Proteins

Question 1

What is a proteome?

Answer 1

The proteome is the entire set of proteins expressed by a genome

Question 2

How is the proteome larger than the number of genes?

Answer 2

The proteome is larger than the number of genes due to alternative RNA splicing and post-translational modification. Not all genes are expressed as proteins in a particular cell.

Question 3

Describe the primary structure of a protein

Answer 3

The primary structure is the sequence in which amino acids are synthesised into a polypeptide.

Question 4

Describe the secondary structure of a protein

Answer 4

Hydrogen bonding along the backbone of the protein strand results in regions of secondary structure - alpha helices, parallel or anti-parallel beta sheets.

Question 5

Describe the main classes of R groups present in the structure of amino acids

Answer 5

Basic (positively charged), acidic (negatively charged), polar and hydrophobic

Question 6

Describe the tertiary structure of a protein

Answer 6

The polypeptide folds into a tertiary structure, this conformation is caused by bonding, such as interactions of the R groups in hydrophobic regions, ionic bonds, van der waals interactions (including hydrogen bonding) and disulphide bridges. They may also include prosthetic groups. Prosthetic group is a non-protein unit tightly bound to a protein necessary for its function

Question 7

Describe the quaternary structure of a protein

Answer 7

Quaternary structure exists in proteins with several connected polypeptide subunits.