nucleotides basics Flashcards
1
Q
define nucleotide
A
monomer which makes up nucleic acids
2
Q
describe the structure of a nucleotide
A
- phosphate
- pentose sugar
- nitrogenous base
3
Q
how do nucleotides join to form nucleic acids?
A
- hydroxyl on 3’ of one nucleotide pentose
- joins 5’ of another nucleotide pentose
- condensation reaction
- forms a phosphodiester bond
- strong sugar phosphate backbone
4
Q
what are the properties of the phosphodiester bond
A
- strong
- covalent
5
Q
what is a purine?
A
- A or G base
- 2 carbon rings
6
Q
what is a pyrimidine?
A
- T, C or U base
- 1 carbon ring
7
Q
describe complementary base pairing
A
- purine always binds with pyrimidine
- maintains constant distance between backbones
- = parallel polynucleotide chains
8
Q
what is the sugar phosphate backbone?
A
part of the nucleotide which the base attaches to
9
Q
describe the structure of a DNA nucleotide (3 marks)
A
a DNA nucleotide consists of a phosphate base, deoxyribose sugar and nitrogenous base
10
Q
describe how the two nucleotide chains in DNA are bonded together (4 marks)
A
- chains are bonded by hydrogen bonds
- between complementary base pairs.
- pairs are A+T, C+G
- a purine always binds to a pyrimidine
11
Q
state three ways in which the structure of DNA differs from RNA (3 marks)
A
- DNA is double stranded
- DNA has deoxyribose, RNA has ribose
- DNA is A+T but RNA is A+U
