Photosynthesis Chapter 8 Flashcards
photosynthesis is a ___ reaction
redox
energy for carb building comes from the
sun
ultimate electron donor is
water
oxygen is formed as
a by-product
what is the equation for photosynthesis?
6CO2 + 6H2O–> C6H12O6 + O2
how is ATP and NADPH made?
movement of electrons through photosynthetic ETC
photosynthesis takes place in which organelle?
chloroplasts
the PETC is located in
the thylakoid membrane
thylakod membranes are grouped into sacs called
grana
carbohydrate synthesis takes place in the
stroma
cellular respiration is one of several features that __ organisms share with ___
heterotrophic; photosynthetic
where does the calvin cycle take place?
in the stroma
the incorporation of CO2 is catalyzed by
the enzyme rubisco
3 major steps of calvin cycle
carboxylation (co2 added to 5 carbon molecule)
reduction (e’s transferred to compounds formed in step 1)
regeneration (of the 5 carbon molecule needed for carboxylation)
first step of calvin cycle?
CO2 added to RuBP which gets catalyzed by rubisco
-RuBP & CO2 rubisco’s active site makes 6 carbon compound that breaks into two 3 carbon molecules
what is the reducing agent of the calvin cycle?
NADPH
what exactly does NADPH do?
reduces compounds made by rubisco by transferring electrons to allow carbs to be made from CO2
the regeneration of RuBP requires
ATP
how much of NADPH and ATP needed to regenerate RuBP for reach CO2 molecule?
2 NADPH for every 3 ATP
carbs are stored in the form of
starch
starch made during the day is later used
at night when the plant can’t photosynthesize
why is chlorophyll so good at absorbing light?
large number of alternating single & dbl bonds in the head
carotenoids
allow photosynthesis cells to absorb broader range of visible light
energy is transferred between ___ molecules until it finally reaches
chlorophyll; reaction center
___ is where light energy is converted to chemical energy
reaction center
the electron transfer from reaction center to __ creates a ___ that leads to the formation of
molecules; redox reaction chain; NADPH
the photosynthetic ETC connects two ___
photosystems
photosystem II is used to __, photosystem I is used to ___
pull electrons from H2O; allow electron transfer to NADP+
photosystem II isn’t strong enough to form ___, photosystem I isn’t strong enough to
NADPH; split water
electrons are passed from ___ to ___ to create NADPH
photosystem I; ferredoxin
the accumulation of ___ in the ____ drives the synthesis of ATP
protons; thylakoid lumen
how do protons accumulate in the thylakoid lumen?
2 features of PETC:
- oxidation of water releases protons & oxygen into lumen
- cytochrome-b6f complex and plastoquinone function as a proton pump
which 2 features does the proton pump involve?
- transport of 2 electrons and 2 protons, by diffusion of plastoquinone, from stroma side of PS II to the lumen side of the cytochrome b6f complex
- transfer of electrons w/n the cytochrome b6f complex toa s different mol of plastoquinone (gets more p’s from stroma and dumps into lumen)
why is cyclic electron transport needed?
not enough ATP is produced by PETC so an additional pathway is needed
what is cyclic electron transport?
e’s from PSI are redirected from ferredoxin back into the ETC by plastoquinone
what are the 2 major challenges of photosynthesis?
- if greater light energy absorbed than the c. cycle uses, excess energy harms the cell
- rubisco can catalyze additional co2 or o2 adding o2 instead of co2 can greatly reduce amount of carbs produced
how do reactive oxygen species come about? what does the cell do to combat this?
when there’s a lack of NADP+
- release chemicals to detoxify
- xanthophylls slow formation of them by reducing excess lt. energy
cold temperatures cause
the c. cycle to run slowly
photorespiration leads to
net loss of energy and carbon
photorespiration drains ___ and results in ___
ATP/energy; oxidation & loss in form of CO2
the better rubisco discriminates between CO2 and O2, the ___
slower it works
the ability to use water as an electron donor in photosynthesis evolved in ___
cyanobacteria
how did the 2 photosystems become incorporated?
duplication & divergence
eukaryotic organisms believed to have gained photosynthesis by __
endosymbiosis
evolution of photosynthesis
UV light was around, so there could have been UV-absorbing compounds to shield cells and then mutations over time to harness this power
light dependent reactions take place in the
thylakoid membrane
___ goes into the light dependent reactions and ___ come outs
photons, water; ATP, NADPH, CO2
