Recurring Exam Questions and Answers

Question 1

Explain why an enzyme only catalyses the reaction of a specific substrate

Answer 1

The enzyme has a specific active site that is only complementary to the shape of the substrate to form enzyme substrate complexes

Question 2

Describe how mRNA is produced in the nucleus of the cell (Transcription process)

Answer 2

1. Helicase breaks the hydrogen bonds between complementary base pairs
2. 1 strand acts as a template strand
3. Free nucleotides inside the pool of the nucleus are attracted to their complementary base pair
4. RNA polymerase joins together RNA nucleotides
5. The pre-mRNA formed is spliced to remove introns and mRNA is produced

Question 3

Describe the structure of proteins

Answer 3

Primary structure = Sequence of amino acids

Secondary structure = Folding of polypeptide due to hydrogen bonding, either alpha helices or beta pleated sheet

Tertiary structure = 3-D folding due to hydrogen bonds and ionic bonding

Quarternary structure = 2 or more polypeptide chains and other groups

Question 4

Describe how proteins are digested in the human gut

Answer 4

Hydrolysis of peptide bonds

Exopeptidases = Hydrolyse terminal amino acids

Endopeptidases = Hydrolyse large polypeptides into smaller ones

Dipeptidases = Hydrolyse peptide bond between dipeptides