Photosynthesis

• What is the function of photosynthetic pigments

  to absorb light energy and begin its conversion to storable chemical energy.
• what are the 4 main photosynthetic pigments

  Chlorophyll a and b + beta carotene and xanthophylls
• What are the adaptations of angiosperm leaves

  Large SA, thin transparent waxy cuticle, palisade cells are packed with chloroplasts
• Main structures in chloroplasts needed for photosynthesis

  Stroma, thylakoid membrane, granum
• What reaction happens in the stroma

  light independent (calvin cycle)
• What reaction happens in the thylakoid membrane

  light dependant
• Why are there multiple grana in a granum


  to increase surface areatoincrease the number of light-dependent reactions
• What is the action spectrum

  rate of photosynthesis by whole plant at specific wavelengths

  
• Why are there multiple photosynthetic pigments not just chlorophyll a


  chlorophyll a is not effective at absorbing every wavelength of light for example green light is reflected by chlorophyll a
• What is the antenna complex

  receives light energy in photosynthetic organisms and transfers it to the reaction center, crucial for photosynthesis.
• what are the basic features of both photosystems

  Photosystem I and Photosystem II each have an antenna complex of all pigment types and a reaction centre of two chlorophyllamolecules. They absorb light at different wavelengths.
• what is the process of light harvesting

  The antenna complex harvests light energy and passes the excitation to the reaction centre (from one pigment molecule to another). At the reaction centre, excited chlorophyll a molecules can each emit one electron.
• Outline non-cyclic phosphorylation


  Light Absorption and Electron Excitation:In Photosystems II and I, light energy excites electrons in chlorophyll, which are transferred through an electron transport chain.ATP Formation via Proton Gradient:Electron transfer drives proton pumping into the thylakoid space, creating a gradient that powers ATP synthesis as protons flow back into the stroma.NADPH Production:In Photosystem I, electrons reduce NADP⁺ to NADPH, which, along with ATP, provides energy for the Calvin cycle to produce sugars.
• Outline cyclic phosphorylation


  excited electrons from PS I can pass from the electron acceptor to the electron carriers and back, via the proton pump, to PS I.
• How does photolysis produce electrons for PSII

  Water Splitting and Electron Replacement:Water molecules in the thylakoid space are split into hydrogen ions, electrons, and oxygen, with the electrons replacing those lost by chlorophyll in Photosystem II.Indirect Role of Light:Light indirectly drives this water-splitting process by energizing chlorophyll, which initiates electron loss and the need for replacement.
• What steps occur in the light independant reactions

  1. uptake of carbon dioxide by 5C ribulose bisphosphate (using the enzyme, Rubisco) to form 2 x 3C glycerate-3-phosphates

  
  

  2. utilisation of ATP and reduced NADP from the light- dependent reactions to reduce glycerate-3- phosphate to the 3C carbohydrate, triose phosphate

  
  

  3. the consequent regeneration of ribulose bisphosphate, via ribulose phosphate, which requires ATP
• Which biological molecules can be produced from triose bisphosphate

  glucose (actually fructose bisphosphate)• lipids• amino acids {with the addition of nitrogen obtained

  from nitrates}
• What is a limiting factor

  something which inhibits or slows the rate of reaction when it is in short supply
• What is the light compensation point

  the plant has no net gas exchange as the volume of gases used and produced in respiration and photosynthesis are equal
• What would happen to the plant if light intensity was a limiting factor

  Rate of photosynthesis would decrease over time as the photosynthetic pigments would be bleached and reflect all wavelengths of light
• Why is CO2 needed in photosynthesis

  It is required for thelight-independent stage of photosynthesis,when CO2 is combined with the five-carbon compound ribulose bisphosphate (RuBP) duringcarbon fixation
• What would happen to the plant if CO2 was a limiting factor

  Rate of photosynthesis would decrease as the stomata would close
• Why is an O temp needed for photosynthesis

  As temperature increases the rate of photosynthesis increases = the reaction is controlled by enzymes
• what are two effects if temp was a limiting factor


  Increasing temperature causesstomataon the leaves to closein order toreduce water loss;The light-dependent reaction relies on aproton gradientforming across thethylakoid membrane;membranepermeabilitycan be influenced by extreme temperatures,
• why is magnesium important for a plant

  production of chlorophyll
• What would happen if a plant had a magnesium deficiancy

  less magnesium = less ATP which means less process like cell production (mitosis) so less growth will be seen in a plant with an magnesium deficiency
• how is Mg absorbed

  absorbed through the root as Mg2+ ion dissolved in the soil solutionand transported to the aerial part by the xylem together with water and other dissolved mineral salts, either as an ion or bound to organic acids by complex bonds.
• Why is N important for a plant

  nitrate ions = active transport and amino acids = nucleic acids
• how does a plant absorb N

  Atmospheric nitrogen (N2) is converted to ammonia (NH3) by nitrogen-fixing bacteria in the soil.
• What would happen to a plant if it had a nitrogen deficiency

  A lack of nitrate ions means that less DNA and protein is synthesised → this will affect a range of processes in the plant including: