3.1.4 Proteins and Enzymes

Question 1

Draw the structure of an amino acid

Answer 1

See notes

Question 2

A polymer on amino acids

Answer 2

Polypeptide

Question 3

Describe how a dipeptide forms

Answer 3

1. Condensation reactions
2. Between carboxyl and amino group
3. Forms a peptide bond

Question 4

Primary sequence of protein

Answer 4

Number, sequence, order

Question 5

Secondary structure of protein

Answer 5

• Hydrogen bonds between carbons and amino group
• Causes a long polypeptide chain to twist in a 3D shape (coil)
• Forms alpha helix or beta pleated sheet

Question 6

Tertiary structure of proteins

Answer 6

• R groups in polypeptide chain determine how it folds into specific 3D shape
• Forms ionic, hydrogen or disulfide bonds

Question 7

Quaternary structure of proteins

Answer 7

Joining of 2 polypeptide chains

Question 8

Describe how to test for proteins

Answer 8

• Biurets reagent
• Blue to purple

Question 9

Lyxose is a sugar which binds to enzymes. It is not involved in inhibition.

Explain why lyxose increases the rate of reaction of enzymes

(4 marks)

Answer 9

1. Lyxose changes the tertiary structure
2. This induces a change in the shape of the active site
3. Making it more complementary
4. Allowing more enzyme substrate complexes to form.