Nucleic Acids Flashcards
What is a nucleotide
Monomers of nucleic acids (DNA and RNA)
Made up of:
- phosphate group (always the same)
- pentose sugar (deoxyribose in DNA , ribose in RNA)
- nitrogenous base (DNA= A T C G. RNA= A U C G )
How many hydrogen bonds hold base pairs together
G-C has 3 hydrogen bonds
A-T has 2 hydrogen bonds
- purines and pyrimidines always pair together (complementary base pairs)
How are nucleotides joined in condensation reactions
Covalent bonds
What are purines
Adenine and Guanine
- purines are larger than Pyrimidines
What are Pyrimidines
Cytosine, Thymine and uracil (RNA)
- Pyrimidines are smaller than purines
Why do purines always bond with pyrimidines
- their structure
- where they can form hydrogen bonds
- to remain parallel (never have 2 large molecules and 2 small molecules)
DNA helicase, DNA polymerase, DNA ligase
DNA helicase- unzips DNA helix
DNA polymerase- catalyses the joining of nucleotides
DNA ligase- sticks DNA fragments together
DNA replication
- DNA helicase unwinds the DNA and forms a replication fork
- helicase unwinds and unzips
- breaks hydrogen bonds - Each strand acts as a template
- free nucleotides pair with the complementary exposed nucleotides - DNA polymerase catalyses the joining together of nucleotides
- hydrogen bonds reform - Hydrogen bonds form down the middle
- this is semi conserved DNA (one old strand, one new strand)
3 parts of the genetic code
Triplet- the bases on DNA form triplet codons consisting of 3 nucleotide bases
Non overlapping- each base will only code for one amino acid in one triplet codon
Degenerate- each amino acid can be coded for by multiple codons
Nucleotide vs Nucleoside
Nucleotide- has a nitrogenous base, deoxyribose sugar and phosphate
Nucleoside- does not have a phosphate
Phosphorylation
The addition of a phosphate group
Energy uses
- muscle contraction
- memory formation
- transmission of nerve impulses
- cell division
- active transport
- translocation
- photosynthesis
Structure of ATP
Adenine — Ribose |
|
3 phosphates
Translation
- mRNA attaches to a ribosome
- The first mRNA codon binds to a tRNA molecule with a complementary anticodon
- The tRNA is bound to an amino acid specific to its anticodon
- A second tRNA (carrying another amino acid) binds the tk adjacent mRNA codon
- A peptide bind forms between the amino acids
- The ribosome continues along the mRNA molecule, from codon to codon
- Amino acids are bonded together in a polypeptide chain until a stop codon is reached
- The polypeptide is released
Transcription
- DNA helicase unwinds and unzips DNA
- RNA nucleotides bind to complementary DNA bases in the template strand (antisense)
- RNA polymerase joins rna nucleotides together with phosphodiester bonds
- A stop codon causes rna polymerase to detach
- The mRNA molecule detaches from the DNA and leaves the nucleus