2.1.3 Nucleotides and Nucleic Acids

Question 1

components of nucleotides

Answer 1

phosphate
nitrogenous base
pentose base

Question 2

nucleotides

Answer 2

carbon, hydrogen, oxygen, nitrogen, phosphorus
monomer of nucleic acids (DNA/RNA)
component of cofactors - coenzyme (NAD/FAD)
component of ATP, ADP, AMP

Question 3

pyrimidines

Answer 3

cytosine, thymine, uracil

Question 4

purines

Answer 4

adenine, guanine

Question 5

reaction that occurs during formation of nucleotides

Answer 5

condensation reaction - removal of water

Question 6

ADP and ATP

Answer 6

phosphorylated nucleotides
nucleotide (sugar, base, phosphate) with extra phosphate groups

Question 7

properties of ATP

Answer 7

small, soluble in water - useful as energy-requiring processes occur in solution
relatively unstable ∴ cannot be stored easily
constantly being made/broken down
releases small quantities of energy

Question 8

adenosine

Answer 8

adenine + ribose

Question 9

adenosine monophosphate

Answer 9

adenine, ribose, 1 phosphate group

Question 10

adenosine diphosphate

Answer 10

adenine, ribose, 2 phosphate groups

Question 11

adenosine triphosphate

Answer 11

adenine, ribose, 3 phosphate groups

Question 12

where is DNA found in eukaryotes

Answer 12

nucleus: chromosomes made up of DNA
mitochondria + chloroplasts

Question 13

where is DNA found in prokaryotes

Answer 13

free in cytoplasm: circular chromosomes + plasma
found in some viruses

Question 14

function of DNA

Answer 14

hereditary material of life
made of genes - code for protein

Question 15

structure of DNA

Answer 15

double helix
anti-parallel strands
sugar phosphate backbone
rungs on ladder
complementary base pairs held by hydrogen bonds

Question 16

how does the genetic code in genes code for proteins

Answer 16

3 bases code for 1 specific amino acid sequence of bases determine the sequence of amino acids
non-overlapping code
more than one codon codes for an amino acid

Question 17

antiparallel

Answer 17

2 strands run in opposite directions

Question 18

transcription

Answer 18

occurs in the nucleolus
DNA unzips exposing bases on the genes
H bonds are broken, revealing the template strand
free activated RNA nucleotides joined to the template strand by complementary base pairing
RNA polymerase moves from 5’ to 3’ direction
RNA nucleotides joined by RNA polymerase by phosphodiester bonds
enzyme reaches stop codons + detaches
two transcripts are modified before leaving nucleus via nuclear pore

Question 19

DNA replication

Answer 19

occurs in the S phase of interphase - leads to creation of sister chromatids

Question 20

materials required for DNA replication

Answer 20

enzymes - DNA helicase, DNA polymerase, DNA ligase
intact DNA - both strands act as templates
activated free nucleotides (phosphorylated)
energy source - ATP, unwinding DNA, activating nucleotides

Question 21

semi conservative model of DNA replication

Answer 21

1. DNA unwinds, unzips which breaks H bonds between complementary bases
2. DNA bases on both template strands exposed
3. in nucleus, 2 Pi are added to each free DNA nucelotide to activate them
4. bases of activated nucleotides pair up with complementary bases on each of the old strands
5. DNA polymerase catalyses formation of phosphodiester bonds joining new nucleotides in 5’ to 3’ directions. 2 extra Pi are broken off and released - hyrdolyses reaction as supplies energy to make bonds
6. before adding next nucleotide, DNA polymerase proof reads previous pair + can correct/repair if needed

Question 22

semi-conservative

Answer 22

in each new DNA molecule, 1 old strand is conserved and paired with 1 new strand

Question 23

RNA structure

Answer 23

single-stranded
uracil instead of thymine
ribose sugar

Question 24

function of RNA

Answer 24

involved in protein synthesis

Question 25

messenger RNA - mRNA

Answer 25

long, single-stranded molecule
made in transcription
copy of coding/sense strand - U replaces T
passes out of nuclear pore into cytoplasm

Question 26

transfer RNA - tRNA

Answer 26

small molecule
folds into clover leaf shape
ACC site can bind to an amino acid
anti-codon determines which amino acid binds, binds to codon on mRNA