1. Health and Disease
OCR AS Biology
A diet high in saturated fat raises blood
cholesterol level. This increases the build
up of fatty deposits in the arteries which
A diet high in salt can cause high blood
pressure. This can damage artery walls
which causes Atherosclerosis.
Health is a state of mental physical and
social wellbeing not just the absence of
Disease; is departure of good health caused
by malfunction of the mind or body
A diet high in saturated fat raises LDL
level (low density lipoproteins) which
carry cholesterol from the liver to the
blood, increasing the risk of CHD.
A diet high in polyunsaturated fat raises
HDL levels (high density lipoproteins)
which carry cholesterol from the blood
the liver, decreasing risk of CHD
2. TB - Tuberculosis
Cause; Mycobacterium tuberculosis, is a small aerobic non-motile bacillus. It divides every 16 to 20 hours, an
extremely slow rate compared with other bacteria. MTB infects the lungs. It is a small bacillus that can withstand
weak disinfectants and can survive in a dry state for weeks.
Risk Factors; People with silicosis (a lung disease), people with chronic renal failure who are on blood dialysis
also have an increased risk: Persons with diabetes mellitus, a body mass index (BMI) below 18.5, Drug
Abuse, leukaemia, Hodgkin's disease, AIDS, immunosuppressive drugs. Living in poor and/or crowded housing
conditions, such as remand centres and prisons. Being in poor health or having a poor diet due to lifestyle.
At risk countries; Many African and Asian countries e.g. Botswana, Zimbabwe, India. Other countries; Papua
New Guinea, Cambodia, Bolivia, Bangladesh, Russia and Peru. Both the highest number of deaths and the
highest mortality per capita are in the Africa Region
How is spread; When people suffering from active pulmonary TB cough, sneeze, speak, or spit, they expel
infectious. A single sneeze can release up to 40,000 droplets. Each one of these droplets may transmit the
disease, since the infectious dose of tuberculosis is very low and inhaling less than ten bacteria may cause an
infection. However, despite being spread in the same way as a cold or the flu, TB is not as contagious. You would
usually need to spend a prolonged period of time in close contact with an infected person before you contracted
the TB infection yourself.
Statistics; In 2007 there were an estimated 13.7 million chronic active cases, 9.3 million new cases, and 1.8
million deaths, mostly in developing countries. Countries with high numbers of HIV cases also often have high
numbers of TB cases. This is because HIV weakens a person’s immune system, which means that they are more
likely to develop a TB infection.
3. HIV AIDS
Cause; AIDS is the most severe acceleration of infection with HIV (Human immunodeficiency virus). HIV infects
special cells, called CD4 cells, that are found in the blood and are responsible for fighting infection. After becoming
infected, the CD4 cells are destroyed by HIV. HIV is a special type of virus known as a retrovirus. Retroviruses
spread by breaking down the DNA in our cells and then reassembling it to make copies of themselves.
Retroviruses are challenging to treat as they can rapidly mutate (alter) into new strains of virus.
Risk Factors; People who inject illegal drugs and share needles, haemophiliacs, recipients of blood transfusions
especially before 1993, are more at risk of contracting HIV, people who have had unprotected sex, people who
have caught another STD.
How is it spread; HIV is transmitted through direct contact of a mucous membrane or the bloodstream with a
bodily fluid containing HIV, such as blood, semen, vaginal fluid, and breast milk. This transmission can involve
anal, vaginal or oral sex, blood transfusion, contaminated hypodermic needles, exchange between mother and
baby during pregnancy, childbirth, breastfeeding or other exposure to one of the above bodily fluids.
At Risk countries; Sub-Saharan Africa remains by far the worst affected region. In 2007 it contained an
estimated 68% of all people living with AIDS and 76% of all AIDS deaths. South Africa has the largest population
of HIV patients in the world, followed by Nigeria and India. South & South East Asia are second worst affected.
Statistics; AIDS is now a pandemic In 2007, it was estimated that 33.2 million people lived with the disease
worldwide, and that AIDS killed an estimated 2.1 million people, including 330,000 children.
Causes; Malaria is a mosquito-borne infectious disease caused by a eukaryotic protist of the genus Plasmodium.
Plasmodium is a Parasite (an organism that lives and feeds off another organism.) In humans malaria is caused
by P. Falciparum (most common, responsible for 90% of Malaria deaths) P. ovale, P. Vivax P. Malariae (relatively
rare in humans) and P. Knowlesi (extremely rare in humans).
Risk Factors; Pregnant women (mosquitoes have a greater attraction to the body of a pregnant women), people
living in poverty, young children and infants, international travel, blood transfusions, sharing needles, mosquito
How it is spread; Malaria is naturally transmitted by the bite of a female Anopheles mosquito. When a mosquito
bites an infected person, a small amount of blood is taken, which contains malaria parasites. These develop within
the mosquito, and about one week later, when the mosquito takes its next blood meal, the parasites are injected
with the mosquito's saliva into the person being bitten. When the parasite enters your blood via a bite, it travels
straight to your liver. It develops there and then re-enters your bloodstream and invades your red blood cells.
Once in the red blood cells the parasites grow and multiply. Eventually, the infected red blood cells burst and
release even more parasites into your blood. The infected cells tend to burst every 48-72 hours.
At risk Countries; Malaria is a health problem in many tropical and subtropical countries, including portions of
Central and South America, Hispaniola (Haiti and the Dominican Republic), Africa, Eastern Europe, Southeast
Asia and the South Pacific. It can also be a problem for people visiting these countries. Ninety percent of malariarelated deaths occur in sub-Saharan Africa.
