1.5

Question 1

What are amino acids? (2)

Answer 1

(1) they’re the BASIC MONOMERS…
(2) that make up the polymer = POLYPEPTIDE

Question 2

What is the structure of an amino acid? (5)

Answer 2

(1) it has a CENTRAL C atom that’s bonded to…
(2) - an NH2 (amine) group
(3) - a COOH (carboxyl) group
(4) - a HYDROGEN atom
(5) - an R group, which is a group that every amino acid has a different one of.

Question 3

How does a peptide bond form between 2 amino acids? (4)

Answer 3

(1) in a CONDENSATION reaction…
(2) where an OH from the COOH of 1 AA binds to an H from the NH2 of the other AA…
(3) to FORM WATER
(4) so the C from the first AA binds to the N from the other AA, which is a peptide bond

Question 4

What are the 4 structure types of proteins? (4)

Answer 4

(1) primary
(2) secondary
(3) tertiary
(4) quaternary

Question 5

Describe the primary structure of proteins. (3)

Answer 5

(1) many AA monomers can be JOINED together by POLYMERISATION…
(2) forming a POLYPEPTIDE chain
(3) but every chain has its specific sequence of AA, which determines its shape, therefore its function.

Question 6

Describe the secondary structure of proteins. (3)

Answer 6

(1) In the peptide bond, the H of the NH group has a + charge & the O of the CO group has a - charge…
(2) so these 2 groups READILY form WEAK HYDROGEN BONDS,
(3) which causes the polypeptide chain to TWIST into an a-HELIX shape.

Question 7

Describe the tertiary structure of proteins. (5)

Answer 7

(1) the a-helices of the secondary structure is twisted & folded even more to make it MORE COMPLEX
(2) the structure is maintained by:
- DISULFIDE BONDS: strong
- IONIC BONDS: formed between groups that aren’t involved in forming peptide bonds. they’re WEAKER than disulfide bonds. (broken by pH change)
- HYDROGEN BONDS: numerous but easily broken
(3) the 3-D shape of a protein determines how it functions

Question 8

Describe the quaternary structure of proteins. (3)

Answer 8

(1) COMPLEX molecules…
(2) containing a NUMBER of POLYPEPTIDE chains that are linked together.
(3) SOMETIMES, there can be PROSTHETIC groups associated with the chains.

Question 9

Describe how to test for proteins. (5)

Answer 9

(1) place the sample of the solution in a test tube
(2) add an equal volume of NaOH to the solution at ROOM TEMP
(3) add a FEW DROPS of VERY DILUTE copper(ll) sulfate solution
(4) mix gently
(5) protein present = purple coloration, protein NOT present = blue.