AS Unit 1 - Practical Work Flashcards
How does someone test for Starch in food, and give the positive colour change
The student would add a few drops of Iodine to the test solution, the test solution should turn yellow/brown to blue/black
How does someone test for Reducing Sugars in food, and give the positive colour change
The student would add an equal amount of Benedicts reagent to the test solution and then place it in a water bath, the test solution should go from blue to green, then yellow, then orange, and finally a brick-red precipitate
How does someone test for Glucose in food, and give the positive colour change
The person would dip a test-strip of Clinistix into the test solution, the positive result varying depending on the amount of Glucose in the solution but a very positive result results in the Clinistix turning brown
How does someone test for Proteins in food, and give the positive colour change
The person would add an equal amount of Potassium hydroxide to the solution. Once that is clear they should then add a few drops of copper Sulfate along the side of the test tube. The test solution should turn blue to violet or a blue ring will appear on the surface
Given a negative result for Reducing sugars, how does someone test for Non-reducing sugars in food, and give the positive colour change
First, the pupil should hydrolyse the test solution with Hydrochloric Acid and Sodium Hydrogencarbonate. After it has been neutralised, they should then put it back into the heated water bath. The test solution should turn blue to green, then yellow, then orange and finally brick-red precipitate
What is the purpose of Hydrolysing the Disaccharide sucrose in the non-reducing sugar test
So that sucrose can be broken down into 2 separate reducing sugars, and give off a positive result
How can someone ensure the validity of the Non-Reducing sugar test
Two Tests can be repeated
The original solution should undergo the original Benedicts test, and must also undergo the iodine test
This is due to sucrose being broken down into Glucose to see if it is present
How do you prepare a Chromatogram, and Chromatography Paper
Chromatogram - Pour Solvent into the tank to a depth of about 3cm and add lid
Chromatography Paper - Wash hands, and draw a pencil line from one end to another with about 5cm in between each gap
How should you add Amino acids to Chromatography paper
Using a micro-pipette place a small drop of each amino acid onto the different points marked by pencil. Once the amino acid has dried, repeat this process about 5-6 times
Why is the drying of the amino acid on Chromatography paper process repeated
To concentrate the amino acids while keeping the spot as small as possible
How do you run a Chromatographam
Suspend the Chromatography paper in the tank, with the solvent just below the pencil origin line, allow the solvent to run up the chromatography paper which will carry the amino acids over a certain time
How can you identify the amino acids in the Chromatography Paper Practical
By finding out how far the spot has moved from the origin line
Rf value ( distance moved by spot )
(————————————————————————)
(distance moved by solvent front from origin line)
Why is a pencil used to mark the lines on Chromatography paper
Lead is inert, meaning it won’t affect the results while also giving a concentrated spot
What are the two types of heated water bath you can use in the property of enzymes practical
A beaker with water heated by a Bunsen Burner
A test tube that has been thermostatically controlled in a water bath
Why are buffers used
They can be used to maintain the pH or a solution at any given value
