• Where is the site of photosynthesis?

  The leaf is the main structure

  Chloroplasts are the organelles where it occurs
• Describe how the structure of a leaf is adapted?

  A large surface area which absorbs a large amount of sunlight

  Arrangement of leaves prevent shadowing so light can hit all leaves

  Thin leaves to reduce diffusion distance

  Transparent cuticle and epidermis which allow light through to mesophyll

  Numerous stomata for gaseous exchange, short diff pathway for mesophyll

  Stomata open and close in response to varying light intensity

  Air spaces in the leaf allow for a rapid rate of diffusion of gases

  Xylem network for efficiently transporting water
• What is the balanced photosynthesis equation?

  6CO2 + 6H2O ------> C6H12O6 + 6O2
• What are the three main stages of photosynthesis?

  Capturing of light energy by chlorophyll (chloroplast pigments)

  Light dependent reaction

  Light independent reaction
• What is the LDR?

  Light dependent reaction

  Some light energy conserved in chemical bonding

  Electron flow created by effect on chlorophyll

  Protons and electrons are split from water through photolysis

  Produced NADPH and ATP
• What is the LIDR?

  Protons are used to make sugars and other organic molecules
• What are the grana and stroma?

  Two distinct regions of the chloroplast

  Grana are stacks of disc structures called thylakoids, LDR occurs here, intergranal lamella join adjacent grana

  Stroma is a fluid filled matrix where LIR occurs these may contain starch grains
• What is light energy used for in the LDR?

  To make ATP by adding an inorganic phosphate to ADP

  Split water into h+ ions and OH- ions, also known as photolysis
• Describe how ATP is produced in the LDR?

  Chlorophyll absorbs light energy, boosts the energy of electrons

  Excited electrons leave chlorophyll

  Chlorophyll becomes ionised by photoionisation

  Taken up by electron carrier

  Chlorophyll is oxidised

  Electron carrier gaining electrons is reduced

  Hydrogen ions move down conc gradient through ATP synthase from thylakoids to stroma

  Electron transport chain in thylakoid, energy lost at each stage

  This is used to form ADP + Pi — ATP
• How can ATP production be explained in LDR?

  Chemiosmotic theory
• What is the importance of NADP?

  Carries electrons with it into the LIR

  Further potential source of energy
• Where does the LDR take place?

  Thylakoid membranes of granum

  Grana
• What are the main products of LDR?

  NADPH (reduced NADP)

  ATP
• Describe the chemiosmotic theory?

  Thylakoids have protons pumped from stroma using protein carriers

  Energy is needed for this and provided by photolysis

  Protons from photolysis also produce protons which increase gradient

  Maintain proton gradient between thylakoid space and stroma

  Protons pass through ATP synthase channels

  When protons pass through the change the shape of the enzyme which then catalysed ADP + Pi — ATP
• Describe the photolysis of water?

  Loss of electrons when light hits chlorophyll

  Electrons must be replaced if light energy absorbed

  Water molecules split using light energy and provide electrons for replacement

  Protons are also produced and pass out of the thylakoid in ATP synthase

  Electrons taken up by NADP which becomes reduced for the LIR
• How are chloroplasts adapted to their function of capturing sunlight?

  Thylakoid membranes have a large surface area for attachment of chlorophyll, electron carriers and enzymes the carry out LDR

  Network of proteins in the grana hold chlorophyll in a specific manner that allows for maximum light absorption

  Granal membrane has ATP synthase channels which catalyse production of ATP, also selectively permeable

  DNA and ribosomes so can quickly manufacture proteins invoiced in LDR
• What products are used in light independent reaction?

  NADP and TP and RUBP
• Where does the LIR take place?

  Stroma of chloroplasts
• What are the uses of the products of the Calvin cycle?

  GP, TP

  Lipids are used for..

