Amino Acids And Proteins

Question 1

What are the different structures of amino acids at

• a low pH
• an intermediate pH
• a high pH

Answer 1

Low:
NH3+-CHR-COOH
Intermediate:
Zwitterion
High:
NH2-CHR-COO-

Question 2

What are the 4 classes of amino acids?

Answer 2

• polar acidic
• polar basic
• polar neutral
• non-polar

Question 3

How is a peptide bond formed?

Answer 3

• condensation reaction
• loss of water molecule
• carboxyl group of one amino acid joins with the amine group of another amino acid

Question 4

What is the primary structure of a protein?

Answer 4

The sequence of amino acids

Question 5

What is the secondary structure of a protein?

Answer 5

The folding of the primary structure to form an alpha-helix or beta-pleated sheet

Question 6

What is the tertiary structure of a protein?

Answer 6

Further folding of helixes and sheets into more densely packed globular structures
With weak chemical bonds: hydrogen, ionic, hydrophobic-hydrophilic interactions and disulphide bridges

Question 7

What is the quaternary structure of a protein?

Answer 7

More than one polypeptide chain with the same bonds as in the tertiary structure

Question 8

What is the genetic code?

Answer 8

• the concept whereby each protein is composed of a unique sequence of amino acids which is specified by a gene
• folding of the polypeptide is determined by the primary sequence
• changes in the sequence leads to an altered structure and therefore altered function

Question 9

What are the genetics behind sickle cell anaemia

Answer 9

• caused by a substitution mutation
• glu (which is negative) is replaced by val (which is hydrophobic)
• this causes Hb to for, insoluble fibres which causes them to stick together
• this distorts the normal disc shape of the RBC to form a sickle shape
• this blocks capillaries and causes breakage of fragile cells= anaemia