Protein

Question 1

the physical and chemical properties that govern protein functionality include

Answer 1

size, shape, amino acid composition and sequence, net charge and distribution of charges, hydrophobicity/hydrophilicity, structure, molecular flexibility/rigidity, ability to interact/react with other components

Question 2

the water binding capacity of proteins is defined as

Answer 2

grams of water bound per gram of protein when a dry protein powder is equilibrated with water vapor at 90-95% relative humidity

Question 3

for most proteins, saturated monolayer(bound water) coverage of water occurs at water activity of about __ and multilayers of water are formed at water activity __

Answer 3

0,7-0,8 and >0,8

Question 4

saturated monolayer water is primarily associated with…

Answer 4

ionic, polar and apolar groups on the surface of the protein

Question 5

water binding capacity of proteins is affected by

Answer 5

pH, ionic strength, temperature, type of salts, protein conformation

Question 6

at low concentrations, salts increase the water binding capacity of proteins. why?

Answer 6

because hydrated salt ions, especially the anions, bind weakly to charged groups on proteins. the increase in water binding essentially comes frmo water associated with the bound ions

Question 7

the water binding capacity of proteins generally decreases as the temperature is raised. why?

Answer 7

because of decreased hydrogen bonding and decreased hydration of ionic groups

Question 8

how is the water binding capacity of proteins affected by denaturation?

Answer 8

generally about 10% greater than that of the native protein. this is due to an increase in surface-area-to-mass ratio with exposure of some previously buried polar and hydrophobic groups. however if denaturation leads to aggregation of the protein, then its water binding capacity may actually decrease because of displacement of water by enhanced protein-protein interactions.