made in bone marrow. They travel in the blood and are often squeezed out into tissue fluid, or can be found on epithelial surfaces. They are short-lived, but are produced in large numbers as a result of infection.
Macrophages are larger cells, also made in bone marrow. They travel in the blood as monocytes, and tend to settle in organs, especially lymph nodes. They develop into macrophages here.
How Phagocytes Work
These engulf and kill pathogens. Pathogens are recognised by their antigens. Antibodies attach to these antigens. Receptors on phagocytes bind to the antibodies, also attached to the pathogen. This is also assisted by other proteins called opsonins. Once the phagocyte is bound to the pathogen, it will undergo phagocytosis. The pathogen is then trapped inside a phagosome. Lysosomes fuse with it, and release enzymes called lysisns, which digest bacterium. The end products are harmless nutrients, which can be absorbed into the cytoplasm.
The Role of Macrophages
Infected cells release chemicals e.g. histamine, which attracts neutrophils to the area. Histamine also makes the capillaries more leaky. As a result, more fluid leaves the capillaries in the area, causing swelling and redness. It also means that more tissue fluid passes into the lymphatic system, which leads pathogens towards the macrophages in the lymph nodes. These initiate a specific response to a disease, called an immune response. this is the activation of lymphocytes in the blood to help fight disease.
These are molecules which can activate/stimulate an immune response. Almost any molecule can act as an antigen. They are usually large, and have a specific shape. A foreign antigen is detected by the immune system which stimulates the production of antibodies. These are specific to pathogens. They are usually glycoproteins or glycolipids.
Antibodies are produced by lymphocytes. They are large, globular proteins, also known as immunoglobulins. They have a complementary shape to a particular antigen They attach to antigens and make them harmless.
The Structure of an Antibody
How Antibodies Work
Most work by attaching to the pathogen's antigens. The pathogen may have needed its antigens to bind to a host cell. Blocking this would stop it from doing so. This is called neutralisation. Some antibodies are much larger; they contain lots of joined up Y shaped molecules, with many specific variable regions. Each of these has a binding site to attach to a pathogen. This allows them to attach to more than one pathogen at once. This is called agglutination. When pathogens are stuck together like this, they can't enter host cells.
Antibodies are produced in response to infection. It takes a few days from the time of infection for the immune system to start producing antibodies, and for their number to be high enough to combat the infection. This is called the primary immune response. Once the pathogens have been dealt with, the number of antibodies in the blood drops rapidly.
Antibodies don't stay in the blood. If the body is infected a second time by the same pathogen, the antibodies must be made again.
Communication Between Cells
The immune response is the specific response to the detection of pathogens in the body. It involves a coordinated response between a wide range of cells. These cells must be able to communicate via cell signalling. This is achieved through cell surface molecules and hormone like chemicals called cytokines. B lymphocytes and T lymphocytes have receptors with a complementary shape to the foreign antigen. Once this has been detected, the lymphocyte is stimulated into action.
What Sort of Information is Communicated?
The first signalling is done by the pathogen. Its antigens act as markers, which are detected by our body cells. When a body cell is infected, it is usually damaged. Internal organelles e.g. lysosomes will attempt to fight the pathogen. Parts of the pathogen often ends up attached to the host's plasma membrane. These can act as a distress signal to the immune system, or tell T killer cells that the cell must be destroyed.
Macrophages do not fully digest pathogens. They separate out its antigens and incorporate them onto their plasma membrane, so that it becomes known as an antigen presenting cell. It then finds lymphocytes that can neutralise a particular antigen.
There are a range of cytokines released by cells. These generally act over short distances at a very low concentration. Once they bind to specific membrane bound receptors, they can alter the cell's behaviour through gene expression.
Macrophages release monokines that attract neutrophils by chemotaxis
They can also release monokines which can stimulate B cells to differentiate and release antibodies
T cells, B cells, and macrophages can release interleukins, which can stimulate proliferation (creation) and differentiation of T and B cells
Many cells can release interferon, which can inhibit virus replication and stimulate T killer cells
The Specific Immune Response
The Immune Response
This is a specific response to the detection of a pathogen by its antigens, involving T and B lymphocytes. These have a large nucleus and specialised receptors on their plasma membranes. The immune response produces antibodies. These actually neutralise the foreign antigens. It also provides long term protection via immunological memory by the release of memory cells.
