Biochemical Test
暂无描述。系统推荐的高质量记忆内容，适合每天坚持背诵学习。
卡片预览 (13 张)
How do you test for reducing sugars?
• add 2cm^3 of the food sample in liquid form into test tube • add 2cm^3 of benedict reagent into test tube • heat in water bath for 5 minutes
What is a positive results when testing reducing sugars?
when the solution turns brick red
Why does Benedict solutions turn red when a sample contains sugar?
• Benedict soltution is an alkaline soltuion of copper(II) sulfer • when heated the sugar donates an electron to the Benedict solution • this reaction creates copper(I) oxide which is a red precipitate
How do you test a non-reducing sugars?
• do reducing sugar test to show that it’s negative • add 2cm^3 of the food sample and diluted hydrochloric acid into a test tube • place test tube into warm water bath for 5 minutes • add sodium hydrocarbonate • then redo reducing sugar test which will give a positive result
Why do you add hydrochloric acid to the sample? of non-reducing sugar test
it will hydrolyse the reducing sugars (which are disaccharide and polysaccharides) into monosaccharides
Why do you add sodium hydrocarbonate to the solution? of non-reducing sugar test
to neutralise the test tube after adding hydrochloric acid as Benedict Solution doesn’t work in acidic condtions
How do you check that the solution is neutralised after adding sodium hydrocarbonate? in the non-reducing sugar test
• using pH paper • it will turn green
How do you test for starch?
add iodine to sample and if it changes from orange to blue/black starch is present
How do you test for lipids?
• put 2cm^3 of the sample in a clean test tube • add 5cm^3 of ethanol • shake to dissolve lipids • add 5cm^3 of water • then repeat with a control group as water as the sample
What will you see if a lipid test is positive?
a white, cloudy solution
How do you test for protein?
• add an equal amount of the sample and sodium hydroxide at room temperature • add diluted copper(II) sulfate soltuion • gently mix
What happens when the test for protein is positive
the solution changes from blue to purple
How does the Biuret Test work?
it tests for the peptide bonds within the protein