Nucleic acids Flashcards
Describe the structure of a nucleotide
Pentose sugar - ribose/deoxyribose
Nitrogenous base - G, C, A, T
Phosphate
Describe the structure of DNA
2 nucleic acid strands bonded by complementary base pairing
Strands twisted to form a double helix
Strands are anti-parallel
A - T
A - U
C - G
what are purines and pyrimidines
Purines are double ringed: A, G
Pyrimidines are single ringed: C, T
what are the differences between DNA and RNA
DNA is deoxyribose, RNA is ribose
RNA contains uracil, DNA contains thymine
DNA is double stranded, RNA is single stranded
DNA forms hydrogen bonds between complementary strands
How are nucleotides connected?
Phosphodiester bonds between phosphate group on one nucleotide and the pentose of the next nucleotide
Condensation reaction catalysed by DNA/RNA polymerase
Describe the structure of ATP
ATP is a phosphorylated nucleotide
Ribose sugar
Adenine
3 phosphate groups
Hydrolysed to form ADP + Pi using enzyme ATP hydrolase and releases energy
What is the process of purifying DNA?
- Blend fruit to break cells
- Mix detergent, salt and distilled water and blended fruit
(Detergent breaks down cell membrane to release DNA
Salt binds to DNA so it clumps together)
- Place in water bath at 60oC for 15 minutes. This denatures enzymes that degrade DNA
- Place in ice bath to cool and take sample to test tube
- Add proteases to break down histone proteins
- add cold ethanol which forms a layer and DNA will precipitate out
What does semi-conservative mean
During DNA replication, one strand is from the original DNA and the other is newly made
Explain semi-conservative replication
DNA helicase unwinds double helix by breaking hydrogen bonds between complementary bases
One strand is a template strand
Free floating nucleotides form hydrogen bonds with complementary bases
DNA polymerase catalyses formation of phosphodiester bonds between nucleotides
complementary strand forms alongside the template strand.
One new strand, one original strand
What is mRNA?
Produced during transcription - RNA polymerase uses DNA as template strand to provide mRNA strand
Carries genetic code from nucleus to cytoplasm to ribosome
Made up of triplets of bases called codons
What is tRNA?
carries amino acids to ribosome during translation
Contains amino acid binding site one end and anticodon opposite end
Anticodon binds to complementary codons on mRNA to convert sequence into polypeptide
What is rRNA
Associates with proteins to form 2 sub units of the ribosome
Ribosome moves along mRNA during translation, catalysing formation of peptide bonds between amino acids
Describe transcription
RNA polymerase unwinds DNA strand and produces a single template strand
RNA polymerase moves along template strands and adds complementary nucleotides by forming hydrogen bonds
Nucleotides are joined by phosphodiester bond by the RNA polymerase
RNA polymerase reaches stop codon
molecule of mRNA has formed which leaves the nucleus and enters the cytoplasm through nuclear pore
Describe translation
mRNA travels to ribosome
Ribosome attaches to RNA and moves along (translocation)
Ribosome reads the mRMA codons
each codon corresponds to an amino acid
tRNA molecule travels to ribosome which has complementary anticodon and corresponding amino acid
tRNA molecules bind with complemtary codon and ribosome catalyses peptide bond formation between amino acids to form polypeptide
what is the structure of tRNA
clover-shaped structure
single strand of RNA folded over on itself through hydrogen bonding
Contains amino acid binding site one end and anticodon opposite end
