Module 3 Flashcards
1
Q
Why do leaves harvest sun energy?
A
To convert CO2 & H2O into chemical energy stored in sugars and other organic molecules
2
Q
What do trees use sugars for?
A
Energy + growth and development
3
Q
Steps of Photosynthesis
A
- Harvesting Light energy
- Photosynthesis in chloroplasts
- Generates organic molecules & molecular O2.
4 . Used in plant cellular respiration + feed other organisms - Generates ATP & heat.
- Generates CO2 & H2O.
- Used in photosynthesis in
chloroplasts.
4
Q
What are autotrophs
A
Producers of their own organic molecules from inorganic sources
5
Q
What are photoautotrophic organisms
A
Use solar energy from sunlight to synthesize organic molecules. Require H2O and CO2
6
Q
What are heterotrophs
A
Consumers who are unable to make their own food, and obtain organic molecules from other organisms.
Depend on photoautotrophs
7
Q
What are decomposers
A
Heterotrophs that consume the remains of organisms and organic little
8
Q
How are fossil fuels formed
A
From the remains of organisms that died hundreds of millions of years ago.
Main product is CO2
9
Q
What can biofuels do?
A
Can supplement fossil fuels, for example: bioethanol and biodeisel
10
Q
Give reasons why growing algae near industrial
plants or highly congested city streets would be a good idea.
A
Algae needs CO2 for photosynthesis, so algae could reduce the CO2 concentration
11
Q
What are chloroplasts
A
-Green parts of the plant
-sites for photosynthesis
-mainly in mesophyll cells
12
Q
How does CO2 and O2 enter and exit leaves
A
CO2 enters and O2 exits through the stomata. CO2 and O2 can diffuse across membranes.
13
Q
What are thylakoid membranes
A
A place where photosynthetic enzymes and other molecules like chlorophyll are stored.
14
Q
What does a chloroplast consist of
A
-outer and inner membrane
-Stroma fluid
-thylakoid space
-thylakoids
-grana
-intermembrane space
15
Q
What does chlorophyll do for organic molecules
A
Chlorophyll absorbs photons that drive the synthesis of organic molecules in the chloroplast
16
Q
What is the equation of photosynthesis
A
6CO2 +12 H2O + Light energy → C6 H12 O6 + 6O2 + 6H2O
17
Q
How do chloroplasts use sun energy
A
Use sun energy absorbed by chlorophyll to split H2O into hydrogen ions, electrons, and molecular oxygen.
18
Q
How is photosynthesis a redox process
A
Reverses the direction of electron flow compared to respiration
Water is split and electrons are transferred with hydrogen ions from H2O to CO2
H2O is oxidized, and CO2 is reduced
19
Q
What processes is photosynthesis made up of
A
Light reactions and the calvin cycle
20
Q
Light-dependent reactions
A
Convert SE to CE, and does not produce sugar.
Uses photons to make ATP and NADP
Supplies chemical energy and NADPH for the calvin cycle
21
Q
Light independent reactions
A
(Calvin cycle)
-Occurs in stroma
-Does carbon fixation
-Uses chemical energy from ATP and NADPH
-Makes glucose
22
Q
What is light?
A
A form of electromagnetic energy/radiation
23
Q
What is white light?
A
A mixture of all wavelengths of visible light
24
Q
How is wavelength related to energy
A
The shorter the wavelength, the greater the energy
25
Why do leaves appear green
Chlorophyll reflects and transmits green light, and absorb violet-blue-red light
26
What are the chloroplast pigments?
- Chlorophyll a
- Chlorophyll b
- Cartenoids
27
Chlorophyll a
A key light-capturing pigment that participates directly in LDR. Is the main pigment.
28
Chlorophyll b
Accessory pigment, which works in conjunction with Chll a
29
Cartenoids
Red/yellow colour
absorb and dissipate excessive light that can damage chlorophyll
30
What does the action spectrum suggest for chlorophyll a
Suggests that violet-blue & red wavelengths of light work best for photosynthesis.
31
What happens when a pigment absorbs a photon
It goes into an excited but unstable state. Excited electrons fall back down to ground state
32
What does each photosystem consist of?
A reaction-centre complex surrounded by light-harvesting complexes
33
What do the light harvesting complexes do
Transfers the energy of photons to the reaction centres
34
Photosystem function
The primary electron acceptor accepted the excited electron from the reaction centre.
