Lectures 5-6-7

Question 1

Passive Transport

Answer 1

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

Question 2

At equilibrium, no further movement occurs unless _________

Answer 2

energy is applied (energy input)

Question 3

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

Answer 3

Active Transport

Question 4

A common way to do active transport

Answer 4

ATP hydrolysis for energy

Question 5

Movement along a concentration gradient is complicated by

Answer 5

membrane permeability and ion passage.

think ions

Question 6

Diffusion of salts across membranes creates

Answer 6

electrical membrane potentials

Question 7

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

Answer 7

-100 mv

Question 8

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

Answer 8

faster

Question 9

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

Answer 9

true

Question 10

Ions and Proton Transport

the diffusion potential is caused by

Answer 10

ions moving across the membrane causing a voltage

Question 11

Ion and Proton Transport

Membrane potential in plant cells ranges from

Answer 11

-200 mV to -100 mV.

Question 12

Ion and Proton Transport

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

Answer 12

H+-ATPase, ATP hydrolysis.

ATP hydrolysis is for energy

Question 13

Proton Transport

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

what do these poisons do

Answer 13

cyanide, deplete

Question 14

Membrane Transport

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

Answer 14

channels, carriers, pumps

Question 15

Membrane Transport Proteins

Channels have….

Answer 15

Selective pores extending across the membrane, enhancing diffusion

Question 16

Channel proteins follow what kind of diffusion

Answer 16

passive transport (high to low), down the gradient

Question 17

A transported molecule follows what kind of diffusion

Answer 17

simple diffusion (high to low, down the gradient)

Question 18

Carriers Proteins…

Answer 18

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

Question 19

Membrane Transport

Pumps….

Answer 19

Use energy (ATP hydrolysis) for primary active transport.

Question 20

Membrane Transport

Secondary Active Transport…

Answer 20

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

Question 21

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

Answer 21

same, opposite

Question 22

pumps move protons against or across the gradient

Answer 22

against (low to high)

Question 23

membrane transport

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

Answer 23

pumps

Question 24

how do symporters work

Answer 24

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.

Question 25

how do antiports work

Answer 25

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.

Question 26

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

Answer 26

primary active, atp for hydrolysis

Question 27

# Phloem Phloem in Secondary Growth is found where

Answer 27

Found in inner bark

Question 28

phloem is generally found where

Answer 28

outer side of xylem in vascular bundles

Question 29

in the primary xylem, cells might be red because

Answer 29

may contain lignin

Question 30

Sieve Elements

Answer 30

Conduct sugars and organic compounds

Question 31

in angiosperms, how specialized are sieve tubes

Answer 31

highly specialized

Question 32

In gymnosperms, how specialized are sieve cells

Answer 32

less specialized

Question 33

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

Answer 33

sieve elements

Question 34

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

Answer 34

companion and parenchyma cells

Question 35

# phloem transport sieve elements have [blank] primary cell walls with no [blank]

Answer 35

thinner, lignin

Question 36

phloem cells are [blank] at maturity

Answer 36

alive

Question 37

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]

Answer 37

companion cell (nurse cell)

Question 38

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

Answer 38

gymnosperm, angiosperms

Question 39

Sieve plates (in angiosperms) contain

Answer 39

pores that interconnect cells.

Question 40

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

Answer 40

ER

Question 41

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

Answer 41

p-proteins

Question 42

p-protein are associated with

Answer 42

angiosperms so sieve plates

Question 43

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

Answer 43

callose | sieve plates found in angiosperms

Question 44

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

Answer 44

plasmodesmata

Question 45

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

Answer 45

protein synthesis and atp supply

Question 46

# companion cells Have chloroplasts and a smooth inner cell wall.

Answer 46

Ordinary companion cells

Question 47

# companion cells Have finger-like wall ingrowths to facilitate solute transfer.

Answer 47

transfer cells

Question 48

# companion cells Highly connected to surrounding cells, aiding in efficient transport.

Answer 48

intermediary cells

Question 49

xylem flows in how many directions

Answer 49

one, roots to leaves

Question 50

phloem moves in which direction

Answer 50

bi-directional, but not at the same time

Question 51

can the direction of the phloem reverse

Answer 51

yes

Question 52

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.

Answer 52

source, sink

Question 53

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

Answer 53

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

Question 54

Sources involve

Answer 54

organs like mature leaves and storage roots.

Question 55

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

Answer 55

roots, developing fruits, immature leaves

Question 56

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

Answer 56

true

Question 57

is the pressure flow model passive or active

Answer 57

passive

Question 58

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

Answer 58

bulk flow of phloem sap

Question 59

# phlome sap movement (pressure flow model) Bulk flow refers to the

Answer 59

mass movement of the sap due to pressure differences.

Question 60

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

Answer 60

- 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

Question 61

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

Answer 61

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

Question 62

3 mechanisms generate high sugar [ ] in sieve elements

Answer 62

- photosynthesis - photoassimilate into sugars - active membrane transport

Question 63

which sieve element maintains water potential

Answer 63

sieve plate cross walls, water dissipates via open tubes

Question 64

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

Answer 64

unobstructed

Question 65

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

Answer 65

does not immediately stop phloem transport

Question 66

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

Answer 66

resistance in sieve plates

Question 67

apoplast loading of phloem sugar

Answer 67

- 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.

Question 68

symplastic loading of phloem sap

Answer 68

- 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).

Question 69

polymer trapping model

Answer 69

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).

Question 70

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

Answer 70

passive, active

Question 71

How do you drive diffusion in symplastic unloading

Answer 71

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

Question 72

apoplastic unloading

Answer 72

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

Question 73

symplastic pathways have a high or low sucrose [ ]

Answer 73

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

Question 74

how do sinks become sources

Answer 74

- 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

Question 75

allocation vs partitioning

Answer 75

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).