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Summary Topic 7: Human nutrition
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Topic 7: Human nutrition: IGCSE Biology course notes which will help you study for your papers. By studying these notes I achieved a 9 - A* on my Igcse
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IGCSE Biology Topic 1 (Characteristics & Classification of Living Organisms)
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Class and mark scheme notes Biology Cambridge IGCSE with Biology Coursebook with CD-ROM
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TOPIC 7: ANIMAL NUTRITION7.1 DIET
→Balanced diet: intake of all of the food groups in the correct proportions.
-The necessary food groups are:
→Carbohydrates NUTRIENTS NEEDED IN A BALANCED DIET:
→Proteins
→Lipids
→Vitamins (organic substances)
→Minerals (inorganic substances)
→Dietary Fibre
→Water
-The amount of energy each person uses per day depends partly on
your age (how old are you), sex (male/female) and your job (if it
requires more or less energy). Males normally require of more
energy and so do teenage and pregnant women (but less than adult
and teenage men).
Fibre
→Peristalsis: Food moves down the alimentary canal because the muscles contract and relax to squeeze it along.
-When there’s fibre in the alimentary canal (hard/less digestible food), the muscles work more strongly.
-Fibre keeps the digestive system working to prevent constipation.
VITAMIN AND MINERAL REQUIREMENTS: CAUSES-EFFECTS OF VITAMIN & MINERAL DEFICIENCIES:
Vitamins
Minerals
Fat and heart disease
-Saturated fat (fat in animal food) contains cholesterol. i.e. milk, butter, cheese…
-A large intake of saturated fats and cholesterol can lead to heart disease.
-Fat deposits and builds up on the inside of the arteries (stiffer and narrower) → blood clot → heart attack
-If it happens in the coronary arteries (supplies heart with blood) then not enough blood can reach the heart
→CORONARY HEART DISEASE.
-Unsaturated fats (vegetable oils) don’t increase this risk.
Obesity
-Caused by taking in more energy than the one you are going to use (too much fat intake).
-Obese people are more likely to get heart disease, diabetes and strokes. (fat on legs – knee joints problems).
-A balanced diet can prevent obesity.
, Malnutrition
-Malnutrition is caused by not eating a balanced diet
-Types of malnutrition:
→Starvation
→Coronary heart disease
→Constipation
→Obesity
Protein Energy Malnutrition
-In many countries in the world, droughts, natural disasters, wars and a
poor economy can lead to mass malnutrition in large areas of the country
-The two types of malnutrition most common in these situations are
termed ‘protein energy malnutrition’ (PEM)and they are:
→Kwashiorkor:
-Caused by a lack of protein in the diet, most common in children under 2.
-Often caused by poverty/lack of knowledge as high protein foods tend to
be more expensive and scarcer.
-Children suffering from kwashiorkor are always underweight for their age
and have a swollen abdomen as their diet may contain a lot of
carbohydrate
→Marasmus:
-The most severe form of PEM, where there is a lack of both protein and
energy in the diet.
-People suffering from this have a much lower body weight than normal
and look emaciated.
7.2 ALIMENTARY CANAL
→Alimentary canal: the long tube that runs from the
mouth to the anus which is part of the digestive
system.
-Food will go through the alimentary canal via
peristalsis.
-Sphincter muscles close the tube completely in
certain places if food has to be kept in a part of the
alimentary canal for a while.
-The alimentary canal is lubricated with mucus so
food slides easily.
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