Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

B > photosynthesis > Flashcards

photosynthesis Flashcards

photosynthesis I photosynthesis II

1
Q

plants and other photosynthetic pigments contain cellular organelles called what

A

chloroplasts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is the basic role of chloroplasts and what is this process called

A

they trap light energy from the sun and convert it to chemical energy that is stored in sugar and other organic molecules. this is photosynthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what are the 2 modes that an organism uses to acquire the organic compounds it uses for energy

A

autotrophic nutrition and heterotrophic nutrition

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what are autotrophs

A

self feeders - they sustain themselves without eating anything derived from other living beings
they produce their own organic molecules from CO2 and other inorganic raw materials from the environment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is the ultimate source of organic compounds for nonautotrophic organisms

A

autotrophs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what are the producers of the biosphere

A

autotrophs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

almost all ……. are autotrophs

A

plants - the only nutrients they require are water and minerals from soil, and CO2 from the air

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what are photoautotrophs

A

organisms that use light as a source of energy to synthesise organic substances - plants are photoautotrophs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

in what organisms does photosynthesis occur

A

plants, algae, some unicellular eukaryotes and some prokaryotes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what are heterotrophs

A

they obtain organic material by the second major mode of nutrition
they are unable to make their own food and they live on compounds produced by other organisms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

how can heterotrophs obtain energy from other organisms

A

they can be decomposers - by decomposing and feeding on organic litter, such as dead organisms, faeces and fallen leaves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

dive some examples of heterotrophs

A

humans
most fungi
many prokaryotes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what are most heterotrophs dependent on

A

photoautotrophs - that’s where they get their food from

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

how were fossil fuels formed

A

from the remains of organisms that died hundreds if millions of years ago
fossil fuels represent the stores of the suns energy from the distant past

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

how are plants being used in renewable fuel research

A

researchers are looking into ways of capitalizing photosynthesis to provide alternative fuels e.g. biodiesel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are the 2 stages of photosynthesis

A

light reactions - capture solar energy and transform it into chemical energy
calvin cycle - uses the chemical energy produced in the light reactions to make organic molecules of food

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

where is photosynthesis likely to have originated from

A

a group of bacteria that had infolded regions of the plasma membrane containing photosynthetic enzymes and other molecules that functioned similarly to the membranes of the chloroplast

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

according to the endosymbiont theory where did the chloroplast originate from

A

the original chloroplast was a photosynthetic prokaryote that lived inside an ancestor of eukaryotic cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what parts of the plant contain chloroplasts

A

all green parts of the plant including green stems and unripened fruit

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what part of the plant is the major site of photosynthesis

A

the leaves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

chloroplast are found mainly in the cells of the ………….

A

mesophyll

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what is the mesophyll

A

the tissue in the interior of the leaf

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what are the stomata

A

microscopic pores through which carbon dioxide enters the leaf and oxygen exits

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

how is water absorbed by the roots delivered to the leaves

A

via veins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what do leaves use veins for

A

to receive water from the roots

export sugar to the roots and other nonphotosynthetic parts of the plant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

how many chloroplasts does a typical mesophyll contain

A

30-40

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

how many membranes does the chloroplast have

A

2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

what is the fluid called on the cellular side of the membranes of the chloroplast

A

stroma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

what is the membrane system called that is suspended in the stroma of chloroplasts

A

the thylakoid membranes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

the thylakoid membranes separate the stroma from what in the thylakoid sacs

A

the thylakoid space

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

what are thylakoid sacs stacked in columns called

A

grana

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

what is chlorophyll and where is it found

A

the green pigment that gives plats their green colour and resides in the thylakoid membranes of the chloroplasts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

where is the intermembrane space of the chloroplast

A

found between the outer membrane and the inner membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

what drives the synthesis of organic compounds in the chloroplast

A

the light energy absorbed by chlorophyll

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

what is the equation of photosynthesis

A

6CO2 + 6H2O + light energy –> C6H12O6 + 6O2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

what is the reverse process of photosynthesis

A

cellular respiration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

what is the oxygen given off by plants derived from

A

water - NOT carbon dioxide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

what does the chloroplast split water into

A

hydrogen and oxygen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

what is used by some bacteria for photosynthesis instead of water and what is the by-product

