Proteins

Question 1

How do polypeptides arrange themselves to form the secondary structure and tertiary structure of a protein?

Answer 1

SECONDARY STRUCTURE
-Attraction occurs between the overall positive charge of the hydrogen and the overall negative charge of the O within a single polypeptide.
-This causes the chain to twist into either an alpha-helix or a beta pleated sheet.

TERTIARY STRUCTURE
-Further twisting and bonding causes an even more specific shape.
-New bonds are formed: 1) Disulfide bridges between sulfur atoms 2) Further ionic bonds, broken by a change in pH 3) Hydrogen bonds, numerous but easily broken

Question 1

How do amino acids link together to form polypeptides?

Answer 1

-Amino acids undergo condensation reactions to form peptide bonds.
-The peptide bond formed is between the amine group and carboxyl group of the amino acid, eliminating a water molecule.
-Polypeptide chains are referred to as the primary structure of a protein.

Question 2

How is the quaternarny structure of a protein formed?

Answer 2

-Polypeptide chains bond together
-Prosthetic groups may be associated with the molecules

Question 3

What is the test for proteins?

Answer 3

-Place a sample of the solution into a test tube and add an equal volume of sodium hydroxide solution at room temperature.
-Add a few drops of dilute copper(II) sulfate solution and mix gently.
-A purple coloration indicats the presence of peptide bonds and hence a protein. If no protein is present, the solution remains blue.