Mass transport in plants Flashcards

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1
Q

Give two ways in which the structure of starch is similar to cellulose.

A
  • 1 - Both polymers

- 2 - Both contain glycosidic bonds

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2
Q

Give two ways in which the structure of starch is different from cellulose.

A
  • 1 - Starch contains alpha glucose

- 2 - No hydrogen bonds between molecules

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3
Q

Using the diagram, suggest and explain one other way in which sieve cells are adapted for mass transport.

A
  • Few organelles

- So more flow of sugars

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4
Q

Using the diagram, suggest and explain one other way in which companion cells are adapted for the transport of sugars between cells.

A
  • Mitochondria release energy

- For active transport

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5
Q

One theory of translocation states that organic substances are pushed from a high pressure in the leaves to a lower pressure in the roots.

Describe how a high pressure is produced in the leaves.

A
  • Water potential lowers as sugars enter the phloem
  • Water enters the phloem by osmosis
  • Increased volume of water increases the pressure
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6
Q

During this experiment, the scientists ensured that the rate of photosynthesis of their plants remained constant.
Explain why this was important.

A
  • Rate of photosynthesis is related to rate of sucrose production
  • Rate of translation is higher when sucrose concentration is higher
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7
Q

The scientist concluded that some translocation must occur in the spaces in the cell walls.
Explain how the information in the figure above supports this conclusion.

A
  • Rate of translocation still occurs after 120 minutes

- however sucrose is no longer able to enter the cytoplasm of phloem cells

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8
Q

Contrast the processes of facilitated diffusion and active transport

A
  • Facilitated diffusion involves channel or carrier proteins whereas active transport only involves carrier proteins
  • Facilitated diffusion doesn’t require ATP however active transport uses ATP
  • Facilitated diffusion occurs down a concentration gradient whereas active transport occurs against a concentration gradient
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9
Q

Calculate the ratio of the mean rate of uptake of chloride ions in the first hour to the rate of uptake of chloride ions in the second hour for group B plants.

A
  • 3.3:1
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10
Q

Explain the results shown in the figure above.

A
  • For group A, initial uptake is slower because diffusion is occurring only it also levels off due to the same concentration of ions inside and outside the cell
  • For group B, uptake is faster as diffusion and active transport are taking place, it also doesn’t level off because no equilibrium is reached
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11
Q

Describe the mass flow hypothesis for the mechanism of translocation in plants.

A
  • In the source, sugars are actively transported into the phloem
  • By companion cells
  • Lowers water potential of sieve cells and water enters by osmosis
  • Increase in pressure causes mass movement
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12
Q

Name the process that produces the ^14CO2 released from the trunk.

A
  • Respiration
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13
Q

How long did it take the ^14C label to get from the top of the trunk to the bottom of the trunk?
Explain how you reached your answer.

A
  • 30 hours

- time between peak ^14C at the top of the trunk and the bottom of the trunk

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14
Q

What other information is required in order to calculate the mean rate of movement of the ^14C down the trunk?

A
  • length of the trunk
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