Required Practical 4 Flashcards

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1
Q

you were provided with beetroot discs that were washed thoroughly before the start of the investigation.

explain why it was important to wash the beetroot discs?

A

to make sure all pigment washed off

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2
Q

describe a suitable control for this investigation

A
  • distilled water
  • 2 beetroot discs
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3
Q

explain why a control would be necessary

A

to show alcohol was causing leakage of pigment

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4
Q

explain why you were instructed to shake the test tubes every minute

A
  • maintain diffusion gradient for pigment
  • prevent discs sticking together
  • increase contact of all surfaces with alcohol
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5
Q

explain why you were instructed to pour the alcohol IMMEDIATELY from the experimental test tube in to the clean test tube

A

make sure all discs were in contact with alcohol for same length of time

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6
Q

you were given discs taken from fresh beetroot in your investigation

explain why your results would have been different if you had used cooked beetroot

A
  • heating destroys plasma membrane
  • denatures proteins
  • lot of pigment released during cooking
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7
Q

you used a water bath in your investigation

explain why a decrease in temperature of 5 degrees would affect the results

A
  • reduces kinetic energy
  • lower rate of diffusion
  • molecules move slower
  • membrane less fluid
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8
Q

2 students carried out the same investigation as you did

they worked in the same practical session and followed the same procedure

they worked accurately but found their results were different

suggest one reason for this

A
  • variation in beetroot
  • variation in judging colour
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9
Q

the student started drawing his curve from the origin,

was he correct to do this

A

No

  • curve drawn on graph should not extend beyond data collected
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10
Q

phospholipids dissolve in alcohol

explain the shape of the increase in the curve between alcohol concentrations of 40 and 80 percent

A
  • phospholipids are IN MEMBRANES
  • membrane breaks down faster at higher conc of alcohol
  • more pigment moves out of cells
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11
Q

after further investigation a student found out that a point was not an anomaly

suggest why the curve levels out

A
  • conc of pigment inside and outside of tissue reached equilibrium
  • maximum membrane damage
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