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PLBI 403 MIDTERM > Lectures 5-6-7 > Flashcards

Lectures 5-6-7 Flashcards

1
Q

Passive Transport

A

Refers to the spontaneous movement of molecules down a chemical potential gradient, from high to low

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2
Q

At equilibrium, no further movement occurs unless _________

A

energy is applied (energy input)

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3
Q

Involves the movement of substances against a chemical potential gradient. This process is not spontaneous and requires energy.

A

Active Transport

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4
Q

A common way to do active transport

A

ATP hydrolysis for energy

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5
Q

Movement along a concentration gradient is complicated by

A

membrane permeability and ion passage.

think ions

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6
Q

Diffusion of salts across membranes creates

A

electrical membrane potentials

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7
Q

A small concentration difference, such as one extra anion in 100,000, can result in a significant membrane potential of around

A

-100 mv

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8
Q

K+ ions cross membranes ____________ than Cl- ions, causing a charge separation (diffusion potential).

A

faster

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9
Q

Some ions are passively transported, while others require active transport, true or false

A

true

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10
Q

Ions and Proton Transport

the diffusion potential is caused by

A

ions moving across the membrane causing a voltage

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11
Q

Ion and Proton Transport

Membrane potential in plant cells ranges from

A

-200 mV to -100 mV.

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12
Q

Ion and Proton Transport

[ blank ] is crucial for generating membrane potential through [blank]

A

H+-ATPase, ATP hydrolysis.

ATP hydrolysis is for energy

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13
Q

Proton Transport

Mitochondrial poisons like [blank], [blank] ATP, affecting membrane potential and passive ion transport.

what do these poisons do

A

cyanide, deplete

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14
Q

Membrane Transport

Biological membranes contain transport proteins such as …… (3)

A

channels, carriers, pumps

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15
Q

Membrane Transport Proteins

Channels have….

A

Selective pores extending across the membrane, enhancing diffusion

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16
Q

Channel proteins follow what kind of diffusion

A

passive transport (high to low), down the gradient

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17
Q

A transported molecule follows what kind of diffusion

A

simple diffusion (high to low, down the gradient)

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18
Q

Carriers Proteins…

A

Do not have pores but bind and transport specific molecules across the membrane (down, high to low)

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19
Q

Membrane Transport

Pumps….

A

Use energy (ATP hydrolysis) for primary active transport.

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20
Q

Membrane Transport

Secondary Active Transport…

A

Uses proton motive force (energy by H+ gradients) for transport

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21
Q

Types of Transporters:
Symports: Transport two molecules in the [blank] direction.
Antiports: Transport two molecules in [blank] directions.

A

same, opposite

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22
Q

pumps move protons against or across the gradient

A

against (low to high)

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23
Q

membrane transport

symports and antiports are type of channels, carriers or pumps?

A

pumps

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24
Q

how do symporters work

A

transports two molecules in the same direction across the membrane. One molecule moves down its electrochemical gradient (providing the energy), while the other molecule is transported against its concentration gradient.

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25
Q

how do antiports work

A

An antiporter moves two molecules in opposite directions. One molecule moves down its electrochemical gradient, which provides the energy to move another molecule in the opposite direction, against its gradient.

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26
Q

membrane transport

most transport processes are energized by a [blank] [blank] transport system coupled to [blank]

A

primary active, atp for hydrolysis

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27
Q

Phloem

Phloem in Secondary Growth is found where

A

Found in inner bark

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28
Q

phloem is generally found where

A

outer side of xylem in vascular bundles

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29
Q

in the primary xylem, cells might be red because

A

may contain lignin

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30
Q

Sieve Elements

A

Conduct sugars and organic compounds

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31
Q

in angiosperms, how specialized are sieve tubes

A

highly specialized

32
Q

In gymnosperms, how specialized are sieve cells

A

less specialized

33
Q

xylem transport

[blank] elements lack nuclei, vacuoles, Golgi bodies, ribosomes, and cytoskeletal elements, making them efficient conduits for transport.

A

sieve elements

34
Q

phloem transport

Associated with sieve elements and perform crucial functions like protein synthesis and ATP supply.

A

companion and parenchyma cells

35
Q

phloem transport

sieve elements have [blank] primary cell walls with no [blank]

A

thinner, lignin

36
Q

phloem cells are [blank] at maturity

A

alive

37
Q

Sieve elements are associated 1:1 with a helper cell or companion cell, the companion cell is complete with everything, so any of the proteins found in metabolic functions, not able to be made by sieve elements are taken over by [blank]

A

companion cell (nurse cell)

38
Q

sieve areas are found in [blank] while sieve plates are found in [blank]

A

gymnosperm, angiosperms

39
Q

Sieve plates (in angiosperms) contain

A

pores that interconnect cells.

40
Q

In gymnosperms (sieve areas), pores are obstructed by the

A

ER

41
Q

Damaged sieve tubes are initially sealed by [blank] (not found in gymnosperms)

A

p-proteins

42
Q

p-protein are associated with

A

angiosperms so sieve plates

43
Q

[blank] (a β-1,3-glucan) is deposited long-term to repair damaged sieve plates.

