Module 2 Section 2 - Biochemical Tests for Molecules Flashcards
What is the biochemical test for sugars
Benedict’s test
What 2 groups can sugars be classified as
Reducing or non reducing
The Benedict’s test differs….
Depending on the type of sugars you’re testing for
What do reducing sugars include
All monosaccharides and some disaccharides
What do you add to a sample of reducing sugars to test for it
Benedict’s reagent
What other step do you do to the sample after adding the Benedict’s reagent
Heat it in a water bath that has been brought to the boil
How does the colour of the precipitate change
Blue - Green - yellow - orange - brick red
What happens if the test is positive
A coloured precipitate will form
Why do I always add excess Benedict’s solution
To make sure all the sugar reacts
What can you conclude about the test
The higher the concentration of reducing sugars the further the colour change goes
What happens if the test of the reducing sugars is negative
There still could be non reducing sugars present
What is the first step of breaking down non reducing sugars
You have to break them down to monosaccharides
How do you break down the sugar to a monosaccharide to test for non reducing sugars
Get a new sample of the test solution, add dilute hydrochloric acid and carefully heating it in a water bath that has been brought to a boil
After diluting hydrochloric acid and heating it what do you do to the sample to test for non reducing sugars
You neutralise it with sodium hydrogencarbonate and then carry the test out as you would for reducing sugars
What happens if the test is positive
It will form a coloured precipitate
What happens if the test is negative
The solution will stay blue meaning it doesn’t contain any sugars
What is glucose best tested using
Test strips coated in reagent
What happens if glucose is present
A colour change
What can the colour change be compared to
A chart which gives the indication of concentration of glucose present
What are the strips useful for
Testing a person’s urine for glucose - indicates they may have diabetes
What test is used for starch
Iodine test
What do you add to the test sample
Iodine which is dissolved in potassium iodide solution
What happens if starch is present
The sample changes colour from brown/orange to a dark blue/black colour
What happens if no starch is detected
It stays brown/orange colour
