[SEC 3] CHAPTER 3 - nutrients

Question 1

what is 3 examples of disaccharides?

Answer 1

• glucose + glucose = maltose + water
• glucose + fructose = sucrose + water
• glucose + galactose = lactose + water

Question 2

what is condensation reaction

Answer 2

a chemical reaction when two simple molecules join together to form a larger molecule with the removal of one molecule of water

Question 3

what is the hydrolysis reaction

Answer 3

a chemical reaction where a water molecule is needed to breakup a complex molecule into smaller molecules

Question 4

name the steps for Benedict’s test

Answer 4

1. place 2cm3 of food sample into a test tube
2. add 2cm3 of Benedict’s solution to the sample and shake to mix well
3. place the test tube in a boiling water bath for 2-3 minutes

Question 5

name the results of Benedict’s test

Answer 5

• remain blue = no reducing sugar
• blue to green precipitate = traces of reducing sugar
• blue to yellow/orange precipitate = moderate amount of reducing sugar
• blue to brick-red precipitate = large amount of reducing sugar

Question 6

what is the prcedure and result of iodine test?

Answer 6

procedure: add a few drops of iodine solution to a food sample

result:
- starch present = solution turn blue-black
- starch absent = solution remain blue

Question 7

procedure for ethanol test and its results

Answer 7

procedure:
1. add 2cm3 of ethanol to a drop of food sample in a test tube
2. add 2cm3 of water to the mixture and shake well

results:
- fat present = while emulsion formed
- fat absent = solution remain clear

Question 8

procedure for biuret test and results

Answer 8

procedure:
1. add 2cm3 of sodium hydroxide solution to 2cm3 of food sample in a test tube and shake well
2. add 1% copper sulfate solution, drop by drop, shaking after every drop

results:
- protein present = violet colouration formed
- protein absent = solution remain blue