Photosynthesis Flashcards
1
Q
Photosynthesis converts
A
light energy to the chemical
energy of food
2
Q
The light reactions convert
A
solar energy to the chemical
energy of A T P and N A D P H
3
Q
The Calvin cycle uses the
A
the chemical energy of A T P and
N A D P H to reduce CO2
to sugar
4
Q
photosynthesis nourishes
A
almost the entire living world
5
Q
autotrophs
A
sustain themselves without eating anything from other organisms
6
Q
autotrophs are
A
producers
7
Q
producers
A
produce organic molecules from CO2 and other inorganic molecules
8
Q
most plants are
A
photoautotrophs
9
Q
photoautotrophs
A
use the energy from sunlight to make organic molecules
10
Q
what organisms can do photosynthesis
A
plants
algae
protists
prokaryotes
11
Q
heterotrophs
A
consumers
12
Q
consumers
A
obtain organic molecules from other organisms
13
Q
heterotrophs consume _____ directly and _____ indirectly
A
plants and animals
14
Q
most heterotrophs depend on
A
photoautotrophs for food and O2
15
Q
how are fossil fuels formed
A
organisms that died hundreds of millions of years ago
16
Q
fossil fuels represent what
A
stores of solar energy from the past
17
Q
chloroplasts are similar to the
A
photosynthetic bacteria that they evolved from
18
Q
photosynthetic enzymes and other molecules are arranged
A
together in thylakoid membranes
19
Q
why is having all photosynthetic enzymes and molecules together good
A
more efficient chemical reactions of photosynthesis can happen
20
Q
where are the major locations of photosynthesis
A
leaves
21
Q
where else can photosynthesis happen
A
anywhere that is green
22
Q
chloroplasts are found in what type of cells in the leaves
A
mesophyll
23
Q
how many chloroplasts in a mesophyll cell
A
30 to 40 each
24
Q
what enters through the stomata
A
CO2
25
what leaves through the stomata
O2
26
what two gases can diffuse across membranes in and out of chloroplasts
CO2 and O2
27
chloroplasts are surrounded by
two envelope membranes
28
what do the two membranes enclose in chloroplasts
a dense interior fluid called the stroma
29
interior thylakoid membranes form
interconnected sacs
30
where is the pigment chlorophyll found
in thylakoid membranes
31
what makes the leaves green in plants
chlorophyll
32
what are the stacks of thylakoids called
grana
33
Chemical equation of photosynthesis
6CO2 + 12H2O → C6H12O6 + 6O2 + 6H2O
34
Net consumption of water photosynthesis equation
6CO2 + 6H2O → C6H12O6 + 6O2
35
the simplest possible form of the photosynthesis reaction
CO2 + H2O → [CH2O] + O2
36
what do the brackets mean in [CH2O]
not an actual sugar but represents the general formula for a carbohydrate
37
Need 6 repetitions of simplest equation to
produce a glucose molecule
38
The actual product of photosynthesis is a
three-carbon sugar that can be used to MAKE glucose
39
One of first clues to the mechanism of photosynthesis
discovery that O2 is given off by plants is derived from H2O and NOT from CO2
40
Chloroplast splits water into
hydrogen and oxygen
41
Photosynthesis in sulphur bacteria
Used hydrogen sulphide rather than water for photosynthesis
CO2 + 2H2S = [CH2O] + H2O + 2S
42
Oxygen-18 isotope
O2 from plants was labelled ONLY with this isotope if water was the source of the tracer
43
If this isotope was introduced to the plant in the form of CO2
it was not in the release of O2
44
electrons released by splitting water
incorporated into sugar
45
oxygen is released as a
by-product
46
what does CO2 give rise to in the equation
Carbon and oxygen in glucose
oxygen in water
47
what does water give rise to in the equation
hydrogen in glucose
hydrogen in water
oxygen
48
what is reversed in photosynthesis compared to respiration
electron flow
49
what is oxidized in photosynthesis
H2O
50
what is reduced in photosynthesis
CO2
51
photosynthesis is an ______ process
endergonic
52
two stages in photosynthesis
1. light reaction
2. Calvin reaction
53
where does light reaction happen
thylakoids
54
what four things does the light reaction do
1. split water
2. releases oxygen
3. reduces NADP+ to NADPH
4. generates ATP from ADP by photophosphorylation
55
Calvin cycle does what to carbon
fixes carbon and incorporates CO2 into organic molecules
56
what is used to drive the Calvin cycle
energy from ATP and NADPH in light reaction
57
chloroplast thylakoids transform
light energy into chemical energy of ATP and NADPH
58
light is a form of
