Photosynthesis Flashcards
where does light dependent + independent stage take place in chloroplasts?
- LDS = thylakoid membrane
- LIS = stroma
where are primary and accessory pigments located + what are they ?
- located in photosystems (funnel-shaped)
- primary pigment = chlorophyll a
- accessory pigment = chlorophyll b + carotenoids
stages of the light-dependent stage
(non-cyclic + cyclic photophosphorylation)
- light energy hits PSII (p680) = causes excitation + release of 2 electrons
- 2e- passed to an electron carrier molecule (protein) + travel down ETC, energy released when electrons pass
- the energy is used to pump protons from stroma through the thylakoid membrane into thylakoid space, creating a proton gradient
- protons diffuse down their conc gradient from the thylakoid space through the ATP synthase channel into stroma again, synthesizing ATP
- light energy hits PSI (reaches p700)= e- excited to a higher energy level
cyclic photophosphorylation = e- from chlorophyll go back to PSI through electron carries which releases energy for proton pump - e- passed to ferredoxin ——-> NADP which also accepts a proton ————> reduced NADP
what products from LDS go to LIR
- reduced NADP
- ATP
Light Independent Reaction
(Calvin cycle )
- CO2 enters leaf through stomata + diffuses into stoma
- combines with RuBP (5C) —–> unstable 6C compound = catalysed by RuBisCO
- 6 C compound into 2x GP
- ATP + reduced NADP from LDS used to turn 2x GP into 2x TP
- NADP recycled back to LDS
- TP regenerated into RuBP using ATP or makes glucose
what other useful organic substances do GP and TP make
- 2xTP = hexose sugar
- triose phosphate makes glycerol + GP makes fatty acid = lipids (fatty acids + glycerol)
- amino acids made from TP and GP
what wavelengths of light does chlorophyll absorb
- absorbs blue + red light = reflects green light
Outline the importance of photosynthetic pigments in photosynthesis
- pigment absorbs light energy
- which excites electrons and causes them to move to a higher energy level
- accessory pigments pass energy to primary pigments
- primary pigments pass e- onto an electron carrier to ETC
Explain what is meant by a limiting factor
- a factor that will stop the rate from inc when it’s low when it is low
eg. low co2 conc = prevent the rate of photosynthesis from increasing
Compare non cyclic and cyclic photophosphorylation
cyclic = ONLY ATP made
- no red NADP
- no photolysis of water
- e- recyclced back to PSI
non-cyclic = produces BOTH red NADP + ATP
- photolysis of water
- electrons not recycled back to PSII (replaced by photolysis)