A

hydrogen sulphide - globules of sulfur are formed as a waste product

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

how did scientist work out that water was split

A

they carried out 2 experiments
1. they marked the oxygen in water - this marked oxygen was found in the oxygen released from the plant
2. they marked the oxygen in carbon dioxide - this marked oxygen was found in the sugar produced and the water produced but not in the released oxygen
from this it is evident that the oxygen produced in photosynthesis comes from the splitting of water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

where does the hydrogen from the splitting of water go

A

it is used to make the sugar and the water produced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

photosynthesis and cellular respiration both involve what type of reaction

A

redox reactions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

electrons increase/decrease potential energy when they move from water to the sugar in photosynthesis

A

increase - so the process requires energy - it is endergonic - the energy boost is provided by light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

give an overview of the light reactions

A
  1. water is split providing a source of electrons and protons and giving off oxygen as a by-product
  2. light absorbed by chlorophyll drives the transfer of electrons and protons to an electron acceptor called NADP+ where they are temporarily stored
  3. the NADP+ becomes reduced to NADPH by adding a pair of electrons along with a hydrogen ion
  4. the light reactions generate ATP by using chemiosmosis to power the addition of a phosphate group to ADP (photophosphorylation)
  5. the light energy has now been transferred to the chemical energy in NADPH and ATP
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

do the light reactions produce any sugar

A

no - this happens in the calvin cycle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

give an overview of the calvin cycle

A
  1. carbon dioxide is incorporated from the air into organic molecules already resent in the chloroplast (carbon fixation)
  2. the carbon cycle reduces the fixed carbon to carbohydrate by the addition of electrons
  3. the reducing power is provided by NADPH which acquired its electrons from the light reactions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

is energy required to convert carbon dioxide to carbohydrate in the calvin cycle

A

yes it requires chemical energy in the form of ATP which is generated in the light reactions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

what are the metabolism steps of the calvin cycle sometimes referred to as

A

the dark reactions or light independent reactions because none of the steps require light directly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

why does the calvin cycle usually occur during the day of it doesn’t require light

A

because it requires the products of the light reactions (ATP and NADPH) which can only occur in the light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

where in the chloroplasts do the light reactions occur

A

the thylakoid membranes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

where does the calvin cycle happen in the chloroplast

A

in the stroma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

what is the chemical energy in NADP and ATP used for

A

their chemical energy is used to synthesise glucose and other molecules that can be used as energy sources

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

light is a form of energy known as what

A

electrochemical energy which is also called electromagnetic radiation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

what is the distance between the crests of electromagnetic waves called

A

wavelength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

what is the entire range of radiation known as

A

the electromagnetic spectrum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

at what point in the electromagnetic spectrum is visible light

A

between 380-750nm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

why is visible light given its name

A

because it can be detected as various colours by the human eye

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

what are photons

A

packages of light - each one has a fixed quantity of energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

the shorter the wavelength of light the smaller/larger the energy per photon

A

larger

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

which photons have more energy - those of violet light or those of red light

A

violet light - about twice as much energy as red

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

what part of the electromagnetic spectrum drives photosynthesis

A

visible light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

when light meets matter what are the 3 things that can happen to it

A

it can be reflected, transmitted or absorbed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

what are substances that absorb light known as

A

pigments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
64
Q

if a pigment absorbs green light is that the colour it appears

A

no - the colour we see is the colour that is transmitted or reflected

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
65
Q

if a pigment absorbs all light what colour does it appear

A

black

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
66
Q

if a substance absorbs no light what colour does it appear

A

white

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
67
Q

what colour of light does chlorophyll absorb

A

absorbs: violet-blue and red light

transmits and reflects: green light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
68
Q

what can the ability of a pigment to absorb light be measured by

A

the use of a spectrophotometer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
69
Q

what is an absorption spectrum

A

a graph plotting the wavelength of light against absorbance by a substance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
70
Q

what are the 2 accessory pigments in chloroplasts

A

chlorophyll b and the carotenoids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
71
Q

what is the key light capturing pigment in chloroplasts

A

chlorophyll a

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
72
Q

what is an action spectrum

A

a spectrum that profiles the relative effectiveness of different wavelengths of radiation in driving the process
e.g. you could use photosynthesis rate as a measure of effectiveness

