biomolecule tests Flashcards

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1
Q

what is the test for starch?

A

iodine test

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2
Q

test for starch

A
  • add a few drops of iodine to the sample
  • iodide ions react with the centre of starch molecules
  • turns blue black in presence of starch
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3
Q

what is the test for reducing sugars?

A

benedicts test

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4
Q

test for reducing sugars

A
  • benedicts test
  • add blue benedicts reagent to a sample solution
  • heat in water bath
  • brick red precipitate forms if reducing sugar is present
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5
Q

test for non-reducing sugars

A
  • after negative result for reducing sugar (stays blue)
  • add acid and boil
  • wait to cool and add alkali to neutralise
  • add benedict’s solution
  • positive test : colour change from blue to green/yellow/orange/red
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6
Q

what is the test for proteins?

A

biuret test

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7
Q

test for proteins

A
  • add biuret solution at 45 degree angle to form a layer.
  • observe colour change, gently mix and observe again.
  • if turns violet indicates presence of protein
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8
Q

what is the test for lipids?

A

emulsion test

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9
Q

test for lipids

A
  • emulsion test
  • dissolve the sample in ethanol by adding ethanol and shaking
  • add distilled water
  • positive test : white emulsion forms
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10
Q

explain the reason for the colour change in the benedicts test

A

copper sulphate being reduced by copper oxide

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11
Q

explain the colour change in the iodine test

A

due to the starch being digested by enzymes

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12
Q

explain the precipitation formation in the emulsion test

A

lipids dissolve in non polar substances but not polar substances like water

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13
Q

risk assessment of biomolecule tests

A

biuret reagent - dont dispose down sink
ethanol - dont use near naked flame

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14
Q

colorimeter method

A
  • to get quantitative answers
  • set filter
  • calibrate
  • insert samples
  • create calibration curve
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15
Q

biosensors

A
  • strand of DNA or protein is immobilised
  • sample will bind to immobilised DNA/protein
  • binding causes change in a transducer
  • current determines concentration of sample
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16
Q

serial dillution

A
  • 5 test tubes
  • each contain a known concentration
  • each test tube is of equal volume
  • each tube has a concentration decrease of the same amount each time
  • e.g. tube 1 = 10cm3 solution
    tube 2 = 8cm3 solution, 2cm3 water
    tube 3 = 6cm3 solution, 4cm3 water
17
Q

what is the purpose of a control test tube? (2)

A

it acts as a blank. this is to show the impact of the manipulation of the IV in comparison to without.

18
Q

how can reliability of experiments be improved (2)

A
  • repeat
  • sample each test tube twice
19
Q

describe how a student could carry out a chemical test for reducing sugar and suggest how they can estimate the amount of reducing sugar in a sample (5)

A
  • add benedicts reagent and observe any colour change
  • colour change will be blue to brick red
  • compare the colour with that of a known solution
  • mass of precipitate formed reflects concentration
20
Q

chromatography of a protein

A
  • separate mixtures
  • mobile phase flows through the stationary phase
  • carries the components of the mixture with it
21
Q

how to measure Rf value

A

distance travelled by compound ÷ distance travelled by solvent = Rf

22
Q

risk assessment/evaluation of chromatography of protein

A
  • plates from compromised powder, dont chip with pencil
  • waft the plate to dry, don’t blow as spit has proteins
  • no fingers on plate