biological molecules- protein

Question 1

chemical elements that make up proteins and formula of proteins

Answer 1

• contains carbon, hydrogen, oxygen, nitrogen and sulphur
• formed from many amino acids in a long chain
• formula: R-CH-NH2-COOH

Question 2

formation of a dipeptide

Answer 2

• 2 amino acids react together with the loss of a water molecule (condensation) forming a peptide bond
• amino group of one amino acid combines with the carboxyl group the other

Question 3

structure of proteins

Answer 3

Primary structure:
- the specific sequence of amino acids that make up a polypeptide chain
- held together by peptide bonds
Secondary structure:
- the folding and coiling of the polypeptide chain to form a-helix or b-pleated sheets
- held by hydrogen bonds
Tertiary structure:
- the unique 3-dimensional structure as a result of further folding of the polypeptide chain
- bonds: van de wall’s forces/hydrogen bonds/hydrophobic interaction/iconic bonds
Quaternary structure:
- when 2 or more polypeptides are involved in forming a biologically functional protein
- the polypeptide chains are sometimes joined with an inorganic component to form a protein
- same bonds as tertiary

Question 4

globular vs fibrous proteins

Answer 4

Globular:

• more spherical in shape
• soluble: has hydrophobic parts located within the centre and hydrophilic towards the edges (can easily interact with the water)
• metabolic/physiological role: e.g. enzymes, haemoglobin, antibodies

Fibrous:
- linear in shape: form long fibres and most concise of repeated sequences of amino acids
- insoluble in water
structural roles: e.g. keratin in fingernails

Question 5

denaturation of protein

Answer 5

• loss of 3-dimensional structure of protein
• bonds that maintain the 3-dimensional shape are broken/changed
• when the shape changes, it ceases to be functional
• caused by heat which disrupts hydrogen and ionic bonds
• small changes in pH of medium may alter iconic charges (however tertiary structure may spontaneously reform given a favourable medium)

Question 6

Role of proteins

Answer 6

• for growth a d repair of worn-out body cells
• synthesis of enzymes and hormones
• synthesis of antibodies to combat diseases