Photosynthesis Flashcards
1
Q
what is the greatest source of light input
A
sun
2
Q
what is the foundation of all terrestrial ecosystems
A
solar energy
3
Q
how is oil formed
A
former plant material compressed over time
4
Q
what is photosynthesis
A
the biological system that acquires energy from the sun
energy is used to produce sugar from CO2 and H2O
also releases oxygen
5
Q
how was energy before photosynthesis
A
all energy was conserved
6
Q
how is energy with photosynthesis
A
solar energy is a new and endless supply of new energy for life to consume
7
Q
what is the photosynthesis equation
A
6 CO2 + 6 H2O + E –> 6 O2 + 2 C3H6O3 (3c sugar)
8
Q
in photosynthesis what is reduced
A
carbon dioxyde
9
Q
in photosynthesis what is oxidized
A
water
10
Q
where does photosynthesis take place
A
in the chloroplast
11
Q
what are the 2 processes in photosynthesis
A
- light dependant reactios
- carbon fixation
12
Q
what are the components of light dependant reactions
A
- photosystem complexes
- electron transport pathways
- cytochrome
- ATP synthase
13
Q
what do photosynthesis complexes consist of
A
- pigments
- reaction center
- antenna complex
14
Q
what are the 2 photosystem complexes
A
PS II
PS I
15
Q
what is in the antenna complex
A
250-400 individual pigment compounds
reaction center
16
Q
what is the role of the antenna complex
A
capture light through pigments
funnel energy derived from light to reaction center
17
Q
what are pigments
A
compounds in a plant that produce visually observable colour
18
Q
what are the 2 main classes of pigments
A
- light responsive pigments
- secondary pigments
19
Q
what are the light responsive pigments
A
chlorophyll a
accessory pigments
20
Q
how is energy transfered to the organism
A
pigments absorb light
21
Q
what is the colour we see
A
the wavelength that is reflected and NOT absorbed
22
Q
what is the most important pigment
A
chlorophyll a
23
Q
why is chlorophyll a the most important pigment
A
it is the only photosynthetic pigment common to all photosynthesizers
24
Q
how is light captured
A
a photon of energy from light is absorbed by the pigment
the energy from the photon excites an electron and energy is held in the chlorophyll
25
why are different photosynthesizers found in different habitats
not all wavelengths can penetrate all habitats
26
what are accessory pigments
they absorb light energy and transfer energy to chlorophyll a for carbon capture
27
what is the role of accessory pigments
to broaden the range of wavelengths of light that can be used for photosynthesis
28
why are they called accessory pigments
they are accessory to the more critical function of chlorophyll a
29
what are types of accessory pigments
chlorophyll b
carotenoids
phycobiliprotein
30
what is chlorophyll a essential for
O2 generation in photosynthesis
31
what is chlorophyll b used for
absorb light and has excited electron and must transfer the energy to chlorophyll a to be used for photosynthesis
32
what are carotenoids
red, orange, yellow lipid soluble pigments embedded in the thylakoid membrane that absorb light and transfer it to chlorophyll a
33
what are the groups of carotenoids
carotenes
| xanthophylls
34
when are carotenoids visible in leaves
when chlorophyll is absent
35
where are carotenes produces
only in plants
36
what colours are reflected and what colours are absorbed in carotenes
reflected: red, orange, yellow
absorbed: UV, violet, blue
37
what colours are reflected and what colours are absorbed in xanthophylls
reflecetd: yellow
absorbed: orange/red
38
where can we find phycobiliprotein
in cyanobacteria in red algae
39
what colour is absorbed in phycobiliprotein
green
40
when are phycobiliproteins necessary
for organisms that live in deep marine environments where other wavelengths dont penetrate
41
how can energy be transferred from the pigments
- fluorescence
- resonance energy transfer
- transfer of excited electron
42
what is fluorescence
when energy is released as a less energetic photon with a slightly longer wavelength
(loses energy)
43
what is resonance energy transfer
when energy is transferred from an excited chlorophyll molecule to a neighbouring chlorophyll molecule
44
what is transfer of excited electrons
when electron is transferred to a neighouring molecules that is part of an electron carrier
45
what is the consequence of electron transfer
oxidation of chlorophyll molecule
| electron is replaced by oxidation of water molecule
46
what compounds can convert light to chemical energy
chlorophylls
47
what is in PS II
P680 chlorophyll that absorbs 680nm light
48
what is in PS I
P700 chlorophyll that absorb 700nm light
49
where is the site of light absorption
PS II and PS I
50
what are light dependant reactions
a series of coupled reactions driven by light energy
51
how do light dependant reactions function
electrons move down a chain of proteins
52
what are the consequences of light dependant reactions
- proton gradient created by releasing H+ ions into the thylakoid
- synthesis of ATP
- synthesis of NADPH
53
explain step 1 in PS II
- light energy is absorbed by a pigment in the antenna complex
- resonance energy transfer of E to P680 chlorophyll in the reaction center
