3.4 Testing Fir Carbohydrates Flashcards
How do you test for reducing sugars?
Play some pool in a boiling tube if it is not in liquid form, grind it and blend in water
Add a equal volume of Benedict reagent
Heat the mixture gently in a boiling water bath for five minutes
What will the reducing sugars react with the Benedict reagent and what does this result in?
They will react with the copper ions and this results in the addition of electrons to the blue Cu2+ ions, reducing them to brick red CU plus ions
What colour indicates a positive result for reducing sugars?
Brick red
What can reducing sugars do in terms of electrons?
They can donate electrons or reduce another molecule or chemical
What would a non-reducing sugar result be in the Benedict test for reducing sugar?
Blue
If a non-reducing sugar is boiled with dilute hydrochloric acid, what will happen?
It will give a positive result when warmed with Benedict solution because the non-reducing sugar has been hydrolysed by the acid and it will become too reducing sugars
How would you test for starch?
Add a few drops of iodine dissolved in potassium iodide solution and mix it with the sample
What is a positive result for starch present?
From yellow brown to purple black
What are reagent strips?
They can be used to test for the presence of reducing sugars and they are a colour-coded chart so concentration of sugar can be determined to
What is a colourimeter
A piece of equipment used to quantitively measure the absorbance or transmission of light by a coloured solution
The more concentration of a solution the more or less light will it absorb and the more or less light will it transmit
More like will be absorbed
Less light will be transmitted
How would you use a colori meter to measure absorbance and transmission?
Filter placed in colourimeter
Calibrate using distilled water
Field solutions to remove precipitate
Measure transmission percentage of each solution in calorie meter
Do this for all solutions
What is an analyte?
A sample