Primary electron acceptor becomes reduced
35
What are the two photosystems
PS II (P680) and PS I (P700)
36
What does linear electron flow produce
ATP & NADPH as well as O2
37
Cyclic electron flow
Electrons cycle back from ferredoxin to PS I
Uses ETC to produce ATP
Only uses PS I
Does not produce NADPH and O2
38
Why can cyclic electron flow be useful
It produces more ATP only for the calvin cycles need for more ATP
It might protect cells from intense light-induced damage while producing ATP
39
What is chemiosmosis
The diffusion of hydrogen ions across a semi-permeable membrane-bound structure, down their proton gradient
40
What does chemiosmosis do
Powers ATP synthesis and uses the ETC and ATP synthase to make ATP
41
What does the calvin cycle use ATP and NADPH for
Uses ATP as an energy source, and consumes NADPH as reducing power
42
Phases of the calvin cycle
1. Carbon fixation
2. Reduction
3. Regeneration
43
Carbon fixation
Fixation of CO2, catalyzed by RUBISCO
After this the 5 carbon sugar splits into 3-c phosphoglycerate
44
Reduction
Reduction of a 3-PG sugar to form hexose sugars
3 molecules of RuBP must be carboxylated for a single G3P molecule to be output
45
Regeneration
Regeneration of the CO2 acceptor (RuBP).
5 molecules of G3P are rearranged into 3 molecules of RuBP
46
Calvin cycle input numbers for one glucose
6 cycles
6 CO2 used
18 ATP used
12 NADPH Used
47
What is photorespiration
Occurs on hot, dry, bright days.
The stomata closes to conserve water.
Consumes O2 and produces CO2 and uses ATP
48
Why do plants have alternate pathways for carbon fixation
C4 and CAM plants developed alternate pathways to minimize the effect of photorespiration has for carbon
49
What do C4 plants do in hot and dry climates
They partially close their stomata to conserve water, but reduce CO2 concentration
Divide photosynthesis spatially
50
What is step 1 of C4 photosynthesis
Carried out by PEP carboxylase which is present only in the mesophyll cells
PEP carboxylase has no affinity for O2 but a high affinity for CO2 so it carries out carbon fixation
51
What is step 2 of C4 photosynthesis
The mesophyll cells export their 4-C product to bundle-sheath cells via plasmodesmata
52
What is step 3 of C4 photosynthesis
In the bundle sheath cells the 4-c products release CO2
53
Why are C4 plants better in hot/dry climates than C3 plants
They can function better than C3 under high temps and low CO2 concentrations.
They also have hight water use efficiency
54
CAM plants and photosynthesis
divide photosynthesis temporally
CO2 accumulation is separated from CO2 utilization temporally
55
CAM photosynthesis method
During the night:
Stomata opens and CO2 fixed into malate
During the day:
Stomata closes, and there is less H2O loss
Malate goes to chloroplasts
Light rxn supplies ATP and NADPH
56
How are carbohydrates transported out of the leaves to the rest of the plant?
In the form of sucrose
57
Photomorphogenesis
Perception of light signals, abiotic stress, and acclimation of plant growth and development patterns
58
How might sunflowers react to sunlight
Sunflowers track the sun and after sunset reverse direction so they are facing the sun for the next sunrise
59
How do plants respond to environmental stimuli
The plants alter/modify their growth and development patterns
60
Cell-signal processing pathways
Reception
Transduction
Response
61
CSP: Reception
Receptor cell receives external signal
62
CSP: Transduction
Receptor proteins undergo changes in shape, and phosphorylated or phosphorylated, Internal signal amplified, hormones used
63
CSP: Response
Responder cells receive endogenous signals and change their activity
64
Plant adaptations to sunlight
Obligate shade plants
Facultative sun/shade plants
Obligate sun plants
65
Obligate shade plants
Unable to adapt to high light
66
Facultative sun/shade plants
Able to adapt to light intensity
67
Obligate sun plants
Unable to adapt to low light intensity
68
What do plant detect in terms of light
The presence, direction, intesntiy, and wavelength
69
Classes of photoreceptors
Blue-light photoreceptors and phytochromes
70
Blue light photoreceptors
Detect blue light
initiates phototropism response in plants
71
Cryptochromes and blue light
BL induced inhibition of stem elongation when seedlings first emerge from soil
72
Phototropins and blue light
BL mediated stomatal opening and chloroplast movements in response to light
73
Zeaxanthin and blue light
A BL response limited to guard cells
Positively correlated with stomatal aperture
74
Phytochromes as photoreceptors
Has pigments that absorbs red light
Regulates plants responses to light
Provides plant info about light quality
75
Shade avoidance in plants
Phytochromes detect light quality and leaves above in the canopy absorb red light while shaded plant tissues receive more Far-red than red light
76
Phytochromes photoreversible states
Conversion of phytochrome red to phytochrome far-red triggers developmental responses
77
What does red light do to phytochromes
Turns them on, triggers Pr to Pfr conversion
78
What does far-red light do to phytochromes
turns them off, triggers Pfr to Pr conversion
79
Which Phytochrome conversion is faster?
