Biological Molecules and Food Tests

Question 1

What chemicals is the human body made up of?

Answer 1

65% oxygen
18% carbon
10% hydrogen
7% other elements

These elements combine to form all the compounds in the body

Question 2

What 3 groups do most molecules found in living organisms fall into?

Answer 2

Carbohydrates
Proteins
Lipids

Question 3

What are carbohydrates made up of?

Answer 3

Simple sugars

Formed from carbon, oxygen and hydrogen

Question 4

Give an example of a simple sugar carbohydrate.

Answer 4

Glucose

Sucrose

Question 5

Give an example of a larger moleculed carbohydrate.

Answer 5

Starch

Glycogen

Question 6

What are proteins made up of?

Answer 6

Chains of amino acids linked together.

Question 7

What are lipids?

Answer 7

What we often call fats.
Made up from fatty acids and glycerol
There are 3 fatty acids and glycerol in each lipid
Lipids contain carbon, hydrogen and oxygen atoms

Question 8

What is the test for glucose (and other reducing sugars)?

Answer 8

Benedict’s reagent test
Blue Benedict’s reagent is added to samples and heated.
Green = small amount of reducing sugars
Yellow = medium amount of reducing sugars
Orange/red = large amount of reducing sugars

Question 9

What is the test for starch?

Answer 9

Iodine solution is added to food sample.

If it changes from brown to blue black starch is present.

Question 10

What is a catalyst?

Answer 10

A substance that helps to speed up a reaction.

Question 11

What are catalysts that cause metabolic reactions inside cells in living organisms called?

Answer 11

Enzymes or biological enzymes

Question 12

What would happen if we did not have enzymes?

Answer 12

Metabolic reactions would happen too slowly for life to carry on.

Question 13

What are biological enzymes made of?

Answer 13

Proteins

Question 14

Are enzymes general or specific?

Answer 14

Specific - they only work with one substance- substrate

Question 15

What is amylase?

Answer 15

Type of carbohydrase enzyme
Produced in the mouth
Starts the digestion of starch in food into simple sugars

Question 16

What is protease?

Answer 16

Digestive enzymes that break proteins into smaller units.

Question 17

What is lipase?

Answer 17

Digestive enzyme that breaks down lipids in food.

Question 18

What temperature do enzymes work best at?

Answer 18

At a particular temperature known as their optimum temperature
35-40*c for human enzymes
At a lower temperature they work more slowly as the molecules have less energy.
At temperatures that are too high the structure of the enzyme changes so will not work - it has become denatured.

Question 19

How can pH affect enzymes?

Answer 19

Very high or very low can slow down the rate of reaction and can in some case denature them.

Question 20

What is a test for protein?

Answer 20

Biuret Test
Prepare a sample of food and transfer 2cm3 to a test tube.
Add 2cm3 of biuret solution and gently shake.
If protein present solution changes colour from blue to pink/purple. If not present then remains blue.

Question 21

What is a test for lipids?

Answer 21

Sudan III test
Prepare a sample of food.
Transfer 5cm3 into a test tube
use a pipette to add 3 drops of Sudan III stain solution and gently shake
Sudan III stain solution stains lipids. If the sample has lipids it will separate into 2 layers. The top layer will be bright red. If there are no lipids then no separate red layer will form.