Protein Flashcards
Protein structure
Determined by amino acid order
Hydrophobic interactions
Hydrophobic amino acids are orientated towards interior
Polar ones are facing outwards
Protein properties
Determined by the order of the AA
Protein molecules shape is stabilised by hydrophobic interactions
Hydrophobic regions are squeezed together by water surface tension
Heat effect on protein
Destabilise the R group interactions of protein
Does not effect hydrophobic interactions
Protein stability and bond strength
Strength of bonds has to be higher than kinetic energy of the most amino acids
Each individual bond is not much greater than the kinetic energy and so needs many bonds to keep it stable
Denaturation
Heat, pH or saline conditions
R group interactions break
Causing protein to unfold
Hydrophobic regions bumps into each other and squeezed together
Gel definition
Gel is a network that immobilises a large amount of water
Intermediate phase between solid and a liquid
Clear gel structure
Chains of protein all interact and can no longer flow
Opaque gel structure
Long chains and individual molecules, bind together but not organised
Gel formation
Denaturation of native proteins
Gradual association to form gel matric
Aggregated gel
Opaque gel
Large and globular protein
Irreversible
Clear gel (particles)
High water holding capacity
Made from smaller fibrous particles
Reversible
Gelatine
Syneresis
Shrinkage of gel and expulsion of trapped liquid
Contraction takes place the pores in matrix decrease and trapped liquid is squeezed out
Milk protein components
Caseins (80%)
Lactalbumin (whey)
Lactoglobulin (whey)
Caesins
Globular proteins
Can be post-translational modified to give phosphoserine
Phosphoserine
Cluster creating hydrophilic (negative area)
k-caesins
Glycosylate near c terminus
Sub-micelles
Aggregates of different caseins
Hydrophobic areas in the centre
Phosphate and carbohydrate groups on surface
Micelles
Formed by cross linkage of sub-micelles
Interactions between phosphate groups and Ca2+
Ionic interactions
Promote protein-water interactions
Electrostatic repulsion
Repulsion between protein molecules and so they do not clump together
Attracts to water instead creating a hydration shell
Isoelectric pH
Is when protein has no net charge compared to environment
Protein is least soluble
Rennet
Produced in stomach of young animals
Proteolytic enzyme
Produced industrially by Kluyveromyces lactis
Splits k-casein into two parts - hydrophobic and carbohydrate sub
Best at pH lower than 6
Hydrophobic region making submicelles sticky
Causing aggregation (curd)
