exam qs 1

Question 1

When bread becomes stale, the structure of some of the starch is changed. This changed starch is called retrograded starch.
Scientists have suggested retrograded starch is a competitive inhibitor of amylase in the small intestine.
Assuming the scientists are correct, suggest how eating stale bread could help to reduce weight gain. (3)

Answer 1

1.Less hydrolysis of starch;
2. (To) maltose;
3. (So) less absorption (of glucose) = less weight gain

Question 2

Describe how the structure of a protein depends on the amino acids it contains. (5)

Answer 2

1.Structure is determined by (relative) position of amino acid/R group/;

2. Primary structure is sequence/order of amino acids;
3. Secondary structure formed by hydrogen bonding (between amino acids);
   Accept alpha helix/β-pleated sheet for ‘secondary structure’
4. Tertiary structure formed by interactions (between R groups);
   Accept for ‘interactions’, hydrogen bonds / disulfide bridges / ionic bonds / hydrophobichydrophilic interactions
5. Creates active site in enzymes
6. Quaternary structure contains >1 polypeptide chain
   OR
   Quaternary structure formed by interactions/bonds between polypeptides;