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- 1. Multiple ChoiceWhat is the role of ATP in a companion cell when sucrose is loaded into a sieve tube element?moving sucrose into the sieve tube elementremoving protons out of the cytoplasm of the companion cell into the surroundingremoving protons from the sieve tube elementtaking up sucrose into the cytoplasm of the companion cell
- 2. Multiple ChoiceHow are co-transport proteins invovled in transport of assimilates through the phloemtransport of sucrose together with protons out of the companion cellstransport of sucrose together with protons into the companion cellstrasnport of sucrose together with protons into the mesophyl cellstransport of sucrose together with protons out of the sieve tube elements
- 3. Multiple ChoiceHow is proton pump involved in the transport of assimilates through the phloemactive transport of protons out of the sieve tube elementsactive transport of protons out of the mesophyl cellsactive transport of protons out of the companion cellsactive transport of protons out of the xylem vessel elements
- 4. Multiple Choicewhich feature of companion cell does not enhance loading?presence of plasmodesmata connecting them to sieve tube elementpresence of cotransport proteins on their cell surface membranespresence of proton pumps on their cell surface membranepresence of golgi apparatus for packaging and modifying assimilates
- 5. Multiple ChoiceWhat is the sequence of events in the translocation of sucrose?active loading of sucrose into sieve elements at the source, increased hydrostatic pressure, mass flow, unloading at the sinkhydrolysis of storage compounds in sinks, lowered water potential, unloading of sucrose from sieve elements, mass flow from the sourcelowered pressure in sieve elements at the source, movement of sucrose down the pressure gradient, mass flow down a diffusion gradient to the sinkmass flow of dissolved sucrose into the sieve elements at the source, lowered hydrostatic pressure, diffusion of sucrose to sink, active unloading
- 6. Multiple Choice
With reference to the table, which changes to the water potential and volume of liquid in the phloem occur when amino acids are taken out of a sink in a phloem sieve tube?
A
B
C
D
- 7. Multiple ChoiceWhat is the most accurate description of translocation in the phloem of plants?transport of water from down hydrostatic pressure gradienttransport of sucrose down hydrostatic pressure gradienttransport of various assimilates down hydrostatic pressure gradienttransport of dissolved ions down hydrostatic pressure gradients
- 8. Multiple ChoiceWhich statement supports the theory of active loading of sucrose into companion cells?The pH decreases in the cell wall of the companion cells compared to the cytoplasmthe pH decreases in the cytoplasm of the companion cells compared to the cell wallthe pH decreases in the plasmodesmata between companion cells and sieve tube elementsthe pH decreases in the sieve tube elements comapred to the companion cells
- 9. Multiple Choice
Which statement about the transport of sucrose is correct?
ATP is synthesised by mitochondria of companion cells provides the energy to move sucrose from phloem sieve tube elements in leaves to sink
Sucrose moves through plasmodesmata by passive diffusion from mesophyl cells through companion cells in phloem sieve tube elements
The water potential in phloem sieve tube elements becomes more negative following the entry of sucrose
Water enters companion cells and hydrostatic pressure builds up to push sucrose into phloem sieve tube elements by mass flow
- 10. Multiple ChoiceATP is used in companion cells to provide the energy for loading a sieve tube element with sucrose. How does the co-transporter mechanism use this energy?to pump protons into the sieve tube elementsto pump protons out of the companion cellsto pump sucrose into the sieve tube elementsto pump sucrose out of the companion cells
- 11. Multiple Choice
With reference to the table, which changes to the water potential and the volume of liquid in the phloem sieve tube element occur when sucrose is moved from the phloem sieve tube elements into an actively dividing shoot tip?
A
B
C
D
- 12. Multiple ChoiceSucrose moves from a phloem sieve tube element into a root cell. Which changes to water potential and the volume of liquid in the phloem sieve tube element are correct?water potential becomes higher, but volume of liquid decreaseswater potential becomes higher and volume of liquid increaseswater potential becomes lower and volume of liquid reduceswater potential becomes lower but volume of liquid increases
- 13. Multiple Choice
The diagram shows the tissues involved in the transport of sucrose in a plant. Where is the highest concentration of sucrose?
A
B
C
D
- 14. Multiple ChoiceWhen does water move into the phloem sieve tube element?after the active pumping of hydrogen ions into the sieve tube elementsafter the diffusion of sucrose into the sieve tube elementsafter the facilitated diffusion of sucrose into the companion cellsafter the diffusion of hydrogen ions into the companion cells
- 15. Multiple ChoiceWhat process ensures the continual diffusion of sucrose through the plasmodesmata into the sieve tube elements?continual active transport of protons into the companion cellscontinual facilitated diffusion of sucrose into the companion cellscontinual active transport of sucrose into the companion cellscontinual photosynthesis by the mesophyl cells
- 16. Multiple ChoiceWhich feature of companion cells are essential to their function? (1) they are connected by plasmodesmata to the sieve tube elements (2) they have a thinner cell wall than a sieve tube elements (3) they contain a nucleus and mitochondria1, 2 and 31 and 2 only1 and 3 only2 and 3 only
- 17. Multiple ChoiceWhat is correct for phloem sieve tube elements?Companion cells provide structural support to the phloem sieve tube elementsLignified walls of phloem sieve tube elements prevent transport of mineral salts by mass flowPhloem sieve tube elements become narrower as movement of sucrose occursPlasmodesmata allow movement of water and solutes across cell walls of phloem sieve tube elements
- 18. Multiple ChoiceSucrose moves from a mesophyl cell in a leaf inot the phloem sieve tube element. Which changes to the water potential and the volume of liquid in the phloem sieve tube element are correct?water potential becomes less negative and volume of liquid decreaseswater potential becomes less negative and volume of liquid increaseswater potential becomes more negative and volume of liquid decreaseswater potential becomes more negative and volume of liquid increases
- 19. Multiple Choice
With reference to the table, which combination of features is characteristic of a phloem sieve tube element as it unloads into a sink?
A
B
C
D
- 20. Multiple ChoiceWhich feature is NOT true about transport through the phloem sieve tubes?transport is passivetransport is by mass flowtransport occurs in one directiontransport occurs from source to sink
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