Biochemical Reactions

• Condensation Reaction- building up the polysaccharides, lipids and polypeptide

  molecules.
• Hydrolysis Reaction- breaking down polysaccharides, lipids and polypeptide molecules.
• DNA Replication- DNA makes identical copies (replicas) of itself to pass on the daughter

  cells (new cells) before cell division.
• Protein Synthesis- DNA encodes for the production of amino acids and proteins. The bases

  on DNA are transcribed and translated into proteins.
• Photosynthesis- plants make food using carbon dioxide, water and sun’s energy.
• Respiration- cells release energy by oxidising the bonds in the food molecules.
• Starch produced by plants is via condensation

  reaction.
• Condensation

   Link small biochemical building blocks to form

  larger molecules.

   Also known as ‘dehydration’ reaction because water

  molecule is lost when joining two small molecules.
• Hydrolysis

   Breaking the large molecules into smaller

  biochemical building blocks.

   This reaction is a ‘hydration’ reaction because it

  uses water.
• hydrolysis

  starch is hydrolysed into glucose,

  fats into fatty acids and glycerol,

  proteins into amino acids.
• DNA is a double strand of nucleic acids joined between the bases of the nucleotides.
• The process of DNA replication is semi-conservative

  because the new DNA copy (replica) retains 50% of the information of the old/parent DNA.
• Steps in DNA Replication

  1)The parent DNA helix unwinds and separates into two separate strands.

  2) Nucleotides are attracted to the complementary bases.

  3) Complementary base pairing occurs.

  4) The new strands join together using enzyme (DNA polymerase).

  5) There are two identical DNA helix, each consisting of the one original strand of DNA and one

  new strand.
• Protein synthesis is a process whereby DNA encodes for the production of amino acids and

  proteins.
• The instructions for how to make a protein are held inside the DNA molecule.
• The major stages in making a protein are: DNA unwinding, transcription and translation.
• i. DNA Unwinding

  -DNA segment unwinds and separates

  -Happens in the cell nucleus
• Transcription

  -mRNA nucleotide matches the DNA base by base and complementary base-pairing occurs.

  -In complementary base-pairing, Cytosine pairs with Uracil since RNA lacks thymine.

  -Occurs inside the cell nucleus.

  -The mRNA serves as messenger which carries the DNA code from the nucleus to the ribosomes on the endoplasmic reticulum. (moves from nucleus to cytoplasm)

  -In the transcribed mRNA, a set of three bases form a code known as the genetic code for

  one of the twenty amino acids present.
• 3 Main Steps in Translation

  -The ribosome moves along the m RNA codon by codon. It assembles the protein in the

  step below:

  1.The ribosome calls RNA to bring the amino acid required by the mRNA codon.

  2.The ribosome forms a peptide bond between the new amino acid and the one already in

  place.

  3.The ribosome moves on to the next codon of the mRNA.
• DNA helicase breaks hydrogen bonds between complementary bases, which is the process of unwinding the DNA helix
• DNA polymerase III is the enzyme that adds nucleotides to the 3' end of the growing strand
• DNA unwinding in protein synthesis happens in the nucleus, and the DNA is transcribed into RNA
• in transcription, mRNA matches the DNA base by base and is then released from the nucleus
• the mRNA in transcription serves as a messengers which carries the information from the DNA to the ribosome
• In the transcribed mRNA, a set of three bases form a code known as the genetic code for one of the twenty amino acids present.
• translation occurs in the cytoplasm of the cell and is the process of converting the information in mRNA into a sequence of amino acids that make up a polypeptide
• ribosomes move along the the mRNA transcript forming peptide bonds between amino acids
• after translation Golgi bodies make final adjustments to the protein and transport it in vesicles to the site where it is going to be used.
• The start codon begins the process; it is the first codon that gets translated. (AUG)(methionine)
• The three stop codons are UAA, UAG, UGA.
• Which three events occur during the light reactions of photosynthesis?

  Photolysis, exciting electrons, electron transport chain