Proteins

Question 1

What is complementation of proteins?

Answer 1

Complementation refers to the intake of a variety of LBV proteins which when mixed and matched complement the deficient amino acid content of the other. If eaten together try will supply the essential amino acid

Question 2

How many amino acids are required in the diet?

Answer 2

8 for adults
9 for children the addition of histidine
(Threonine, tryptophan, valine, leucine, isoleucine, phenylalanine, lysine, methionine)

Question 3

What is biological value?

Answer 3

Is a measure of protein quality. It is the percentage of absorbed protein which is converted into body protein. Proteins that contain more of the essential amino acids and which are of higher BV are of more use to the body

Question 4

What are the best sources of high BV protein?

Answer 4

Animal sources

Soya

Question 5

Why do vegetarians need to eat a wider range of vegetable sources of protein?

Answer 5

Because they tend to be lower BV so need to ensure that essential amino acids are obtained

Question 6

What is the effect of heat on proteins?

Answer 6

Causes secondary structure of egg whites to denature where the molecule unfold and changes shape but the sequence of amino acids remains the same at approx 60C
Senators room breaks cross links which maintain shape of molecule
The properties of the proteins alter and become less soluble and more viscous
Unfolded molecules tend to form clumps as they bond resulting in the setting or hardening of the egg white known as coagulation and change of colour

Question 7

What effect does mechanical action have on proteins?

Answer 7

Violent agitation such as whisking can cause partial coagulation of protein
Protein molecules unfold and from a reinforcing network round the air bubbles thus stabilising the foam

Question 8

What effect does acid have on protein?

Answer 8

Denature proteins and speed up time it takes for foaming

Question 9

Describe structure of a globular protein

Answer 9

Round
Soluble
Cross linked
Proteins 
Colloids
Not closely packed

Question 10

Describe structure of fibrous proteins

Answer 10

Elastic:
Coiled
Cross linked chains 
Insoluble
Forms elastin 
Closely packaged
Gluten 

In elastic:
Straight
Cross linked
Insoluble
Collagen
Closely packed