Biochemical Tests

Question 1

3 types of carbohydrates

Answer 1

Starch
Reducing sugars
Nonreducing sugars

Question 2

Test for starch

Answer 2

-Add iodine
-A positive test = solution turns from orange to blue/black

Question 3

Test for reducing sugar.

Answer 3

• glucose, fructose, galactose, lactose, maltose
  -Add Benedict reagent and heat
  -positive= turns from blue to green, yellow, orange, or brick red. The more red the higher the conc of reducing sugar
  Reduce it to copper oxide

Question 4

Test for non reducing sugars

Answer 4

• Eg sucrose
  -following negative Benedict’s test add acid and boil
• cool the solution then add alkaline to neutralise(hydrolises sucrose)
• add Benedict’s then heat
• positive test= blue to green, yellow, orange, or brick red.

Question 5

Test for proteins

Answer 5

• add biuret
• Positive test= turns from blue to purple

Question 6

Test for lipids

Answer 6

Dissolve the lipid in ethanol
Add distilled water
Positive= a white emulsion forms