Starting the Response
Once the correct T/B cells detect an antigen, the immune response can begin. However, there may only be a few of the T/B cells in the body, so it could take some time for them to find the antigens. Cells which are attacked by the pathogen will display antigens on their surface to increase the chance of T/B cells identifying them, as well as macrophages. The selection of the correct T/B cells is known as clonal selection. Before they can become effective, they must increase in number by clonal expansion/proliferation by mitosis.
T/B cells do not manufacture the antibodies directly. T lymphocytes develop into 3 types of cell:
T helper cells which release cytokines which stimulate B cells to develop and stimulate phagocytosis
T killer cells which attack and kill infected body cells
T memory cells
B lymphocytes develop into 2 types of cell:
Effector/plasma cells which make antibodies
B memory cells which act as the immunological memory
This All Takes Time
Each process takes time. It may be a few days before the number of antibodies in the blood starts to rise. The immune response leaves memory cells in the body. This means that if there is a second invasion by the same pathogen, plasma cells and antibodies can be produced more quickly.
What is a Vaccination?
A vaccination provides immunity to specific diseases. It is artificial active immunity; deliberate exposure to the antigenic material that has been rendered harmless. The immune system treats this as a real disease and so produce antibodies and memory cells for long-term immunity.
Antigenic material can be:
a less harmful live microorganism (e.g. for smallpox)
A harmless version of the pathogen (e.g. measles and TB)
A preparation of the antigens (e.g. Hepatitis B)
Or a harmless toxin or 'toxoid' (tetanus)
Herd and Ring Vaccination
Herd vaccination is when it is provided to most-all of the population at risk. For smallpox. 80-85% needed to be vaccinated. For measles, 95% was needed to eradicate the disease. Young people have an NHS available vaccination programme for MMR, Polio, Meningitis, Whooping Cough, Tetanus, and Diptheria.
Ring vaccination is used when a new case is reported, and involves vaccinating people in its immediate vicinity. It is often used to control the spread of livestock disease.
Possible Future Threats
Many pathogens can form a new strain by mutation. Existing vaccines may therefore be rendered useful. Viruses are a particular threat.
Influenza is a killer disease. People over 65 years or with respiratory diseases/conditions are particularly vulnerable. Sometimes new particularly violent strain comes about, and could cause an epidemic. H1N1 was a flu in Hong Kong which became a pandemic due to its large scale outbreak. Very old/young people are vaccinated against the flu. The vaccine used changes each year.
Active and Passive Immunity
Active immunity is that which is achieved by the activation of the immune system. Antibodies can remain in the blood for many years, or even for a whole lifetime. Passive immunity is when you receive antibodies which you have not made yourself. They can be received across the placenta or via breast milk. They can also be provided by intravenous injection, although this is often short lived.
Natural and Artificial Immunity
Natural immunity is gained through the normal living process e.g. as a result of an infection. Artificial immunity is gained by deliberate exposure to antibodies or antigens. Both can be either active or passive.
Provided via the placenta or breast milk, so the baby becomes immune to what the mother is immune to
Immunity provided by the antibodies as a result of an infection e.g. immunity to chicken pox
Provided by infection of another individual's antibodies e.g. for tetanus
Provided by antibodies made as a result of vaccination e.g. immunity to TB or influenza
The Effects of Smoking
What Harm Does Tar Cause?
Cigarette smoke contains over 4,000 different chemicals, including tar, carbon monoxide, and nicotine.
Short Term Effects
Tar settles on the linings of the airways and alveoli. This increases the diffusion distance for gaseous exchange. Chemicals present in tar may cause an allergic reaction, so the smooth muscles constrict and narrow the lumen of the airways. Tar paralyses and destroys the cilia, so they no longer waft mucus away. Tar also stimulates goblet cells to secrete more mucus. Bacteria is therefore not removed, and this phlegm can block the bronchioles. This makes smokers more susceptible to other infections.
Long Term Effects
Smoker's cough is a result of the irritation of the airways, and the need to clear them of mucus. This can damage the delicate lining of the airways and alveoli, so that they are replaced by inflexible scar tissue. The layer of smooth muscle thickens, so air flow is permanently restricted.
Frequent infections will also inflame the linings of the airways. This damages the epithelial layer, which attracts leucocytes. They make their way out of the blood and into the airways by releasing enzymes which digest parts of the linings of the lungs. The enzyme elastase is used.