electromagnetic energy or radiation
59
light travels in
waves
60
wavelength
the distance between crests of waves
61
wavelength determines
the type of electromagnetic energy
62
electromagnetic spectrum
the entire range of electromagnetic energy or radiation
63
visible light
wavelengths that produce colours we can see
64
light also behaves as discrete particles
photons
65
shorter wavelengths
higher energy
66
wavelength with most energy
gamma rays and purple light
67
longer wavelengths
lower energy
68
wavelength with lowest energy
radio waves and red light
69
pigments
molecules that absorb visible light
70
different pigments
absorb different wavelengths
71
wavelengths that are not absorbed
are transmitted
72
why do leaves appear green
chlorophyll is reflected and transmits green light
73
is green light used IN photosynthesis
no, its reflected
74
absorption spectrum
plots a pigment's light absorption versus its wavelength
75
absorption spectrum of chlorophyll a
violet-blue and red wavelengths are best for photosynthesis
76
action spectrum
profiles the effect of different wavelengths on a process
77
Englemann experiment
the growth of algae in red and purple light was higher in gree light
78
chlorophyll a
main photosynthetic pigment
79
accessory pigments
chlorophyll b
carotenoids
80
chlorophyll b
broadens spectrum used for photosynthesis
81
carotenoids
absorb excess light that can damage chlorophyll and the cell
82
CH3 is in
chlorophyll a
83
CHO is in
chlorophyll b
84
what happens when a pigment absorbs light
it becomes excited but VERY unstable
85
what has higher energy ground or excited state
excited state
86
how can energy be released in the form of protons of light or heat
excited electrons have high energy and fall back to the ground state with lower energy
87
a solution of isolated chlorophyll will do what when illuminated
will fluoresce and give off red light and heat
88
photosystem
consists of a reaction-centre complex that is surrounded by light harvesting complexes
89
light-harvesting complexes transfer
the energy of photons to the reaction center
90
what are light-harvesting complexes made from
pigments bound to proteins
91
primary electron acceptor
in the photosystem, it accepts excited electrons from the reaction centre chlorophylls
92
where is chlorophylls oxidized
in the reaction centre
93
what is reduced in a photosystem
primary electron acceptor
94
first step of light reactions
transfer of an electron from chlorophyll a to primary electron acceptor
95
two types of photosystems in thylakoid membranes
1. photosystem 2 (PS II)
2. photosystem 1 (PS I)
96
what photosystem functions first
PS II
97
what is the reaction centre of PS II called
P680
98
why is reaction centre of PS II called P680
chlorophyll a is best at absorbing 680 nm wavelengths
99
reaction centre of the PS I
P700
100
Why is the reaction centre of PS I called P700
absorbs the 700 nm wavelength best
101
Two possible routes for electron flow
cyclic and liner
102
linear electron flow involves
BOTH photosystems
103
linear electron flow produces
ATP and NADPH
104
step 1 in linear electron flow
a photon of light is absorbed by PS II and the energy is transferred amongst pigments until it reaches P680
105
step 2 in linear electron flow
excited electron is transferred from P680 to the primary electron acceptor
It has generated P680+
106
step 3 in linear electron flow
the electrons come from water and the electrons are transferred to P680+ which reduces it back to P680
107
step 4 in linear electron flow
the electron falls down an electron transport chain from primary electron acceptor of PS II to the PS I
108
step 5 in linear electron flow
the energy released during the fall is used to move protons across the thylakoid membrane which generates a proton gradient that drives ATP synthesis
109
step 6 in linear electron flow
light energy excites the P700 reaction centre in PS I like in PS II
P700 becomes P700+ as it loses an electron
missing electron from P700+ is replaced when it accepts electron passed from PS II
110
step 7 in linear electron flow
electron falls from PS I to ferredoxin (Fd)
111
step 8 in linear electron flow
electrons are transferred to NADP+ reducing it to NADPH
112
how is NADP+ reduced to NADPH in linear system
NADP+ reductase
113
what drives the ATP synthesis
generating a proton gradient by the energy released during fall of electron at PS I