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
73
Q

why do chlorophyll a and b absorb light at different wavelengths

A

they have a small structural difference

chlorophyll a has a CH3 group whereas chlorophyll b has a CHO group

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
74
Q

what colour is chlorophyll a

A

blue-green

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
75
Q

what colour is chlorophyll b

A

olive green

76
Q

what are carotenoids

A

hydrocarbons that are various shades of yellow and orange because they absorb violet and blue-green light

77
Q

what is the structure of chlorophyll

A

its made of a porphyrin ring (light absorbing head) and a hydrocarbon tail (interacts with hydrophobic regions of proteins inside the thylakoid membranes)

78
Q

how do some carotenoids provide photoprotection

A

the compounds absorb and dissipate excessive light energy that would otherwise damage chlorophyll or interact with oxygen, forming reactive oxidative molecules that are dangerous to the cell

79
Q

what vegetable is rich in carotenoids and how does this affect your eyes

A

carrots - they have a photoprotective role in the human eye

80
Q

what is the difference between plant and human antioxidants

A

plants produce all the antioxidants they need whereas humans need to consume some of them in their diets

81
Q

what happens when isolated chlorophyll absorbs light

A

when a molecule absorbs a photon of light, one of its electrons is elevated to an orbital where it has more potential energy - this is the excited state of the pigment
the only photons absorbed are the ones whose energy is exactly equal to the energy difference between the ground state and the excited state
the excited state of the pigment is unstable and the electrons drop back down to ground state releasing their energy as heat and/or light
as the light/heat is released the chlorophyll fluoresces

82
Q

what is a photosystem

A

a photosystem is composed of a reaction centre complex surrounded by several light harvesting complexes
the organisation of chlorophyll molecules along with other small organic molecules an proteins in a complex in the thylakoid membranes

83
Q

what is the reaction centre complex of a photosystem

A

an organised association of proteins holding a special pair of chlorophyll a molecules and a primary electron acceptor

84
Q

what is the light harvesting complex of a photosystem

A

they consist of various pigment molecules bound to proteins

85
Q

why can photosystems harvest light over a larger portion of the electromagnetic spectrum compared to a single pigment molecule

A

the number and variety of pigment molecules in a light harvesting complex allows a photosystem to absorb more light

86
Q

when a pigment absorbs a photon where is the energy passed

A

it is transferred from pigment molecule to pigment molecule within a light harvesting complex until it is passed to the pair of chlorophyll a molecules in the reaction centre complex

87
Q

what makes the pair of chlorophyll a molecules in the reaction centre complex “special”

A

molecular environment - their location and the other molecules which they are associated with
their environment enables them to use energy from light not only to boost one of their electrons to a higher energy level but also to transfer it to a different molecule - the primary electron acceptor

88
Q

what is the primary electron acceptor

A

a molecule capable of accepting electrons and becoming reduced

89
Q

what is the first step in the light reactions

A

the solar powered transfer of an electron from the reaction centre complex chlorophyll a pair to the primary electron acceptor

90
Q

when the chlorophyll electron is excited to a higher energy level the …………….. captures it in a redox reaction

A

primary electron acceptor

91
Q

why does isolated chlorophyll fluoresce

A

because there is no electron acceptor so the electrons of the excited chlorophyll drop right back down to ground state instead of being captured by an electron acceptor

92
Q

what are the 2 types of photosystems found in the thylakoid membrane that cooperate in the light reactions of photosynthesis

A

photosystem II and photosystem I

they were named in order of discovery but photosystem II functions first in the light reactions

93
Q

what is the difference between photosystem I and II

A

they have characteristic reaction centre complexes

94
Q

what is the reaction centre complex chlorophyll a of photosystem II known as and why

