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Chemical Basis of Life Grade 10 Science lesson 01 Quiz 01

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Free G.C.E. O/L Science MCQ quiz on Chemical Basis of Life with 20 questions in English medium. Answer each question, see the correct answer and explanation straight away, and get your score at the end. Use the study section below to review every question and answer.

සාමාන්‍ය පෙළ Science බහුවරණ ප්‍රශ්න නොමිලේ පුහුණු වන්න.

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About this quiz

Chemical Basis of Life Free Online Quiz: Practice MCQs & Exam Revision

Test your understanding of the foundational principles of biology and biochemistry with this free interactive quiz on the Chemical Basis of Life. Whether you are preparing for term tests, competitive school exams, or international board evaluations, this practice test is designed to reinforce core concepts and identify knowledge gaps.

Mastering the molecular building blocks of organisms is essential for excelling in general science and advanced biology. This quiz features exam-standard multiple-choice questions (MCQs) structured to evaluate both theoretical recall and practical application.

Key Topics Covered:
Major Biomolecules: Structure, classification, and biological roles of carbohydrates, proteins, lipids, and nucleic acids (DNA & RNA).

Biochemical Food Tests: Diagnostic identification tests, including Benedict’s test for reducing sugars, Iodine test for starch, Biuret test for proteins, and Sudan III/emulsion tests for lipids.

Water & Essential Minerals: Polarity, universal solvent properties, thermal buffering, and the physiological importance of macro and micro minerals.

Enzymes & Biological Regulators: Enzyme-substrate specificity, factors affecting reaction rates (pH, temperature), and essential vitamins.

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High school science and biology students preparing for unit assessments and final exams.

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Independent learners looking to build a rock-solid foundation in life sciences.

All questions & answers (20)

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  1. Q1. What percentage of the mature human body mass is composed of oxygen?

    • A)10%
    • B)18%
    • C)65%
    • D)3%
    Show answer & explanation

    Answer: C) 65%

    Oxygen is the most abundant element in the human body by mass, making up approximately 65%.

  2. Q2. Which of the following elements is classified as a micro element in the human body?

    • A)Calcium
    • B)Iron
    • C)Potassium
    • D)Sodium
    Show answer & explanation

    Answer: B) Iron

    Iron, along with chlorine and iodine, is listed among the micro elements, whereas calcium, potassium, and sodium are macro/essential major elements.

  3. Q3. Compounds that contain carbon are known as:

    • A)Inorganic compounds
    • B)Organic compounds
    • C)Mineral salts
    • D)Aqueous solutions
    Show answer & explanation

    Answer: B) Organic compounds

    Organic compounds are defined by the presence of carbon in their structure.

  4. Q4. What is the general molecular formula for carbohydrates?

    • A)Cx(H2O)y
    • B)C6H12O6
    • C)C12H22O11
    • D)C6H10O5
    Show answer & explanation

    Answer: A) Cx(H2O)y

    The common molecular formula for carbohydrates is expressed as Cx(H2O)y, where carbon combines with water components.

  5. Q5. Which of the following is an example of a monosaccharide?

    • A)Sucrose
    • B)Lactose
    • C)Fructose
    • D)Maltose
    Show answer & explanation

    Answer: C) Fructose

    Fructose is a simple sugar (monosaccharide) with the formula C6H12O6, whereas sucrose, lactose, and maltose are disaccharides.

  6. Q6. Which sugar is known as "fruit sugar"?

    • A)Glucose
    • B)Fructose
    • C)Galactose
    • D)Maltose
    Show answer & explanation

    Answer: B) Fructose

    Fructose is found abundantly in ripened fruits, bee honey, and vegetables like pumpkin and carrots, earning it the name fruit sugar.

  7. Q7. What is the structural unit of polysaccharides like starch, cellulose, and glycogen?

    • A)Amino acid
    • B)Nucleotide
    • C)Glucose
    • D)Fatty acid
    Show answer & explanation

    Answer: C) Glucose

    Starch, cellulose, and glycogen are polymers formed by the polymerization of glucose molecules.

  8. Q8. Which disaccharide is formed by the union of a glucose molecule and a fructose molecule?

    • A)Maltose
    • B)Sucrose
    • C)Lactose
    • D)Galactose
    Show answer & explanation

    Answer: B) Sucrose

    Sucrose (found in sugar cane, beet, and table sugar) is a disaccharide composed of glucose and fructose.