114
P680+ is a very strong
oxidizing agent
115
what is available to help drive the Calvin cycle
high-energy electrons of NADPH
116
NADPH formation removes
hydrogen ion from the stroma
117
what is not involved in the cyclic electron flow
PS II
118
what direction does the electron flow in the cyclic cycle without PS II
back from Fd to PS I
119
what is NOT released in cyclic cycle
oxygen
120
what is used in cyclic electron flow
only PS I
121
what is produced in cyclic electron flow
ATP and NOT NADPH
122
why is it important that the cyclic cycle only produces ATP
satisfies the Calvin cycle's need for more ATP than NADPH
123
what may have evolved first
cyclic electron flow or linear
cyclic electron flow
124
what does the cyclic electron flow may do
protect the cell from light-induced damage
125
how is chemiosmosis in chloroplast similar to mitochondria
both generate ATP by chemiosmosis
126
what differs in chloroplast and mitochondria during chemiosmosis
sources of energy
127
mitochondria transfer
chemical energy from food to ATP
128
chloroplasts transform
light energy into the chemical energy of ATP
129
where does chemiosmosis take place in mitochondria
the inner membrane
130
where does chemiosmosis take place in chloroplasts
the thylakoid membrane AND the stroma
131
where is there a higher hydrogen concentration (PH) during chemiosmosis
inter-membrane space (mitochondria)
thylakoid space (chloroplast)
132
where is there a lower hydrogen concentration (PH) during chemiosmosis
mitochondria matrix (mitochondria)
stroma (chloroplast)
133
where does the Calvin cycle take place
in the stroma
134
the Calvin cycle regenerates
its starting material
135
the Calvin cycle builds new organic molecules that leads to
the production of sugar
136
the Calvin cycle uses _____ and the _____ power of electrons carried by ____
ATP
reducing
NADPH
137
NADPH is a
reducing power that can be passed along the electron acceptor
138
ATP is a
versatile energy currency of cells
139
what part of photosynthesis makes NO sugar
light reaction
140
white pigment
the colour we see is the colour most reflected by the pigment
141
black pigment
absorbs all wavelengths
142
when there is high light, where are chloroplasts found in the cell
closer to the wall
143
when there is lower light, where are chloroplasts found in the cell
closer to the center
144
is photosynthesis going towards equlibrium
NO
145
what parts of the light reactions are endergonic
reducing NADP+ to NADPH
generates ATP from ADP
146
what is known as the dark reaction
Calvin cycle
147
what s known as the photo part of photosynthesis
the light reactions
148
what s known as the synthesis part of photosynthesis
Calvin cycle
149
where does electrons come from in linear electron flow
the splitting of water
150
where does electrons end in linear electron flow
the NADP+
151
can the PS I and PS II work interchangeably in linear electron flow
NO
152
where does O2 come from
linear or cyclic
linear
153
ration of ATP to NAPH in linear
1:1
154
how many carbons on there for the phase 1 and 2 of Calvin cycle
18
155
phase 1 of Calvin cycle
carbon fixation
156
phase 2 of Calvin cycle
reduction
157
phase 3 of Calvin cycle
regeneration of CO2 acceptor
158
how many CO2 enters per cycle of Calvin cycle
1
159
what is total input of CO2 in Calvin cycle
3
160
what is the short lived intermediate formed with the addition of CO2 in Calvin cycle
its 3 6-carbon sugar that is highly unstable
161
what does the short-lived sugar in Calvin cycle turn into
6 3-carbon sugar called 3-phosphoglycerate
162
how much ATP is spent to form 3-phosphoglycerate
6 ATP molecules
163
what does 3-phosphoglycerate split into with the ATP
6 3-carbon sugars called 1,3-Bisphosphoglycerate
164
what is used to break down 1,3-Bisphosphoglycerate into G3P
6 molecules of NADPH
165
what does 1,3-Bisphosphoglycerate turn into with the usage of NADPH
6 molecules of G3P
166
what is released to have a total of 5 G3P molecules
a G3P molecule in the form of a sugar
167
what are the 5 molecules of G3P turned into
3 molecules of ribulose biphosphate (RuBP)
168
what must be used to transform G3P into RuBP
3 ATP molecules
169
RuBP becomes what with the addition of a CO2 group
the short-lived intermediate molecule once again
170
in the Calvin cycle, carbon enters as _____ and leaves as _____
CO2 and G3P
171