A

P680

because this pigment is best at absorbing light of wavelength 680 nm (red part of the spectrum)

95
Q

what is the reaction centre complex chlorophyll a of photosystem I known as and why

A

P700

because this pigment is best at absorbing light of wavelength 700 nm (far-red part of the spectrum)

96
Q

P680 and P700 are nearly identical chlorophyll a molecules but how are they different

A

their association with different proteins in the thylakoid membrane affects the electron distribution in the two pigments and accounts for the slight differences in their light absorbing properties

97
Q

what is linear electron flow

A

when ATP and NADH energize the two photosystems. the do this by flowing electrons through the photosystems and other molecular components built into the thylakoid membrane
this occurs during the light reactions of photosynthesis

98
Q

what are the steps of linear electron flow

A
  1. a photon of light strikes one of the pigment molecules in a light harvesting complex of PS II, boosting one of its electrons to a higher energy level
  2. as this electron falls back to tis ground state, an electron in a nearby pigment molecule is simultaneously raised to an excited state. the energy continues to be relayed to other pigment molecules until it reaches the P680 pair of chlorophyll a molecules in the PS II reaction centre complex. an electron in the pair of chlorophylls is excited to a higher energy state
  3. the electron is transferred form the excited P680 to the primary electron acceptor (the P680 becomes P680+ on the loss of the electron)
  4. an enzyme catalyses the splitting of a water molecule into 2 electrons, 2 H+ and an oxygen atom. the electrons are supplied one by one to the P680+ pair, each electron replacing one that was transferred to the electron acceptor. the hydrogen ions are released into the thylakoid space and the oxygen atom binds with another oxygen atom from the splitting of another molecule of water
  5. each photoexcited electron passes from the primary electron acceptor of the PS II to the PS I via an electron transport chain which is made up of the electron acceptor plastoquinone (a cytochrome complex) and a protein called plastocyanin
  6. as electrons floe down the electron transport chain each component carries out redox reactions, releasing free energy that is used to pump hydrogen ions into the thylakoid space, contributing to a proton gradient across the thylakoid membrane
  7. the potential energy stored in the proton gradient is used to make ATP by chemiosmosis
  8. meanwhile, light energy has been transferred via light harvesting complex pigments to the PS I reaction complex, exciting an electron of the P700 pair of chlorophyll a molecules
  9. the photoexcited electron is then transferred to the PS I primary electron acceptor creating P700+which can now act as an electron acceptor, accepting an electron that reaches the bottom of the electron transport chain from PS II
  10. photoexcited electrons are passed in redox reactions from the primary electron acceptor of PS I down a second electron transport chain through the protein ferredoxin (this doesn’t create a protein gradient and so ATP isn’t produced)
  11. the enzyme NADP+ reductase catalyses the transfer of electrons from ferredoxin to NADP+. 2 electrons are required for its reduction to NADPH. this process also removes H+ from the stroma
  12. electrons in NADPH are at a higher energy level than they are in water (where they started) so they are more readily available for the reactions of the calvin cycle
99
Q

what is cyclic electron flow

A

when photoexcited electrons take an alternative path which uses PS I but not PS II - it is a shorter circuit

100
Q

what happens in cyclic electron flow

A
  • the electrons cycle back from ferredoxin to the cytochrome complex, then via a plastocyanin molecule to a P700 chlorophyll in the PS I reaction centre complex
  • there is no reduction of NADPH and no release of oxygen from this process but cyclic flow does generate ATP
101
Q

when does cyclic electron flow occur

A

in photosynthetic bacteria that only have one PS

in photosynthetic species that possess both PSs (all eukaryotes and some prokaryotes

102
Q

what evidence suggests that cyclic electron flow may be photoprotective

A

plants with mutations that render them unable to carry out cyclic electron flow are capable of growing well in low light, but not well where light is intense

103
Q

what is chemiosmosis

A

the process that uses membranes to couple redox reactions too ATP production

104
Q

how do chloroplasts and mitochondria generate energy

A

an electron transport chain pumps protons across a membrane as electrons are passed through a series of carriers that are progressively more electronegative
the electron transport chains transform redox energy to a proton motive force, potential energy stored in the form of a H+ gradient across a membrane
an ATP synthase complex in the same membrane couples the diffusion of hydrogen ions down their gradient to ATP synthesis

