Chapter 8 Flashcards
Autotrophs
“self feeders”
consume h2o and co2
produce sugar and o2
producers/base of food web
Hetertrophs
“other feeders”
consume autotrophs
consumers
decomposers
Photosynthetically active plant tissue/cells
anything green (from chlorophyll)
majority in leaves
mesophyll cells
stomata (gas exchange underside of leaf)
Chloroplasts
30 to 40 per cell
double membrane
stroma (space)
thylakoids (with pigment)
grana
stacks of thylakoids
photosynthesis formula
light energy (+686kcal) + 6co2 + 6H2O -> C6H12O6 + 6CO2
Light dependent rxn.
first half
thylakoids, water oxidization, photo phosphorylation (create atp), ATP + NADPH
O2
Light independent rxn.
second half
calvin cycle, co2 reduction, stroma, ADP+ and NADP+
“sugar”
Wavelength
distance from peak to peak
short : high energy tightly packed
long: lower energy
range of visible light
380-740 nm
most E violet - red least E
what we see is reflection not absorption
7-8 min for sunlight to reach us
Photosynthetic pigments
large organic molecules, interact with light
(reflected [green], transmitted, absorbed)
Major plant pigments
Chlorophyll a
violet-blue and red
Chlorophyll b
blue and yellow
(Chlorophyll main photosynthetically active)
Carotenoids
violet and blue green
Excitation of electrons
ground state (stable)
excited state
electrons absorb energy and “jump” to high energy state
unstable and short lived
when electrons fall back down they release energy
Photosystems
embedded complexes in the thylakoid membrane, think olive
mix of protein and pigments
light harvesting complex and
reaction center complex
Light harvesting complex photosystems
outside of olive, absorb photons, energy passed like wave between pigments, excited electrons
Reaction center complex
photosystems
pit of olive, surrounded by light harvesting complex
proteins and many pigments
special chlorophyll a (p680 and p700)
Photosystem 2
first photosystem (discovered second), chloro-a p680 (Shorter wavelength will absorb more E)
Photosystem 1
second photosystem (discovered first), chloro-a p700 (longer wavelength absorbs less E)
Electron flow
- pigments absorb photon and excite electrons; fall back down and absorbed by another pigment
- p680 of P2
passes e- to primary acceptor, becomes oxidized and can split H20 - enzyme helps split H2O; begins PMF through H into thylakoid space (O2 from H2O)
- e- to P1 through ETC
O2 at beginning; terminal acceptor p700+.
free energy -> H pump - PMF
used to make ATP - light photons in P1
excited with P2 simultaneously
p700 chloro-a excites to primary acceptor; becomes oxidizer and attracts e in ETC - e- go to second ETC through Fd protein makes more NADPH
- NADP+ reductase reduces to NADPH takes H from stroma (keeps gradient)
- then ATP and NADPH leave for the calvin cycle
Photosynthesis gradient
Stroma -> Thylakoid space
light -> chemical E (atp)
water -> ATP (split allows)
ATP; TS-> stroma
Calvin cycle phases
carbon fixation, reduction, regeneration
RuBP
Ribulose bisphosphate
regenerated in the calvin cycle
Carbon fixation
calvin cycle
C from CO2 fixed into RuBP
Rubisco used to catalyze
Rubsico
RuBP carboxylase-oxygenase
enzyme called rubisco used to catalyze carbon fixation
G3P
Glyceraldehyde 3-phosphate
product of calvin cycle
3 carbon sugar
takes 3 co2 for 1 net G3P (6 for 2)
3 turns of cycle
Reduction
Calvin cycle
reduction to G3P
6 G3P for 3 CO2 (1 usable 5 recycled)
6 ATP and NADPH used
recycled G3P into RuBP
Regeneration
Calvin cycle
regenerating CO2 acceptor (RuBP)
multiple rxns
rearrange G3P molecules
5 G3P -> 3 RuBP
3 ATP consumed
Tally from 3 CO2 in calvin cycle
1 G3P to be used
5 G3P for RuBP regen
9 ATP consumed
6 NADPH consumed
6 CO2? double it
Problems with photosynthesis
H2O loss, Photorespiration, Reactive oxygen species
