Required Practical 3 - Calibartion Curve of Dilution Series/Water Potential of Plant Tissue Flashcards

1
Q

Suggest what a calibration curve is used for

A

Determine concentration of a substance in an unknown sample by comparing it to a set of standard samples of known concentrations

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2
Q

Suggest why it is important all samples are from the same plant tissue

A
  • standardise test

- different plant tissues could have different water potentials

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3
Q

Suggest why a potato chip cutter is used to cut samples

A

Provide constant cross sectional area

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4
Q

Suggest why sucrose solution is used to determine water potential of plant tissue

A
  • sucrose molecules too large to pass through cell-surface membrane
  • so any change in mass of samples is due to osmosis
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5
Q

Suggest why bungs are placed on top of sucrose solutions with samples

A
  • prevent evaporation of sucrose solution

- water potential of solution does NOT change

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6
Q

Suggest why thin samples of potato are cut

A
  • large surface area to volume ratio

- more water taken up per unit time

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7
Q

Suggest why skin of potato is removed

A
  • skin prevents passage of water in and out of cells

- ensures osmosis can occur

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8
Q

Suggest why samples are blotted before they are weighed

A

Remove excess water which could alter the weight

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9
Q

Suggest why it is important not to squeeze samples when drying

A

So that water is not removed that entered by osmosis

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10
Q

Suggest how to determine water potential of plant tissue

A
  • plot calibration curve (mention what is in each axis)
  • interpolate concentration when ratio one / percentage change in mass zero
  • use another resource to convert concentration of solution to water potential
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