Core Concepts (Nucleic Acids)

Question 1

What are the monomers of
nucleic acids?

Answer 1

Nucleotides

Question 2

State the three components of
nucleotides.

Answer 2

● Pentose sugar
● Nitrogenous base
● Phosphate group

Question 3

Draw the structure of a nucleotide.

Answer 3

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Question 4

What are the two types of organic base?

Answer 4

Purine and pyrimidine

Question 5

DEL

Answer 5

DEL

Question 6

What is a purine?

Answer 6

● Class of organic bases
● Double ring structure
● Includes adenine (A) and guanine (G)

Question 7

What is a pyrimidine?

Answer 7

● Class of organic bases
● Single ring structure
● Includes cytosine (C), thymine (T), uracil (U)

Question 8

Describe the structure of a DNA
nucleotide.

Answer 8

● Deoxyribose
● Organic base (A, T, C or G)
● Phosphate group

Question 9

Describe the structure of an RNA
nucleotide.

Answer 9

● Ribose
● Organic base (A, U, C or G)
● Phosphate group

Question 10

Describe the structure of an ATP
nucleotide.

Answer 10

● Ribose
● Adenine
● Three phosphate groups

Question 11

What is an endergonic reaction?

Answer 11

A non-spontaneous reaction that
requires an input of energy, e.g. ATP
formation.

Question 12

What is an exergonic reaction?

Answer 12

A spontaneous reaction that overall
releases energy, e.g. ATP hydrolysis.

Question 13

DEL

Answer 13

DEL

Question 14

Describe the role of ATP.

Answer 14

Universal energy currency. Hydrolysed to
release energy:
ATP + Water ⇌ ADP + Pi + Energy

Question 15

What is complementary base pairing?

Answer 15

● Describes how hydrogen bonds form between
complementary purine and pyrimidine bases
● Two bonds form between A and T (or U)
● Three bonds form between G and C

Question 16

Describe the structure of DNA.

Answer 16

● Double-stranded polymer of nucleotides twisted to form a
double helix
● Nucleotides joined by phosphodiester bonds
● Hydrogen bonds form between complementary base pairs,
A and T, C and G
● Antiparallel strands

Question 17

Why are the strands of a DNA double
helix described as ‘antiparallel’?

Answer 17

The complementary strands run parallel but
in opposite directions, 5’ to 3’ and 3’ to 5’.

Question 18

Describe the structure of RNA.

Answer 18

● Single-stranded polymer of nucleotides
● Nucleotides joined by phosphodiester bonds
● Hydrogen bonds form between complementary base
pairs, A and U, C and G

Question 19

Name the three types of RNA
found in cells.

Answer 19

● Transfer RNA (tRNA)
● Messenger RNA (mRNA)
● Ribosomal RNA (rRNA)

Question 20

What is the function of tRNA?

Answer 20

It carries specific amino acids to the
ribosomes

Question 21

Describe the structure of tRNA.

Answer 21

● 80 nucleotides
● Single helix
● Clover leaf shape
● Anticodon on one end, amino acid binding
site on the other

Question 22

What is the function of mRNA?

Answer 22

Carries genetic information from the
nucleus to the ribosomes for protein
synthesis.

Question 23

Describe the structure of mRNA.

Answer 23

• 2000 nucleotides
  ● Single helix
  ● Unstable

Question 24

What is the function of rRNA?

Answer 24

Associates with proteins in the cytoplasm
to form ribosomes.

Question 25

Describe the structure of rRNA.

Answer 25

● 1800 to 5000 nucleotides ● Two subunits: one large, one small

Question 26

What is semi-conservative replication?

Answer 26

The replication of DNA to produce two new DNA molecules which both contain one new strand and one old strand from the original DNA molecule.

Question 27

What is the role of DNA helicase in semi-conservative replication?

Answer 27

It catalyses the unzipping of double-stranded DNA into two single strands, each of which acts as a template.

Question 28

What is the role of DNA polymerase in semi-conservative replication?

Answer 28

It catalyses the formation of phosphodiester bonds between nucleotides during the synthesis of a new DNA strand.

Question 29

What is the genetic code?

Answer 29

The rules by which triplets in a DNA base sequence code for the sequence of amino acids in a polypeptide chain. The genetic code is degenerate, universal and non-overlapping.

Question 30

Why is the genetic code described as degenerate?

Answer 30

More than one triplet can code for a particular amino acid.

Question 31

Why is the genetic code described as universal?

Answer 31

The same codons code for the same amino acids in almost all organisms.

Question 32

What is meant by ‘non-overlapping’?

Answer 32

Each base in a sequence is read once and is only part of one triplet

Question 33

Describe the ‘triplet code’ for amino acids.

Answer 33

A specific sequence of three nucleotides (known as a codon) on a molecule of DNA or RNA codes for a particular amino acid in protein synthesis.

Question 34

What is an exon?

Answer 34

A region of DNA that codes for an amino acid sequence.