Chapter 2 Nucleic Acids

Question 1

What are the two types of nucleic acid?

Answer 1

RNA - Ribonucleic Acid
DNA - Deoxyribonucleic Acid

Question 2

What is the role of DNA?

Answer 2

It carries genetic information

Question 3

What is the role of mRNA?

Answer 3

It transfers genetic information from DNA to the ribosomes.

Question 4

Name the monomer of a nucleic acid.

Answer 4

Nucleotide

Question 5

State the three components to a nucleotide.

Answer 5

Pentose sugar + Nitrogen containing organic base + Phosphate group

Question 6

State the five possible bases of a nucleotide.

Answer 6

Adenine, guanine, thymine, cytosine, uracil

Question 7

What is a pentose sugar?

Answer 7

A sugar which contains 5 carbons.

Question 8

What is the pentose sugar present in DNA?

Answer 8

Deoxyribose

Question 9

What is the pentose sugar present in RNA?

Answer 9

Ribose

Question 10

What type of reaction binds nucleotides to form a sugar phosphate backbone?

Answer 10

Condensation reaction

Question 11

What bond is formed when two nucleotides are combined?

Answer 11

A phosphodiester bond

Question 12

What is one nucleotide by itself called?

Answer 12

A mononucleotide

Question 13

What are two bonded nucleotides called?

Answer 13

Dinucleotides

Question 14

What is a long chain of nucleotides called?

Answer 14

A polynucleotide.

Question 15

Describe the structure of DNA.

Answer 15

A DNA molecule is a double helix with two polynucleotide chains held together by hydrogen bonds between specific complementary base pairs.

Question 16

Give 5 ways that the structure of DNA is related to its function.

Answer 16

1. It has a very stable structure which can pass from generation to generation without change
2. It contains two separate strands joined by hydrogen bonds to allow for replication.
3. It is a large molecule so carries large amount of genetic information.
4. The genetic information is protected by the sugar-phosphate backbone.
5. Base pairing leads to DNA being able to replicate and transfer information as mRNA.

Question 17

State the complementary base pairings.

Answer 17

A-T/U, C-G

Question 18

State the number of hydrogen bonds formed between adenine and thymine/uracil.

Answer 18

2

Question 19

State the number of hydrogen bonds formed between cytosine and guanine.

Answer 19

3

Question 20

Describe the structure of RNA

Answer 20

An RNA molecule is a relatively short polynucleotide chain/ single strand.

Question 21

What are the three differences between DNA and RNA?

Answer 21

1. DNA is double stranded; RNA is single stranded
2. DNA has deoxyribose; RNA has ribose
3. DNA has thymine; RNA has uracil

Question 22

How does complementary base pairing allow us to work out the frequency of relative bases?

Answer 22

Knowing the frequency of one base will indicate the frequency of its complementary pair. Knowing the frequency of all bases equal to 1 or 100% will allow the other bases to be calculated.

Question 23

State the mechanism of DNA replication.

Answer 23

Semi-conservative replication.

Question 24

Describe semi-conservative replication

Answer 24

DNA helicase causes the two strand of DNA to separate, free nucleotides bind to their complementary bases, they are joined together by DNA polymerase which makes phosphodiester bonds

Question 25

Why is semi-conservative replication important in the genetic continuity between cells?

Answer 25

It ensures genetic continuity between generations of cells. It means that there will always be a strand of the former DNA molecule used as a template. Semi-conservative means half is preserved, half is new.

Question 26

What are the main stages in DNA replication?

Answer 26

1. DNA unwinds. 2. Hydrogen bonds break. 3. New nucleotides attracted to the template strands. 4. Condensation reactions bond nucleotides together.

Question 27

State the enzymes involved in DNA replication.

Answer 27

DNA helicase + DNA polymerase

Question 28

What does DNA helicase do?

Answer 28

It unwinds the DNA and breaks the hydrogen bonds.

Question 29

What does DNA polymerase do?

Answer 29

Catalyses the condensation reaction creating phosphodiester bonds between nucleotides. This forms the sugar-phosphate backbone

Question 30

The two strands of the double helix are ............. to each other, in terms of direction.

Answer 30

Antiparallel

Question 31

What are the new strands of DNA formed from?

Answer 31

Free nucleotides.

Question 32

How do the free nucleotides get into the right order when they form the new strand of DNA during replication?

Answer 32

The original strand acts as a template and the free nucleotides attach to complementary bases by specific base pairing.

Question 33

How was semi conservative replication proven true?

Answer 33

DNA was marked with a heavy nitrogen isotope It was then replicated using a light nitrogen isotope The mass of the DNA was determined by which isotopes it contained. By centrifuging the solution the DNA was separated by mass. The results showed that DNA strands were separating and forming a new strand each generation. Parent DNA was shown to be all heavy nitrogen isotope The 1st Generation DNA was shown to be half heavy and half light isotope. The 2nd generation was either half and half or entirely light.

Question 34

Give 4 things that make ATP a suitable energy source for cells.

Answer 34

1. ATP releases manageable amounts of energy. 2. It releases energy instantaneously 3. ATP phosphorylates other compounds so they are more reactive. 4. ATP can be rapidly re-synthesised.

Question 35

Give 5 uses of ATP.

Answer 35

1. Metabolic processes 2. Movement(muscle contraction) 3. Active transport 4. Secretion 5. Activation of molecules

Question 36

Give 5 properties of water.

Answer 36

1. It is a polar molecule 2. There are hydrogen bonds between molecules 3. It has a high specific heat capacity. 4. It has a high latent heat of evaporation. 5. There is cohesion and surface tension between molecules.

Question 37

What is the importance of water to living organisms?

Answer 37

In metabolism water is used to break down complex molecules(hydrolysis). It acts as a solvent, water readily dissolves other substances.