ATP Synthesis


ATP production

  • In photosynthesis, light provides the energy needed to build organic molecules such as glucose. 
  • This energy can be used to form chemical bonds within ATP, it is the breaking of these bonds which releases energy used to form bonds as glucose is made.
  • Glcuose and other organic molecules are broken down in respiration, the energy realeased from this is used in the syntehsis of ATP
  • The ATP is then used in the cells to break bonds in metabnollic reactions. 

Energy (sun) ➡ ATP ➡ Large organic molecules (glucose) ➡ ATP ➡ processes requiring energy

  • Photosynthesis 
  • Respiration
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  • The ATP that is made in photosynthesis and respiration is usually synthesised by chemiosmosis. 
  • Chemiosmosis- involved the diffusion of protons fron a region of high concentration to a region of low concentration through a partially permeable membrane.
  • As the protons flow down the cocnentration gradient, energy is released which is used to attach a phosphate (Pi) to ADP
  • ADP + Pi ➡ ATP
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Excited Electrons

There are two ways in which electrons can be excited: 

  • Those present in pigment molecules can be excited by absorbing light from the sun. Chlorophyl is an example of one such pigment. 
  • High energy electrons are released when chemiocal bonds are broken in respiratory substrate molecules (glucose)
  • The excited electrons pass into an electron transportchain and are then use to generate a proton gradient. 
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Electron Transport Chain

  • Consists of a series of electron carriers, each one has a progressively energy levels.
  • As the high energy electrons move from carrier to carrier energy is released.
  • The release of energy pumps protons across a membrane in turn creating a concentration gradient across the membrane, this is a proton gradient. 
  • The proton gradient is maintained due to the impermeability of the membrane to hydorgen ions. 
  • The only way that protons can move back through the membrane down their concentration gradient is through hydrophilic membrane channels that are linked to the enzyme ATP synthase. 
  • The flow of proons through these channels provides the energy required to synthesis ATP. 
  • In photosynthesis, ATP is used to synthesise glucose, the ATP produced in respiration provides the energy required by metabollic processes. 
  • Oxidative phosphorylation and photophosphorylation are also vital to chemiosmosis. 
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