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PROTEIN
| Term | Definition |
|---|---|
| essential amino acid | cannot be manufactured by the b body, therefore must be obtained from food. there are 10 . 8 for adults and 10 for children eg. valine and lysine |
| non-essential amnio acid | can be manufactured by the body, therefore do not need to be obtained from food . there is 10 eg. cysteine and glycine |
| condensation reaction | loss of water molecule |
| hydrolysis | reverse of condensation reaction. involves the addition of water and enzyme action. occurs during digestion, when proteins are being b broken down into amino acids. |
| primary structure | is the order or sequence of amino acids in protein . can be arranged in many different combinations eg insulin simplest protein contains 51 amino acids. |
| secondary structure | involves folding of the primary structure of proteins into definite shapes. polypeptide chains either fold on themselves or cross-link with another polypeptide chain. this cause the chains to form a spiral shape. |
| two types of cross- links | disulfide bonds and hydrogen bonds |
| disulfide bonds | occur when two sulfurs from two amino acids join together from either a single polypeptide chain or two different polypeptide chains eg. amino acid cysteine contains sulfur. two can form this bond .. insulin contains this bond |
| hydrogen bonds | occurs when a hydrogen from N-H group of one amino acid and an oxygen from the C=O group of another amino acid join together from a single polypeptide chain/ two different polypeptide bonds eg. serine and tyrosine are capable of forming this bond |
| tertiary structure | involves folding of the secondary structure of proteins into 3-dimensional shapes further cross-linking between amino acids from define shapes which may be fibrous or globular |
| fibrous | polypeptide chains are arranged in straight, spiral or zigzag shapes insoluble in water and not easily denatured eg. gluten or elastin/collagen. |
| globular | polypeptide chains are arranged in a globular shape(spherical) soluble in water and easily denatured eg. ovalbumin(egg white) lactalbumin (milk) |
| classification of proteins | simple or conjugated proteins |
| simple proteins | group: animal - fibrous -elastin/collagen -meat connective tissues animal - globular-ovalbumin/lactalbumin- egg white/milk plant- glutenin's-glutenin/oryzenin-wheat/rice plant- protamines-gliadin/zein-wheat/maize |
| conjugated | group: lipoproteins-lecithin-eggs phosphoproteins - caseinogen- milk |
| source of protein. | animal source: meat, fish,eggs,milk and cheese plant source: beans, nuts,lentils, peas and cereals |
| HBV protein? | complete proteins contain all 10 essential amino acids eg. eggs , milk meat |
| LBV protein? | does not contain all essential amino acids eg. rice wheat maize |
| complementary role/supplementary value of protein | consuming two LBV protein foods together each lacking different essential amino acids can ensure all essential amino acids are obtained. eg. beans on toast (beans low in methionine and high in lysine.. toast opposite) |
| denaturation | change in the nature of a protein chain. unfolding of a protein chain resulting in an irreversible change in shape. brought about by physical or chemical means incl: heat,chemicals, mechanical action or enzymes. results- hardening or setting of protein |
| causes of denaturation | heat chemicals mechanical action enzymes |
| elasticity | some fibrous proteins eg. gluten in wheat, quite elastic CU: gluten makes Yeast dough... |
| maillard reaction | non-enzymic browning of food due to reaction between certain amino acids and sugars under DRY HEAT. .. produces attractive brown colour and a crust with an appetising flavour |
| solubility | insoluble in water .. apart from collagen in meat and eggs albumin. |
| gel formation | collagen is heated .. converted to gelatine. gelatine can absorb large amounts of water when heated, as protein chains uncoil and water becomes trapped.. forms a sol.. on cooling forms a gel |
| foam formation | egg white whisked, protein chains unfold and air bubbles form. protein chains entrap air, creating a foam. whisking also creates heat that begins to set the egg albumin .. known as a temporary foam... will collapse after a while if not heated |
| effects of dry and moist heat | coagulation eg. egg white coagulate at 60degrees and egg yolk at 68degrees colour change. myoglobin in meat change to haematin overcooking causes proteins to become indigestible |
| dry heat | maillard reaction eg. roast beef |
| moist heat | tenderising meat: collagen in meat converts to gelatine, causing the fibres to tenderise eg. pulled pork |
| structural proteins | production of cell memebranes, music le tissue an d skin cell repair and replacement growth |
| physiologically active proteins | hormonal proteins: help to coordinate bodily activities eg. production of insulin. enzymes: speed up chemical reactions eg. pepsin .. proteins antibodies blood proteins |
| nutrient proteins | provide the body with essential amino acids excess can be used as a source of energy when carb and fat reserves are used. |
| RI children | 30-50 g |
| RI adolescents | 60-80g |
| RI adults and older people | 50-75g |
| RI pregnant and lactating women | 70-85g |
| energy value | 1g of proteins provides 4kcal of energy 17KJ |
| digestion of protein stomach | secretion:gastric juice enzymes: rennin/pepsin substrate : caseinogen/proteins product : casein/ peptones |
| digestion of protein pancreas | secretion: pancreatic juice enzymes: trypsin substrate: peptones product : peptides |
| digestion of protein small intestine ileum | secretion: intestinal juice enzymes: peptidase substrate: peptides product: amino acids |
| deamination | is the process through which excess amino acids are broken down by the body in the liver. NH2 group of amino acids is removed, converted to ammonia,-urea &excreted- kidneys the COOH group of the amino acid is oxidised to produce engird and heat |
| absorption and utilisation of proteins | pass through the wall of villi and into blood stream .. hepatic portal vein transports the amino acids to the liver used to maintain&repair liver cells passed into the bloodstream and body tissues to form new cells. |
Created by:
maeve2021
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