PROTEIN Flashcards
What elements are protein made up of
carbon hydrogen oxygen nitrogen
what is the chemical structure of proteins
proteins are large molecules composed of amino acids
basic structure of amino acids
NH2 to the left carbon in the middle H to the top R down below and cooh to the right
what is essential amino acids
cannot be manufactored by the therefore need to be obtained by food
example is lysine and leucine
what is non essential amino acid
can be manufactored by the body therefore dont need to be obtained by food
examples glycine proline
how is a peptide bond formed
a peptide bond is formed when two amino acids join together. the cooh loses a oh and the nh2 loses a h the oh and h join togther and make up a H20 molecule which is water that is then loss. this is called a codensation reaction
what is the strcuture of proteins
primary structure, secondary structure, tertiary structure
what is primary structure
involves the order or sequence of amino acids in protein chains
what is secondary structure
secondary structure involves the folding of primary structure of proteins into defiinite shapes.
what are the two types of crosslinks
disulfide bonds and hydrogen bonds
what is a disulfide bond
occurs when 2 sulfur of two amino acids join together to form either a single polypeptide chain or two different polypeptide chains
what is a disulfide bond
occurs when 2 sulfur of two amino acids join together to form either a single polypeptide chain or two different polypeptide chains
what is a disulfide bond
occurs when a hydrogen from the nh group of one amino acid and an oxygen from the c=o group of another amin acid join together to form either a single polypeptide chain or two different polypeptide chains
what is a tertiary structure
involes the folding of the secondary structure of proteins into three dimensional shapes.
what is denaturation
change in nature of a protein shape. unfolding of a
protein chain. resuting in an irreversible change in shape.
can be caused by heat enzymes, mechanical action. whipping and beating
what are the causes of denaturation
heat, enzymes,mechanical action
heat
causes protein chain to unfold and bond together. causing food to coagulate and set.
enzymes
cause a change to the nature of proteins structure
elasticity
some fibrous proteins, eg gluten in wheat, are quite elastic
culinary application of elasticity
gluten makaes yeast dough elastic enough to trap the CO2 gas produced bby yeast, helping it rise
heat culinary application
eggs white coagulate and change from translucent to opaque at 60 degress celcius and egg yolks coagulate at 68 degrees celcius
maillard reaction
the non enzymic browning of foods due to certain amino acids and sugars under dry heat. it produces an attractive brown colour and a crust with an appetising flavour
maillard reaction culinary appliacation
roast potatoes and roast meat
solubility
most proteins are insoluble in water. apart from collagn in meat.
and egg albumin
culinary application of solubility
mosit heat tenderisises meat by converting collagen to gelantine
Gel formation
gelatine can absorb large amounts of water when heated as protein chains uncoil and water becomes trapped.
this froms a solution
on cooling a solution forms a gel, a semi solid viscous solution that has a 3 dimensional protein matrix
gel formation culinary application
cheesecakaes, jelly sweets
foam formation
when an egg white is whisked, protein chains unfold and air bubbles form.
protein chain entrap air creating a foam
whisking also creates heat that begins to set the egg albumin (known as temporary foam)
foam will collapse after a while unless subjected with heat
