Biological molecules

Question 1

List the chemical elements present in carbohydrates

Answer 1

Carbon, hydrogen, oxygen

Question 2

List the chemical elements present in proteins

Answer 2

carbon, hydrogen, oxygen, nitrogen

Question 3

List the chemical elements present in lipids

Answer 3

Carbon, hydrogen, oxygen

Question 4

Why do we need carbohydrates?

Answer 4

Carbohydrates are an important source of energy for your body

Question 5

Why do we need proteins?

Answer 5

They break down into amino acids that help the body grow and repair.

Question 6

Why do we need lipids?

Answer 6

We need it as an energy store, as insulation and to make cell membranes.

Question 7

Describe the food test for starch

Answer 7

-Place food sample in a dimple dish
-Add 2 drops of dilute iodine to the food
-If black-blue then starch is present
-If orangey-brown, starch isn’t present

Question 8

Describe the food test for fat

Answer 8

-Small sample of food into a test tube
-Measure some ethanol and pour it into the tube
-Gently shake the tube and leave it to stand for 1 minute
-If a cloudy suspension forms fat is present

Question 9

Describe the food test for protein

Answer 9

-Place the food sample into a test tube with a bit of water
-Add the biuret solution or…
-Add sodium hydroxide
-Add dilute copper sulphate and shake
-If the solution is purple, protein is present
-If it’s blue protein isn’t present

Question 10

Describe the food test for glucose

Answer 10

-Make sure it’s in liquid form
-Add benedict’s solution (blue)
-Place the test tube into a hot water bath and leave for 2 minutes
-If glucose is present the solution will turn (green/yellow/brick red(lots of glucose present))
-Blue means glucose isn’t present