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41 Cards in this Set
- Front
- Back
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Composition of protein |
Protein is made up of the elements: carbon, hydrogen, oxygen and nitrogen
Protein contains nitrogen an element essential for growth
Some proteins contain trace amounts of sulphur, phosphorus, and iron |
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Basic structure of protein |
H | NH2----C-----COOH | R
C= carbon atom H= hydrogen atom NH2= amino group COOH= carboxyl group R= variable |
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Essential and non-essential amino acids |
Essential amino acids: Are amino acids that cannot be made in the body and must be obtained from food eg: lysine and methionine
Non-essential amino acids: Are amino acids that can be made by the body and do not need to be obtained by food eg: glycine and aspartic acid |
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Peptide bonds |
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Primary structure of protein |
Primary structure: Is the order and number of amino acids in a chain |
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Secondly structure of protein |
Secondary structure: Is the folding of the polypeptide chain caused by cross links in the chain examples of this are
Disulphide links: this link occurs when two sulphur join together. The amino acid cytosine contains sulphur. When two cytosine units, either in the same chain or in two different chains, are adjacent, a disulphide link may be formed
Hydrogen bonds: Polypeptide chains can also be linked by hydrogen bonds. The hydrogen in one chain joins with the oxygen in a neighbouring chain |
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Tertiary structure |
Fibrous: The polypeptide chain is arranged in a straight, spiral or zigzag shape. Eg: gluten and collagen which are insoluble in water Globular: The polypeptide chain is arranged in a globe shape. Eg: ovalbumin and myoglobin which are soluble in water |
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Classification of protein |
1. simple: (a) Animal- (1) Fibrous, eg: collagen in skin,myosin in muscle (2) Globular, eg: albumin in egg, myoglobin in meat (b) plant- (1) Glutelins, eg: glutenin in wheat, oryzenin in rice. (2) prolamines, eg: glia den in wheat, zinc in maize 2. Conjugated Consist of amino acids + a non-protein molecule eg: (1) Lipoprotein (lipid +protein), eg: lecithin in egg yolk (2) Phosphoprotein (phosphate + protein), eg: caesinogen in milk |
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Sources of protein |
Animal protein plant protein cheese soya beans Chicken TVP foods Meat nuts Fish lentils Eggs peas Milk beans Cereals |
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Properties of protein: denaturation |
Proteins can be denatured which is the unfolding of the protein chain resulting in an irreversible change in shape protein can be denatured by (1) Heat: albumin in egg hardens/coagulates (2) Acids: acetic acid in vinegar tenderise meat (3) Enzymes: renin in stomach, coagulate milk (4) Mechanical action: whisking egg whites causes them to foam |
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Properties of protein: solubility |
Most proteins are insoluble in water except egg whites in cold water and collagen in hot water |
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Properties of protein: maillard reaction |
The maillard reaction is the browning of food that is not caused by enzymes. It occurs as a result of a reaction between amino acids and carbohydrates on heating eg:fried potatoes, brown crusts on bread |
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Properties of protein: elasticity |
Elasticity is a property of some proteins, including gluten, which allows baked goods to rise. |
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Properties of protein: gel formation/gelling |
Gelatine can absorb large amounts of water forming a gel. This property enables gelatine to be used as a setting agent eg: in soufflés and mousses |
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Effects of dry and moist heat on protein |
(1) Coagulation: proteins set or harden when subjected to heat. (2) colour change (3) Maillard reaction (dry heat ) (4) tenderising (moist heat) (5) overcooking causes proteins to become indigestible |
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Biological functions of proteins |
(1) structural role- production of: . Cell membranes . Muscle and skin = growth and repair (2) physiologically active proteins- production of: . Hormones . Enzymes . Antibodies . Blood proteins and nucleotide ins (3) nutrient proteins . Supply body with essential amino acids . Excess protein used for energy |
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Recommend daily amount (RDA) |
The RDA of protein is based on the > Body weight > Rate of growth On average 1g of protein is required per 1kg of body weight Extra is required during periods of rapid growth (adolescents) |
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Protein digestion |
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Absorbtion and utilisation of amino acids |
