photosynthesis Flashcards
what is the name of the things that do photosynthesis
photoautotrophs
photo-light energy
auto-self
troph-feeder
autotroph
get own carbon from inorganic source (feed themselves)
Chemoautotroph
get energy by breaking down chemicals
carbon fixation
Atomospheric CO2 is ‘fixed’ (attached) to an organic molecule called RuBP
The enzyme Rubisco mediates this rxn
RuBP + CO2 forms unstable intermediate
Intermediate splits into 2 PGA (3 C each)
light reactions begin at
photosystem two- chlorophyll a p680
Light-harvesting complex
surrounding complex of proteins and pigments containing
chlorophyll a, chlorophyll b, carotenoids pass energy along to reaction center
reaction center
holds 2 special chlorophyll a molecules and primary e-acceptor protein
light reactions
start at photosystem two
go to light harvesting complex
which go to the reaction center where electron jumps out of chlorophyll a onto 1˚e- acceptor chlorophyll a of photosystem II is now P680+
photosystem 2
more modern version PS w/ specialized enzyme (p680)
light reaction step two
water is split which releases O2 as a waste product, H+ go into thylakoid space and sends an e- through PS 2 for e- transport chain
step 3 light reaction
e - from PS 2 move down e- transport chain
Give energy to proton pumps
e- enter photosystem I
light Re-energized e- in e- chain to exit thylakoid
And are picked up by NADP+
NADPH moves to Calvin cycle to provide reducing power
step four light reaction
Proton pumps powered by e-transport chain
Pump H+ ions into center of thylakoid
H+ ions flow out of thylakoid space through ATPase by facilitated diffusion
Energy of flowing H+ used by ATPase to make lots of ATP
ATP sent to Calvin cycle to provide energy
light independent reactions
Use ATP to make glucose
Take place in the stroma
Require ATP and NADPH from light rxn
Require CO2 from atmosphere
Stroma is filled with thousands of enzymes
Hundreds of Calvin cycles are running simultaneously
how many cycles of the calvin cycle forms a glucose
six cycles
photosynthesis waste product
oxygen
chemical put in to photosynthesis
water
useful thing you get out of photosynthesis
NADPH and ATP
calvin cycle PGAL formation
ATP from light rxn gives a phosphate group to each PGA by substrate level phosphorylation
NADPH reduces each PGA (adding H to them) making them into PGAL (Pi is released)
PGAL also called
G3P
calvin cycle reformation of RuBP
2 of the 12 PGAL are spit out of the cycle and made into glucose
The remaining PGAL are reformed into RuBP using energy from more ATP
Most glucose is converted to sucrose for transport or into starch for storage
photosynthesis chemical equation
6 CO2 + 12 H2O –> C6H12O6 + 6 O2 + 6 H2O
photosynthesis equation with net water
6 CO2 + 6 H2O –> C6H12O6 + 6 O2
evolution of photosynthesis
1st photosynthetic bacteria did cyclic psyn
Only makes ATP not sugar
Still used by many bacteria
Evolution of PS II
Non-cyclic psyn because e- obtained from H2O (not recycled)
Allowed production of high energy carbs
A way to transport & store chemical energy
Allowed larger more complex organisms
All plants and some bacteria have PS II and do non-cyclic psyn
chloroplast structure
green in leaves
wax on the outside
stoma strata space in between to open and close for CO2 to enter
waxy cuticle used to
prevent dehydration
closing stomata causes
increase in O2 and decrease in CO2
photorespiration
closed stomata so more O2 less CO2
Rubisco starts binding to O2
Puts O2 into calvin cycle
bad less glucose
plants that do photorespiration are called
C3
how do plants avoid photorespiration
Close stomata but keep CO2 levels near rubisco high by doing C4 cycle in mesophyll cells
In C4 cycle carbon fixation binds CO2 to PEP instead of RuBP
The enzyme binds CO2 to PEP ignores O2
PEP + CO2 = oxaloacetate ( a 4C molecule)
Oxaloacetate converts to malate
malate drops off CO2 to rubisco in bundle sheath cells that run C3 calvin cycle
PEP + CO2 =
oxaloacetate ( a 4C molecule)
CAM plants
cacti and desert plants
fix carbon by C4 cycle only at night
Store malate until day time
Close stomata and us malate as CO2 source to run Calvin cycle in day time when ATP and NADPH become available
Carotenoids absorb
violet and bluegreen light
carotenoids protect the leaf from
excessive light
what kinda of reaction is photosynthesis
uses light nergy to build
catabolic
photosystem one
p700
what are the products of the light reactions/ ET chain and where are they sent
NADPH and ATP sent to the calvin cycle
what kind of reaction is the calvin cycle
Endergonic, anabolic reaction forming
glucose
parts of photosynthesis
e- transport chain/light reactions
calvin cycle where carbon fixation, PGAL formation, and RuBP formation take place
where does the calvin cycle happen
in bundle sheath cells
