CCEA AS HOME ECONOMICS- PROTEINS

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  • Created on: 02-05-13 20:31
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Protein
Functions:
1. Source of amino acids for various productive processes e.g. growth, repair and
turnover of tissues
2. Secondary source of energy (when tissue protein is being mobilised in starvation)
Amino acids:
Amino acids are the building blocks of protein (what protein is made up of)
Amino aids are compounds containing hydrogen, oxygen, nitrogen and possibly sulphur.
There are 20 different amino acids commonly found in plant and animal proteins.
8 are essential in the diet (not synthesised properly in the body) these are known as
indispensable amino acids.
1. Dispensable (non-essential): Sometimes it is possible for the amino group of an
amino acid to be transferred to another molecule by a process called
transamination
In this way the human body is able to make some amino acids itself.
Dispensable amino acids can be synthesised by the body by converting one amino
acid into another within the body cells
2. Indispensable (essential): It is not possible for this process to occur with every
amino acid; they must be supplied by the diet.
Children require an extra amino acid as they are not able to make enough to
meet their needs:
9 amino acids: essential in children for growth and repair
8 amino acids: required by adults for repair and maintenance
Protein Quality:
When protein foods are eaten the proteins are hydrolysed during digestion to produce
amino acids.
After absorption the amino acids are transported by the blood to the cells where they
recombine and new proteins are formed.
The Biological Value of protein is a measure of protein quality. The BV is the percentage
of absorbed protein which is converted into body protein (protein that is retained for
growth etc.)
The quality of protein may be judged by its:
Protein content
Number of essential amino acids it contains
The degree to which its protein is digested and absorbed.
The highest quality protein foods are those which provide all the indispensable amino
acids in the proportion needed by humans.

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Animal Foods Vegetable proteins
Good sources of indispensable amino acids Poor sources of indispensable amino acids
i.e. have all the necessary amino acids. i.e. are missing one or more amino acids
Sources: eggs, meat, fish, milk and Soya (limiting amino acids)
beans Sources: rice, peas, wheat, corn and
HBV gelatine
LBV
Complementary action of proteins:
Mixtures of proteins taken together (in particular plant foods) can complement each
other by supplying the full range of amino acids needed by humans, hence becoming
HBV.…read more

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Formation of enzymes:
These facilitate most of the chemical reactions in the body e.g. digestion of nutrients.
3. Production of hormones:
E.g. Vasopressin is a hormone responsible to control blood pressure (protein is needed to
produce this hormone)
4. Immunity:
Plays a key role in the immune system; if your immune system is poor you are more
susceptible to disease
5. Transport
Many substances need to be carried around the body from wither the digestive system or
to sites of action e.g.…read more

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Protein forms the major components of the hair and nails as well as the structural
framework of the bones
Sources of protein
HBV LBV
Egg Rice
Meat Corn
Fish Wheat
Milk Peas
Soya bean (only plant source) Gelatine (only animal source)
Different foods contain different proteins: each with a unique amino acid
composition
The proportions of essential amino acids in foods may differ from the proportions
needed by the body to make proteins
The proportion of each of the essential amino acids in foods containing…read more

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Cheap source of HBV protein
NSP- prevents bowel disorder and contributes to healthy blood cholesterol
Source of isoflavones- helps to prevent cancer and CHD (type of anti-oxidant)
Good source of iron
2. Tofu
Tofu is produced from ground soya beans, which has been sieved. The proteins
coagulate, producing soft cheese like products. Available in plain and smoked form;
absorbs flavour well.
3. Tempeh
Mass of soya beans which have been allowed to ferment. Solid with a white fluffy outer
layer; can be sliced.…read more

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In fevers and wasting diseases the body is in negative nitrogen balance (output exceeds
input)
Healthy adults excrete the same amount as ingested (nitrogen equilibrium)…read more

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