Nucleic Acids and Nucelotides

Question 1

Draw, and label, the basic structure of a nucleotide.

Answer 1

A phosphate group attached to a nitrogenous base attached to a pentose sugar.
They all contain the elements H, P, O, N

Question 2

Draw a nucleotide showing the structure of the pentose sugar and where the phosphate group and nitrogenous base attach using the standard system for numbering the carbons in the sugar.

Answer 2

The phosphate group attaches to the 5’ (prime) carbon.

The base attaches to the 1’ carbon of the pentose.

Question 3

State the two main types of nucleic acid.

Answer 3

Deoxyribonucleic acid

Ribonucleic acid

Question 4

Draw a table to show the similarities and differences between the nucleotides of DNA and RNA.

Answer 4

1. DNA= deoxyribose, RNA= ribose
2. DNA and RNA both have adenine and guanine purines
3. DNA and RNA both have cytosine BUT DNA= Thymine, RNA= Uracil pyradimines

Question 5

Draw the structures of ribose and deoxyribose and identify the difference between the two pentose sugars.

Answer 5

Deoxyribose- on 2’ carbon only has an -H below

Ribose- on 2’ carbon has an -OH below

Question 6

List the full names of the 5 possible nitrogenous bases in nucleic acids.

Answer 6

1. Guanine- Purine
2. Adenine- Purine
3. Thymine- Pyrimidine
4. Cytosine- Pyrimidine
5. Uracil- Pyrimidine

Question 7

Outline the structure of the two types of nitrogenous base.

Answer 7

Purines- larger bases which contain a double carbon ring structure
Pyrimidines- smaller bases which contain a single carbon ring structure

Question 8

Define the term monomer

Answer 8

An individual molecule that makes up a polymer.

Question 9

Define the term polymer

Answer 9

A long-chain molecule composed of bonded multiple individual monomers in a repeating pattern

Question 10

Define the term nucleic acid

Answer 10

Large polymers formed from nucleotides. Contain C, N, P, N, O

Question 11

Define the term polynucleotide

Answer 11

A molecule made up of lots of nucleotide joined together in a long chain.

Question 12

Define the term nucleotide

Answer 12

The monomers used to form nucleic acids. Made up of pentose monosaccharide, a phosphate group and a nitrogenous base.

Question 13

Define the term phosphodiester bond

Answer 13

Covalent bonds formed between the phosphate group of one nucleotide and the hydroxyl group of another.

Question 14

Draw and label a diagram to show how nucleotides can link together to form polynucleotides (including the production of water).

Answer 14

The phosphate group of the 2nd nucleotide bonds to the hydroxyl group of the 3’ carbon of the pentose sugar in the 1st nucleotide to form a phosphodiester bond. This forms a strong, long sugar-phosphate backbone.
This releases a water moleucules

Question 15

State the name of the reaction that joins nucleotides to other nucleotides and the name of the reaction that breaks phosphodiester bonds.

Answer 15

Condensation reaction- releases water

Hydrolysis reaction- breaks the bond using water

Question 16

State 3 main types of activity for which cells require energy.

Answer 16

1. Anabolic reactions- synthesis of large molecules
2. Movement- e.g protein fibres in muscle cells that cause muscle contraction
3. Transportation of ions and molecules across the membrane.

Question 17

Draw and label a diagram of ATP

Answer 17

Has 3 phosphate groups, the base adenine and ribose.

ATP (adenosine triphosphate)

Question 18

Draw and label a diagram of ADP.

Answer 18

Has 2 phosphate groups, the base adenine and ribose.

ADP (adenosine diphosphate)

Question 19

List 2 similarities and 2 differences between the structure of ATP and DNA and RNA nucleotides.

Answer 19

1. RNA and ATP both have a ribose sugar, but DNA had deoxyribose.
2. DNA and RNA both have 1 phosphate group, but ATP has 3.
3. They all have one base.

Question 20

Draw a reaction to show how energy is released from ATP to provide energy for cellular activities.

Answer 20

Energy is stored in the phosphate bond, when energy is needed ATP is broken down to ADP and inorganic phosphate. Energy is released from the phosphate bond and used by the cell.

Question 21

Draw a diagram to show the interconversion of ATP and ADP, the names of the types of reactions involved, where energy is released and the role of respiration.

Answer 21

Hydrolysis- ADP, P and energy is produced from ATP and H2O (energy is release for use by cells)
Condensation- ATP and water is produced from ADP and P (energy is supplied from respiration)

Question 22

State 5 properties of ATP and explain why each makes it ideally suited to function as an energy transfer molecule.

Answer 22

1. Small- moves easily into, out of and within cells
2. Water soluble- energy-requiring processes happen in aquoeus environments.
3. Contains bonds between phosphates- with intermediate energy large enough to be useful for cellular reactions but not so large that energy is wasted
4. Releases energy is small quantities- quantities are suitable to most cellular needs, so energy is wasted as heat.
5. Easily regenerated- can be recharged with energy

Question 23

Define the term phosphorylation

Answer 23

The addition of a phosphate group to a molecule

Question 24

Draw and label a diagram of the structure of DNA.

Answer 24

DNA is composed of two polynucleotide strands joined together by hydrogen bonding in a double-helix shape.
The two polynucleotide strands are anti parallel- this means they run in opposite directions.

Question 25

Define the term complementary base pairing

Answer 25

Specific hydrogen bonding between nucleic acid bases. A-T/U and C-G

Question 26

Define sugar phosphate backbone

Answer 26

A backbone is composed of alternating sugar and phosphate groups, that forms the structural framework of nucleic acids.

Question 27

Define antiparallel

Answer 27

Two parallel strands that are arranged so they run in opposite directions

Question 28

State the complementary base pairing rules, name the bond that holds them together, and state the number of bonds that hold each pair together.

Answer 28

1. Adenine-Thymine/ Uracil form two hydrogen bonds
2. Cytosine- Guanine form 3 hydrogen bonds
   These rules means a small pyrimidine base always binds to a purine base.

Question 29

Explain why a DNA molecule has equal amounts of adenine and thymine and equal amounts of cytosine and guanine.

Answer 29

They always pair up together, so you can’t have one without the other.

Question 30

Describe how purines and pyrimidines are arranged in the complementary base pairing rules.

Answer 30

One pyrimidine always binds to a purine- this maintains a constant distance between the DNA backbones.

Question 31

Describe the significance of the double stranded, complementary base paired nature of DNA for its function.

Answer 31

Complementary base pairing - allows itself to replicate easily
It’s long- stores a lot of information
Coiled into double helix- stores a lot of info in a small space.
It’s stable- double helix and backbone

Question 32

Describe the significance of the sequence of bases in a DNA strand for its function.

Answer 32

The sequence of bases allow it to carry coded information for the synthesis of proteins.

Question 33

Describe, and explain the importance of the steps in the isolation and purification of DNA by precipitation.

Answer 33

1. Grind sample- breaks cell wall
2. Mix with detergent- breaks cell membrane, releasing cell contents into solution
3. Add salt- breaks H bonds between the DNA and water molecules.
4. Add protease enzymes- break proteins associated with DNA in nuclei.
5. Add layer of alcohol on top of sample- causes DNA to precipitate out of solution
6. White strands will form- DNA- between layer of sample and layer of alcohol