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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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