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BISC 205 > plant mt > Flashcards

plant mt Flashcards

1
Q

what responses does the CO gene trigger?

A

long day plants: stimulates flowering
short day plants: inhibits flowering

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2
Q

what are the steps for a C4 pathway?

A
  1. CO2 + H2O = HCO3 (bicarbonate)
  2. bicarbonate + 3-C forms malate (4-C) catalyzed by PEPCase
  3. malate diffuses into vascular bundles
  4. NADP-malate dehydrogenase removes a CO2 from malate, end result is a pyruvate, CO2 is sent to rubisco directly
  5. pyruvate diffuses out and enzyme regenerates 3-C
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3
Q

briefly describe the phosphorylation cascade

A

after ligand binds to receptors, chain of enzymes phosphorylating each other (adds P from ATP)

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4
Q

briefly describe C3 plants

A
  • calvin cycle (RuBP + CO2 = 3 PGA)
  • found in seasonal environments
  • stomata open in daytime
  • high photorespiration
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5
Q

briefly describe C4 plants

A
  • C4 pathway (3-carbon + CO2 = malate)
  • hot/tropical/dry conditions
  • stomata open shorter periods (less water loss)
  • low photorespiration
  • Kranz leaf structure
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6
Q

what were the four experiments done by Darwin? what conclusion did they lead to?

A

1) control: coleoptiles intact, shoot bends
2) experiment 1: coleoptile removed, shoot stays straight
3) experiment 2: coleoptiles covered, shoot stays straight
4) experiment 3: “jackets” put below coleoptiles, shoot bends

conclusion: substance found in coleoptiles causes bending

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7
Q

what are some auxin receptors and where are they found?

A
  • ABP 1 found in membrane
  • T1R1 found inside cell
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8
Q

what is phototrophism?

A

directed movement in response to light

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9
Q

what do brassinosteroids do?

A
  • promotes growth and regulation of body size
  • alters gene expression
  • helps with other hormonal responses
  • BRI1 and BRL receptors
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10
Q

briefly describe secondary messaging

A

after ligand binds to receptors, messengers activate other molecules that initiate response

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11
Q

how are gibberellins and ABA related?

A

gibberellins - stimulates seed germination by releasing alpha-amylase, digesting nutrients in endosperm
ABA - inhibits seed germination when conditions require dormancy, stores nutrients in endosperm, receptors cause K + Cl to move out, water follows to exit and stomata to close

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12
Q

(calvin cycle) what happens during regeneration?

A
  • 5 G3P + 3 ATP forms the initial 3 RuBP from fixation
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13
Q

what responses does de-etiolation cause?

A
  • opening of apical hooks
  • lateral growth
  • production of chloroplasts (photosynthesis can occur)
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14
Q

how is auxin involved in gravitrophism?

A
  • auxin unevenly distributed in favour of gravity, collects on bottom side of root cap
  • cell elongates in direction of auxin and pulls plant downward
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15
Q

what two conditions are needed to elongate a cell?

A

1) expansins need to loosen cell wall
2) proton pumps need to create electrochemical gradient of ions by pumping out protons, allowing water to diffuse in and create turgor pressure

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16
Q

what responses do ligands trigger?

A

gene expression, activation of transport proteins, changing electropotential/pH

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17
Q

what experiment did Went do? what conclusion did it lead to?

A
  • agar tips infused with auxin placed offf center. shoots bend away from auxin
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18
Q

what role does auxin have in plant maturation?

A
  • promotes fruiting (seeds)
  • lack of auxin causes abscission (leaves/fruit)
  • differentiation of xylem and phloem (roots/shoots)
  • stimulates root growth
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19
Q

briefly describe CAM plants

A
  • extremely arid conditions
  • stomata only open at night
  • low photorespiration
  • very few but thick/waxy stomata
  • can be obligates or switch between C3 and CAM depending on water avail.
  • aquatic CAM plants adapted to limited CO2 availability vs limited water
20
Q

(calvin cycle) what happens during reduction?

A
  • 6 3-PGA + 6 ATP + 6 NADPH makes 6 G3P (1 as an output, 5 to regenerate)
  • enzymes = 3-PGA kinase (adds P from ATP), NADP-glyceraldehyde-3-phosphate dehydrogenase (adds H from NADPH)
21
Q

what is the kranz structure of C4 plants?

A
  • bundle sheath cells surround vascular tissue, mesophyll cells surround bundle sheaths
  • mesophyll make C4
  • bundle sheaths undergo calvin cycle
  • creates a barrier for diffusion
  • provides separation of CO2 and O2 so less competition
22
Q

what is rubisco?

