Nucleic Acids

• Nucleic Acids


  macromolecules containing hydrogen, oxygen, nitrogen, carbon, and phosphorus. A group of the most important molecules of which are best known as ribonucleic acid (RNA) and deoxyribonucleic acid (DNA)
• Structure of a nucleotide

  phosphate group

  pentose sugar

  nitrogenous organic base

  
  

  between the phosphate group and the pentose sugar we have a kinky bond.

  
• Formation of a mononucleotide


  all components are joined together by a condensation reaction to form a single nucleotide
• Formation of dinucleotide and poly nucleotides


  two nucleotides can be joined by a condensation reaction between a deoxyribose sugar and one phosphate group of another nucleotide. the bond between them as a result is called a phosphodiester bond.
• The 5 nitrogen containing bases

  guanine

  Thymine (only in DNA)

  Cytosine

  adenine

  Uracil (Only in RNA)

  
• RNA structure


  Polymer made up of nucleotides. Its a single relatively short polynucleotide chain in which the pentose sugar is always RIBOSE and the thymine base is replaced with Uracil

  
• 3 types of RNA

  1. transfer genetic material from DNA to Ribosomes

  
  

  2. ribosomes are made up of RNA and proteins

  
  

  3, carries out protein synthesis
• Structure of DNA


  Pentose sugar is Deoxyribose and has the organic base Thymine instead of Uracil.

  
  

  DNA has two strands of nucleotides twisted in a anti paralell double helix.

  Each stand is extremely long and they are joined by hydrogen bonds between the nitrogen containing bases on each strand.

  
• DNA DIAGRAM

  
• Base Pairing


  A - T ( A is complementary to T)

  G - C ( G is complementary to C)
• DNA Stability


  DNA is a stable molecule this is because:

  
  

  - The Phosphodiester backbone protects the more chemically reactive bases inside the double helix

  
  

  -the higher the proportion of G-C the more hydrogen bonds there are as there are 3 bonds between each base pairing.
• Function of DNA


  The hereditary material responsible for passing genetic information from cell to cell and generation to generation
• How is DNA adapted to carry out its function

  -A very stable structure which normally passes from generation to generation without change most mutations are repaired so persistent ones are rare

  - Two separate strands are joined only with hydrogen bonds which allow them to separate during DNA replication and protein synthesis.

  - It is extremely large molecule and therefore carries on immense amount of genetic information

  -by having the base pairs within the helical cylinder of the deoxyribose- phosphate backbone, the genetic information is to some extent protected from being corrupted by outside chemical and physical forces.

  - Base pairings leads to DNA being able to replicate and to transfer information as mRNA.
• DNA REPLICATION


  the process of making a copy of DNA
• Division


  Before a nucleus divides its DNA is replicated to ensure all daughter cells have the genetic information to produce all the enzymes and proteins they need.
• What is needed for semi semiconservative replication to take place

  - The four types of nucleotide

  - both strands of a DNA molecule act as a template for the attachment of these nucleotides

  - the enzyme DNA polymerase

  a source of chemical energy is required to drive the process
• Process of Semi conservative DNA replication

  1. the enzyme DNA helicase breaks the hydrogen bonds between the base pairs

  2. therefore the double helix separates into its two strands and unwinds

  3.each exposed polynucleotide then acts a template to complementary free nucleotides to bind by complementary base pairing through condensation reactions which are carried out by DNA polymerase which forms the 2nd missing polynucleotide strand

  4. each new molecule now contains one original strand and one new strand

  
• who worked out the structure of DNA

  James Watson and Francis Crick in 1953 - had the idea of a semi conservative method
• what were their two models before tested to find out which one was actuality

  the conservative model + the semi conservative model
• conservative model of DNA replication

  parental double helix remains intact, both strands of daughter helices are newly synthesized
• Semi conservative model of DNA


  in the process of DNA synthesis each original strands of the molecule acts as a template on which a new complementary strand is created.
• what facts did they base their work on

  All bases in DNA contain Nitrogen, Nitrogen has two isotopes one of which is lighter N14 and one of which is heavier N15, Bacteria incorporate nitrogen from their growing medium into anything they make.
• how did they do it?

  They labelled the bacteria first by growing on an agar plate of N15 . they would then transfer this to an agar plate of N14 for a single generation and allow it to replicate once. the mass of each new DNA molecule would depend entirely on what model took place. To separate the DNA types they centrifuged them in a special solution. their results them showed that the semi conservative model was correct.
• What is the structure of ATP?

  Adenine

  Ribose

  3 phosphates
• How does ATP store energy?

  The bonds between the 3 phosphates have a low activation energy an d thus are easily broken.

  When broken they release a considerable amount of energy.
• ATP + H2O -> ADP + inorganic phosphate + energy
• How is ATP synthesised?

  the reaction of ATP to ADP is reversible and therefore with the addition of energy and a phosphate can be turned back into ATP

  
  

  This reaction is catalysed by ATP synthase, and is a condensation reaction
• Roles of ATP

  Immediate energy source

  Doesn't need to be stored and constantly being produced
• How is ATP used?

  metabolic processes

  movement

  Active Transport

  secretion

  Activation of molecules