photosynthesis

• where does the light dependent reaction occur in plants?

  thylakoid
• where does the light independent reaction occur in plants?

  stroma
• role of light in photoionisation?

  • chlorophyll absorbs light energy exciting electrons causing them to be released from chlorophyll
• 2 main stages involved in atp production in ldr?

  1. electron transfer chain
  2. chemiosmosis
• what happens in electron transfer chain?

  • electrons released from chlorophyll move down etc & release energy
• how is a proton gradient established during chemiosmosis?

  energy released from etc used to pump hydrogen from stroma across thylakoid membrane
• how does chemiosmosis produce atp in ldr?

  hydrogen moves down proton gradient via atp synthase which provides energy needed for adp + pi = atp
• role of light in photolysis?

  light energy splits molecules of water
• what happens to products of photolysis of water?

  • hydrogen - used to reduce nadp - nadph
  • electrons - replaces those lost from chlorophyll
  • oxygen - used for respiration/diffuses out of leaf as waste product
• how is nadph produced in ldr?

  electrons & hydrogen used to reduce nadp
• where is nadp found?

  stroma
• where do h ions & electrons used to reduce nadp come from?

  • hydrogen - photolysis of water
  • electrons - chlorophyll
• name stages in calvin cycle/lir?

  1. carbon fixation
  2. reduction
  3. regeneration
• carbon fixation?

  • carbon dioxide combines with rubp forming 2 molecules of gp
• reduction in calvin cycle?

  • gp reduced into 2 molecules of tp
  • requires nadph & energy from atp
• how does lir result in production of useful organic substances?

  1 carbon atom leaves cycle

  some tp converted to glucose
• regeneration in calvin cycle?

  • rubp reforms
  • regenerated from tp
• role of atp & nadph in lir?

  atp - provides energy to reduce gp into tp

  nadph - provides hydrogen to reduce gp into tp
• number of carbon atoms in rubp, gp, tp?

  rubp - 5

  gp - 3

  tp - 3
• structure of chloroplasts?

  • thylakoid membranes - large surface area for attachment of chlorophyll/enzymes
  • atp synthase channels within grana - catalyse atp production
  • grana membranes are selectively permeable - allows for proton gradient
  • contains dna & ribosomes - can quickly produce proteins
• define limiting factor?

  factors that determines rate of a reaction even if other factors change to become more favourable
• factors limiting rate of photosynthesis?

  1. temperature
  2. carbon dioxide levels
  3. light intensity
• overcoming effects of limiting factors?

  1. artificial lighting - specific wavelengths
  2. paraffin burners - release heat & carbon dioxide
  3. ventilation
  4. glass panels - prevents heat loss & allows light in
  5. thermometer
  6. humidifier
• why do farmers try to overcome effects of limiting factors?

  to increase yield

  additional costs must be balanced with yield to ensure maximum profit
• what is cyclic photophosphorylation?

  only atp produced

  no nadph produces
• what is non cyclic photophosphorylation?

  produces atp, nadph & oxygen
• where is rubisco found?

  stroma
• temperature affecting rate of photosynthesis?

  • 25C - optimum
  • below 10C - enzymes become inactive
  • above 45C - enzymes denature
  • at high temps stomata close to prevent water loss so less carbon dioxide diffuses into plant
• carbon dioxide levels affecting rate of photosynthesis?

  • 0.4% - optimum
  • if too high stomata start to close
• light intensity affecting rate of photosynthesis?

  • higher light intensity means more energy for ldr - more glucose produced - faster rate
  • too high - chlorophyll become damaged
• calvin cycle/lir?

  1. carbon dioxide combines with rubp - catalysed by rubisco enzyme
  2. produces 2 molecules of glycerate phosphate
  3. gp is reduced into triose phosphate
  4. uses nadph & energy from atp
  5. some tp converted to glucose
  6. most tp used to regenerate rubp to continue the cycle
• light dependent reaction?

  • chlorophyll absorbs light energy exciting eletrons - photoionisation
  • excited eletrons released & move down electron transport chain releasing energy
  • energy used to create proton gradient across thylakoid membrane by pumping hydrogen
  • movement of protons through atp synthase provides energy needed for adp + pi - atp
  • electrons & hydrogens used to reduce nadp - nadph
  • photolysis of water produces protons, electrons(replaces those lost from chlorophyll) & oxygen