OCR AS BIOLOGY: Food and Health Spec notes

Notes I made using the Specification for AS Biology. 

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  • Created on: 06-04-12 15:19
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Food and Health Notes
Define the term `balanced diet'
A balanced diet is one that contains all the nutrients required for health in appropriate
Explain how compumption of an unbalanced diet can lead to malnutrition, with reference
to obsesity.
Malnutition is caused by an unbalanced diet. Obseity is a form of malnutrition by comsuming too
much energy. This excess energy is deposited as fat in the adipose tissues. Body mass indes of
30 or above is obsese. The formula for BMI is mass in kg/ (height in m)².
Discuss the possible links between diet and coronary heart disease.
Eating a diet high in saturated fat increases the LDLs in the blood. This increases the deposits of
LDL in the arteries which if it blocks up the coronary artey causes a myocardial infarction and
leads to heart disease. Increasing the energy consumed increases the risk of obseity which is an
important factor in cardiovascular disease and high blood pressue (hypertension).
Dicuss the possible effects of a high blood cholesterol level on the heart and circulatory
system, with reference to HDLs and LDLs.
If you have a high blood cholesterol level you have lots of LDLs in your blood which increases the
fatty deposits in your arteries and atherosclerosis. This narrows the size of the lumen and
restricts blood flow causing oxygen starvation. This can make you have a heart attack.
Explain that humans depend on plants for food as they are the basis of all food chains.
Plants carry out photosynthesis can can convert light into energy stored in a chemical form. They
can make carbohydrates and store energy as starch. As humans we are omnivores so we can get
nutrition from both plants and animals.
Outline how selective breeding is used to produce plants with high yeild, disease
resistance and pest resistance.
There are three stages; isolation, artifical selection, and inbreeding or line breeding. We can
produce plants with high growth rate, increase the yield, disease resistance, standardising plant
size and improve plant responses to fertilisers. Tomatoes have been bred with improved
disease resistance. Wild tomato with good resistance to yellow leaf curl virus was found and it
was identified and bred into the domestic variety.
Outline how selective breeding is used to produce domestic animals with high
We can use the same three stages but using cows as an example. Farmers breed cattle for high
yield and meat producion. Salmon have been selected to grow more quickly so that the time to
market can be cut.

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Describe how the use of chemicals, including fertilisers and pesticides (plants) and
antibiotics (animals) can boost food production.
Fertilisers replace minerals in the soil which have been removed by previous crops. They increase
the rate of growth and the overall size of the crops. Pesticides kills organisms that cause disease
to crops. Animals can also be treated with pesticides to kill tics etc. Infected animals can be
treated with anti-biotics which redice the spread of disease amng the animals.…read more

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HIV/AIDS is transmitted through exchange of bodily fluids, unprotected sex, unscreened blood
transfusions, unsteralised surgical equipment, sharing needles, across placenta or during
childbirth, from mother to baby through breastfeeding.
TB is caused by bacterium Mycobacterium tuberculosis. It is transmitted through droplet infection
and when a person coughs, sneezes, laughs or talks. It spreads easier if there is overcrowding,
poor ventilation, poor health, poor diet, homelessness and living or working with people
infected with the disease.
Discuss the global impact of malaria, HIV/AIDS and TB.…read more

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Describe, with the aid of diagrams, the structure of antibodies
Four polypeptide chains held together by disulfide. Constant region which is the same for all
antibodies which allows phagocytic cells to attach to it. Varible regions which has a specific shape
amd differs in each antibodies which means that it will only stick to the certain antibodies. Hinge
regions which allow some flexibility which allows them to move further apart in order to allow
attachment to more than one antigen.…read more

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Differentiation: T helper cell release cytokines that stimulate B cells to develop which stimulate
phagocytocis by the phagocytes. T killer cells which attack and kills infected cells. T memory cells.
B lymphocytes develop into plasma cells which flow around the bloos releasing antibodies or
memory cells which remain in the body over a number of years and provide an immunilogical
Explain how vaccination can control disease.
Her vaccination is used to provide immunity to all or most of the population at risk.…read more

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Natural sources from tropical plants, because there are a great many species so they may be
many new medicinal drugs to discover. Antibiotics like bacterium Streptomyces have many
antibiotics which can be developed from them.
Describe the effects of smoking on the mammalian gas exchange, with reference to the
symptoms of chronic bronchitis, emphysema and lung cancer.
Short term: increases the distance for oxygen entering the blood because chemicals settles on
the lining of the airways.…read more

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There are 3 forms of CHD: angina, which is a sever pain in the chest, heart attack which is the
death of part of the heart muscle and heart failure which is when the heart cannot sustain its
pumping action.
Stroke is the death of part of a brain tissue caused by loss of blood flow to that part of the brain,
this can be because of a blood clot or an artery leading to the brain bursts (haemorrhage).…read more


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