2.3 Nucleic acids

Question 1

What are the 3 components of nucleic acids

Answer 1

phosphate
five carbon sugar
nitrogenous base

Question 2

Name the four nitrogenous bases

Answer 2

Adenine
Guanine
Thymine
Cytosine

Question 3

What are the 2 purines (2 rings)?

Answer 3

Adenine

Guanine

Question 4

What are the 2 pyrimadines (3 rings)?

Answer 4

thymine

cytosine

Question 5

Which bases do thymine and cytosine always pair to? and how many hydrogen bonds are there between each?

Answer 5

Thymine-adenine (2 hydrogen bonds)

Cytosine-guanine (3 hydrogen bonds)

Question 6

What is the term used to describe how DNA replicates? (1)

Answer 6

Semi-conservative replication

Question 7

Describe the process of DNA replication.

Answer 7

DNA helicase enzyme unzips by hydrolysing hydrogen bonds between nucleotide bases
Gyrase enzyme unwinds
Free phosphorylated nucleotides bond to exposed bases following the complimentary base pairing rules
DNA polymerase adds new nucleotide bases in the 5’ to 3’ direction using each strand as a template
Leading strand is synthesized continuously but lagging strand is in fragments discontinuously that are later joined by ligase enzymes
Phosphodiester bonds form between sugar of one nucleotide and phosphate of the next nucleotide

Question 8

How does DNA code for proteins

Answer 8

Transcription- DNA unwinds and unzips
Hydrogen bonds between complimentary base pairs break
mRNA is produced that is complimentary to the template strand
mRNA passes out of the nucleus (its single stranded so can fit through the nuclear pores)
attaches to a ribosome
tRNA has an amino acid attached t it, and when its anticodon binds to the complimentary codon on the mRNA, a peptide bond forms between adjacent amino acids

Question 9

What are the 4 enzymes used in semiconservative DNA replication- in order?

Answer 9

1 Gyrase
2 Helicase
3 Polymerase
4 Ligase

Question 10

Give three ways in which RNA differs from DNA.

Answer 10

RNA has ribose sugar not deoxyribose
RNA in single stranded not double stranded
RNA has uracil instead of thymine

Question 11

Which number carbon of deoxyribose is the nitrogenous base attached to?

Answer 11

c1

Question 12

Which number carbon of deoxyribose is the phosphate group attached to

Answer 12

c5 or c3

Question 13

How does DNA structure allow it to be replicated?

Answer 13

double stranded ;
each / both (strands) act as template ;
hydrogen bonds , easily , break / form , between
bases ;
complementary (specified) base , pairing / AW ;
purine (only able to) bind to pyrimidine ;
(due to) different sizes of purines and pyrimidines ;
hydrogen bonding different between A & T and C & G
or
3 H bonds between C & G and
2 H bonds between A & T ;