Energy transfers

• How does an increased surface area increase the rate of photosynthesis?


  Allows the absorption of as much sunlight as possible.
• How does overlapping of leafs benefit photosynthesis?


  Shading is minimised.
• How does a thin life benefit photosynthesis?


  Short distance for gas exchange.
• How does a transparent cuticle benefit photosynthesis?


  Allows light into palisade cells.
• How does a long, narrow palisade layer benefit photosynthesis?


  Many chloroplasts so increase rate of photosynthesi.
• How does numerous stomata benefit photosynthesis?


  Allows for fast gaseous exchange.
• How does a network of xylem and phloem benefit photosynthesis?


  To bring water and carry away sugars.
• What type of reaction is photosynthesis and why?


  Endothermic takes light in.
• What is a photoautotroph?


  An organism which makes their own food from light energy.
• How do accessory pigments benefit plants?


  All have different wavelengths of light, which maximises amount of light absorbed.
• What are the 2 products of the light dependant reaction?

  ATP, NADPH, Oxygen
• Where does the light dependant reaction take place?

  Happen in the thylakoid membranes of the grana.
• Where does the light independent reaction take place?


  Stroma fluid in the chloroplasts
• What are the 3 stages of the light dependant reaction?

  Non-cyclic phosphorylation,

  Cyclic phosphorylation,

  Photolysis,
• Explain non-cyclic phosphorylation


  Light hits photosystem 2 which allows chlorophyll the absorb the light energy.

  The energy allow electrons to get excited and leave the chlorophyll.

  An electron acceptor accepts excited electrons and becomes reduced.

  Electrons passed down electron transfer chain to photosystem 1, which releases ATP.

  Chlorophyll in photosystem 1 accepts electrons.

  Electrons leave photosystem 1 and are accepted by electron acceptor.

  Electrons taken by NADP to form NADPH.

  NADPH passes into light independent reaction.
• What is the chemiosmotic theory?


  The movement of protons down a concentration gradient coupled with ATP synthesis in cellular respiration and photosynthesis
• Where does cyclic phosphorylation take place thats different to non-cyclic?


  Only takes place in photosystem 1.
• What does Non-cyclic phosphorylation produce?


  ATP, NADPH
• What does cyclic phosphorylation produce?


  ATP
• Explain Cyclic phosphorylation


  Light hits the chlorophyll in photosystem 1.

  Electrons become excited and are released.

  Electron acceptor becomes reduced after gaining electrons.

  Electrons travel along electron transfer chain from electron acceptor.

  Accepted by second electron acceptor.

  Electrons are transferred back to photosystem 1 which produces ATP.
• Where does photolysis occur?


  Photosystem 2.
• What does photolysis mean?


  The splitting of water using the energy of light.
• Explain the process of photolysis


  Light hits a molecule of water. Water is split into protons, electrons and oxygen.
• What are the 3 main stages of calvin cycle?


  Carbon fixation

  Reduction

  Regeneration of carbon dioxide acceptor.
• What enzyme catalyses the decarboxylation of ribulose bisphosphate?


  Rubisco
• What happens to ribulose Bisphosphate at the beginning of calvin cycle?


  2 glycerate-3-phosphate produced
• What does the chemiosmotic theory explain?


  It explains how ATP is generated in chloroplasts and mitochondria through a proton gradient.
• What are electron carriers?


  They are proteins embedded into the thylakoid membrane.
• What is the function of the electron transfer chain?


  It facilitates the transfer of electrons from one carrier to another.
• What happens to electrons as they pass through the electron transfer chain?


  They lose energy at each transfer.
• How does the energy lost by electrons contribute to proton transport?


  The energy lost allows active transport of protons from stroma to thylakoid membrane.
• What is the result of proton transport from the stroma to the thylakoid membrane?


  It creates a concentration gradient, high in thylakoid and low in stroma.
• How do hydrogen ions return to the stroma?


  They return by facilitated diffusion via ATP synthase channel in the thylakoid membrane.
• What effect does the passage of protons through ATP synthase have?


  It causes a change in the synthase enzyme that allows ADP to join Pi.
• What are the key steps in the chemiosmotic theory related to ATP synthesis?


  • Electron carriers transport electrons through the electron transfer chain.
  • Energy lost during electron transfer is used for active transport of protons.
  • A concentration gradient of protons is established.
  • Protons return to the stroma via ATP synthase.
  • ATP is synthesized from ADP and Pi.
• Explain the Calvin cycle


  Carbon dioxide diffuses into lead through stomata.

  Carbon dioxide combines with 5 carbon ribulose bisphosphate helped by the enzyme rubisco.

  Two 3 carbon glycerate-3-phosphates are created.

  Glycerate 3 phosphate is reduced and phosphorylated by NADP and ADP to make triose phosphate.

  Triose phosphate goes on to make sugars.

  Ribulose bisphosphate it regenerate.
• How is 2x glycerate 3-phosphate converted into 2x triose phosphate?


  Glycerate 3 phosphate is reduced and phosphorylated by ATP and NADPH to make triose phosphate.