Cambridge IGCSE · Biology 0610

IGCSE Biology: Biological molecules — Practice Questions & Answers

Learn the structure of carbohydrates, fats and proteins, and the food tests used to detect them for IGCSE Biology.

581 practice questions available for this topic — here are 10 with full answers and explanations.

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Practice questions with answers

1 Multiple choice · Easy

Which elements are always found in carbohydrates?

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WhyCarbohydrates contain only carbon, hydrogen and oxygen.
2 Multiple choice · Easy

Which reagent is used to test for starch?

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WhyIodine solution turns from orange-brown to blue-black in the presence of starch.
3 Multiple choice · Easy

What are the basic building blocks (monomers) of proteins?

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WhyProteins are made of amino acids joined together.
4 Multiple choice · Easy

A lipid molecule is made from glycerol and which other type of subunit?

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WhyA fat (lipid) is built from one glycerol and three fatty acids.
5 Multiple choice · Easy

Which reagent is used to test for proteins?

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WhyBiuret solution turns from blue to purple/violet when protein is present.
6 Multiple choice · Easy

Which large carbohydrate is used by plants to store glucose?

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WhyStarch is the storage carbohydrate found in plants.
7 Multiple choice · Easy

What is the chemical test for fats and oils (lipids)?

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WhyThe ethanol emulsion test gives a milky-white emulsion when a lipid is present.
8 Multiple choice · Easy

Which of these is a simple sugar (monosaccharide)?

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WhyGlucose is a monosaccharide; sucrose and maltose are disaccharides and starch is a polysaccharide.
9 Multiple choice · Medium

A student adds Benedict's solution to a food sample and heats it. The mixture turns brick-red. What does this show?

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WhyA brick-red precipitate after heating with Benedict's solution indicates a high concentration of reducing sugar.
10 Multiple choice · Medium

Cellulose is important to a plant cell because it

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WhyCellulose forms the plant cell wall, giving the cell strength and support.

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Key terms in Biological molecules

Biological molecule: A molecule made and used by living organisms, such as a carbohydrate, protein, lipid or nucleic acid.
Carbohydrate: A biological molecule made of carbon, hydrogen and oxygen that includes sugars and storage polymers, and serves mainly as an energy source for respiration.
Protein: A biological molecule built from a chain of amino acids and containing carbon, hydrogen, oxygen and nitrogen, used for growth, repair, enzymes, hormones and antibodies.
Lipid: A biological molecule made of fatty acids and glycerol, containing carbon, hydrogen and oxygen, used for energy storage, insulation and forming cell membranes.
Fat: A lipid that is solid at room temperature, used by animals as a concentrated energy store and for insulation.
Oil: A lipid that is liquid at room temperature, often used by plants as an energy store in seeds.
Chemical elements: The basic substances from which all matter is made; biological molecules are built from a small number of them such as C, H, O and N.
Carbon: A chemical element (C) present in all biological molecules, forming the backbone of their structures.

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Practise other IGCSE Biology topics

Topic 1: Characteristics and classification of living organisms Topic 2: Organisation of the organism Topic 3: Movement into and out of cells Topic 5: Enzymes Topic 6: Plant nutrition Topic 7: Human nutrition Topic 8: Transport in plants Topic 9: Transport in animals Topic 10: Diseases and immunity Topic 11: Gas exchange in humans Topic 12: Respiration Topic 13: Excretion in humans Topic 14: Coordination and response Topic 15: Drugs Topic 16: Reproduction Topic 17: Inheritance Topic 18: Variation and selection Topic 19: Organisms and their environment Topic 20: Human influences on ecosystems Topic 21: Biotechnology and genetic modification