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OCR Biology A - 2.1.3 - Nucleotides and Nucleic Acids Part 1

Biology25 CardsCreated about 1 month ago

This deck covers the fundamental concepts of nucleotides and nucleic acids, including their structure, function, and the processes of DNA replication and transcription.

What is a nucleotide made of

Pentose monosaccharide Phosphate Group PO4 2- Nitrogenous base
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Key Terms

Term
Definition
What is a nucleotide made of
Pentose monosaccharide Phosphate Group PO4 2- Nitrogenous base
Phosphodiester bonds
Formed in a condensation reaction between nucleotides Phosphate group at 5’ forms covalent bond with hydroxyl group 3’ (H2O) Forms a long, strong suga...
Difference between ribose and deoxyribose
Deoxyribose doesn’t have an oxygen atom at 2’
Bases
Adenine Cytosine Guanine Thymine/ uracil
Pyrimidines
Smaller bases Single carbon ring structures Thymine/ Cytosine
Purine
Larger bases Double carbon ring structures Adenine/ Guanine

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TermDefinition
What is a nucleotide made of
Pentose monosaccharide Phosphate Group PO4 2- Nitrogenous base
Phosphodiester bonds
Formed in a condensation reaction between nucleotides Phosphate group at 5’ forms covalent bond with hydroxyl group 3’ (H2O) Forms a long, strong sugar-phosphate backbone with a base attached to each sugar
Difference between ribose and deoxyribose
Deoxyribose doesn’t have an oxygen atom at 2’
Bases
Adenine Cytosine Guanine Thymine/ uracil
Pyrimidines
Smaller bases Single carbon ring structures Thymine/ Cytosine
Purine
Larger bases Double carbon ring structures Adenine/ Guanine
How do bases pair up
A purine with a pyramidine Cytosine pairs with guanine - 3 H bonds Adenine pairs with thymine (uracil - RNA) - 2 H bonds
Structure of DNA
Hydrogen bonding between complementary bases Double helix composed of two twisted antiparallel strands (phosphate group 5’ - OH 3’/ OH 3’ - phosphate group 5’) Each strand is a polynucleotide
Why are polynucleotide chains parallel
Complementary base pairing rule: When a small pyramidine base binds to a larger purine base a constant distance between the DNA ‘backbones’ There will also always be equal amounts of A, T, C, G
Types of RNA
Messenger RNA (mRNA) Transfer RNA (tRNA) Ribosomal RNA (rRNA)
mRNA
Carries the code held in the genes to the ribosomes where the code is used to manufacture proteins
tRNA
Transports amino acids to the ribosomes
rRNA
Makes up the ribosomes along w/ protein complexes
Phosophorylated nucleotides
ADP and ATP Contain a pentose sugar (ribose) A nitrogenous base (adenine) 2/3 inorganic phosphates
Semi conservative replication
One old strand and one new strand
Process of semi-conservation replication
Helicase causes the DNA to untwist and breaks the hydrogen bonds between bases Polynucleotides with exposed bases act as new template for new double strands Free DNA nucleotide bases pair with their complementary bases - H bonds DNA polymerase catalyses the formation of phosphodiester bonds between the nucleotides and also checks base pairing Sugar phosphate backbone reforms Each new molecule then twists to form it’s double helix
Purpose of DNA replication
Genetic info needs to be conserved with accuracy so each cell from cell division has the correct amount of genes
Continuous replication
DNA polymerase binds to the end of a strand Free DNA nucleotides added without any breaks This occurs in the leading strand (3’ to 5’)
Discontinuous replication
DNA polymerase cannot bind to the end of a strand (5’- 3’) Free DNA nucleotides are added in sections (Okazaki fragments) Sections are later joined by DNA ligase
Mutations
Incorrect sequences may occur in the newly-copied strand Errors happen randomly and spontaneously Leads to change in the sequence of bases
Codon
Triplet of bases that code for an amino acid
Genetic code
Triplet code
Genetic code is universal
All organisms use this same code
Degenerate code
64 different codons possible (444) but only 20 amino acids An amino acid can be coded for by more than one codon
Non-overlapping
DNA base sequence is read from base 1 not base 2 or 3