  9. Q9. Which sugar is notable for being absent in plants?

    • A)Glucose
    • B)Fructose
    • C)Maltose
    • D)Lactose
    Show answer & explanation

    Answer: D) Lactose

    Lactose is found exclusively in dairy products (such as cow and human milk) and is the only sugar absent in plants.

  10. Q10. What color change is observed during a positive starch test using iodine solution?

    • A)Brick red precipitate
    • B)Purplish blue colour
    • C)Pinkish purple colour
    • D)Green yellow colour
    Show answer & explanation

    Answer: B) Purplish blue colour

    Starch reacts with iodine to form a distinct purplish-blue (or blue-black) complex.

  11. Q11. What is the final color observed when monosaccharides are heated with Benedict's solution?

    • A)Purplish blue
    • B)Yellow green
    • C)Brick red precipitate
    • D)Colorless
    Show answer & explanation

    Answer: C) Brick red precipitate

    Heating reducing sugars with Benedict's solution yields a progressive color change ending in a characteristic brick-red precipitate.

  12. Q12. Which disaccharide requires boiling with dilute sulfuric acid before it gives a positive Benedict's test?

    • A)Maltose
    • B)Lactose
    • C)Sucrose
    • D)Fructose
    Show answer & explanation

    Answer: C) Sucrose

    Sucrose is a non-reducing disaccharide and must first be hydrolyzed into its constituent monosaccharides using dilute sulfuric acid and heat.

  13. Q13. What percentage of the mature human body mass is composed of proteins?

    • A)3%
    • B)7%
    • C)17%
    • D)65%
    Show answer & explanation

    Answer: C) 17%

    Proteins constitute approximately 17% of the mature human body mass.

  14. Q14. The simplest amino acid, where Hydrogen (H) is present as the R group, is:

    • A)Alanine
    • B)Glycine
    • C)Valine
    • D)Serine
    Show answer & explanation

    Answer: B) Glycine

    Glycine is the simplest amino acid, featuring a single hydrogen atom as its side chain (R group).

  15. Q15. Which protein is found in red blood cells to transport oxygen?

    • A)Keratin
    • B)Osein
    • C)Myosin
    • D)Haemoglobin
    Show answer & explanation

    Answer: D) Haemoglobin

    Haemoglobin is the specialized protein inside red blood cells responsible for oxygen transport.

  16. Q16. What is the structural protein found in hair and feathers?

    • A)Collagen
    • B)Keratin
    • C)Albumin
    • D)Legumin
    Show answer & explanation

    Answer: B) Keratin

    Keratin is a tough fibrous protein that makes up hair, nails, and feathers.

  17. Q17. Which test is used to identify proteins in food samples?

    • A)Iodine test
    • B)Sudan III test
    • C)Biurette test
    • D)Benedict's test
    Show answer & explanation

    Answer: C) Biurette test

    The Biurette test (using sodium hydroxide and copper sulfate) produces a pinkish-purple or dark purple color in the presence of proteins.

  18. Q18. Enzymes are biological catalysts that are chemically classified as:

    • A)Carbohydrates
    • B)Lipids
    • C)Proteins
    • D)Nucleic acids
    Show answer & explanation

    Answer: C) Proteins

    Almost all enzymes are specialized proteins produced within organisms to accelerate biochemical reactions.

  19. Q19. Lipids are insoluble in polar solvents like water, but they dissolve readily in:

    • A)Organic solvents
    • B)Dilute acids
    • C)Mineral solutions
    • D)Alkaline buffers
    Show answer & explanation

    Answer: A) Organic solvents

    Due to their chemical nature, lipids dissolve in organic solvents rather than water.

  20. Q20. Which fatty acids contain the maximum possible number of hydrogen atoms attached to their carbon atoms?

    • A)Unsaturated fatty acids
    • B)Saturated fatty acids
    • C)Polyunsaturated fatty acids
    • D)Essential fatty acids
    Show answer & explanation

    Answer: B) Saturated fatty acids

    Saturated fatty acids have carbon atoms fully saturated with hydrogen atoms and typically exist as solids or semi-solids at room temperature.

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