- P680 loses electron
54
what happens when P680 loses an electron
it is replaced through the oxidation of water
- oxidation of water releases 2 H+ into the lumen of the thylakoid
- oxygen gas is produced
55
explain step 2 in between PS II and cytochrome b6f
- electron from P680 travels down a chain of proteins through oxidation/reduction reaction
56
what are the proteins involved with sending the electron from the PSII to cytochrom b6f
- pheophytin
- plastiquinone a
- plastiquinone b
57
what is a consequence of the electron traveling from PSII to cytochrome b6f
2H+ are sent to the thylakoid lumen
58
explain step 3 between cytochrome b6f and plastocyanin
- plastiquinone donates electron through b6/f complex and releases H+
- cytochrome b6f complex gives the electron to plastocyanin (molecule in the lumen)
- plastocyanin carries electron to PS I
59
explain step 4 in PS I
- plastocyanin gives electron to PS I
| - PS I also absorbs light
60
explain step 5 between PS I and ferredoxin
- electrons oxidized on pS I are used to reduce NADP+ to NADPH
- electrons travel from P700 to ferredoxin
- ferredoxin sends electrons to NADP+ using the catalyst: FNR
61
what is the consequence of electron going from PSI to ferredoxin
- NADPH produced
| - H+ is removed from stroma
62
explain step 6 of H+ gradient and ATP synthase
- electron train is over
- there is an accumulation of H+ within the thylakoid lumen
- H+ powers phosphorylation of ADP to ATP
63
what is referred to as noncyclic electron flow
when electrons have passed down the electron transport chain from photosystem complex II and produced NADPH
electron move uni-directionally from the chlorophyll to ferredoxin
64
How many H+ are released during the noncyclic electron flow
4H+ from the stroma to the thylakoid lumen
| 3H+ removed from the stroma (1 from reduction of NADP, 2 from transfer of e from plastoquinone to cytochrome)
65
What does the proton gradient power
the synthesis of ATP from ADP + P
66
what are the 2 methods for ATP synthesis
1. proton gradient created by the electron transport chain
| 2. PS I functions independently and creates a proton gradient alone
67
what is the end product of noncyclic electron flow and noncyclic phosphorylation
6 NADPH and 6 ATP
68
why is cyclic phosphorylation necessary for carbon-fixation
it generates more ATP than NADPH
| the carbon fixation require 3ATP:2NADPH
69
what is carbon fixation
using energy to create sugars
70
where does carbon fixation take place
calvin benson bassham cycle
71
what compound begins and ends the C3 photosynthesis (also calvin-benson-bassham cycle)
ribulose 1,5-biphosphate (RuBP)
72
in what a part of the cell is the calvin cycle
the stroma of the chloroplast
73
what are the 3 phases of the calvin cycle
1. fixation of CO2
2. Reduction
3. Regeneration of RuBP
74
what happens in fixation of CO2
CO2 is bonded to 3 molecules of RuBP
| fixation is catalyzed by Rubisco
75
what is the most abundant enzyme on earth
Rubisco
76
what happens in reduction
6 molecules of 3-phosphoglycerate (PGA) are converted to 6 molecules of glyceraldehyde 3-phosphate (PGAL)
77
what happens with the PGAL after reduction
5 continue in the cycle
| 1 is converted into sugar
78
what is consumed during reduction
6 ATP and 6 NADPH
79
what happens in the regeneration of RuBP
5 molecules of PGAL reduced to 3 molecules of RuBP
80
what is consumed during regeneration of RuBP
3 ATP
81
what is the calvin cycle equation
3 CO2 + 9 ATP + 6 NADPD + 6 H+ --> PGAL + 9 ADP + 8P + 6 NADP+ + 3 H2O
82
what is the fate of fixed carbon
most PGAL transported to the cytosol and converted into sucrose
some PGAL remain in the chloroplast is converted into starch and stored in the stroma
83
what is photorespiration
where O2 is fixed by Rubisco instead of CO2
84
what are the systems that minimize photorespiration
- C4 photosynthesis with/without Kranz anatomy
- C3-C4 intermediates
- CAM photosynthesis
85
what is C4 photosynthesis
Photosynthesis has an extra step to concentrate CO2 around rubisco
86
what is Kranz anatomy
when there are bundle sheath cells that surround the vascular bundle and mesophyll cells that surround the bundle sheath cells
87
what are the steps of C4
1. CO2 fixed to PEP and form oxaloacetate in cytosol of mesophyll cells
2. Oxaloacetate is converted to malate
3. malate moves from mesophyll cell to neighbouring bundle-sheath cell
4. malate is converted to form CO2 and pyruvate
5. CO2 enters the calvin cycle in the bundle sheath cell
6. pyruvate returns to the mesophyll cell, reacts with ATP to regenerate PEP
88
when is C4 more efficient than C3
high temperatures
89
What is CAM photosynthesis
an extreme adaptation to high temps and dry environments
| can fix carbon in the absence of light
90
what are the steps of CAM at night
1. CO2 is fixed to PEP to form oxaloacetate
2. Oxaloactetate is immediately converted to malate
3. malate is stored in the vacuole as malic acid
91
what are the steps of CAM at day
1. malic acid is transported out of the vacuole and into the cytosol as malate
2. malate is converted and the released CO2 enters the chloroplast
3. CO2 fixed to RuBP by Rubisco and calcin cycle begins and sugar and starch can be produced
