IGCSE Biological Molecule & Enzymes (COMBINED SCIENCE)

Which row identifies the graphs that show the effect of temperature and the effect of pH on an enzyme-controlled reaction?

• A

• B

• C

• D

The graph shows how the activity of an enzyme varies. Which label for the x-axis of this graph is correct?

• enzyme activity

• pH

• temperature

• time

Small molecules are used as the basic units in the synthesis of large food molecules. Which statement is correct?

• Amino acids are basic units of carbohydrates

• Fatty acids are basic units of glycogen

• Glycerol is a basic unit of oils

• Simple sugar is a basic unit of protein

The diagram shows part of a protein molecule. What does X represent?

• amino acid

• fatty acid

• glycerol

• sugar

Four different foods were tested for their composition. The results are shown in the table. Which food contains protein but not reducing sugar or starch?

• A

• B

• C

• D

What are the basic units of fat molecules?

• amino acids

• simple sugars

• fatty acids and glycerols

• starch

Which nutrient produces a purple colour when mixed with biuret solution?

• fat

• protein

• reducing sugar

• starch

Which food-testing reagent shows a positive result when it turns from blue to purple?

• Benedict's solution

• Biuret reagent

• Ethanol

• Iodine solution

The diagram shows two food tests carried out on solution X. Which nutrients are present in solution X?

• protein and starch

• protein and sugar

• starch and fat

• starch and sugar

The data show the concentrations of sugar and starch in an onion.

• A

• B

• C

• D