General properties of proteins

Question 1

What is the general structure of an amino acid?

Answer 1

• Carboxyl group
• Amine group
• R group

Question 2

How many amino acids are common in all organisms?

Answer 2

20 that only differ in their R group

Question 3

How do amino acids join together?

Answer 3

condensation reaction removes a molecule of water between carboxyl group of 1 & amine group of another forming a peptide bond

Question 4

What are dipeptides & polypeptides?

Answer 4

• dipeptides are 2 amino acids joined together
• polypeptides are many amino acids together

Question 5

What is the primary structure of a protein?

Answer 5

the sequence of amino acids in a polypeptide chain joined by peptide bonds

Question 6

What is the secondary structure of protein?

Answer 6

folding of polypeptide chain forming beta pleated sheets or alpha helix due to hydrogen bonds between NH of 1 amino acids & C=O of another

Question 7

What is the tertiary structure of a protein?

Answer 7

• 3D folding of polypeptide - chain formed by interactions between R groups
• forms H bonds, ionic bonds & disulfide bridges

Question 8

What is the quaternary structure of a protein?

Answer 8

more than 1 polypeptide chain formed by interactions between them from the H bonds, ionic bonds & disulfide bridges

Question 9

What is the test for proteins?

Answer 9

1. add biuret reagent (sodium hydroxide + copper (ll) sulfate to sample
2. Positive result shows purple colour