105
Q

what is the difference in the ATP generation process in mitochondria and chloroplasts

A

mitochondria use chemiosmosis to transfer chemical energy from food molecules to ATP
chloroplasts use chemiosmosis to transform light energy into chemical energy in ATP

106
Q

describe the pumping of protons in the mitochondria

A

electron transport proteins in the inner membrane of the mitochondria pump protons from the mitochondrial matrix out to the intermembrane space which serves as a reservoir of hydrogen ions

107
Q

describe the pumping of protons in the chloroplast

A

electron transport proteins in the thylakoid membrane of the chloroplast pump protons from the stroma into the thylakoid space which serves as a reservoir of hydrogen ions

108
Q

what 3 steps in the light reactions contribute to the hydrogen gradient across the thylakoid membrane

A
  1. water is split by PS II on the side of the membrane facing the thylakoid space
  2. a plastoquinone transfers electrons to the cytochrome complex, 4 protons are translocated across the membrane into the thylakoid space
  3. a hydrogen is removed from the stroma when it is taken up by NADP+
109
Q

how do H+ power ATP synthesis in photosynthesis

A

the diffusion of H+ from the thylakoid membrane to the stroma powers ATP synthase

110
Q

on what side of the thylakoid membrane is NADPH produced

A

the side of the membrane facing the cytosol, where the calvin cycle reactions take place

111
Q

how is the calvin cycle similar to the citric acid cycle

A

the starting material is regenerated after some molecules enter and others exit the cycle

112
Q

is the calvin cycle catabolic or anabolic

A

anabolic - it synthesises carbohydrates and consumes energy

113
Q

in what form does carbon enter the calvin cycle

A

as CO2

114
Q

how does the calvin cycle use NADPH

A

as a reducing power for adding high energy electrons to make sugar

115
Q

what is the carbohydrate called that is produced directly from the calvin cycle

A

glyceraldehyde 3 phosphate (G3P)

116
Q

for the net synthesis of one molecule of G3P, how many times does the cycle need to take place

A

3 times - fixing a total of 3 molecules of CO2 (one per cycle)

117
Q

what does carbon fixation refer to in photosynthesis

A

the initial incorporation of CO2 into the organic material

118
Q

what are the 3 phases of the calvin cycle

A
  1. carbon fixation
  2. reduction (gaining electrons)
  3. regeneration of the CO2 acceptor (RuBP)
119
Q

describe phase 1 of the calvin cycle: carbon fixation

A
  • each CO2 molecule is incorporated one at a time, by attaching it to a 5 carbon sugar RuBP. the enzyme that catalyses this is rubisco
  • the product of the reaction is a 6 carbon intermediate that is short lived because it is so unstable and immediately splits in half forming 2 molecules of 3 phosphoglycerate (per CO2 molecule)
120
Q

what is the most abundant protein in chloroplasts

A

rubisco

121
Q

describe phase 2 of the calvin cycle: reduction

A
  • each molecule of 3 phosphoglycerate receives an additional phosphate group from ATP, becoming 1,3 - bisphosphoglycerate
  • a pair of electrons donated from NADPH reduces 1,3 - bisphosphoglycerate, which loses a phosphate group in the process to glyceraldehyde-3-phosphate (G3P) which stores more potential energy
122
Q

for every 3 CO2 molecules that enter the calvin cycle how many G3P molecules are produced

A

6 - but only one molecule can be counted as net gain because the rest are required to complete the cycle

123
Q

how many carbons are in 5 molecules of G3P

A

15

124
Q

one molecule of G3P is used by the plant cell but what happens to the other 5

A

they are recycled to regenerate the 3 molecules of RuBP

125
Q

describe phase 3 of the calvin cycle: regeneration of the CO2 acceptor (RuBP)

