Nucleic Acids

• Examples of nucleic acids include RNA and DNA.
• DNA’s function is to carry genetic material through generations.

  RNAs function is protein synthesis.
• Nucleotides are the monomers which make up DNA and RNA.
• Nucelotides consist of a pentose sugar, a phosphate group, and a nitrogenous base. These are all joined by condensation reactions.
• A phosphodiester bond is the bond between the sugar and the nucleotide of the next base.
• When many nucleotides are joined together, they form a polynucleotide.
• RNA is a single stranded polymer made up of nucleotides.
• RNA carries out protein synthesis by translating its genetic information using ribosomes into various proteins that are needed for cellular processes.
• The bases in the nucleotides of RNA are:

  Adenine

  Guanine

  Cytosine

  Uracil
• DNA is made up of two long strands joined by weak hydrogen bonds.
• DNA molecules have a sugar phosphate backbone for strength. The DNAs nitrogen bases are attached to this backbone.
• The bases in nucleotides of DNA are:

  Adenine

  Guanine

  Cytosine

  Thymine
• DNA molecules are very stable because:

  The backbone protects the chemically reactive bases on the inside of the molecule.

  There are hydrogen bonds linking the base pairs (three for cytosine and guanine, two for adenine and thymine).

  Large number of hydrogen bonds over the length of the DNA
• DNA is suitable to pass genetic information through generations because:

  It is a stable structure that rarely mutates.

  It has two separate strands joined with weak hydrogen bonds which can be broken to separate during DNA replication and protein synthesis.
• In one strand of the DNA, the nucleotides are arranged so that:

  The 5th carbon has an attached phosphate group.

  The 3rd carbon has an attached pentose sugar.

  In the other strand of the DNA, this is switched. The strands are described as being antiparallel.
• Cells are always formed from pre-existing cells. This process is called cell division and occurs in two different ways:

  Nuclear division, the process by which the nucleus divides.

  Cytokinesis, the process by which the whole cell divides.
• The process of DNA replication is described as semiconservative. This is because one of the strands of the DNA molecule is new and the other is from the original DNA molecule.
• The process of DNA replication:

  1. The two strands of a DNA molecule are broken apart by DNA helicase.
  2. This causes the double helix to separate and unwind.
  3. Each exposed strand then acts as a template on which free nucleotides attach by complementary base pairing.
  4. Nucleotides are joined together in a series of condensation reactions using the enzyme DNA polymerase.
  5. Each of the new molecules contains one of the original DNA strands and a new strand that has been synthesised.