protein Flashcards
what elements make up protein
carbon, hydrogen, oxygen, nitrogen
what is the smallest unit of a protein
amino acid
what is created when amino acids are joined by peptide links
a polypeptide chain
what are the 5 components of an amino acid
an amino group (NH2), a carboxyl group(COOH), a central carbon, a single hydrogen and a variable group that changes
how many essential and non essential amino acids are there
20, 10 essential and 10 non-essential
how are essential amino acids obtained
through food as the body cannot make them.
how many essential amino acids do children and adults require
10 for children and 8 for adults
name three amino acids
lysine, leucine and isoleucine
what are the two essential amino acids for children
histidine and arginine
how are non essential amino acids obtained
they are manufactured in the body
name three non essential amino acids
alanine, cysteine and serine
what results when two amino acids join together
peptide links are formed and there is a loss of water (condensation reaction)
what occurs in the formation of a peptide link
the COOH group of one amino acid loses an OH and the NH2 group of another loses a H which form H2O that is lost. the remaining CO-NH bond, the new molecule is a dipeptide.
how many amino acids join together to make a polypeptide chain
20
how many amino acids join together to make a protein
50
what is the reverse of the condensation reaction
hydrolysis
what occurs during hydrolysis
the addition of water and enzyme action that occurs during digestions when proteins are broken back down into amino acids
what is the primary structure of protein
the order or sequence of amino acids in protein chains
what is the secondary structure of protein
involves the folding of the primary structure into two dimensional shapes, polypeptide chains either fold in on themselves or crosslink with another chain.
what is the purpose of protein secondary structure
gives proteins their unique properties eg: elasticity of gluten
what are the two main types of cross links
disulfide and hydrogen
what is a disulfide bond
occurs when two suflurs from two amino acids join together from either a single polypeptide or two different chains
what is a hydrogen bond
occurs when the hydrogen from the amino group joins with an oxygen of another amino acids carboxyl group
what is the tertiary structure of protein
involves the folding of the secondary structure into two or three dimensional shapes
what is the fibrous shape of protein
polypeptide chains are arranged in straight, spiral or zigzag two dimensional shapes
what are the properties of fibrous shape protein
insoluble in water and not easily dentaured
what are examples of fibrous shape protein
gluten, elastin and collagen
what do globular shape proteins look like
polypeptide chains are arranged in spherical three dimensional shapes
what are the properties and examples of globular shape proteins
soluble in water and easily dentaured, examples: ovalbumin and lactalbumin
what is a conjugated protein
when a protein combines with a non protein molecule
what are the two subgroups of plant protein
glutenins and prolamines
what are the sub groups of conjugated proteins
lipoproteins(lecithin) and phosphoproteins (caseinogen)
what is biological value of protein
a measure of protein quality that is determined by the number of essential amino acids
where are HBV proteins found
mostly animal sources besides soya beans
what are LBV proteins and where are they found
they lack one or more essential amino acids and are mostly found in plant sources besides gelatin
what is an example of food with 100% biological value
eggs
what is the supplementary role of protein
when two LBV foods are eaten together to provide all the essential amino acids
what is an example of supplementary role of protein
bread lacks lysine but is high in methionine whereas beans are lacking methionine but are high in lysine
what are the properties of protein
denaturation, elasticity, maillard reaction, solubility, gel formation and foam formation
what is denaturation of protein
involves the unfolding of a protein chain which is irreversible, it is brought about by physical or chemicals means like heat chemicals, mechanical actions and enzymes. It results in the hardening or setting of protein foods known as coagulation
what is a culinary application of denaturation of protein by heat
albumin in egg white coagulates at 60 degrees and the colour changes from transparent to an opaque and it becomes a solid
what is a culinary application of denaturation of protein by chemicals
Vinegar based marinade tendersies meat by denaturation
what is a culinary application of denaturation of protein by mechanical action
the beating of eggs to make meringues
what is a culinary application of denaturation of protein by enzymes
the enzyme rennin in rennet causes caseinogen in milk to coagulate during cheese making forming curds and whey
what is a culinary application of elasticity of protein
gluten makes yeast dough elastic enough to trap CO2 gas produced by yeast helping it to rise
what is a culinary application of the maillard reaction of protein
shortbread biscuits
what is the maillard reaction
the non enzymic browning of food due to a reaction between amino acids and sugar under dry heat. it produces an attractive brown colour and a crust with an appetising flavour
what is a culinary application of solubility of protein
moist heat tenderises meat by converting collagen to gelatine eg during stewing
what is a culinary application of gel formation of protein
setting cheesecakes and jelly sweets
what is the gel formation of protein
when collagen is heated and converted to gelatine which can absorb large amounts of water which becomes trapped as the protein chains are heated, this forms a sol which forms a gel
what is the foam formation of protein
when an egg white is whisked, protein chains unfold and air bubbles form , the protein traps air, creating a foam which is temporary until heated
what is a culinary application of foam formation of protein
meringues
what are the effects of dry and moist heat on proteins
coagulation, colour changes and overcooking causes protein to be indigestible
what are the effects of dry heat only on proteins
maillard reaction
what are the effects of moist heat only on proteins
tenderising meat
what are the biological functions of structural proteins
production of cell membranes, muscle tissue and skin, cell repair and replacement and growth
what are the biological functions of physiologically active proteins
production of hormonal proteins, enzymes, antibodies, blood proteins and nucleoproteins
what are the biological functions of nutrient proteins
provide the body with essential amino acids and excess are use as an energy source when carb and fat reserves are used
what is a result of a deficiency of structural proteins
retarded growth and delayed healing
what is a result of a deficiency of physiologically active proteins
body organs and systems malfunction, easily infected
what is the recommended daily allowance of protein
0.75g per kg of body weight
how many kcal in 1 g of protein
4 kcal
what occurs in the stomach to break down proteins
HCL denatures proteins, rennin breaks down caseinogen to casein and pepsin breaks down proteins into peptones
what occurs in the pancreas to break down proteins
pancreatic juice is secreted into the duodenum which contains trypsin which breaks down peptones into peptides
what occurs in the small intestine to break down proteins
the ileum secretes intestinal juice which contains peptidase that breaks down peptides into amino acids which can now be absorbed and utilised
what is the order of breakdown of proteins
protein->peptones->peptides->amino acids
what happens to amino acids when they enter the liver
they are used to maintain and repair liver cells and passed into the bloodstream and body tissues to form new cells, hormones, enzymes and antibodies
what is deamination
the process by which excess amino acids are broken down in the liver, the amino group is converted to ammonia then urea and excreted and the carboxyl group is oxidised to produce heat and energy