Carcinogens can be found within cigarette smoke. Benzopyrene one of the most harmful. These enter the cells of the lung tissue and alter their genetic material. This is called a mutation, and can therefore lead to rapid cell division. Cancers often start at the entrance to the bronchi, as the smoke hits the fork in the airway and deposits tar. Lung cancer often takes 20-30 years to develop, and may have been growing for many years before it is detected.
What Diseases are Associated With Smoking?
This is the inflammation of the linings of the airways. The cilia are also damaged, and the overproduction of mucus means that it collects in the lungs. Symptoms include continual coughing, coughing up yellow mucus, and lung infection.
This is the loss of elasticity in the alveoli, causing them to burst. This reduces the surface area for gaseous exchange, making sufferers short of breath when exerting energy. They find it harder to exhale, so their breathing is more shallow and rapid. Blood is less well oxygenated, and they are often fatigued.
COPD (Chronic Obstructive Pulmonary Disease) is a combination of bronchitis, emphysema, asthma, and all their symptoms.
In lung cancer, symptoms include continual coughing, shortness of breath, angina, and coughing up blood.
Smoking - Nicotine and Carbon Monoxide
Nicotine and Carbon Monoxide
These 2 chemicals can enter the lungs and pass through the lung surface into the blood. Here they cause changes to the circulation. These include atherosclerosis, coronary heart disease, and stroke.
This is the chemical which causes addiction. Smokers don't feel good until they get a hit of that nicotine. It mimics the action of transmitter substances at synapses between nerves, making the nervous system more sensitive so that the smoker feels more alert.
It releases adrenaline. This increases the heart and breathing rates, and causes constriction of the arterioles. This raises blood pressure
Nicotine also causes constriction of the arterioles leading to the extremities of the body. This reduces blood flow and oxygen delivery to the extremities. This can cause a need for amputation when it gets really bad
It also affects platelets, making them more sticky. This increases the risk that a blood clot or thrombus will form.
This enters red blood cells and combines with haemoglobin more readily than oxygen. (It has a higher affinity for carbon monoxide than oxygen). This forms the stable compound carboxyhaemoglobin. This reduces the oxygen carrying capacity of the blood. The body detects the lower level of oxygen, particularly during exercise, causing the heart rate to rise.
It can also damage the lining of the arteries.
Problems Caused by Changes to the Blood System
The changes described are part of a chain of events that can lead to serious diseases such as coronary heart disease. CHD is a multifactorial disease - there is no single factor that causes it. Risk factors are what contribute to the risk of getting CHD.
Carbon monoxide can damage the endothelium of arteries. If a person has hypertension, this will add to the damage done. This is repaired by the action of phagocytes. These encourage the growth of smooth muscle, and the deposition of fatty substances. The deposits include cholesterol from LDLs. The deposits called atheromas may include fibres, dead blood cells, and platelets. The process of deposition is called atherosclerosis.
The build up of atheromas occurs under the endothelium in the wall of the artery. This can grow enough to break through the endothelium. The atheroma eventually forms a plaque which sticks out into the lumen of the artery. This makes the artery wall thicker and less flexible and reduces the lumen of the arteries, which reduces blood flow.
Blood flowing past the plaque can't flow smoothly. The stickiness of the platelets, caused by nicotine, increases the chance of a blood clot forming. If the membrane that covers the plaque is damaged, red blood cells also stick to the exposed fatty deposits. This can create a thrombus. This may stop blood flow in the arteries. The clot could also break free and be carried around the body until it reaches a narrow artery. Then it will lodge and stop blood flow.
Coronary Heart Disease
Coronary arteries branch off the aorta close to the heart and carry blood at high pressure. They are therefore more prone to damage and atherosclerosis. When the lumen becomes narrowed, heart muscle receives less oxygen for respiration. This can lead to one or more of 3 forms of CHD:
2. Myocardial Infarction (death of part of the heart muscle)
3. Heart Failure (when the heart cannot sustain its pumping action)
This is death of a part of the brain tissue. It is caused by the loss of blood flow to that part of the brain. 2 possible causes are:
1. a blood clot floating around the body blocks a small artery leading to the brain
2. An artery leading to the brain burst (haemorrhage)
Symptoms of CVD
High blood pressure and hypertension are usually the first signs of CVD. Narrowed arterial lumen increases the friction between the blood and artery wall. The heart pumps against said friction, raising the blood pressure. The atheroma makes the artery walls less elastic, so they are unable to dilate and recoil as easily.
