Biological Molecules

Question 1

What elements are carbohydrates made up of?

Answer 1

• Carbon
• Oxygen
• Hydrogen

Question 2

What elements are lipids made up of?

Answer 2

• Carbon
• Oxygen
• Hydrogen

Question 3

What elements are protein made up of?

Answer 3

• Carbon
• Oxygen
• Hydrogen
• Nitrogen
• Sometimes sulphur

Question 4

What are the monomers of carbohydrates?

Answer 4

Simple sugars

Question 5

What are the monomers of lipids?

Answer 5

3 fatty acid molecules and a glycerol molecule

Question 6

What are the monomers of proteins?

Answer 6

Amino acids

Question 7

Describe the test for the presence of glucose (2)

Answer 7

• Benedict’s solution
• Heat in 60°C water bath

Question 8

Colour change for presence of glucose

Answer 8

Blue to green/yellow/brick red (low to high concentration)

Question 9

Describe the test for the presence of starch

Answer 9

Iodine solution

Question 10

Colour change for presence of starch

Answer 10

Yellow to blue-black

Question 11

Describe the test for the presence of protein

Answer 11

Biuret solution

Question 12

Colour change for presence of protein

Answer 12

Blue to lilac purple

Question 13

Describe the test for the presence of fat (2)

Answer 13

• Add 2cm3 ethanol
• Add 2cm3 distilled water

Question 14

Colour change for presence of fat

Answer 14

Milky white emulsion will form

Question 15

What are enzymes? (3)

Answer 15

• Biological catalysts in metabolic reactions
• Increases the rate of reaction without being used up
• The shape of the substrate is complementary to the shape of the active site

Question 16

What is the effect of temperature on enzyme function? (3)

Answer 16

• Before optimum: temperature increases = rate of reaction increases
• Optimum: 37°C for body temperature
• After optimum: bonds in the structure will break, changes shape of active site so substrate can no longer fit in = denatured

Question 17

Investigate how enzyme activity can be affected by changes in temperature (5)

Answer 17

• Starch solution is heated
• Amylase added
• Iodine added to each well
• Measure the time until iodine stops turning blue-black (starch is no longer present)
• Repeat for different temperatures

Question 18

What is the effect of pH on enzyme function? (2)

Answer 18

• pH too high or too low: forces that hold the amino acid chains are affected
• Changes the shape of the active site = denatured

Question 19

Investigate how enzyme activity can be affected by changes in pH (7)

Answer 19

• Beaker of water on a gauze above a bunsen burner (so temperature is a controlled variable)
• Iodine added to each well
• Add 2cm3 of amylase solution, 2cm3 of starch solution and 1cm3 of pH solution in a test tube and mix
• Put test tube in beaker and start a stopwatch
• Every 10 seconds, use a pipette to place solution into one of the wells containing iodine, should turn blue-black
• Keep repeating until solution becomes orange (starch has been full broken down)
• Repeat for different pHs and graph