1.4 - Proteins

Question 1

1) Draw the structure of an amino acid and label the amino, carboxyl and R group

Answer 1

Check notes

Question 2

1) Describe the reaction which forms a dipeptide.

Answer 2

A condensation reaction between amine/NH2 group and carboxyl/COOH group produces a dipeptide linked by a peptide bond, and releases a molecule of water.

Question 3

1) Draw a dipeptide and circle the peptide bond.

Answer 3

Check notes

Question 4

1) Describe the formation of a polypeptide

Answer 4

A polypeptide is formed by the condensation of MANY amino acids.

Question 5

Primary structure protein

Answer 5

sequence of amino acids form a polypeptide chain
peptide bonds between the amino group and the carboxyl group of the adjacent amino acid

Question 6

Secondary structure protein

Answer 6

polypeptide chain is folded to form an alpha-helix or beta-pleated sheet
Hydrogen bonding between NH of one amino acid and C=O of another amino acid

Question 7

Tertiary structure protein

Answer 7

Further folding of the secondary structure forms a unique 3-D structure (can be globular or fibrous) disulphide bonds, hydrogen bonds and ionic bonds between different R groups

Question 8

Quaternary structure of protein

Answer 8

More than one polypeptide chain folded and twisted. (Can also contain a non-protein (prosthetic) groups)

Question 9

The primary structure is fundamental in the formation of the subsequent structures. Explain why

Answer 9

● A different sequence of amino acids means
● There are different R groups present
● So there is hydrogen, ionic, disulphide bonds in different places between different R groups
● which changes the tertiary structure
● which ultimately affects the function of protein

Question 10

1) Describe the Biuret Test for Proteins

Answer 10

The Biuret Test
● Add the NaOH
● copper sulphate (too)
● If it turns purple there is protein (for you)!