Coronary Heart Disease
A person with CHD may find it more difficult to exercise and feel out of breath with only a small amount of exertion. This is due to atherosclerosis in the coronary arteries. The atheroma narrows the lumen and reduces blood flow to the cardiac muscle. When exercising, the heart needs to increase its output and is put under strain in an effort to pump more blood. Reduced blood flow to the cardiac muscle means that it does not pump as strongly as required, so body cells get less blood.
Symptoms are always sudden:
Sudden numbness or weakness of the face, arm, or leg, especially on one side
Sudden confusion and difficulty speaking or understanding
Difficulty with seeing in one or both eyes
Trouble walking - dizziness, loss of balance, lack of coordination
Sudden, severe headache with no known cause
What Factors Increase the Risk of CHD?
CHD is multifactorial, so it does not have one known cause. Here are its risk factors:
Age - increases with age
Sex - men are more likely than women
High blood cholesterol level
Sedentary lifestyle (inactive)
Diet - high salt and animal fat intake, not enough polyunsaturated fats
Absence of antioxidants (vitamins A, C, and E)
Evidence Linking Smoking to Disease
Smoking and Disease
Smoking became a thing after the start of the 20th century as men took up the habit during WW1. The number of women increased in the 1940s and 50s. Later that decade, it became clear to the medical profession that certain diseases had become more common, including lung cancer, mouth and throat cancers, chronic bronchitis, emphysema, and CVD.
This is the study of the distribution of a disease in populations, and the factors that influence its spread Health professionals and organisations like the WHO can use this to identify links between diseases and risk factors. It may help to identify:
which countries are at greater risk
which age range
which lifestyle factors
In the 1960s experiments were carried out on dogs to see the effects of smoking. This method of testing is very controversial though. The dogs which had inhaled cigarette smoke developed COPD type signs and symptoms. Some even had cells which were shown to be developing cancers.
Smoking - The Future
Whilst the number of adult smokers is decreasing, the number of young smokers is increasing. More people in LEDCs are smoking, which is a concern to the WHO, especially as effects won't be seen until symptoms develop over 20 years or so.
Finding New Drugs
The Need For New Drugs
New drugs are needed because:
New diseases are emerging
There are still many existing diseases without effective treatment
How Are New Drugs Discovered?
Alexander Fleming discovered penicillin by accident. Most bacteria are resistant to this though. Most antibiotics at the moment are made from the Streptomyces are bacterium.
Many drugs have been used for centuries. The WHO says that 80% of the world's population relies on traditional medicines. In India, around 7000 plants are used for their medicines. In China it is around 5,000. In Europe, some of our modern drugs have their origins in traditional medicine.
The sap of unripe poppies was used in Neolithic times in parts of southern Europe and Egypt. In the 12th century, opium from poppies was used as an anaesthetic, and by the 19th century, morphine and opium were being used. These reduce the nervous action in the CNS. This makes it so that pain is not felt.
Wildlife and Modern Research
Many animals are self medicating e.g.
monkeys, bears, and other animals rub citrus oils on their coat as insecticides and antiseptics to prevent insect bites and infection
Chimpanzees swallow leaves folded in a certain way to remove parasites from their digestive tract
Elephants roam miles to find clay to counteract dietary toxins
Birds line their nets with medicinal leaves to protect chicks from blood-sucking mites
Scientists have used traditional plant medicines and animal behaviour as a starting point in their search for new drugs. Research into plants used allows them to isolate the active ingredient.
The Example of Aspirin
Hippocrates used an extract from willow bark to relieve pain and fever. This was used throughout the Middle Ages in Britain. In 1828, Johann Bruchner extracted the active ingredient salicin. This could be used to relive pain, but caused stomach bleeding as a side effect. In 1897, the use of an acetyl group stopped this. By 1971, further research revealed that salicin works by inhibiting enzymes involved in the synthesis of prostoglandins. These are hormone like substances that have a variety of rolls in cell communication. Further research showed that other drugs have the same effect.
The Hunt is On
The discovery of natural drugs has been concentrated on tropical plants due to their great diversity. This could also be done in the UK from both wild and cultivated plants. New chemical fingerprinting technology enables scientists to screen natural chemicals more effectively for their activity as potential medicines.
Biologists hope to learn what how the bacterium Streptomyces produces antibiotics by looking at its genes. They can use this to improve current production methods.
