Module 2: section 3 - Nucleotides And Nucleic Acids

Question 1

What is a nucleotide?

Answer 1

Monomer from which nucleic acids ,like DNA and RNA are formed

Question 2

What is the basic structure of a nucleotide

Answer 2

Pentose sugar(made of 5 carbons)
A phosphate group
A nitrogenous base

Question 3

What is a polynucleotide

Answer 3

Polymer of nucleotides

Question 4

How do nucleotides join and what bond do they form

Answer 4

Via a condensation reaction between a phosphate group of one nucleotide and the sugar of another
and they form a phosphodiester bond

Question 5

What are the bonds between bases

Answer 5

Hydrogen

Question 6

What is anti parallel orientation

Answer 6

Helix’s two strands run in opposite directions

Question 7

What is complementary base pairing

Answer 7

Each base can only join with one particular partner

Question 8

What bases pair with each-other in DNA

Answer 8

Adenine and thymine
Guanine and cytosine

Question 9

How many hydrogen bonds form between A and T and G and C

Answer 9

A and T= 2
G and C =3

Question 10

Why is the hydrogen bonds being weak so important

Answer 10

It allows the DNA to separate so replication and transcription can occur

Question 11

What does DNA being semi conservative mean

Answer 11

One strand from the original polynucleotide and the other is a new complementary strand

Question 12

What is helicase and what does it do

Answer 12

It’s and enzyme
It breaks the hydrogen bonds between the base pairs on the two polynucleotide DNA strands

Question 13

What is polymerase and
what does it do

Answer 13

It’s an enzyme
It forms phosphodiester bonds between the nucleotides

Question 14

What is the process of DNA replication

Answer 14

1) DNA helicase breaks hydrogen bonds between base pairs, unwinding the helix to form two single strands
2) free floating nucleotides form hydrogen bonds with complementary bases
3) condensation reaction join the nucleotides of the new strands together using DNA polymerase

Question 15

What does it mean when it states a code is degenerate

Answer 15

Multiple codons can encode a single amino acid

Question 16

Is DNA or RNA a nucleic acid

Answer 16

Both

Question 17

What are the two categories nitrogenous bases can be categorised into

Answer 17

purines and pyrimidines

Question 18

How many carbon-nitrogen rings do purines have and what are the examples

Answer 18

Have 2 carbon-nitrogen rings
adenine and guanine

Question 19

How many carbon-nitrogen rings do pyrimidines have and what are the examples

Answer 19

Has 1 carbon-nitrogen ring
thymine, uracil and cytosine

Question 20

What are the sugars in RNA and DNA called

Answer 20

RNA-ribose (sugar)
DNA- deoxyribose(sugar)
*in exam refer to the type of sugar or you don’t get a mark

Question 21

What is ATP’s structure

Answer 21

a pentose sugar (ribose)
a nitrogenous base (always adenine)
three phosphate groups

Question 22

How is ATP made

Answer 22

ADP+ Pi –>ATP+ H2O
Made during both types of respiration via a condensation reaction and using the enzyme ATP synthase

Question 23

How does ATP release energy

Answer 23

-It is hydrolysed using the enzyme ATP hydrolase
- Breaking one of the Phosphoanhydride bonds between the phosphate group releases a small amount of energy

Question 24

What is phosphorylation

Answer 24

when the inorganic phosphate released can bond onto a completely different compound to make them more reactive

Question 25

How does DNA structure relate to its function

Answer 25

-stable structure due to the sugar phosphate backbone (covalent bonds) and the double helix -double stranded so replication can occur using both strands as a template -weak hydrogen bonds between bases for easy separation of the two strands in a double helix during replication -complementary base pairing allows identical copies to be made

Question 26

what are the three types of RNA

Answer 26

-mRNA -tRNA -rRNA

Question 27

What is mRNA

Answer 27

a copy of one gene from DNA

Question 28

what is a codon

Answer 28

three bases on mRNA that codes for a specific amino acid

Question 29

what does the 5'(prime) end or 3' (prime) end mean

Answer 29

these numbers refer to what which carbon in the deoxyribose sugar is closest to the top/bottom

Question 30

What are the special features of the genetic code

Answer 30

degenerate, universal and non overlapping

Question 31

what does the term universal mean

Answer 31

the same triplet of bases codes for the same amino acid in all organisms

Question 32

what does the term non overlapping mean

Answer 32

each base in a gene is only part of one triplet of bases that codes for one amino acid

Question 33

What happens in transcription

Answer 33

mRNA is created from a copy of one gene on DNA

Question 34

What happens in translation

Answer 34

where mRNA joins with a ribosome and a corresponding tRNA molecule brings the specific amino acid the codon codes for

Question 35

what is a nucleic acid

Answer 35

A nucleic acid is a chain of nucleotides which stores genetic information in biological systems

Question 36

describe the process of transcription

Answer 36

1) DNA helicase breaks the hydrogen bonds between the bases 2) this causes the DNA helix to unwind and one strand acts as a template 3) Free mRNA nucleotides align opposite exposed complementary DNA bases 4)The enzyme RNA polymerase joins together the adjacent RNA nucleotides, forming phosphodiester bonds to create a new mRNA polymer chain

Question 37

describe the process of translation

Answer 37

1)once the modified mRNA has left the nucleus it attaches to the small subunit of the ribosome at the start codon 2) The tRNA molecule with the complementary anticodon to the start codon aligns opposite the mRNA held in place by the ribosome. The ribosome can hold 2 tRNA molecules at one time. 3) The two amino acid that have been delivered together are joined together via a peptide bond 4)The ribosome will move along the mRNA molecule to the next codon and another complementary tRNA will attach to the next codon 5)This continues until the ribosome reaches the stop codon at the end of the mRNA molecule causing the ribosome to detach and end translation

Question 38

compare DNA transcription and replication

Answer 38

Similarities · DNA unwinds and unzips · Helicase enzymes · Template DNA · Complementary base pairing · Hydrogen bonds · Free, activated nucleotides · Polymerase enzymes Differences · Only a small section of DNA (where the gene is located) unzips during transcription · Both strands act as templates in replication · RNA vs DNA free nucleotides · RNA vs DNA polymerase · Different helicase enzymes · Products are two new daughter strands of DNA in replication and one mRNA strand in transcription · mRNA leaves nucleus whereas the new DNA strand remains bound to the template strand

Question 39

what elements do all nucleotides contain

Answer 39

carbon hydrogen oxygen nitrogen phosphorus

Question 40

What are the steps involved in purifying DNA using ethanol precipitation?

Answer 40

1)Cell Lysis: Break open the cells using a detergent solution (e.g., sodium dodecyl sulphate, SDS) to release DNA. 2)Remove Contaminants: Add a salt solution (e.g., sodium chloride) to neutralize DNA and help remove proteins and lipids. Precipitate DNA: Add ice-cold ethanol to the mixture. DNA will precipitate out of the solution. 3)Collect DNA: Centrifuge the solution to form a DNA pellet at the bottom of the tube. Wash and Dry: Wash the DNA pellet with cold ethanol to remove impurities and air-dry the DNA.