A
  • in a complex series of reactions, the carbon skeletons of 5 molecules of G3P are arranged by the last steps of the calvin cycle into three molecules of RuBP
  • to do this, the cycle spends 3 more molecules of ATP
    the RuBP is now prepared to receive CO2 again and the cycle continues
126
Q

how many carbons are there in 6 molecules of G3P

A

18 - 3 carbons in each

127
Q

to synthesise one glucose molecule, the calvin cycle uses ……… molecules of CO2, …………. molecules ATP and …………….. molecules NADPH

A

6
18
12

128
Q

to synthesise one molecule of G3P, the calvin cycle uses ……… molecules of CO2, …………. molecules ATP and …………….. molecules NADPH

A

3
9
6

129
Q

what are c3 plants

A

plants whose initial fixation of carbon occurs via rubisco and their first product is a 3 carbon compound, 3-phosphoglycerate

130
Q

give examples of c3 plants

A

rice, wheat and soybean

131
Q

what happens to c3 plants on hot, dry days

A

they produce less sugar because the declining level of CO2 in the leaf starves the calvin cycle due to stomata being partially closed

132
Q

when CO2 becomes scarce what is the response of c3 plants

A
  • they use oxygen in place of CO2 for the calvin cycle - rubisco is able to bind to oxygen
  • this process produces 2 carbon compounds
  • peroxisomes and mitochondria within the cell rearrange and split this compound, producing CO2
  • this is photorespiration
133
Q

what is the difference between normal respiration and photorespiration

A

photorespiration uses energy instead of generating it

134
Q

how do photorespiration and photosynthesis differ

A

photorespiration produces no sugar - in fact it actually decreases photosynthetic output

135
Q

what are c4 plants

A

they preface the calvin cycle with an alternate mode of carbon fixation that forms a 4 carbon comound as its first product

136
Q

what are the 2 most important photosynthetic adaptations

A

c4 photosynthesis

crassulacean acid metabolism (CAM)

137
Q

give examples of some c4 plants

A

sugarcane
corn
members of the grass family

138
Q

in c4 plants what are the two distinct types of photosynthetic cells

A

bundle sheath cells and mesophyll cells

139
Q

what are bundle sheath cells

A

they are arranged into tightly packed sheaths around the veins of the leaf

140
Q

where are the mesophyll cells found

A

between the bundle sheaths and the leaf surface

141
Q

are the bundle sheaths and mesophyll cells close together

A

they are closely associated and never more than 2-3 cells away from each other

142
Q

describe the c4 pathway

A
  1. the first step is carried out by the enzyme PEP carboxylase found in the mesophyll cells. this enzyme adds CO2 to PEP forming the 4 carbon product, oxaloacetate. PEP carboxylase has a much higher affinity for CO2 than does rubisco and no affinity for oxygen. PEP carboxylase can fix carbon when rubisco can’t (when stomata are partially closed - low CO2)
  2. the 4 carbon product is transported to the bundle sheath cells through plasmodesmata
  3. the 4 carbon compounds release CO2, which is re-fixed into organic material by rubisco and the calvin cycle. ATP is used to convert pyruvate to PEP, which can accept addition of another CO2, allowing the reaction cycle to continue
143
Q

how do bundle sheath cells generate ATP

A

by cyclic electron flow

144
Q

why is cyclic electron flow the only mode of generating ATP by bundle sheath cells

A

because they only contain PS I not PS II

145
Q

in what environments is the c4 adaptation particularly useful

A

in hot regions with intense sunlight - where stomata partially close during the day

146
Q

what effect does increasing C2 concentration have on c3 and c4 plants

A

c3 - benefits c3 plants by lowering the level of photorespiration that occurs
c4 - largely unaffected

147
Q

what effect does increasing temperature have on c3 and c4 plants

A

c3 - negative effect - would increase levels of photorespiration
c4 - largely unaffected

148
Q

what is more efficient c3 or c4 photosynthesis

A

c4 - because it uses less water and resources

149
Q

what kind of plants have the CAM adaptation

A

water storing plants such as pineapples and cacti
these plants open their stomata during the night and open them during the day - this helps them conserve water but also prevents CO2 from entering the leaves

