topic 5.2.1: photosynthesis Flashcards
describe the structure of chloroplasts
thylakoid membranes (folded membranes containing photosynthetic pigments and ECPs) stack to form grana which are joined by lamellae
stroma (fluid centre containing enzymes)
inner and outer membrane
what is chlorophyll
located in the photosystems on the thylakoids
mix of coloured proteins that can absorb light
what are the 4 key types of pigment in chlorophyll
chlorophyll a- blue/green
chlorophyll b- yellow/green
caratenoids- orange
xanthophylls- yellow
what are the accessory pigments
chlorophyll b, caratenoids and xanthophyll
embedded in thylakoid membrane forming light harvesting system
energy is absorbed and transferred to reaction centre
what is the reaction centre
contains chlorophyll a
where LDR occurs
forms photosystem with light harvesting system and antennae
how is chromatography carried out
pigments added to tlc plate which is placed in solvent which dissolves pigments
more soluble- more movement up plate
rf value= distance travelled/ solvent front
what is the purpose of the light dependent reaction
to harvest light energy to split water and to create atp and reduced nadp
where does the ldr occur
thylakoid membranes
what happens in non-cyclic photophosphorylation
both photosystems involved
light excites electrons, which are released from ps2 to etc. atp produced through chemiosmosis
lost electron replaced from H2O broken down using sun energy
excited electrons released from ps1, passed to etc, atp produced
electrons leaving etc accepted by nadp along with a H+ to produce reducerd NADP
what happens in photolysis
H2O split into H+, electrons and O2 using energy from sun
electrons replace those lost in ps2
H2O -> 2H+ + 2e- + 1/2O2
O2 is byproduct
protons released into thylakoid lumens
as protons flow back across membranes atp is produced (chemiosmosis)
when back in stroma, combine with NADP and an electron from PS1 to form reduced NADP
what happens in cyclic photophosphorylation
electrons leaving ETC after PS1 can be returned to PS1
PS1 can then still lead to ATP production without electrons from PS2
no reduced NADP
where does the light independent reaction take place
stroma
what happens in the calvin cycle
CO2 enters through stomata, diffuses into stroma
combines with RuBP- C is fixed
RuBisCo catalyses reaction, unstable 6C intermediate produced
RuBisCo competitively inhibited by O2
unstable compound breaks into GP then TP using H+ from reduced NADP and ATP
most TP recycled to regenerate RuBP
1 glucose produced from 6 CO2
what is a limiting factor
any factor that reduces the rate of photosynthesis
what are the 3 limiting factors
CO2- low conc, less fixation, RuBP builds up, less GP and TP
TEMP- increase, increased rate of reactions, RuBP builds up, less GP until denaturing
LIGHT INTENSITY- needed for production of ATP and reduced NADP
