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biochemistry > chapter 22 > Flashcards

chapter 22 Flashcards

1
Q

autotroph

A

photosynthetic organism

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2
Q

heterotroph

A

organism that obtains energy from chemical fuels

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3
Q

what are the light reactions

A

reactions powered by sunlight that produces high energy electrons and creates a proton - motive force similar to the ETC

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4
Q

relate photosynthesis and cellular respiration

A

photosynthesis is the exact inverse of cellular respiration and they are ONLY the same in terms of end products and nothing else!!!!!

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5
Q

features of the chloroplast

A

-double membrane organelle
-inner membrane surrounds a space called the stroma: site of dark reaction
-thylakoid membranes: location of light reactions

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6
Q

how does photosynthesis begin

A

absorption of light by photoreceptor molecule = pigment!!

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7
Q

what is the main photoreceptor in the chloroplast of green plants

A

chlorophyll a

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8
Q

what happens when a photon is absorbed by a pigment?

A

an electron in the pigment molecule jumps to a higher energy state

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9
Q

what are the two fates of the “excited” higher energy electron

A
  1. fall to its original state, releasing the energy as light
  2. move to a nearby molecule that has a lower excited state, a process called electron transfer
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10
Q

what is the result of electron transfer

A

photoinduced charge separation because the initial molecule is now positively charged and the molecule that accepted the electron is negatively charged

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11
Q

where does separation of charge happen

A

the reaction center

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12
Q

what are the two photosystems

A

photosystem 1 and photosystem II

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13
Q

what does photosystem I do

A

generates biosynthetic reducing power in the form of NADPH

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14
Q

what does photosystem II do

A

replenishes the electrons of photosystem I while generating a proton gradient that is used to synthesize ATP

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15
Q

the missing electrons in photosystem II are replaced by…

A

the photolysis of water

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16
Q

what is the first accepter of electrons?

A

photosystem I

17
Q

photosystem I uses light energy to generate what powerful reductant

A

reduced ferredoxin

18
Q

the reaction center in photosystem I is called

A

p700

19
Q

the electrons from excited P700 go where

A

flow down an electron-transport chain to the iron-sulfur protein ferredoxin

20
Q

what does ferredoxin-NADP+ reductase do

A

transfers electrons from ferredoxin to form NADPH, biosynthetic reducing power

21
Q

the formation of NADPH occurs

A

on the stromal side of the thylakoid membrane, where it is used for carbohydrate synthesis

22
Q

the reaction center in photosystem II is called

A

P680

23
Q

excited P680 does what

A

transfers electrons from water to photosystem I in an ETC that includes pheophytin, a chlorophyll with protons replacing magnesium, plastoquinone, and cytochrome bf complex

24
Q

what does the ETC of pP680 contain

A

pheophytin, a chlorophyll with protons replacing magnesium, plastoquinone, and cytochrome bf complex

25
Q

how is a proton gradient generated by P680

A

electrons are transferred from water to plastoquinone

26
Q

P680 is bound to….

A

D1 and D2 subunits of the photosystem

27
Q

how do electrons flow upon excitation of P680

A

electrons flow from pheophytin, then to plastoquinone, and finally to reduce a mobile plastoquinone (QH2)

28
Q

what does P680+ do

A

extracts electrons from water bound at the manganese center to maintain redox balance

29
Q

what does cytochrome bf do

A

transfers electrons from plastoquinol (QH2) to plastocyanin (Pc)

30
Q

how is the proton-motive force generated

A

protons from plastoquinol are released into the thylakoid lumen, and cytochrome bf pumps 2 more protons from the stroma into the lumer

31
Q

the proton-motive force generation in plants is similar to what in cellular respiration

A

the mechanism of the Q cycle of Complex III

32
Q

where does photolysis of water occur

A

at the water-oxidizing complex (manganese center) of photosystem II

33
Q

how many photons are required to generate one water molecule

A

four photons

34
Q

the four electrons extracted from water are used to reduce

A

two Q to two QH2

35
Q

what is the source of O2 for all life

A

the photolysis of water

36
Q

what is the ATP synthase of the chloroplast called

A

CF1-CF0

37
Q

newly synthesized ATP is released where

A

into the stroma

38
Q

how does the membrane orientation of CF1-CF0 compare to the mitochondrial ATP synthase

A

it is reversed

39
Q

what happens to the cycle is the NADPH needs are met

A

ATP is generated without forming NADPH

the electrons flow from ferredoxin through cytochrome bf to plastocyanin and then return to P700

biochemistry (16 decks)

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