Protein Flashcards
Element
Carbon
Oxygen
Hydrogen
Nitrogen
Basic structure amino acid
Labelled
Formation of peptide link
Oxygen and hydrogen from first amino acid in the carboxyl group joins with the first hydrogen in the amino group in their second amino acid which forms water
The end of carbon and oxygen in the first amino acid in the carboxyl group joins with nitrogen and a seven hydrogen in the amino group and the second amino acid which forms the peptide link and the process is called condensation process
Essential amino acid
Cannot be made in the body and must be obtained from food
Example histidine, argarinine
Non-essential amino acid
Made in the body and not essential to go from food
Example proline
Three structures of protein
- primary structure
- secondary structure
- territory structure
Primary structure
Order a number of amino acid in the protein chain
Secondary structure
Coiling of primary structure giving spiral shape Held in place by either= 1. disulphide bond Or 2. hydrogen bond
Tertiary structure
Folding of the secondary structure
A) fibrous eg gluten base difficult to tear
Or
B) globular eg albumin in egg white
Classification of proteins
- simple proteins
2. conjugated proteins
Simple proteins
Animal - fibrous e.g. collagen in meat
- globular e.g. albumin in egg white
Plant - glutenins e.g. gluteninin in wheat is soluble in acid and alkaline
- prolamins e.g. zein in maze is soluble in alcohol
Conjugated proteins
- Protein combines with non-protein molecule
- e.g. lipoprotein e.g. lechtin in egg yolk
- e.g. phosphoprotein e.g. caesinogen in milk
High biological value protein
Contains all the essential amino acid in the correct proportion needed by the body
e.g. eggs milk cheese meat
low biological value protein
Does not contain all essential amino acids in the correct proportion a divided body
e.g. wheat maize rice
Complimentary/ supplementary value protein
Two low biological value protein foods combined together so all essential amino acids are in the correct proportion a divided body
e.g. beans (lysin) on toast (methionine)
Properties/characteristics
Denaturation Mailard reaction solubility elasticity Gel formation Foam formation
Denaturation
Invertible change in protein structure Caused by heat eg fried eggs chemicals eg lemon juice curdle milk agitation eg whipping eggs white foam enzymes eg renin causes casein in milk form curd cheese
Mailard reaction
Amino acid+sugar+dry heat= browning
Eg toast
Solubility
Insoluble in water accept albumin in egg white
Elasticity
Fibrous protein elastic
e.g. gluten and bread
Gel formation
Collagen heated from gelatine setting agent used in cheesecakes jelly and sweet
can absorb large amount of water when heated
Foam formation
Egg white whisked
form temporary foam trapping air
Oven sets as permanent foam
Digestion
Stomach- gastric juice - rennin/ Pepsin
pancreas- pancreatic juice - trypsin
small intestine- intestinal juice - peptidase
Dry and moist heat effect on protein
- coagulation eg egg white coagulate at 60’C and yolk at 68’C
- colour change (myoglobin (red pigment) to haematin(brown pigment)
- overcooking (indigestible)
Dry heat affect on protein
Mailard reaction eg roast beef
Moist heat effect on protein
Tenderising meat= collagen in meat coverts to gelatine causing fibres to tenderise eg pulled pork
Stomach
Gastric juice
= rennin - caesogin - casein
= pepsin - protein - peptones
Pancreas
Pancreatic juice
= trypsin- peptones - peptides
Small intestine
Intestinal juice
= peptidase - peptides - amino acids
Deamination
Excess amino acids broken down by the body in the liver
=NH2 - ammonia + urea = excreted as urine through kidneys
=COOH - oxidised for heat and energy
