3.8 NUCLEIC ACIDS

Question 1

Why are some acids ‘nucleic’?

Answer 1

as they were found in the nucleus of a cell (and are quite acidic when in a solution) - by Friedrich Miescher in 1868.

Question 2

What components do almost every human cell contain?

Answer 2

46 chromosomes, 2 metres of DNA, around 3 billion nucleotides

Question 3

What are them main nucleic acids?

Answer 3

DNA and RNA

Question 4

How do base pairs bond with each other?

Answer 4

under neutral conditions the remaining OH group of the phosphate is deprotonated, and oxygen atoms bear a positive charge - this masks the basic properties of the phosphate, allowing hydrogen bonds to form between the base pairs.

Question 5

What are nucleotides?

Answer 5

monomers of nucleic acids (nucleic acids are polymers of nucleotides)

Question 6

What are the three subunits of a nucleotide?

Answer 6

Phosphate group, Pentose sugar, a nitrogenous base.

Question 7

What are the components/ types of nitrogenous base?

Answer 7

Adenine, Thymine (Uracil as RNA), Guanine, Cytosine.
They are organic, and are made of nitrogen and carbon.

Question 8

What are the components of the phosphate group?

Answer 8

Inorganic, PO4 2-.
One phosphorous and 4 oxygen (bottom one is double bonded 3 are single bonded).

Question 9

What are the components of a pentose sugar?

Answer 9

organic, monosaccharide, 5 carbon sugar, 3’ joins to next nucleotide.

Question 10

What are the differences between RNA and DNA?

Answer 10

DNA is double stranded, RNA is single stranded.
DNA has deoxyribose pentose sugar, RNA has ribose pentose sugar.
Adenine pairs with Uracil in RNA, and Thymine in DNA.
Found in nucleus in eukaryote and cytoplasm in prokaryote in DNA, found in/out of nucleus in eukaryote, and cytoplasm in prokaryote.

Question 11

What is the symbol equation for DNA/ RNA?

Answer 11

DNA = C5 H10 O4
RNA = C5 H10 O5

Question 12

What are the pyrimidine bases in DNA and RNA?

Answer 12

Cytosine/ Thymine (Uracil)
They are the smaller bases.

Question 13

What are the purine bases in DNA and RNA?

Answer 13

Adenine/ Guanine
They are the larger bases.

Question 14

What does planar mean?

Answer 14

Flat - a component of the nitrogenous bases.

Question 15

How many bonds are between Thymine (uracil) and Adenine?

Answer 15

2 Hydrogen bonds

Question 16

How many bonds are between Cytosine and Guanine?

Answer 16

3 hydrogen bonds

Question 17

How many DNA base pairs are there on Earth?

Answer 17

5.0 x 10 37
mass of 50 billion tonnes

Question 18

What does base pairing allow?

Answer 18

Allows DNA polymerase to replicate DNA and RNA polymerase to transcribe DNA to RNA.

Question 19

What are phosphodiester bonds?

Answer 19

Strong covalent bonds which hold polynucleotide together (sugar to the next phosphate)

Question 20

How can the two DNA stands be held together?

Answer 20

The first strand runs in a 5’ to 3’ direction and acts as a template strand. The second strand is antiparallel and runs in a 3’ to 5’ direction.

Question 21

What is Uracil?

Answer 21

Demethylated form of Thymine found in RNA.

Question 22

What type of base pair does Uracil form with Adenine in RNA?

Answer 22

Watson- Crick base pair with only two hydrogen bonds in between.

Question 23

In what form is RNA found in nature as?

Answer 23

A single stranded molecule, folded onto itself, shorter than a DNA molecule.

Question 24

What shape does DNA form?

Answer 24

A double helix

Question 25

What does labile mean?

Answer 25

RNA is more labile than DNA so it breaks down easier making it more unstable. This lowers the activation energy needed for hydrolysis.

Question 26

How do many viruses encode their genetic information?

Answer 26

Using an RNA genome

Question 27

What rough structure does tRNA from?

Answer 27

A cloverleaf structure - folding and hydrogen bonding on itself with its own base pairs.

Question 28

What are the steps of DNA extraction from a plant material?

Answer 28

1. Grind sample in pestle and mortar - breaks down the cell walls.
2. Mix sample with detergent - breaks down cell surface membrane, releasing cell contents into solution.
3. Add salt - breaks Hydrogen bonds
4. Add protease enzymes - break down proteins associated with DNA in nuclei
5. Add a layer of alcohol (ethanol) - causes DNA to precipitate.
6. DNA is picked up by spooling it onto a glass rod - DNA will be seen as white strands forming between the layer of sample and the layer of alcohol.