ATP synthesis

• what is ATP?

  universal energy currency in cells
• true or false? the bonds in inorganic molecules like oxygen and water are stronger than the bonds in organic molecules like glucose

  TRUE- glucose bonds between C-H require less energy to break and release less energy when formed than bonds between inorganic molecules
• what are organic molecules?

  molecules containing C-H bonds- eg glucose and lipids
• what's the relationship between, photosynthesis, respiration and ATP?

  • in photosynthesis, light provides energy to form bonds between ATP. When bonds in ATP are broken again, they release energy. This energy is used for the formation of bonds to make glucose
  • during respiration, bonds between glucose molecules are broken to release energy
  • this energy is used to synthesise ATP
  • ATP is then used to break bonds in metabolic reactions of cells

  
• in photosynthesis AND respiration, what process involving ETCs is used to synthesise ATP?

  chemiosmosis
• what is chemiosmosis and where does the energy come from to drive this process?

  • involves the diffusion of protons from regions of high to low concentrations through a partially permeable membrane
  • movement of protons as they flow down their concentration gradient releases energy that is used for the phosphorylation of ADP to ATP
  • chemiosmosis depends on the creation of a proton gradient (chemiosmosis ITSELF doesn't require energy as its diffusion)
  • this energy comes from high energy (excited) electrons being raised to higher energy levels
• what two ways are electrons raised to higher energy levels?

  • electrons present in pigment molecules like chlorophyll are excited by absorbing light energy from the sun
  • high energy electrons are also released when chemical bonds are broken in respiratory substrate molecules like glucose

  these electrons pass into an electron transport chain (ETC) and used to generate a proton gradient
• what is an electron transport chain? How does it create a proton gradient?

  • series of electron carriers, each with lower energy levels
  • as high energy electrons move from one energy level to another, energy is released
  • this energy is used to pump protons across a membrane, creating a concentration difference across the membrane and therefore a proton gradient
  • the gradient is maintained as a result of the impermeability of membrane to hydrogen ions
  • protons move back into membrane down their conc gradient through hydrophillic membrane channels linked to the enzyme ATP synthase
  • flow of protons provides energy to synthesise ATP

  
• state the role of ATP synthase

  • linked to hydrophilic channels that allow the facilitated diffusion of protons back into the membrane down conc grad
  • the flow of protons across ATP synthase through these channels provides it with the energy to synthesise ATP