A
  • most abundant enzyme on earth
  • has 8 different binding sites
  • CO2 and O2 compete for binding sites (leads to different results)
  • active when light is available, inactive when CO2 is low
23
Q

what is the statolith hypothesis?

A

mechanoreceptors detect amyloplasts (starch storage) and causes them to be pulled in direction of gravity to bottom of root caps

24
Q

what are the 7 steps of a plant’s action potential?

A

phase 0: rest
phase 1: depolarization from Ca+ channels opening
phase 2: activation of K+ and Cl- channels and movement out
phase 3: peak K+ outward movement
phase 4: repolarization as channels close
phase 5: hyperpolarization
phase 6: inward K+ and Cl- movement reverses hyperpolarization

25
Q

what is the acid-growth hypothesis?

A
  • auxin binds to receptors, signalling an increase of proton pump production
  • more H+ ions out, lowering pH
  • cell elongates
26
Q

what are the different fates of a G3P molecule?

A
  • can make amino acids/nucleotides
  • can be broken down in cellular respiration to make ATP
  • converted into starch for storage
  • converted into sucrose for sugar delivery through phloem
27
Q

how can multiple hormones be active at once?

A

different receptors

28
Q

what responses does etiolation cause?

A
  • hypocotyl growth
  • yellow colour (no chloroplast/photosynthesis)
  • thin upward growth
29
Q

what do cytokinins do and where are they produced?

A
  • produced in root apical meristems
  • causes budding
  • regulates growth by binding to receptors in target cell ER
  • maintains cell cycle (CycD3)/cell division (Cdc25)
30
Q

how does overgrazing/gardening practices affect a plant’s growth?

A

clipping of apical buds from wildlife or gardeners stops upward growth (no auxin) and allows lateral growth instead, resulting in shorter bush like appearance

31
Q

where is auxin located and what physiological response does it trigger?

A
  • found in stems and leaves
  • causes elongation of cells
32
Q

how does the venus fly trap respond to touch?

A
  • sensory hairs inside trap send signals after contact
  • signals travels through plasmodesmata as APs
  • AP causes swelling in outer trap cells, shutting trap
33
Q

how does ABA cause stomata to close?

A
  • inhibits ATPase in guard cells
  • Cl- ions move outward, electrochemical potential changes
  • K+ ions move out, water follows and guard cells become flaccid
34
Q

what are the major end products of photosynthesis?

A

ATP and NADPH

35
Q

what is thigmotrophism and what are the two types?

A
  • movement in response to physical touch
  • positive thigmotrophism: plant grows towards contact (i.e tendrils grappling)
  • negative thigmotrophism: plant grows away from contact (i.e roots and obstacles)
36
Q

what is heliotrophism?

A

movement tracking the sun

37
Q

how do plants sense gravity?

A

starch granules in root caps sense direction of gravity

38
Q

what are phototropins? what responses do they trigger?

A
  • receptors for blue light
  • causes chloroplasts to move towards light and triggers opening of stomata
39
Q

how is flowering triggered?

A

Ft gene activated by florigen enzyme and travels from leaves –> shoot apical meristems to become flowers

40
Q

what is the difference between red and far red light?

A

red light (Pfr) = germination of seeds, de-etiolation
far red light (Pr) = dormancy of seeds, etiolation

41
Q

(calvin cycle) what happens during fixation?

A
  • 3 RuBP binds to 3 CO2 (+ 3 H2O) to make 2 3-PGA (carbon molecules)
  • enzyme = rubisco
42
Q

what is the CAM pathway?

A

nighttime:
1. stomata opens, CO2 + H2O = HCO3 (bicarbonate) (C4)
2. bicarbonate + 3-C forms malate (4-C) catalyzed by PEPCase (C4)
3. malate sent to vacuoles
daytime:
4. stomata closes, no new CO2 enters, malate is released from vacuoles
5. malate converted to pyruvate and CO2, CO2 enters calvin cycle

43
Q

what happens to rubisco during photorespiration? what happens during photosynthesis?

A

photorespiration: RuBP + O2 -> 1 3-phosphoglycerate + 1 2-phosphoglycolate

photosynthesis: RuBP + CO2 -> 2 3-phosphoglycerate

44
Q

what conditions triggers the release of gibberellins?

A
  • break in seed coat to expose seed
  • exposure to red light
45
Q

what happens when ethylene triggers fruit ripening?

A
  • starch turned into sugar
  • cell walls break down
  • chloroplasts break down
  • changes colour to signal for consumers
46
Q

what happens during leaf senescence?

A
  • auxin levels drop
  • enzymes in leaf stem activate and causes stem to weaken at the tip
  • protective cap forms on tip and leaf drops

BISC 205 (10 decks)

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