Topic One

• What are the two conditions for enzyme action?

  Collision with substrate. Active site complementary to substrate.
• Why does bonding of G-C make it more stable than A-T?

  Triple hydrogen bonding in G-C bonding makes it more stable than the double hydrogen bonding in A-T bonding.
• How does phosphodiester backbone make DNA stable?

  Reactive bases are protected inside double helix.
• What are the three stages of the Meselsohn and Stahl experiment which showed that the semi-conservative model was correct?

  Grew bacteria with DNA strands containing heavy Nitrogen isotopes. They placed them in broth containing light isotopes. After one replication every heavy strand was paired with a light one.
• In what three situations does ATP synthesis occur?

  Photosynthesis, Respiration, Transfer of phosphates from donors to ADP.
• What are five uses of ATP?

  Metabolic Processes, Movement, Active Transport, Secretion, Activation of Molecules.
• Why does water have a high specific heat capacity and high latent heat of vaporisation?

  Takes extra energy to overcome hydrogen bonds between water molecules.
• In what three ways is water used in metabolism?

  Hydrolysis reactions, Chemical reactions in a aqueous medium, Photosynthesis.
• Water is transparent. Why does this make it useful for eye fluid?

  Light can pass through and reach retina.