chapter 22 Flashcards
autotroph
photosynthetic organism
heterotroph
organism that obtains energy from chemical fuels
what are the light reactions
reactions powered by sunlight that produces high energy electrons and creates a proton - motive force similar to the ETC
relate photosynthesis and cellular respiration
photosynthesis is the exact inverse of cellular respiration and they are ONLY the same in terms of end products and nothing else!!!!!
features of the chloroplast
-double membrane organelle
-inner membrane surrounds a space called the stroma: site of dark reaction
-thylakoid membranes: location of light reactions
how does photosynthesis begin
absorption of light by photoreceptor molecule = pigment!!
what is the main photoreceptor in the chloroplast of green plants
chlorophyll a
what happens when a photon is absorbed by a pigment?
an electron in the pigment molecule jumps to a higher energy state
what are the two fates of the “excited” higher energy electron
- fall to its original state, releasing the energy as light
- move to a nearby molecule that has a lower excited state, a process called electron transfer
what is the result of electron transfer
photoinduced charge separation because the initial molecule is now positively charged and the molecule that accepted the electron is negatively charged
where does separation of charge happen
the reaction center
what are the two photosystems
photosystem 1 and photosystem II
what does photosystem I do
generates biosynthetic reducing power in the form of NADPH
what does photosystem II do
replenishes the electrons of photosystem I while generating a proton gradient that is used to synthesize ATP
the missing electrons in photosystem II are replaced by…
the photolysis of water
what is the first accepter of electrons?
photosystem I
photosystem I uses light energy to generate what powerful reductant
reduced ferredoxin
the reaction center in photosystem I is called
p700
the electrons from excited P700 go where
flow down an electron-transport chain to the iron-sulfur protein ferredoxin
what does ferredoxin-NADP+ reductase do
transfers electrons from ferredoxin to form NADPH, biosynthetic reducing power
the formation of NADPH occurs
on the stromal side of the thylakoid membrane, where it is used for carbohydrate synthesis
the reaction center in photosystem II is called
P680
excited P680 does what
transfers electrons from water to photosystem I in an ETC that includes pheophytin, a chlorophyll with protons replacing magnesium, plastoquinone, and cytochrome bf complex
what does the ETC of pP680 contain
pheophytin, a chlorophyll with protons replacing magnesium, plastoquinone, and cytochrome bf complex
how is a proton gradient generated by P680
electrons are transferred from water to plastoquinone
P680 is bound to….
D1 and D2 subunits of the photosystem
how do electrons flow upon excitation of P680
electrons flow from pheophytin, then to plastoquinone, and finally to reduce a mobile plastoquinone (QH2)
what does P680+ do
extracts electrons from water bound at the manganese center to maintain redox balance
what does cytochrome bf do
transfers electrons from plastoquinol (QH2) to plastocyanin (Pc)
how is the proton-motive force generated
protons from plastoquinol are released into the thylakoid lumen, and cytochrome bf pumps 2 more protons from the stroma into the lumer
the proton-motive force generation in plants is similar to what in cellular respiration
the mechanism of the Q cycle of Complex III
where does photolysis of water occur
at the water-oxidizing complex (manganese center) of photosystem II
how many photons are required to generate one water molecule
four photons
the four electrons extracted from water are used to reduce
two Q to two QH2
what is the source of O2 for all life
the photolysis of water
what is the ATP synthase of the chloroplast called
CF1-CF0
newly synthesized ATP is released where
into the stroma
how does the membrane orientation of CF1-CF0 compare to the mitochondrial ATP synthase
it is reversed
what happens to the cycle is the NADPH needs are met
ATP is generated without forming NADPH
the electrons flow from ferredoxin through cytochrome bf to plastocyanin and then return to P700
