dna, atp, proteins

• Semi conservative dna replication: double helix unwinds and hydrogen bonds between base pairs are broken due to enzyme dna helicase ,enzyme dna polymerase joins adjacent nucleotides together to form new phosphodiester bonds
• ATP is re synthesised from ADP and a phosphate molecule using enzyme ATP synthase during respiratio/photosynthesis
• Amino acids are joined by peptide bonds to make polypeptides which can fold into different shapes depending on the sequence of amino acids
• Protein structure: primary = linear chain of amino acids, secondary = alpha helix or beta pleated sheet, tertiary = folded protein with active site, quaternary = multiple subunits held together by non-covalent interactions - more than one polypeptide
• What is the name of the enzyme that breaks terminal peptide bonds to break down a protein?

  exopeptidase
• what is the name of the enzyme that breaks bonds in the middle of a peptide?

  endopeptidase
• What is the role of dna helicase in dna replication?

  UnwindsDNA double helix by breaking hydrogen bonds
• what is the role of DNA polymerase in dna replication?

  Joins adjacent nucleotides, forming phosphodiester bonds
• A condensation reaction between two amino acids forms a peptide bond.
• • Dipeptides are formed by the condensation of two amino acids.
  • Polypeptides are formed by the condensation of many amino acids.
• induced-fit model of enzyme action: enzyme changes active site shape to fit substrate and form an e-s-c to catalyse the reaction
• in all living cells, DNA holds genetic information and RNA transfers genetic information from DNA to the ribosomes
• Ribosomes are formed from RNA and proteins
• • A condensation reaction between two nucleotides forms a phosphodiester bond.
• atp is composed of 3 phosphate groups, adenine and a ribose sugar
• enzyme ATP synthase is involved in the condensation reaction of ADP and phosphate
• enzyme ATP hydrolase is involved in the hydrolysis of ATP to ADP and Pi
• Describe two ways in which ATP is a suitable energy source in living organisms.

  releases small amounts of energy   

  releases energy immediately  

  phosphorylates other compounds to make them more reactive

  can be rapidly resynthesised

  does not leave cells
• semi conservative DNA replication - two identical copies produced consisting if one new stand and one original