Food tests + Tests for Enzymes + Calorimetry

Question 1

Test for starch + result?

Answer 1

Test: Iodine
Colour of reagent: Orange-Brown.
Positive result: Blue- Black.

Question 2

Test for Sugar + result?

Answer 2

Test: Benedict’s solution.
Colour of reagent: Light Blue.
Positive result: Green to Brick-Red.

Question 3

Test for Lipids + result?

Answer 3

Test: Ethanol.
Colour of reagent: Colourless.
Positive result: Cloudy Emulsion.

Question 4

Test for Protein + result?

Answer 4

Test: Biuret solution.
Colour of reagent: Blue.
Positive result: Lilac-Purple.

Question 5

What happens to carbohydrates?

Answer 5

• They are digested in the MOUTH, STOMACH and SMALL INTESTINE.
• Carbohydrase enzymes break down STARCH into SUGARS.

Question 6

What happens to Proteins?

Answer 6

• Proteins are digested in the STOMACH and SMALL INTESTINE.
• Protease enzymes break down PROTEIN into AMINO ACIDS.

Question 7

What happens to Lipids?

Answer 7

• Lipids (fats + oils) are digested in the SMALL INTESTINE.
• Lipase enzymes break down fat into FATTY ACIDS and GLYCEROL.

Question 8

How can you find the energy in a sample of food by using a calorimetry?

Answer 8

1) the temperature of the water at the start is measured.

2) the mass of the food sample is measured.

3) the food is set alight in a Bunsen flame, then placed immediately under the tube.

4) the temp of the water at the end is measured, the change in temp is calculated.

Question 9

A student used calorimetry with a test tube that contained 10cmcubed of water. Why might this not be an accurate result?

Answer 9

• taking too long to move the burning food to under the tube, or holding the tube at different distances from the tube.
• this would effect how much energy is transferred to the surrounding air and not the tube.