  Triosphosphate for production of glycerol

  Fatty acids for the production of glycerate 3 phosphate

  Glycerate 3 phosphate for amino acids
• What are the three main stages of the LDR, describe them (6)

  Photolysis - light energy absorbed by the chlorophyll is used to split water to hydrogen, o2, electrons, NADP picks this up for the LIR and becomes NADP, electron in ETC, o2 used in respiration

  Photoionisation -light energy absorbed by chlorophyll, electrons become excited, electrons leave chlorophyll

  Chemiosmotic- electrons with energy move down proteins in ETC, energy released which is used for pumping protons across chloroplast membrane, through atp synthase, producing ATP, protons reduce NADP
• Describe the process of the light independent reaction?

  Co2 diffuses from the environment into the leaf through stomata and dissolves in water around the walls of the mesophyll, cell surface membrane and chloroplast membrane and then into the stroma

  Co2 reacts with ribulose bisphosphate (5c) ands catalysed by rubisco

  This reaction causes formation of 2 3 carbon glycerate three phosphate molecules

  Reduced NADP is used to reduce the glycerate three phosphate to triose phosphate using energy supplied by ATP

  The NADP is re formed and goes back to LDR to be reduced again

  Some triosphosphate molecules are converted to organic products such as starch cellulose lipids

  Most triosphosphate molecules are used to regenerate ribulose bisphosphate using ATP from the LDR
• How is the chloroplast adapted for the light independent reaction?

  Fluid of stroma contains enzymes needed to carry out LIDR

  Stroma fluid surround the grana and therefore the products of the LDR can readily diffuse

  Contains both DNA and ribosomes so can quickly produce proteins and DNA
• What factors effect the rate of photosynthesis?

  Light intensity, CO2 concentration, temperature
• What are limiting factors?

  Least favourable value that is responsible for preventing the reaction or prevent it from increasing any further
• Describe how the rate of photosynthesis would be affected as you move from darkness to bright light?

  More light

  More photosynthesis as more light energy absorbed by chlorophyll

  This rate would increase until another factor becomes limiting
• How is the rate of photosynthesis measured?

  the amount of O2 released per unit time

  Amount of co2 used up and glucose produced
• Suggest what happens to levels of o2 produced and co2 used with increasing light intensity?

  More co2 used means more photosynthesis

  More photosynthesis causes more glucose therefore more co2
• What is the name of this occurrence 'photosynthesis=respiration?

  Compensation point
• What two human activities cause an increase in co2?

  Agriculture

  Deforestation
• Why do crop growers increase co2 in green houses?

  Greater crop yield as more glucose allowing for more respiration and growth

  Sweeter produce as more glucose
• Explain why co2 concentration effects photosynthesis?

  Co2 related with increase acidity

  Affecting enzyme activity

  Such as ribulose bisphosphate in respiration.
• What is the relationship between increase in temperature and photosynthesis?


  Increase temperature increased photosynthesis
• What is the optimum temperature for photosynthesis?

  25 degrees C
• Why does the rate of photosynthesis decline at higher temperatures?

  Denature enzymes

  Change shape of active site

  Such as rubisco
• Describe how light energy absorbed by chlorophyll molecules is used to synthesis ATP?

  Excitation of electrons in chlorophyll

  Electrons leave chlorophyll

  Down electron transport chain

  Loss of energy down each carrier

  Energy used for synthesis of ATP

  ADP + Pi — ATPSee an expert-written answer!We have an expert-written solution to this problem!
• In which part of the chloroplast do LDR occur?

  Grana
• What is the role of chlorophyll in photosynthesis?

  Chlorophyll absorbs some of the energy from visible light

  Loses electrons and becomes oxidised

  Accept new electrons from water which cause water to be lost
• How is light converted to chemical energy in light dependent reactions?

  Electrons raise to higher energy levels

  Use of electron carriers

  ATP synthase channel

  Diffusion down electron transport chain

  Production of ATP
• Explain why an increase in dry mass of a plant over twelve months is less than the mass of hexose produced over the same period?

  Some hexose sugars used in respiration

  Co2 produced is lost to environment so less carbon biomass

  Plant may be eaten or decomposed
• Explain why it is important to check the repeatability of the results in an investigation. (2)

  Increases the reliability of the measurements;

  If results are repeatable, anomalies are unlikely.