A

callose

sieve plates found in angiosperms

44
Q

companion cells

Sieve elements are connected/associated with to [blank] cells and connect via [blank]

A

plasmodesmata

45
Q

Companion cells are responsible for: (they take over these functions from sieve elements)

A

protein synthesis and atp supply

46
Q

companion cells

Have chloroplasts and a smooth inner cell wall.

A

Ordinary companion cells

47
Q

companion cells

Have finger-like wall ingrowths to facilitate solute transfer.

A

transfer cells

48
Q

companion cells

Highly connected to surrounding cells, aiding in efficient transport.

A

intermediary cells

49
Q

xylem flows in how many directions

A

one, roots to leaves

50
Q

phloem moves in which direction

A

bi-directional, but not at the same time

51
Q

can the direction of the phloem reverse

A

yes

52
Q

A [blank] is any tissue that has more sucrose than it needs, so it can export that solute. A [blank] does not produce enough product to support themselves.

A

source, sink

53
Q

why does water only flow from roots to leaves and not the other way

A

transpiration pull causing negative pressure, cohesion-tension theory, water potential gradient (moves from high in roots to low in leaves bc water is lost in leaves via transpiration), root pressure causing positive pressure

54
Q

Sources involve

A

organs like mature leaves and storage roots.

55
Q

Sinks involve Organs that need more photosynthetic products than they produce, such as

A

roots, developing fruits, immature leaves

56
Q

source and sink status of the same organ can change, true or false

A

true

57
Q

is the pressure flow model passive or active

A

passive

58
Q

The [blank] is driven by an osmotically generated pressure gradient between the source (leaf) and the sink (root, fruit, etc.).

A

bulk flow of phloem sap

59
Q

phlome sap movement (pressure flow model)

Bulk flow refers to the

A

mass movement of the sap due to pressure differences.

60
Q

how does the osmotic (solute) gradient work in the bulk flow of phloem sap

A
  • sugars loaded in phloem (high solute)
  • high solute = low water.
  • water moves into phloem from xylem, creatives positive turgor in sieve elements
  • sugars unloaded into sink
  • less solute = high water, water moves out and reduces this pressure
61
Q

Why is energy is needed at both the source and sink:

A

At the source, active phloem loading occurs (requiring ATP). At the sink, phloem unloading also requires energy.

62
Q

3 mechanisms generate high sugar [ ] in sieve elements

A
  • photosynthesis
  • photoassimilate into sugars
  • active membrane transport
63
Q

which sieve element maintains water potential

A

sieve plate cross walls, water dissipates via open tubes

64
Q

sieve plate pores must be totally [blank] (open or closed)

A

unobstructed

65
Q

how does limitation of atp affected bulk flow movement of phloem sap

A

does not immediately stop phloem transport

66
Q

pressure gradient must be greater than [blank] for bulk flow occur

A

resistance in sieve plates

67
Q

apoplast loading of phloem sugar

A
  • Active Transport
  • Sucrose moves from mesophyll into the apoplast (the cell wall space)
  • actively transported into sieve and companion cells.
    -Requires (ATP) to actively transport sucrose into the phloem using sucrose-H+ symporter. - (H+ ions) drive this symport, created by H+-ATPase (proton pump), which uses ATP to pump protons into the cell.
68
Q

symplastic loading of phloem sap

A
  • sucrose moves from mesophyll to phloem cells via plasmodesmata (cytoplasmic connections between cells).
  • No energy required
  • Larger sugars like raffinose and stachyose are synthesized in intermediary cells
  • prevents them from diffusing back into mesophyll cells, ensuring they move into sieve elements (this is known as the polymer-trapping model).
69
Q

polymer trapping model

A

Larger sugars like raffinose and stachyose may be synthesized in intermediary cells, preventing them from diffusing back into mesophyll cells, ensuring they move into sieve elements (this is known as the polymer-trapping model).

70
Q

symplastic unloading is [blank] while apoplastic unloading is [blank]

A

passive, active

71
Q

How do you drive diffusion in symplastic unloading

A

Once in the sink cells, sugars are metabolized or stored, maintaining a low sugar concentration, which drives the diffusion from the sieve elements.

72
Q

apoplastic unloading

A

especially in tissues like seeds, sugars are unloaded into the apoplast (the space outside cells) and then transported into sink cells by active transporters.

73
Q

symplastic pathways have a high or low sucrose [ ]

A

low, which drives concentration gradient of sugars form sieves to sink

74
Q

how do sinks become sources

A
  • young leaves start as sinks
  • becomes sources when 25% expanded
  • starts at the tip to the base
  • plasmodesmata close and become few
  • reduced symplastic connectivtiy
75
Q

allocation vs partitioning

A

Allocation: how much of the carbon fixed in photosynthesis is used for various functions (e.g., growth, storage, respiration).

Partitioning: Refers to how the fixed carbon (sugars) is distributed between different plant organs (e.g., roots, shoots, fruits).

76
Q
A

PLBI 403 MIDTERM (7 decks)

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