3.4- Testing For Carbohydrates Flashcards

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1
Q

What is meant by reducing sugars?

A

All monosaccharides and some disaccharides are reducing sugars. This means that they can donate electrons to (or reduce) another molecule/chemical.

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2
Q

Benedict’s test for reducing sugars.

A
  1. Place sample in a boiling tube in liquid form.
  2. Add an equal volume of Benedict’s reagent.
  3. Heat the mixture gently in a water bath for 5mins.
  • reducing sugars react with copper ions in Benedict’s reagent. Results in the addition of electrons to the blue Cu2+ ions, reducing them to brick red Cu+ ions.
  • brick red precipitate represents positive result.
  • the more reducing sugar present, the more precipitate formed so colour depends on conc of reducing sugars present = qualitative test.
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3
Q

Test for starch.

A

Iodine test:

  1. A few drops of iodine dissolved in potassium iodide solution are mixed with the sample.
  2. Yellow/brown to purple/black indicates presence of starch.
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4
Q

What is the use if reagent strips?

A

Can be used to test for reducing sugars, most commonly glucose.

advantage: with the use of a colour coded chart, concentration of the sugar can be determined.

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5
Q

What are the 2 quantitative methods to find concentration?

A
  1. Colorimetry

2. Biosensors

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6
Q

Explain colorimetry.

A

Allows you to estimate glucose present in a solution.
It quantitatively measures the absorbance/transmission of light by a coloured solution.
More concentrated solution= higher absorbance & less transmission.

  1. Place filter in colorimeter.
  2. Calibrate using distilled water.
  3. Benedict’s test done on a range if conc.
  4. Solutions filtered to remove precipitate.
  5. % transmission of solution measured.
  6. Calibration curve plotted then used to calculate concentration in unknown sample.
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7
Q

Explain biosensors.

A

They use biological components to find the presence and concentrations of molecules.
Analyte= compound under investigation.j

  1. Molecular recognition= a protein/ single DNA strand is immobilised to a surface which will interact/ bind to the specific molecule under investigation.
  2. Transduction = transducer detects changes (eg. pH) and produces a response (such as a dye or electric current being released).
  3. Display= produces visible (quantitative or qualitative) signal.
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