Nucleic Acids

Question 1

What are the 3 types of nucleic acid?

Answer 1

ATP
DNA
RNA

Question 2

What are the 3 chemical components of nucleic acids?

Answer 2

Pentose sugar
Phosphate group
Backbone

Question 3

Where does the phosphate group of one of the nucleotides join to on the adjacent nucleotide?

Answer 3

The phosphate group at the fifth carbon of the pentose sugar joins to the OH group at the third carbon of the pentose sugar of the other nucleotide

Question 4

What is the name of the covalent bond between nucleotides?

Answer 4

Phosphodiester

Question 5

Name the 3 pyrimidines

Answer 5

Uracil
Thymine
Cytosine

Question 6

Name the 2 purines

Answer 6

Adenine
Guanine

Question 7

What does adenine pair with instead of thymine in RNA?

Answer 7

Uracil

Question 8

What is the base pairing rule?

Answer 8

A pyramidine always pairs with a purine - ensuring the width of the DNA double helix is maintained as a constand

Question 9

How many nitrogen rings do pyrimidines have?

Answer 9

1

Question 10

How many nitrogen rings to purines have?

Answer 10

2

Question 11

Define anti parallel

Answer 11

Each strand of DNA runs opposite to each other - one points up (in a 5’ direction) and the other points down (in a 3’ direction)

Question 12

How is DNA well adapted to its function?

Answer 12

Strong sugar phosphate backbone (held by phosphodiester bonds)
Hydrogen bonds (can be broken by DNA helicase allowing for replication)
Complementary base pairing (ensures that when DNA separates, each strand can act as a template strand allowing for transcription)
DNA molecules can store lots of info (compact as long sequences)

Question 13

What are the 3 differences between RNA and DNA?

Answer 13

In RNA:
Pentose sugar is ribose (not deoxyribose)
Contains uracil (not thymine)
Form single stranded molecules (not double stranded)

Question 14

What are the differences between ATP and DNA+RNA

Answer 14

Only one type of base present - adenine
Pentose sugar is always ribose
Contains 3 phosphate groups linked together

Question 15

What is the similarity between ATP and DNA+RNA?

Answer 15

Consists of a base, a pentose sugar and phosphate

Question 16

What is formed when water is added to ATP?

Answer 16

ADP and inorganic phosphate (Pi) and releases energy

Question 17

What enzyme catalyses the reaction when water is added to ATP?

Answer 17

ATP hydrolase

Question 18

What enzyme catalyses the reaction between Pi group and ADP?

Answer 18

ATP synthase

Question 19

Give the properties of ATP

Answer 19

ATP releases energy in small amounts (none is wasted)
Small and soluble (easily transported around the cell)
Only 1 bond is hydrolyzed to release energy (energy release is immediate)
Can transfer energy to another molecule via phosphorylation (transferring one of its phosphate groups)
ATP cannot leave the cell (cells always have immediate supply of energy)

Question 20

(DNA extraction from plant) Give the reason for homogenisation (pestle and mortar)

Answer 20

destroys cell walls

Question 21

(DNA extraction from plant) give the reason for adding detergent

Answer 21

Disrupts phospholipid bilayer of cell membranes

Question 22

(DNA extraction from plant) give the reason for adding salt

Answer 22

Neutralises the charge of the phosphate groups of sugar so reduces solubility of DNA

Question 23

(DNA extraction from plant) give the reason for adding protease

Answer 23

Hydrolyses histones, leaving only DNA

Question 24

(DNA extraction from plant) give the reason for adding ethanol

Answer 24

So DNA can be seen as white strands

Question 25

Give the steps of DNA replication

Answer 25

- 2 strands of DNA separate, hydrogen bonds between bases break by DNA helicase - free nucleotides attracted to their complementary bases - once the 2 new nucleotides have lined up, they are joined by DNA polymerase - nucleotides join using DNA polymerase = semi conservative replication

Question 26

What is a mutation?

Answer 26

A change in the base sequence

Question 27

What are Okazaki fragments?

Answer 27

Lagging strands (strands that run in the opposite direction - antiparallel) Discontinuous DNA replication

Question 28

How does replication occur of the lagging strands?

Answer 28

- small section of lagging strand is unzipped - free DNA nucleotide bases are attracted to their complementary bases on the lagging strand - DNA polymerase joins together these few nucleotides - DNA ligase joins together the Okazaki fragments

Question 29

What are the 4 features of the genetic code?

Answer 29

Universal - all species use same code Triplet - sequence of 3 bases = codon Non overlapping - each nucleotide base only contributes towards one codon Degenerate - can be more than one codon for an amino acid

Question 30

How many different codons does a triplet code allow for?

Answer 30

64 (4x4x4)

Question 31

Give the steps of DNA transcription?

Answer 31

- section of the DNA containing the gene unwinds and separates into 2 strands by DNA helicase - one strand acts as a template strand for the complementary mRNA strand - free RNA nucleotides pair with their complementary bases on the template strand - RNA polymerase forms phosphodiester bonds between adjacent RNA nucleotides, until the mRNA detaches and leaves the nucleus via nuclear pore

Question 32

How is transcription similar to DNA replication?

Answer 32

Both involve DNA as template Both produce nucleic acids. Both use helicase and polymerase

Question 33

How are transcription and DNA replication different?

Answer 33

DNA replication uses both strands, transcription only uses 1 as a template Replication involves whole length of DNA, transcription only uses a section DNA replication produces a double stranded molecule, transcription only produces a single stranded molecule DNA replication uses DNA polymerase, transcription only uses RNA polymerase

Question 34

Give the steps of translation

Answer 34

- mRNA attaches to a ribosome and tRNA collects amino acids from the cytoplasm and brings the. To the ribosome - tRNA attaches itself to mRNA by complementary base pairing ( max 2 molecules attach to mRNA at a time) - amino acids attached to 2 tRNA molecules join by a peptide bond, then tRNA molecules detach themselves from the aminos acids, leaving them behind - this process is repeated leading to the formation of a polypeptide chain until a stop codon is reached on mRNA and ends the process of protein synthesis