test for reducing sugars Flashcards

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1
Q

what is the name of the test for reducing sugars?

A

benedict’s test

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2
Q

what do reducing sugars do?

A

give electrons

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3
Q

what does benedict’s solution contain?

A

Cu+2 ions which make the solution blue

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4
Q

what are examples of reducing sugars?

A

all monosaccharides and disaccharides except sucrose

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5
Q

explain the process of the benedict’s test

A
  • add a small amount (2cm^3) of the sample into a test tube with 2cm^3 of benedict’s solution
  • heat in a water bath for 5 minutes
  • brick red or orange colour is a positive result and a reducing sugar is present
  • if benedict’s solution remains blue , no reducing sugar is present and this is a negative result
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6
Q

what state must the sample be in before the benedict’s test is carried out?

A

it must be a liquid

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7
Q

what is the order of colours of the solution from highest concentration of reducing sugar to lowest concentration of reducing sugar?

A

red, orange, yellow, green

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8
Q

what are the controlled variables of this test?

A
  • same volume of benedict’s solution and the same volume of test solutions
  • samples must be heated for the same amount of time
  • samples must be heated at the same temperature
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9
Q

how to accurately compare the colour intensity produced?

A

with a colorimeter

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10
Q

how do you use a colorimeter?

A
  • set up colorimeter to absorb a particular wavelength of light
  • calibrate the colorimeter (set the zero concentration mark by measuring the absorbance of a sample of distilled water)
  • measure the absorbency of solutions with a known concentration
  • produce a calibration curve
  • place the solution of an unknown concentration of reducing sugar in the colorimeter
  • measure the absorbency and use the calibration curve to determine the concentration
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