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Plant Physiology > Exam 3 > Flashcards

Exam 3 Flashcards

1
Q

what is membrane potential?

A

the difference in electrical potential between the inside and outside of a cell (mV)

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2
Q

what are the main 2 contributing factors to the establishment of membrane potential?

A
  • proton transport (proton pumps)
  • different ions have different diffusion rates
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3
Q

passive transport occurs along a ____

A

gradient

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4
Q

active transport requires ____

A

energy

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5
Q

short distance transport mechanisms

A

plasmodesmata (diffusion)

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6
Q

long distance transport mechanisms

A
  • xylem and phloem (pressure-driven bulk flow of solutes)
  • apoplastic space (diffusion)
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7
Q

what are the major solutes?

A

mineral nutrients, carbs, dissolved gases, phytohormones, amino acids

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8
Q

loss of ATP causes a ______ in membrane potential

A

drop

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9
Q

2 forms of active transport

A

primary and secondary

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10
Q

primary active transport

A

ATP hydrolysis generates energy, and that energy is used directly for ion/solute transport

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11
Q

secondary active transport

A

carrier proteins take advantage of the proton gradient and couple solute movement with the movement of protons into the cell

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12
Q

symport proteins

A

protons moving along their electrochemical gradient are coupled with solutes so the solutes can move into the cell against their gradient

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13
Q

antiport proteins

A

when a proton moves into the cell, the solute moves out of the cell, against its gradient

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14
Q

Light reactions

A

absorption of light, evolution of CO2, electron transfer, ATP and NADPH synthesis

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15
Q

where do the light rxns occur?

A

thylakoids

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16
Q

carbon reactions

A

utilization of NADPH and ATP, CO2 fixation, generate triose phosphates

17
Q

where do carbon rxns occur?

A

stroma

18
Q

what are the roles of accessory pigments in photosynthesis?

A
  • they help absorb different wavelengths of light and funnel it down towards chlorophyll
  • they help deal with excess light by releasing it as heat or reflecting it
19
Q

what are the 3 fates of light incident on a leaf?

A

absorption, reflection, transmission

20
Q

what are the fates of light absorbed by a pigment?

A

photochemistry, dissipates as heat, fluorescnce, resonance energy transfer

21
Q

photochemistry

A

the pigment molecule gets excited, donates an electron to an electron acceptor, starts the electron transport chain

22
Q

resonance energy transfer

A

energy gets transferred from one pigment molecule to the neighboring pigment, losing some energy each time

23
Q

Where does oxygen evolution occur?

A

right before photosystem II, it releases O2, H+, and an electron that gets used in the ETC

24
Q

what is the primary electron donor in linear electron transfer?

A

water

25
Q

what is the primary electron acceptor in linear electron transfer?

A

NADP+

26
Q

cyclic photo-phosphorylation

A

in photosystem 1, an electron gets transferred to ferrodoxin, then to the cytochrome complex, and eventually ATP is generated and the electron is cycled back into photosystem 1

27
Q

xanthophyll cycle

A

xanthophylls (type of carotenoid) can be interconverted depending on light levels (usually on a diurnal cycle) to reduce damage due to excess light

28
Q

violaxanthin

A

present during low light conditions

29
Q

zeaxanthin

A

present at high light levels

30
Q

adaptations to excess light

A
  • increase carotenoids (dissipate as heat)
  • increase anthocyanins (filter light)
  • reflection
  • leaf bending (avoidance)
  • reorientation of plastids
31
Q

carboxylation

A

rubisco catalyzes a reaction between CO2 and RuBP to form 3PGA

32
Q

reduction

A

3PGA undergos reactions using ATP and NADPH to make triose phosphates

33
Q

regeneration

A

triose phophates react with ATP to create RuBP

34
Q

What are the 3 phases of C reactions?

A

carboxylation, reduction, regeneration

35
Q

Oxygenation

A

rubisco binds to O2 instead of CO2, resulting in excess 2-PG, which cannot be used in photosynthesis

36
Q

C4 metabolism

A

spatial separation of carbon fixation, reduces oxygenation and photorespiration

37
Q

CAM metabolism

A
  • temporal separation of C-fixation
  • stomata only open at night, carbon rxns occur and malic acid accumulates in vacuoles
  • malic acid is used for light rxns during the day
  • CO2 gets trapped in the plastid
38
Q

where is starch generated?

A

chloroplast

39
Q

where is sucrose generated?

A

cytoplasm

Plant Physiology (3 decks)

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