Chemical tests and chromatography Flashcards
describe the method and explain the results of the biuret test.
BUIRET TEST FOR PROTEINS.
the test uses buiret reagent made from biuret A - sodium hydroxide and biuret B - copper sulfate.
add the protein to the buiret reagent and mix gently.
positive - purple/lilac
negative - light blue
describe the method and results of the benedicts test.
BENEDICT’S REAGENT TEST FOR REDUCING SUGARS.
add benedicts reagent and heat the sample.
positive - green, yellow, orange, red, brown
negative - stays blue
describe the method and results for the iodine test
IODINE TEST FOR STARCH.
add iodine solution
positive - blue/black
negative - pale yellow
describe the method and results for the emulsion test.
EMULSION TEST FOR LIPIDS.
add to ethanol and shake. then add water and shake again.
positive - a milky-white emulsion forms
negative - no milky-white emulsion forms.
define the term qualitative test
a test which does not provide a numerical answer, something more descriptive like a colour. it tells you whether a substance is present but not how much of the substance.
define the term semi-quantitative test.
a test which gives you some indication of the amount of substance present but does not provide an exact figure.
define the term quantitative test
a test that gives you a numerical figure as to how much of a substance is present.
how can the benedicts test for reducing sugars be made semi-quantitative?
the colour of the result will vary depending on the concentration of the sugar. having a chart that shows the estimated concentration of each colour would allow you to make a comparison and the test would therefore be semi-quantitative.
list five examples of a reducing sugar.
- glucose (alpha and beta)
- ribose
- galactose
- fructose
give one example of a non -reducing sugar.
sucrose
explain why reducing sugars are called reducing sugars.
a reduction reaction is any reaction involving the gain of electrons. reducing sugars are sugars that can donate an electron to reduce another chemical or molecule.
what are reagent test strips?
small strips containing enzymes on one end. most commonly used to test for glucose they come with a colour chart for comparison.
describe how a colorimeter works.
a colorimeter measures the amount of light that can pass through a solution. it shines a beam of light through a pure solvent first and a sensor picks up the percentage of light that passes through. the same is then done for the sample being tested.
