1.5 Nucleic acids and their functions Flashcards
What does a nucleotide consist of?
- Pentose sugar
- phosphate
- nitrogenous base
What does DNA mean?
Deoxyribonucleic acid
What is the name of the sugar and the bases of DNA?
Sugar: Deoxyribose
Bases: Adenine, Thymine, Guanine, Cytosine
What does RNA mean?
Ribonucleic acid
What is the name of the sugar and the bases of RNA?
Sugar: Ribose
Bases: Adenine, Uracil, Guanine, Cytosine
What does ATP mean?
Adenosine triphosphate
What does ATP consist of?
Sugar: Ribose
Base: Adenine
+ 3 phosphate heads
How is ATP formed?
In an endergonic reaction (a reaction that uses energy)
What is the process of ATP forming?
- ADP and phosphate are combined
- energy to form bond comes from exergonic energy from respiration
- this is a condensation reaction as water in eliminated and the bond is formed
- catalyst for reaction: ATP synthetase
Why is ATP known as the universal energy currency?
It provides energy to all reactions to all cells in all species
What are the purine bases?
Adenine and Guanine
What is a purine base?
a double ring structure
What are the pyrimidine bases?
Thymine, Cytosine and Uracil
What is a pyrimidine base?
a single ring structure
What are the complimentary base pairs?
Adenine - Thymine (uracil in RNA)
Cytosine - Guanine
What are the two functions of DNA?
- base sequence codes for amino acid sequences in protein synthesis
- replicating prior to cell division so each daughter cell gets equal DNA
What is the structure of DNA?
- two complimentary polynucleotide strands
- sugar - phosphate molecules joined by condensation reaction
- sugar-phosphate molecules form ‘backbone’ of the molecule
- bases joined by hydrogen bonds form the ‘rungs’ in the middle
- double helix structure
What is the structure of RNA?
- single stranded polynucleotide
- pentose sugar ribose
- shorter than DNA
- bases present: Adenine, uracil, guanine and cytosine
What is rRNA?
Ribosomal RNA - made in the nucleolus, component of ribosome. Single polynucleotide folded into globular structure
What is tRNA?
Transfer RNA - Single stranded polynucleotide twisted into clover leaf shape. Carries amino acids to ribosomes.
What is mRNA?
Messenger RNA - made in nucleus, three bases code for one amino acid. Carries code from DNA in nucleus out the nuclear pore and into cytoplasm where mRNA then attaches to ribosomes
What are the steps to extracting DNA from cells?
- crush the source cells in detergent, salt and water to release DNA
- Filter cell debris and collect extract
- Pour ice cold alcohol down the tube containing extract
- DNA precipitates at the juntion of the extract and alcohol
- CNA can be stained red using acetic orcein
What does Meselson and Stahl’s experiment propose?
- Conservative replication
- Dispersive replication
- Semi-conservative replication
What is conservative replication?
DNA molecule is copied from the original, leaving the original as it was
What is semi-conservative replication?
two polynucleotide chains would part, new nucleotides attach to each of the chains, new molecule nowhas one old and one new chain
What is dispersive replication?
Sections of DNA molecule are copied and spliced together making each new DNA molecule a mix of original and new
How did Meselson and Stahl conduct their experiment?
Meselson and Stahl used E.coli bacteria as the source of DNA. E.coli are easily grown in a flask of culture medium and replicate their cells (and DNA) every 20 minutes under optimal conditions.
What did Meselson and Stahl discover with their experiment?
‘New’ and ‘original’ nucleotides were distinguished by the isotope of nitrogen (N) in the nitrogenous bases. 15N is heavier in mass than 14N, so DNA molecules containing bases with 15N and DNA molecules containing 14N can be separated by mass in centrifugation.
Why is DNA said to be semi-conservative?
Consists of one original strand and one newly synthesised strand of DNA
Where does 14N sit in the test tube?
At the top
Where does 15N sit in the test tube?
At the bottom
What is DNA Helicase and what does it do?
DNA Helicase is an enzyme that breaks hydrogen bonds holding the two polynucleotide chains together in DNA. ‘Unzipping’ DNA into two strands
What is DNA Polymerase and what does it do?
DNA Polymerase is an enzyme that adds free nucleotides from nucleoplasm to exposed bases by forming H bonds between them
What is DNA Ligase and what does it do?
DNA Ligase is an enzyme that rewinds the double helix of DNA
What is the triplet code?
Three bases that code for a single amino acid
What’s the other name for the triplet code?
a codon
What is Transcription?
The process of copying a segment of DNA into RNA.
What is the process of transciprtion?
- DNA unzipped by DNA Helicase
- RNA Polymerase attaches to DNA
- Only one DNA strand is copied
- Free RNA nucleotides align with their complimentary nucleotides on DNA strand
- Bonds formed between the nucleotides
- results in synthesis of mRNA
- mRNA carries DNA code out the nucleus through nuclear pore to cytoplasm and attaches itself to a ribosome
What happens when mRNA attaches itself to the ribosomes?
- ribosome read the DNA code on mRNA
- tRNA attach to specific amino acids and carry them to the mRNA molecule
- anticodon-codon bases align and a codon-anticodon complex is formed
- Peptide bonds are formed between adjacent amino acids by condensation reaction
