photosynthesis

Question 1

what are chloroplasts?

Answer 1

transducers
- they convert light energy into chemical energy

Question 2

what are photosystems?

Answer 2

light-capturing complexes
located in the thylakoid membranes that contain
different pigments, each of which absorbs different wavelengths of light

Question 2

what is in the atennae complex of a photosystem? what occurs here?

Answer 2

• contains chlorophyll a,
  chlorophyll b, and the carotenoids xanthophyll and beta carotene.
• Light energy is absorbed and passed to the reaction centre

Question 3

what is in the reaction centre of a photosystem? what occurs here?

Answer 3

• contains 2 molecules of
  chlorophyll a.
• Electrons in these molecules are excited and rise to a higher energy level

Question 4

what is the purpose of chromatography?

Answer 4

used to observe and identify the different pigments involved in photosynthesis

Question 5

what is the absorption spectrum?

Answer 5

show the peak absorbances of the different wavelengths of light for each pigment

Question 6

what is the action spectrum?

Answer 6

shows the rate of photosynthesis at different wavelengths of light

Question 7

describe the Light dependent reaction
(Non-cyclic photophosphorylation)

Answer 7

• A photon of light is absorbed by PSII.
• The energy is passed to the reaction centre
  where electrons are excited to a higher energy level
  -Electrons are passed along ETC powering proton
  pumps to pump protons from the stroma into the thylakoid space, decreasing the pH.
• This causes them to flow down the gradient back out of the thylakoid space
  through ATP synthetase
• A photon of light hits PSI
  and the same process occurs but this time the electron acceptor passes the electron to NADP, reducing NADP

Question 8

describe photolysis and its significance

Answer 8

• Light splits molecules of water into hydrogen ions, electrons and oxygen.
• The electrons replace those lost by PSII.
• The protons pass into the stroma and are picked up by reduced NADP
• The oxygen is a by-product and is removed

Question 9

describe cyclic photophosphorylation

Answer 9

• the electron acceptor that received electrons from PSI passes them back down the ETC to PSI
• Plants obtain a good source of ATP for the light-independent stage
• high-energy electrons are needed to power the electron transport chain to drive ATP synthetase
• ATP and Reduced NADP will now be used in the stroma for the light independent stage

Question 9

where does the calvin cycle occur?

Answer 9

stroma

Question 10

describe the calvin cycle

Answer 10

• the 5C compound
  ribulose bisphosphate takes up carbon dioxide to form an unstable 6C compound, catalysed by the enzyme RUBISCO
• The unstable 6C compound breaks down into 2 3C compounds called glycerate-3 phosphate
• GP is reduced
  by reduced NADP and using energy from ATP The 2 GP are converted into 2x triose phosphate
• 1C from the TPs will
  be used to synthesise a hexose sugar, the other 5C form ribulose phosphate
  which is regenerated to ribulose bisphosphate using ATP and the cycle
  begins again

Question 11

describe the function and deficiency of nitrogen

Answer 11

• Synthesis of proteins,
  nucleic acids and
  chlorophylls
• Reduced growth of all
  organs and yellowing of
  leaves (chlorosis)

Question 11

describe the function and deficiency of magnesium

Answer 11

• Chlorophyll production
• Yellowing of the leaves
  (chlorosis)