Pr to Pfr is faster than the reverse
80
Phytochrome mediated responses to light stress
-Shade response de-etoilation
-Seed germination
-Flowering responses
-daylength measuring
81
What are 3 types of flowering responses to daylength
Long day
Short day
Day neutral
82
What is daylength
Environmental stimulus plants use to detect time of year and the relative lengths of day and night
83
Long day response
-Need short nights
-Flower in late spring or early to mid-summer
Short days are for vegetative growth and long days are for flowering
84
Short day response
-Need long nights
-Flower in late summer, sping/fall
- Long days are for vegetative growth
-Short days are for flowering
85
Day-neutral response
Flowering is not affected by daylength
86
Florigen
Signal molecule that triggers flowering when photoperiod is detected by leaves
87
How is flowering locus T activated
It is activated during conditions favouring flowering
88
Gravitropism
The bending of an organ in response to gravity
89
Thigmotropism
A growth response to touch
90
What are the major determinants of crop yield
Climate change and environmental stresses
91
How does drought affect plants
-Reduces photosynthesis
-Diminishes crop yield
- Water loss exceeds the rate of water absorption and plants wilt
92
How do plants response to water deficit
They conserve H2O by reducing their rate of transpiration
Gaurd cells lose turgor and closes stomata
increased release of ABA
93
ABA (Abscisic Acid)
Accumulates in leaves and causes stomata to close rapidly, reducing transpiration and preventing further water loss
Causes K channels in plasma membrane of guard cells to open
94
How does salt stress affect plants
It lowers the water potential of the soil solution
As the water potential become more negative the water potential gradient from soil to roots is lowered thereby reducing water uptake
95
How do plants respond to salt stress
They produce solutes that are well tolderated at high concentrations to keep water potential of cells more negative than soil potential
96
How does heat stress affect plants
Can denature enzymes and disrupt metabolism
Can limit xylem sap flow and nutrient availability
97
How do plants respond to heat stress
They synthesize heat-shock proteins which protect other proteins from heat stress
Close stomata, but cant transpire
98
How does cold stress affect plants
Causes a change in fluidity
Lipids become crystallized
Solute transport is altered
99
How do plants respond to cold stress
They increase proportion of unsaturated fatty acids which keep membrane fluid at lower temps and prevent crystallization
100
What things contribute to plant growth
Water, air, and soil
101
How much of a plants weight is water
80-90%
102
How much of a plants weight is dry matter
10-20%
103
How much of a plant consists of carbs
96%
104
What carbohydrates do plants consist of
cellulose and starch
105
What accounts for 4% of a plants dry matter
inorganic substances, which are essential for plant survival
106
What is nitrogen to plants
An essential mineral, contained n plants proteins, amino and nucleic acids, chlorophyll, and RuBisCO
It is a limiting soil nutrient
107
What are the important sources of nitrogen for plants
NH₄+ and NO₃-
108
Why does nitrogen uptake require lots of ATP
Because inorganic nitrogen forms need ot be reduced before incorporated into organic molecules. It is toxic in its uptake form
109
Nitrogen transport and assimilation in temperate species
Most nitrate assimilation in the root and transports nitrogen as glutamine/asparagine
110
Nitrogen transport and assimilation in warm season species
Transports nitrate through the xylem then assimilates it in the leaves
111
How can nitrate poisoning come to be
Drought stress causes nitrate-loaded soil or corn. Nitrate prevents oxygen from binding to hemoglobin
112
Why does drought cause higher level of nitrate
Drought slows the rate of nitrate-to-ammonium conversion
113
Legume-Rhizobium associations
Rhizobia depends on nutrient like sugars and amino acids from plant cells
in return the plants reap benefits from bacteria like root nodule formation
114
What are the two types of plant-mycorrhizae associations
1. Ectomycorrhizae
2. Endomycorrhizae
115
Ectomycorrhizae
Forms a dense sheath of mycelia on root surface and outside cell walls
116
Endomycorrhizae
Hyphae grow through cell walls then penetrate and enter root cortex but don't pierce cell membrane
117
What is chemical antagonistic association
Plants can protect themselves chemically through cyanogenic compounds
118
Cyanogenic glycosides
Glycosides are stored in vacuoles and released when cell walls are broken which releases toxins
119
What does HCN do
blocks cytochrome C oxidase in ETC and stops ATP formation
120
What are striga
Obligate root-parasitic plants of major agricultural cereal crops that cause severe crop loss
121
What is Cuscuta spp
a type of parasitic vine that grow rapidly covering host plants
