How can two amino acids, ‘A’ and ‘B’, that are far apart along the polypeptide chain somehow end up next to each other in an active site? [4m]

Editor’s note: similar to questions asking is it necessary for amino acids at active site/ amino acids in tertiary structure to be close together in primary structure

1. STRUCTURES

The primary structure (unique number and linear sequence of amino acids) of the enzyme, which consists of the sequences and lengths of its amino acids, determine the secondary and tertiary structures.

The final shape of the protein is due to its primary structure, which refers to type, number and sequence of amino acids.

2. BONDS & INTERACTIONS

The polypeptide chain is folded into its secondary structure, either as an α-helix or β-pleated sheet, through hydrogen bonding between the CO and NH groups, along the polypeptide backbone.

The secondary structure is further folded and twisted into its tertiary structure by various interactions between the different R groups of the different amino acids; via hydrogen bonds, ionic bonds, hydrophobic interactions and disulphide linkages.

3. 3D CONFORMATION

The folding and twisting of the polypeptide chain forms the 3D conformation of the enzyme, which results in a globular structure such that the amino acid residues far apart in the primary structure can be brought closer together in the active site.

Describe:

State in words the main points of the topic –either phenomena or experiments

implies answer should include reference to (visual observations) associated with phenomena

 GIVE OBSERVATIONS!! WHAT CAN BE SEEN

Eg. Describe the differences between X and Y

Compare X and Y.

Note: Point-to-point comparison between X and Y is needed

Explain:

May imply reasoning or some reference to theory, depending on context

GIVE REASONS!! ANSWER THE ‘WHY”

EXPLAIN= Describe + give reasons.  Students have to quote values if a figure/ graph/table was given in the question.