net synthesis of 1 G3P how many times must the Calvin cycle turn
three times to fix three CO2
172
what catalyzes the carbon fixation step of Calvin cycle
Rubisco
173
most common enzyme in plants
Rubisco
174
what is the molecule that accepts CO2 in the Calvin cycle
RuBP
175
what is a problem for plants
dehdyration
176
when do plants close their stomata
on hot days
177
what does closing the stomata conserve for plants
H2O but it also limits photosynthesis
178
why does closing the stomata reduce photosynthesis
reduces access to CO2 and causes a build up of O2
179
Photorespiration
take up oxygen in the light and give out some carbon dioxide
180
C3 plants
initial fixation of CO2 is by Rubisco and makes a 2-carbon compound
181
during photosynthesis of C3 plants
Rubisco uses O2 instead of CO2 which produces a two-carbon sugar
182
what does photorespiration use instead of making
ATP
183
does photorespiration make a sugar
NO
184
when did Rubisco first evolve
when the atmosphere had less O2 and more CO2
185
why does Rubisco not exclude O2 in photorespiration
evolved in time that it didn't have to
186
benefit of photorespiration
can limit damaging products of light reactions
187
disadvantage of photorespiration
can drain almost 50% of the carbon fixed by Calvin cycle
188
C4 plants
the Calvin cycle forms a four-carbon sugar as a first product
189
types of cells in C4 plants
bundle-sheath cells and mesophyll cells
190
bundle-sheath cells
arranged in tightly packed sheaths around the veins of the leaf
191
mesophyll cells
more loosely packed between the leaf structure and bundle-sheath cells
192
how do C4 plants minimize the cost of photorespiration
first using CO2 into a 4-carbon compound and THEN increasing CO2 near Rubsico
193
why would C4 plants increase CO2 near Rubisco
to increase its carbon-fixing efficiency
194
3 stages of the C4 sugar production
1. the 4-carbon compound is produced by Pep Carboxylase
2. the 4-carbon compounds are exported to the bundle-sheath cells
3. CO2 is released from the 4-carbon compound in bundle-sheath cells and enters the Calvin cycle
195
what is the 4-carbon compound called in stage 1 of C4 plant sugar production
Oxaloacetate
196
what has a higher affinity for CO2 than Rubisco in C4 plants
PEPC (pep carboxylase)
197
Does PEPC have a higher affinity for CO2 than Rubisco in C4 plants even with O2 present
YES
198
how does the CO2 released by the 4-carbon compound in C4 plants enter the Calvin cycle
through fixation by Rubisco
199
CAM plants
Open stomata during the night and close them during the day
200
how do some plants use to fix carbon that is a variation of C4 metabolism
Crassulacean acid metabolism (CAM)
201
what happens in CAM plants with stomata open at night
CO2 is incorporated into 4-carbon organic acids
202
what happens in CAM plants with stomata closed during the day
CO2 is released from the organic acids and used in the Calvin cycle
203
when is the CO2 released from the organic acids and used in the Calvin cycle
when the CAM stomata's are closed during the day
204
the C4 photosynthesis process takes place in
two separated cells (physically)
205
what takes place in the mesophyll cell of C4 plants
organic acid creation
206
what takes place in the bundle-sheath cell in C4 plants
Calvin cycle
207
what does the photosynthesis process look like in CAM plants
its the SAME cell, not separated, but split into night and day usage
208
what is done at night in CAM plants
organic acid formation
209
what is done in the day in CAM plants
Calvin cycle
210
where is excess sugar stored as starch
roots, tubers, seeds and fruits
211
where does the pigment go in the cyclic electron flow after reaching the primary acceptor
to Fd through the Cytochrome complex to Pc
212
what are the enzymes of the first electron transport chain in linear electron flow
Pq - cytochrome complex - Pc
213
what are the enzymes of the second electron transport chain in linear electron flow?
Fd to NADP+ reductase to the products of NADPH
214
how many linear and cyclic cycles are needed to form a molecule of glucose
12 linear cycles for 12 NADPH and 12 ATP
6 cyclic cycles for 6 ATP
215
how many molecules of ATP and NADPH for one molecule of glucose
18 ATP and 12 NADPH
216
NADPH is an _____ agent because it _____
oxidizing and gives
217
the Calvin cycle is _______
cyclic
218
Rubisco has a higher affinity for
oxygen