BMIs are only an estimate due to the fact that they do not take into account age, gender, whether someone's pregnant, the time of day, etc.
This narrows the arteries' lumen, which restricts blood flow, leading to oxygen starvation. Some components of the diet reduce the risk of CHD. Fibre, oily fish, and small amounts of alcohol all help.
Saturated fats decrease the activity of LDL receptors, so less cholesterol is removed from the blood, causing atherosclerosis. Unsaturated fats increase the activity of LDL receptors, so more is removed from the blood.
Free from disease
Able to carry out normal physical and mental tasks
Are well fed with a balanced diet
Have a positive outlook
Are suitably housed with proper sanitation
Are well integrated into society
Once inside, they must then overcome any secondary defences, and the immune system. The most common forms of transmission are through a vector, by physical contact, or droplet infection.
HIV can be transmitted in blood to blood contact, unprotected sex, unscreened blood transfusions, unsterilised surgical equipment, sharing hypodermic needles, across the placenta, through breast feeding, and in accidents such as needle stick.
The spread is more likely in overcrowded places, due to poor ventilation, poor health, poor diet, homelessness, and living or working with migrants from places where TB is more common. TB can also be contracted from the milk or meat of cattle, which tends not to be a problem in MEDCs.
They are Y shaped with 2 distinct regions. They are made up of 4 polypeptide chains held together by disulphide bridges. They have a constant region, which is the same in all antibodies. This allows them to attach to phagocytes in phagocytosis
A variable region, which differs between antibodies. This is a result of its amino acid sequence. This allows the antibody to only attach to the necessary pathogens.
Hinge regions which allow a degree of flexibility so that they can attach to more than one pathogen.
This damages the elastic tissue in the smaller bronchioles and alveolus walls. During exhalation, the walls do not recoil to push air out of the alveoli. This causes the bronchioles to collapse. Trapped air in the alveoli with increasing pressure causes them to burst.
CVDs can be disabling and will eventually cause death. Treating CVDs can be very expensive, and may involve long treatments with drugs to reduce blood pressure and cholesterol levels, or even surgery.
Health-promotion centres focus on reducing the risk factors of CVDs, so that the need for treatment later in life is reduced.
These are diseases that affect the heart and circulatory system, including atherosclerosis, CHD, stroke, and arteriosclerosis.
It is one of the greatest causes of premature death in MEDCs. A sufferer is often unaware until the symptoms become very obvious. Atherosclerosis may start in adolescence. Fatty deposits may take decades before they have a serious effect on blood flow.
The process of arteriosclerosis (hardening of the artery walls) makes this worse, as they become even less flexible. This is caused by the deposition of minerals such as calcium, in the walls, and particularly in the atheromas.
Angina may occur in advanced cases. The pain subsides quickly after exercise. Myocardial infarction may occur. This is often felt as a severe and disabling pain in the chest and arm. If not treated quickly, this could lead to heart failure.
CHD is less of a problem in LEDCs as their different lifestyles give them less of these risk factors, and they have lower life expectancies. They are more at risk of HIV/AIDS or malaria before they live long enough to get CHD. They often have more active lifestyles and their diet contains fewer harmful elements. They are also less likely to be heavy smokers. This figure however is increasing...
CVD is more difficult as it has a very large range of risk factors. This can be used to help countries and organisations target further spending, target screening procedures, give out advice and education, predict where diseases may become more prevalent, target geographical areas at risk using preventative measures, and check how well prevention measures are working.
A regular smoker is 3x more likely to die of a smoking related disease
Lung cancer is 18x more likely in smokers
COPD is rare in non smokers
This led to filters being put on cigarettes to remove some of the harmful substances. Further research was then done on tar. This revealed the presence of the carcinogen benzopyrene and others. They put some of these carciongens on the bare skin of mice, which then went on to develop cancer.
Some antibiotic treatments are becoming less effective due to new resistance evolving in bacteria as antibiotics provide a selection pressure. New generations of the microorganism are therefore more resistant.
Pharmeceutical companies have been conducting research into how microorganisms cause disease. Many use cell surface receptors e.g. HIV uses a receptor called CD4. This can later be isolated and sequenced. Once this is known, molecular modelling can be used to work out the shape of the receptor. DNA sequencing can show the potential medicinal drugs from DNA. This is called genomic. It has potential uses in vaccines.