Biological Molecules

Question 1

Give 5 functions of proteins.

Answer 1

• Structural molecules (ie keratin and collagen)
• Controlling chemical reactions (enzymes)
• Messenger molecules (hormones)
• Combating disease (ie antibodies)
• Transport (ie haemoglobin and cell membrane proteins)

Question 2

Give 5 functions of lipids.

Answer 2

• Energy storage (can be used for respiration too)
• Part of cell membranes
• Thermal insulation
• Electrical insulation around nerve cells
  -Buoyancy (ie for whales so they float)

Question 3

What is the function of carbohydrates?

Answer 3

They are broken down in a chemical reaction, respiration, to release energy in the form of ATP. This energy is used for other reactions and processes in cells.

Question 4

Test for glucose?

Answer 4

-Benedicts solution
-Water bath at 80C for 5 minutes
-Colour change from blue to brick red if glucose is present

Question 5

Test for starch?

Answer 5

-Add a few drops of iodine solution to the sample
-A blue/black colour indicates the presence of starch

Question 6

Test for protein?

Answer 6

-Add 2cm3 of water to food sample and shake
-Add equal volume of dilute potassium hydroxide and shake
-Add 2 drops of 1% copper sulfate solution
-If protein is present it will turn purple

Question 7

Test for lipids?

Answer 7

-Place food sample in test tube
-Add small volume of absolute ethanol and shake to dissolve any lipid in the alcohol
-Add an equal volume of water
-A cloudy white colour OR emulsion OR red layer (caused by emulsion forming) indicates the presence of a lipid