Statistics; Each year, there are approximately 350–500 million cases of malaria, killing between one and three
million people. If the prevalence of malaria stays on its present upwards course, the death rate could double in the
next twenty years. Many babies and children die from malaria - WHO estimates that a child dies of malaria every
6. Effect of Smoking on the Lungs
Short term effects;
Tar settles in the lining of the airways and the alveoli. This increases the diffusion
distance for O2 entering the blood and for CO2 leaving the blood
The presence of chemicals in the tar may cause an allergic reaction. This causes the
smooth muscle in the walls of the airway to contract. The lumen of the airway gets
smaller and there is restricted flow of Air to the Alveoli
The tar paralyses or destroys the cilia. So they are unable to move the layer of mucus
up the airway.
The tar also stimulates the goblet cells and mucus secreting glands to release more
mucus. This mucus collects in the airways
Bacteria and Viruses that become trapped in the mucus are not removed, eventually
the combination of mucus and bacteria may block the bronchioles
The presence of bacteria and virus’ mean that the lungs are more susceptible to
infections. Smokers are more likely to catch diseases such as Influenza or
7. Effect of Smoking on the Lungs
Long term effects
Smoker’s cough is an attempt to move the bacteria laden
mucus that collects in the lungs
A constant cough causes the delicate lining of the airways
and Alveoli to be damaged. The lining will eventually be
replaced by scar tissue which is thicker and less flexible.
The layer of smooth muscle in the wall of the bronchioles
becomes thicker. This reduces the lumen of the airway and
the flow of air is permanently restricted.
Frequent infections caused by the presence of bacteria in
the mucus inflame the airways causing damage to the lining
and in particular the layer of epithelium
White blood cells release enzymes which digest part of the
lining of the lungs in order to pass from the blood into the air
spaces in the lungs to fight infection. The enzyme elastase is
used which damaged the elastic tissue in the lining of the
Lost of elasticity can reduce the elasticity of the Alveoli wall.
This can cause the alveoli to burst as pressure in the lungs
increases as the alveoli cannot recoil to push the air out.
8. Diseases caused by Smoking
Carcinogenic chemicals found in cigarette smoke enter the cells of the lungs. The enter
the nucleus of these cells and have a direct effect upon genetic material. If the mutation
effects the cells that controls cell division then uncontrolled cell division may occur. This
is cancer. Cancer often starts at the entrance to the bronchi. Symptoms; continual
coughing, shortness of breath, chest pain, blood coughed up in sputum
Is the inflammation of the lining of the airways. This is accompanied by damaged cilia
and overproduction of Mucus. Symptoms; irritation of the lungs, continual
coughing, coughing up mucus often filled with bacteria and white blood cells
Is the loss of elasticity in the alveoli which causes the Alveoli to burst. The lungs have a
reduced surface area for gaseous exchange. A person with emphysema may experience
shortness of breath, tiredness, and difficulty exhaling.
9. Smoking; Nicotine and
Nicotine mimics the action of transmitter substances at the synapses between the
nerves This makes the nervous system more sensitive making the smoker feel more
Nicotine causes the release of Adrenalin. Adrenalin increases the heart
rate, breathing rate and causes constriction of the Arterioles. This raises the blood
pressure in the arterioles.
Nicotine can cause constriction of arterioles leading to the extremities,
Nicotine effects the platelets to make them sticky. This increases the risk of a blot clot
or a thrombus forming.
• Carbon monoxide enters the red blood cells and combines with Haemoglobin to form
carboxyhaemoglobin. This reduces the oxygen carrying capacity of blood. Smokers
may feel this when they exercise
• Carbon monoxide also damages the lining of the arteries.
1) Carbon monoxide can damage the inner lining of
the arteries, If the person has a high blood
pressure this will add to the damage.
2) The damage is repaired by the action of white
blood cells (phagocytes) This encourages the
growth of smooth muscle and the deposition of
3) The deposits include cholesterol from low density
lipoproteins. High blood pressure also increases
the deposition of cholesterol
4) The deposits, or Atheromas, may also include
fibres, dead blood cells and platelets. The process
of deposition is called atherosclerosis
5) Eventually the build up of Atheromas under the
endothelium may grow enough to break through
the inner lining of the artery. The Atheroma
eventually forms a plaque which sticks out into the
lumen of the artery.
6) This leaves the Artery wall rougher and less
flexible than a healthy artery and also reduced the
size of the lumen and so also reduces blood flow
11. Problems caused by changes in the blood system
Thrombosis; blood cannot flow smoothly past the plaque and the stickiness of the platelets
caused by nicotine increases the chance of a clot. If the membrane that covers the plaque is
damaged red blood cells may also stick to the fatty deposits. A blood clot is known as a
thrombus. A blood clot in the artery may stop blood flow.
Coronary heart disease; when the lumen of a coronary artery is narrowed by plaques
this reduced the blood flow to the heart muscles, which will receive less oxygen. This can lead
to CHD which takes place in three forms
1) Angina – a severe pain in the chest
2) Heart attack – the death of part of the heart muscle, usually caused by a clot in the
coronary artery blocking the flow of blood to the heart muscle
3) Heart failure- when the heart cannot sustain its pumping action, this can be due to major
blocking in the coronary artery
Stroke ; This is the death of part of the brain tissue. It is caused by loss of blood flow to that
part of the brain. There are two possible causes; a thrombus floating around blocks a small
artery leading to part of the brain or an artery leading to the brain bursts (haemorrhage)