Nucleic Acids Flashcards
What are the 3 types of nucleic acid?
ATP
DNA
RNA
What are the 3 chemical components of nucleic acids?
Pentose sugar
Phosphate group
Backbone
Where does the phosphate group of one of the nucleotides join to on the adjacent nucleotide?
The phosphate group at the fifth carbon of the pentose sugar joins to the OH group at the third carbon of the pentose sugar of the other nucleotide
What is the name of the covalent bond between nucleotides?
Phosphodiester
Name the 3 pyrimidines
Uracil
Thymine
Cytosine
Name the 2 purines
Adenine
Guanine
What does adenine pair with instead of thymine in RNA?
Uracil
What is the base pairing rule?
A pyramidine always pairs with a purine - ensuring the width of the DNA double helix is maintained as a constand
How many nitrogen rings do pyrimidines have?
1
How many nitrogen rings to purines have?
2
Define anti parallel
Each strand of DNA runs opposite to each other - one points up (in a 5’ direction) and the other points down (in a 3’ direction)
How is DNA well adapted to its function?
Strong sugar phosphate backbone (held by phosphodiester bonds)
Hydrogen bonds (can be broken by DNA helicase allowing for replication)
Complementary base pairing (ensures that when DNA separates, each strand can act as a template strand allowing for transcription)
DNA molecules can store lots of info (compact as long sequences)
What are the 3 differences between RNA and DNA?
In RNA:
Pentose sugar is ribose (not deoxyribose)
Contains uracil (not thymine)
Form single stranded molecules (not double stranded)
What are the differences between ATP and DNA+RNA
Only one type of base present - adenine
Pentose sugar is always ribose
Contains 3 phosphate groups linked together
What is the similarity between ATP and DNA+RNA?
Consists of a base, a pentose sugar and phosphate
What is formed when water is added to ATP?
ADP and inorganic phosphate (Pi) and releases energy
What enzyme catalyses the reaction when water is added to ATP?
ATP hydrolase
What enzyme catalyses the reaction between Pi group and ADP?
ATP synthase
Give the properties of ATP
ATP releases energy in small amounts (none is wasted)
Small and soluble (easily transported around the cell)
Only 1 bond is hydrolyzed to release energy (energy release is immediate)
Can transfer energy to another molecule via phosphorylation (transferring one of its phosphate groups)
ATP cannot leave the cell (cells always have immediate supply of energy)
(DNA extraction from plant) Give the reason for homogenisation (pestle and mortar)
destroys cell walls
(DNA extraction from plant) give the reason for adding detergent
Disrupts phospholipid bilayer of cell membranes
(DNA extraction from plant) give the reason for adding salt
Neutralises the charge of the phosphate groups of sugar so reduces solubility of DNA
(DNA extraction from plant) give the reason for adding protease
Hydrolyses histones, leaving only DNA
(DNA extraction from plant) give the reason for adding ethanol
So DNA can be seen as white strands
Give the steps of DNA replication
- 2 strands of DNA separate, hydrogen bonds between bases break by DNA helicase
- free nucleotides attracted to their complementary bases
- once the 2 new nucleotides have lined up, they are joined by DNA polymerase
- nucleotides join using DNA polymerase
= semi conservative replication
What is a mutation?
A change in the base sequence
What are Okazaki fragments?
Lagging strands (strands that run in the opposite direction - antiparallel)
Discontinuous DNA replication
How does replication occur of the lagging strands?
- small section of lagging strand is unzipped
- free DNA nucleotide bases are attracted to their complementary bases on the lagging strand
- DNA polymerase joins together these few nucleotides
- DNA ligase joins together the Okazaki fragments
What are the 4 features of the genetic code?
Universal - all species use same code
Triplet - sequence of 3 bases = codon
Non overlapping - each nucleotide base only contributes towards one codon
Degenerate - can be more than one codon for an amino acid
How many different codons does a triplet code allow for?
64 (4x4x4)
Give the steps of DNA transcription?
- section of the DNA containing the gene unwinds and separates into 2 strands by DNA helicase
- one strand acts as a template strand for the complementary mRNA strand
- free RNA nucleotides pair with their complementary bases on the template strand
- RNA polymerase forms phosphodiester bonds between adjacent RNA nucleotides, until the mRNA detaches and leaves the nucleus via nuclear pore
How is transcription similar to DNA replication?
Both involve DNA as template
Both produce nucleic acids.
Both use helicase and polymerase
How are transcription and DNA replication different?
DNA replication uses both strands, transcription only uses 1 as a template
Replication involves whole length of DNA, transcription only uses a section
DNA replication produces a double stranded molecule, transcription only produces a single stranded molecule
DNA replication uses DNA polymerase, transcription only uses RNA polymerase
Give the steps of translation
- mRNA attaches to a ribosome and tRNA collects amino acids from the cytoplasm and brings the. To the ribosome
- tRNA attaches itself to mRNA by complementary base pairing ( max 2 molecules attach to mRNA at a time)
- amino acids attached to 2 tRNA molecules join by a peptide bond, then tRNA molecules detach themselves from the aminos acids, leaving them behind
- this process is repeated leading to the formation of a polypeptide chain until a stop codon is reached on mRNA and ends the process of protein synthesis
