2.1.3 Nucleotides and nucleic acids

Question 1

What is the structure of a nucleotide?

Answer 1

phosphate, pentose sugar and nitrogenous base

Question 2

How many carbon rings do purines have?

Answer 2

two

Question 3

How many carbon rings do pyrimidines have?

Answer 3

one

Question 4

What is the sugar in a DNA nucleotide?

Answer 4

deoxyribose

2 OH

Question 5

What is the sugar for a RNA nucleotide?

Answer 5

ribose

1OH

Question 6

What bases does ribose bind to?

Answer 6

guanine
cytosine
uracil
adenine

Question 7

What bases does DNA bind to?

Answer 7

adenine
thymine
guanine
cytosine

Question 8

What are the purine bases?

Answer 8

adenine
guanine

Question 9

What are the pyrimidine bases?

Answer 9

thymine
cytosine
uracil

Question 10

How are polynucleotides formed?

Answer 10

the OH of the phosphate and the H from the sugar bind to form a phosphodiester bond = condensation reaction water is released

= 3’ to 5’ phosphodiester bond = sugar phosphate backbone

Question 11

How are polynucleotides broken down?

Answer 11

add water = hydrolysis reaction

Question 12

What is the structure of ATP?

Answer 12

3 phosphate groups
ribose sugar
adenine base

Question 13

When water is added to ATP what happens?

Answer 13

the hydrolysis reaction causes ADP to be produced and energy; inorganic phosphate is released

Question 14

What is the structure of DNA?

Answer 14

anti-parallel = double helix
3’ to 5’

Question 15

How many hydrogen bonds are formed between C and G?

Answer 15

three hydrogen bonds

Question 16

How many hydrogen bonds are formed between A and T?

Answer 16

two hydrogen bonds

Question 17

PAG 9; Why do you have to crush the piece of fruit using a pestle and mortar?

Answer 17

this helps break down the cellulose cell wall

Question 18

PAG 9; Why is detergent added?

Answer 18

this dissolves the cell surface membrane

Question 19

PAG 9; Why is a protease enzyme/pineapple juice?

Answer 19

breaks down the histones/proteins associated with DNA

Question 20

PAG 9; Why is cold ethanol added for observe DNA?

Answer 20

DNA insoluble in alcohols = float to the top

Question 21

What is the process of semi-conservative DNA replication?

Answer 21

1) the enzyme DNA helicase breaks down hydrogen bonds between bases = the double helix unwinds = each strand acts as a template
2) free DNA nucleotides from cytoplasm of cell and assemble on the template of the DNA in complementary base pairs
3) hydrogen bonds reform between the bases - the enzyme DNA polymerase joins the nucleotides forming a new sugar phosphate back bone by new phosphodiester bonds formed
= two identical DNA molecules are produced

Question 22

What is meant by semi-conservative DNA?

Answer 22

the new DNA molecules contains one new and one old strand of DNA

Question 23

What is the nature of the genetic code?

Answer 23

1) non-overlapping = coded by triplets once
2) degenerate = some amino acids have more than one triplet code
3) universal = used across all organisms/languages

Question 24

What is a gene?

Answer 24

a gene is a section of DNA that codes for the sequence of amino acids in a polypeptide

Question 25

Describe the process of transcription? (nucleus)

Answer 25

1) DNA helicase breaks hydrogen bonds between bases
2) Free RNA nucleotides attach forming a complementary mRNA strand (no thymine = uracil)
3)RNA polymerase helps forms the phosphodiester bonds in between the RNA nucleotides = mRNA is formed
4) mRNA leaves nucleus through the nuclear pores and the DNA helix reforms

Question 26

Describe the process of translation?

Answer 26

1) mRNA attaches to ribosome = made of two subunits of rRNA (one large one small)
2) the anti-codon on the tRNA will find the complementary codon on the mRNA, bringing a specific amino acid that corresponds with that codon
3) amino acids are joined by a peptide bond to give a protein with a specific primary structure