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Protein - Coggle Diagram
Protein
Functions
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Production of hormones, enzymes and antibodies
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Properties
Denaturation
This is the unfolding of the protein chain and it looses its three dimensional shape.
Causes -
(i) heat - cooking of boiled eggs brings about denaturation and coagulation (setting)
(ii) Acids - Addition of lactic acid bacteria to milk when making cheese causes the milk protein to denature, set and turn into curds
(iii) Enzymes - Addition of rennet to milk when making cheese causes the milk protein to denature, set and turn into curds
(iv) Mechanical action - whisking of eggs when making a sponge generates heat which causes the protein to denature and coagulate around trapped air bubbles
Maillard reaction
This is a form of non enzymic browning where amino acids react with carbohydrates to give a brown colour to the food. e.g. the browning of fried potatoes
Gel formation
The protein gelatine which is extracted from the bones of animals and dried has the ability of absorb large amounts of water. On heating it thickens to form a sol and on cooling it changes into a semi-solid viscous solution called a gel. Gelatine is used in the setting of meringues and souffles
Elasticity
Some proteins e.g gluten is quite elastic when moistened. This property is useful in baking as it the presence of gluten in baked goods allows them to rise
Solubility
Most proteins are insoluble in water - Exception = egg whites in cold water and collagen in hot water
Teh ability of collagen to dissolve in water, changes it to gelatine during cooking and gelatine is more tender than collagen so meat tenderises
Structure
Primary
This is the number and sequence of amino caids in the polypeptide chain
Each amino acid is joined to the next with a peptide bond (the amino end of one amino acids joins with the carboxyl end of the next with the loss of a water each time (condensation reaction) Know how to draw
Secondary
Further linking of the primary structure with cross bonds or cross links to give a two dimensional shape
Examples = DIsulphide links and Hydrogen bonds (describe each)
Tertiary
This is the further folding of the secondar structure of a protein to give a three dimensional shape (normally fibrous or globular)
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Classification
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Conjugated
These contain amino acids and a non protein molecule in the polypeptide chain e.g. lipoproteins contain a lipid within the chain of amino acids e.g. lecithin in egg yolk is an example of a lipoprotein
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These are the ones the body needs to survive but they can't be made in the body.
They have to be got from foods (mainly animal foods)
There are eight of them e.g. Valine, Lysine, Leucine
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Protein deamination
This is the breakdown of excess protein in the body and using it as a source of heat and energy.
It occurs in the liver
The amino end of the amino caid is removed, converted into ammonia, then urea and excreted
The carboxyl end (COOH) end is removed and oxidized to form heat and energy
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