150
Q

what happens in CAM plants

A

when their stomata are open at night they take up CO2 and incorporate it into a variety of organic acids
this is called cam

151
Q

what do the mesophyll cells of CAM plants store

A

organic acids they make during the night, in their vacuoles until morning when the stomata close

152
Q

what happens to CAM plants during the day

A

light reactions supply ATP and NADPH for the calvin cycle

CO2 is released from the organic acids made the night before to become incorporated into sugars in the chloroplasts

153
Q

how is the CAM pathway similar to the c4 pathway

A

CO2 is first incorporated into the organic intermediates before it enters the calvin cycle

154
Q

how is the c4 pathway different from the CAM pathway

A

in c4 the initial steps of carbon fixation are separated structurally from the carbon cycle whereas in CAM the two steps occur in the same cell but at different times

155
Q

what proportion of the organic material made by photosynthesis is consumed as fuel for cellular respiration in plant cell mitochondria

A

50%

156
Q

what can the sugar produced from photosynthesis be used to synthesise

A

lipids, proteins, cellulose and other products
sucrose - for in the cytosol
starch - for in the chloroplast
cellulose - for the cell wall

157
Q

what is the main ingredient of cell walls

A

cellulose

158
Q

what process is responsible for the presence of oxygen in our atmosphere

A

photosynthesis

159
Q

ATP and NADPH are used too convert CO2 to what kind of phosphates

A

hexose (6 carbon)

160
Q

what are phototrophs

A

photosynthetic organisms

161
Q

where do the light reactions take place

A

the thylakoid membrane

162
Q

where does the calvin cycle take place

A

the stroma

163
Q

what reduces NADP+ to NADPH in the light dependent reactions

A

a hydride ion - a hydrogen with one proton and two electrons

164
Q

the organelles inside the chloroplasts are prokaryotic/eukaryotic

A

prokaryotic

165
Q

chlorophyll contains chlorin which is similar to heme but contains which ion instead of iron

A

magnesium 2+

166
Q

what are the major pigments in anaerobic photosynthetic bacteria

A

bacteriochlorophylls a and b

167
Q

in order to absorb light what features do pigments need to have

A

the molecules of the pigment must have a conjugated bonding system (alternating double bonds)

168
Q

which pigments increase the range of absorbance of plants

A

carotenoids

169
Q

where are the PS

A

they contain many proteins and pigments embedded in the thylakoid membrane

170
Q

how are the two PS connected

A

by cytochrome complex

171
Q

PS I are concentrated in the lamella membranes (not grana stacks) and are actively engaged in what type of electron transport

A

cyclic electron transport

172
Q

electron falls downhill/uphill in energy between the two photosystems

A

downhill

173
Q

light is capture by ………. complexes

A

antenna

174
Q

…………… drives the transport of electrons from PS II through the cytochrome complex to PS I and ferredoxin and then to NADPH

A

light energy

175
Q

in order to be used in chemiosmosis what characteristic must a membrane have

A

it must be impermeable to hydrogen ions so that they can’t just flow back through

176
Q

what is photophosphorylation

A

synthesis of ATP that is fully dependent on light energy

177
Q

what are the 2 major particles of chloroplast ATP synthase

A

CF0 and CF1

178
Q

what does CF0 do

A

it spans the membrane and forms a pore for hydrogen ions

179
Q

what does CF1 do

A

protrudes into the stroma and catalyses ATP synthesis from ADP and Pi

180
Q

for each CO2 reduced in the calvin cycle, how many ATP and NADPH are required

A

2 NADPH

3 ATP

181
Q

what cycle balances the ATP use in thee calvin cycle

A

cyclic electron transport - it produces ATP but not NADPH

182
Q

cyclic flow increases the …………… force and increases ATP production, but no NADP+ is produced

A

proton motive

183
Q

the enzymes in the reductive phase of the calvin cycle are all found in which other biological pathway

A

glycolysis

184
Q

the reaction of RuBP and CO2 using the enzyme rubisco is reversible/irreversible

A

irreversible

185
Q

rubisco doesn’t discriminate well between which two molecules

A

oxygen and carbon dioxide

B (19 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions