Protein

Question 1

Protein structure

Answer 1

Determined by amino acid order

Question 2

Hydrophobic interactions

Answer 2

Hydrophobic amino acids are orientated towards interior

Polar ones are facing outwards

Question 3

Protein properties

Answer 3

Determined by the order of the AA
Protein molecules shape is stabilised by hydrophobic interactions

Hydrophobic regions are squeezed together by water surface tension

Question 4

Heat effect on protein

Answer 4

Destabilise the R group interactions of protein

Does not effect hydrophobic interactions

Question 5

Protein stability and bond strength

Answer 5

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

Question 6

Denaturation

Answer 6

Heat, pH or saline conditions

R group interactions break
Causing protein to unfold
Hydrophobic regions bumps into each other and squeezed together

Question 7

Gel definition

Answer 7

Gel is a network that immobilises a large amount of water

Intermediate phase between solid and a liquid

Question 8

Clear gel structure

Answer 8

Chains of protein all interact and can no longer flow

Question 9

Opaque gel structure

Answer 9

Long chains and individual molecules, bind together but not organised

Question 10

Gel formation

Answer 10

Denaturation of native proteins

Gradual association to form gel matric

Question 11

Aggregated gel

Answer 11

Opaque gel
Large and globular protein
Irreversible

Question 12

Clear gel (particles)

Answer 12

High water holding capacity
Made from smaller fibrous particles
Reversible
Gelatine

Question 13

Syneresis

Answer 13

Shrinkage of gel and expulsion of trapped liquid

Contraction takes place the pores in matrix decrease and trapped liquid is squeezed out

Question 14

Milk protein components

Answer 14

Caseins (80%)
Lactalbumin (whey)
Lactoglobulin (whey)

Question 15

Caesins

Answer 15

Globular proteins

Can be post-translational modified to give phosphoserine

Question 16

Phosphoserine

Answer 16

Cluster creating hydrophilic (negative area)

Question 17

k-caesins

Answer 17

Glycosylate near c terminus

Question 18

Sub-micelles

Answer 18

Aggregates of different caseins
Hydrophobic areas in the centre
Phosphate and carbohydrate groups on surface

Question 19

Micelles

Answer 19

Formed by cross linkage of sub-micelles

Interactions between phosphate groups and Ca2+

Question 20

Ionic interactions

Answer 20

Promote protein-water interactions

Question 21

Electrostatic repulsion

Answer 21

Repulsion between protein molecules and so they do not clump together
Attracts to water instead creating a hydration shell

Question 22

Isoelectric pH

Answer 22

Is when protein has no net charge compared to environment

Protein is least soluble

Question 23

Rennet

Answer 23

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)