Biochemistry Packet
Part 4: Nucleic Acids
Directions: Using chapter 24 in the Chemistry 1 book to answer the following questions about nucleic
acids
1. Define nucleic acid
Information storage molecules found in the nucleus of cells
2. What is the monomer of the nucleic acid polymer?
Nucleotide
3. What are three structural features of a nucleotide?
a. Phosphate group
b. Nitrogen containing base
c. Sugar – 5 or 6 carbon sugar
4. Which of the three structural features is the same in all nucleotides? Phosphate group
5. Describe or sketch how the three structural features are bonded to form a nucleic acid polymer.
6. What kind of bonds hold together the backbone of the nucleic acid?
(ionic/covalent/intermolecular forces)
7. What kind of bonds hold together the three dimensional structure (e.g. helix) of nucleic acids?
Intermolecular forces/ hydrogen bonds
8. DNA is an important nucleic acid made up of 4 different organic/nitrogen bases. RNA has 3 of
the same bases + 1 more. Identify them below:
NH2
NH2
N
N
N
NH
N
adenine
NH
cytosine
O
N
O
NH
O
NH
N
guanine
NH2
O
NH
NH
uracil
O
H3C
NH
NH
thymine
O
9. Describe how the DNA double helix is formed
There is a phosphate/sugar backbone. Nitrogen bases are attached to sugars. Each strand has a
staircase shape because of the way the sugar bonds to the phosphate and the way the nitrogen base
bonds to the sugar. Two strands (backbone + nitrogen bases) bond together kind of like a zipper. The
teeth are the nitrogen bases which hydrogen bond with only certain other nitrogen bases – called base
pairing. Because of the staircase shape and the base-pairing, DNA gets the double helix shape.
10. Cut out the structures attached and arrange with the right orientation then draw in the bonding
between the base-pairs (hint see fig 24.18)
11. Cut out the two base pairs below. Arrange them with the correct orientation to show that they
cannot hydrogen bond. Use this to explain why adenine always bonds with thymine and
cytosine always bonds with guanine.
For number 10:
H
N
H
NH
N
NH
N
N
N
O
H
N
N
H
N
H
NH
For number 11:
NH
N
N
N
O
H
O
NH
N
H
H
O
NH
N
O
H
N
H
N
H
O
N
H
O