3) Nucleotides and Nucleic Acids Flashcards
What is the structure of a nucleotide
Pentose sugar
Nitrogenous base
phosphate group
Why are nucleotides important?
Give examples
They’re monomers that make up DNA and RNA .
ADP + ATP
What is DNA?
Describe DNA
Deoxyribose Nucleic Acid
Adenine, guanine,cytosine ,thymine
Contain 2 plynucleotide chains that run antiparralel.
What is a purine?
Give eg
Contain 2 carbon-nitrogen rings.
Adenine , guanine
What is a pyrimidine?
Give eg
Contain 1 carbon-nitrogen ring
Much smaller
Cytosine , thymine
What is Rna?
Describe it
Ribose Nucleic Acid
Adenine , cytosine ,guanine , uracil
Single chain polynucleotide
What is ADP and ATP
Phosphorylated nucleotides
How do you phosphorylate a nucleotide?
Add one or more phosphate groups to it.
Describe the structure of ADP and ATP
ADP - Adenine base , ribose sugar , 2 phosphate groups
ATP - Adenine base , ribose sugar , 3 phosphate groups
How does ATP provide enegy for chemical reactions
ATP is synthesised from ADP and inorganic phosphate group from energy-releasing reactions
ADP is phosophorylated to form ATP and a phosphate bond is formed.
Energy is stored in the bond, when ATP breaks fown , energy is released
How does a nucleotide join together to form polynucleotides
Join between phosphate groups by condensation reactions
Form phosphodiester bonds
Create sugar-phosphate backbone
How does 2 polynucleotide join to make an alpha-helix
Join by hydrogen bonding
By complementary base pairing
Adenine - Thymin
Guanine- Cytosine
Run antiparallel , hence double helix
How does DNA Self replicate
eg . semi-conservative replication
1) DNA helicase breaks hydrogen bonds , sttrands unzips
)2) Original strand acts as a template. Exposed bases join template by complementary base pairings.
3)Nucleotide join together by DNA Polymerase .Reform sugar-phosphate backbone . Hydrogen bonds between bases.
Strand twist into A-Helix
4) Each strand contains 1 strand from original DNA and new DNA strand
What is a gene
Sequence of DNA Nucleotides that code for a polypeptide.
How is DNA copied into RNA for protein synthesis
DNA found in nucleus.
DNA is too large to leave the nucleus.
Copied into mRNA by transcription
mRNA leaves nucleus and join with ribosomes to synthesis a protein by translation
What is mRNA
Made in nucleus
3 bases = codon
Carries genetic code , used to make protein from translation
What is tRNA
Found in cytoplasm
Amino acid binding site at one and anticodon on other
Carries amino acid that are used to make proteins to ribosome during translatioin
What is rRNA
Form subunites in ribosome
Moves alongthe mRNA strand during protein synthesis.
Helps catalyse formation of peptide bonds
How is a genetic code Non-overlapping,degenerate and universal
Sequence of base triplets
Non-overlapping - Base triplets don’t share their bases.Each triplet is read in sequence
Degenerate - Some amino acids are coded for by more than one base triplets.
*Universal * - Same specific base triplets code for the same amino acids in all living things
Describe Transcription
RNA Polymerase attatches to DNA helix
H Bonds break and strands unwind
One strand acts as a template to make an mRNA copy
RNA Polymerase lines up free RNA Nucleotides alongside template strand
Complementart copy of the strand ( T replaces with U )
RNA Nucleotides pair up bases and are joined together.
RNA Polymerase assemble mRNA Strands. H Bonds reform
Reach stop codon , Detatch from DNA.
mRNA moves out of nuclear pore
Describe Translation
Amino acids join to make a polypeptide chain
mRNA attatches to ribosome.
Anticodon complementary to start codon attatch itself to mRNA .
“nd tRNA attatches itself to next codon on mRNA
rRNA catalyse formation of a peptide bond.Join amino acids together.
3rd tRNA brings next codon , previous tRNA moves away.
COntinues until reaches stop codon.
Polypeptide moves away from ribosome.
