Protein

Question 1

Elemental compositions of protein

Answer 1

Carbon,hydrogen,oxygen and nitrogen

Question 2

Essentiall amino acids

Answer 2

-cannot be manufactured by the body therefore must be obtained by food
-ten essential amino acids,adults require eight and children require all ten
E.gs valine,lysine,leucine

Question 3

Non-essential amino acids

Answer 3

-can be manufactured by the body therefore they don’t need to be obtained by food
-there are ten non-essential amino acids
-e.gs alanine,glycine,proline

Question 4

Primary structure

Answer 4

-primary structure is the order of sequence of amino acids in a protein chain
-amino acids can b en arranged in many different ways for e.g insulin contains 51amino acids
-draw straight line with shapes

Question 5

Secondary structure

Answer 5

-Secondary structure involves the folding of the primary structure of proteins into definite shapes
-Polypeptide chains either fold in on themselves or cross-link with another polypeptide chain this causes the spiral shape
-There are two types of cross-links: disulfide and hydrogen bonds

Question 6

Tertiary structure

Answer 6

-Involves the folding of the secondary structure into three-dimensional shapes
-further cross-linking between amino acids forms definite shapes which may be fibrous or globular
-Fibrous
-polypeptide chains are arranged in straight, spiral or zig-zag shapes
-Insoluble in water
-not easily denatured
-e.g. gluten
-Globular
-polypeptide chains are arranged in a globular shape (squiggle and interlinking)
-soluble in water
-easily denatured
-e.g. ovalbumin(egg white)

Question 7

Properties of protein

Answer 7

-Denaturation
-Gel formation
-Foam formation

Question 8

Denaturation

Answer 8

Denaturation is a change in the nature of a protein chain. It involves the unfolding of a protein chain resulting in a irreversible change in shape. It is brought about by physical or chemical means including heat ,chemicals ,mechanical action and enzymes. This results in the hardening or setting of protein food known as coagulation.

Question 9

Gel formation

Answer 9

When collagen is heated it is converted to gelatine. Galantine can absorb large amounts of water when heated as protein chains uncoil and water becomes trapped
-e.g. Setting of cheesecake

Question 10

Foam formation

Answer 10

When an egg white is whisked protein chains unfold and air bubbles form. The protein chains entrap air creating a foam.
-e.g. meringues