2.3 Nucleic Acid

Question 1

What are the 3 components that make up a deoxyribonucleic acid (DNA) nucleotide?

Answer 1

• a deoxyribose sugar
• a phosphate group
• a nitrogenous base (A,C,G or T)

Question 2

What are the 3 components that make up a ribonucleic acid (RNA) nucleotide?

Answer 2

• a ribose sugar
• a phosphate group
• a nitrogenous base (A,C,G or U)

Question 3

What bond forms between the complementary bases?

Answer 3

Hydrogen Bond

Question 4

How many polynucleotide strands make up DNA?

Answer 4

2

Question 5

How many polynucleotide strands make up RNA?

Answer 5

1

Question 6

How is a polynucleotide strand formed?

Answer 6

Two nucleotides bond together in a condensation reaction. A phosphodiester bond forms between the sugar-phosphate backbones of the two nucleotides.

Question 7

What are the functions of DNA?

Answer 7

• is the genetic material for all living organisms
• has code instructing cells what proteins to make
• has the entire genetic content of the cell.

Question 8

What are the functions of RNA?

Answer 8

• involved in synthesising proteins (transcription)

- a component of ribosomes

Question 9

What is mRNA?

Answer 9

DNA never leaves the nucleus so it uses messenger RNA to transfer genetic information to the rest of the cell.

Question 10

Why is DNA replication semi conservative?

Answer 10

One polynucleotide strand is conserved as a template strand and one new strand is made. Half of the old DNA has been conserved.

Question 11

What is Adenosine Triphosphate (ATP)?

Answer 11

The primary energy currency of cells.

Question 12

What does ATP consist of?

Answer 12

• adenine base
• ribose sugar
• 3 phosphate groups

Question 13

What does the hydrolysis of ATP release?

Answer 13

Energy

Question 14

Describe the hydrolysis of ATP.

Answer 14

ATP combines with water to produce ADP (adenosine diphosphate) and an inorganic phosphate group. This releases energy. The hydrolysis of ATP is catalysed by ATP hydrolase.

Question 15

Describe the condensation of ATP.

Answer 15

ADP combines with an inorganic phosphate group and energy to produce ATP and water. This reaction requires energy and is reversible. The condensation of ATP is catalysed by ATP resynthase.

Question 16

Which enzyme breaks the hydrogen bond between the complementary bases of the polynucleotide strands?

Answer 16

DNA helicase

Question 17

Which enzyme forms phosphodiester bonds between adjacent nucleotides?

Answer 17

DNA polymerase

Question 18

Why must a cell duplicate its DNA?

Answer 18

Because when a cell divides it forms two new daughter cells.

Question 19

Describe DNA replication.

Answer 19

1) DNA helicase binds to the DNA and breaks the hydrogen bonds between the two polynucleotide strands. This unwinds the DNA.
2) Free floating nucleotides bind to the template DNA strand and a new strand is formed.
3) DNA polymerase forms phosphodiester bonds between the new adjacent nucleotides.

Question 20

What is transcription?

Answer 20

The process of making messenger RNA from a DNA template.

Question 21

Describe transcription.

Answer 21

1) DNA helicase unzips the hydrogen bonds between the polynucleotides
2) RNA polymerase catalyses temporary hydrogen bonds between the complementary bases of the template DNA and the free floating RNA nucleotides
3) The mRNA is complementary to the DNA and passes out of the nucleus.

Question 22

What is translation?

Answer 22

The formation of proteins at the ribosome according to instructions in the mRNA.

Question 23

Describe translation.

Answer 23

1) tRNA molecules bind to the mRNA and bring amino acids with them.
2) The ribosomes move over the mRNA and read the code
3) Peptide bonds form between the amino acids until the stop codon is reached
4) The order of amino acids is determined by the order of nucleotides in the DNA
This process requires energy.

Question 24

Which nitrogenous bases are purines?

Answer 24

Adenine and Guanine

Question 25

Which nitrogenous bases are pyrimidines?

Answer 25

Cytosine and Thymine?