Amino acids are absorbed by the villi of the small intestine into the bloodstream. The portal vein carries them to the liver. In the liver: >They are used to maintain and repair liver cells >They are sent into the blood stream to fork new cells, repair damaged cells and manufacture hormones, enzymes, antibodies, blood proteins, and nucleoproteins >the excess is deaminated to produce heat and energy |
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Element composition of carbohydrates |
Carbohydrates are made up of the elements carbon, hydrogen and oxygen |
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Classification of carbohydrates |
> monosaccharides- one sugar unit- C6H12O6 Examples include: Glucose, found in fruit Fructose, found in honey >diasaccharides- two sugar units- C12H22O11 Examples include: Sucrose, found in table sugar Lactose, found in milk Polysaccharides- many sugar units- (C6H10O5)N Examples include: Starch, found in potatoes Cellulose and pectin, found in fruit |
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Biological functions of carbohydrates |
1. Carbohydrates are used to produce heat and energy 2. They free protein for its primary function of growth and repair 3. Excess carbohydrate is converted into glycogen and stored in the liver and muscles as an energy reserve 4. Cellulose assists movement of food through the digestive system preventing constipation |
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The properties of carbohydrates: solubility |
Sugars are white crystalline compounds which are soluble in water |
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The properties of carbohydrates: Flavour |
Sugars are of varying degrees of sweetness, sucrose being much sweeter than lactose |
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The properties of carbohydrates: Maillard reaction |
Browning occurs when sugars and amino acids react when heated |
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The properties of carbohydrates: Carmelisation |
When sugar is heated on it'd own it melts and then camelises I.e. changes to a brown syrup. Eventually it carbonises (burns) |
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The properties of carbohydrates: hydrolysis |
Sugars are capable of hydrolysis this means that they react with water and enzymes and break down into monosaccharide units, as in digestiin |
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The properties of carbohydrates: inversion |
Sugars are capable of being inverted. Invert sugars are the monosaccharides which result from hydrolysis of disaccharides eg when sucrose is hydrolysed it is inverted to glucose and fructose |
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The properties of carbohydrates: crystallisation |
This occurs if more sugar is added than can be absorbed by a liquid. Crystal particles deposited from the solution. Crystallisation is used in the confectionary and sweet industry |
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The properties of carbohydrates: assists aeration |
Sugar denatured egg protein allowing aeration to occur |
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The properties of starch: Flavour |
Starch is not sweet in flavour |
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The properties of starch: solubility |
Starch is a white powder which is insoluble in cold water |
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The properties of starch:gelatinisation |
When starch grains are heated in a liquid they swell and bust and absorb the liquid, forming a thickened solution. eg the thickening of soups and sauces with flour |
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The properties of starch: hydroscopic |
Starch absorbs moisture. Eg biscuits soften if not stored in a sealed container |
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The properties of starch:dextrinisation |
When carbohydrate foods are heated, short chains of polysaccharides (dextrins) form, causing the food to brown. Eg toast |
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The properties of starch: hydrolysis |
Starch may undergo hydrolysis |
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Elemental composition of lipids |
Carbon hydrogen and oxygen |
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Chemical structure of lipids |
Lipids are made up of 3 fatty acids and a glycerol molecule, referred to as a trigly-ceride. |
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Classification of fatty acids |
Three classes of fatty acids: saturated fatty acids, mono -unsaturated fatty acids and polyunsaturated fatty acids |
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Saturated fatty acids |
> Each carbon has a full quota of hydrogen > There are no double bonds between the carbon atoms of a saturated fatty acids > Saturated fatty acids are solid at room temperature > Saturated fatty acids are generally from animal sources. Eg butyric acid (butter) and stearic acid (meat) |
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Mono - unsaturated |
> All carbon atoms are not saturated with hydrogen > There is one double bond in the carbon chain > Fatty acids are generally soft/liquid at room temperature > They generally come from plant sources and fish. Eg oleic acid (olive oil) |
