Introduction
Biochemistry is an important branch of chemistry that studies the chemical substances and reactions occurring in living organisms. This chapter introduces the major biomolecules, including carbohydrates, proteins, lipids, and nucleic acids, along with their structures, properties, and biological functions. Students also learn about enzymes, vitamins, metabolism, and the importance of biochemistry in medicine, agriculture, food science, biotechnology, and industry.
These Class 10 Chemistry Chapter 4 MCQs are prepared according to the Punjab and Sindh Board syllabus to help students strengthen their concepts, improve revision, and prepare effectively for board examinations.
Learning Outcomes
After studying this chapter, students will be able to:
- Define biochemistry and explain its importance.
- Classify the major biomolecules found in living organisms.
- Describe the structure and functions of carbohydrates, proteins, lipids, and nucleic acids.
- Explain the role of enzymes as biological catalysts.
- Identify the factors affecting enzyme activity.
- Describe the functions and sources of essential vitamins.
- Recognize common vitamin deficiency diseases.
- Explain the applications of biochemistry in medicine, agriculture, and industry.
Quick Notes – Chapter Summary
- Biochemistry studies the chemistry of living organisms.
- Carbohydrates are the primary source of energy for the body.
- Proteins are made of amino acids and are essential for growth and tissue repair.
- Lipids store energy and form important components of cell membranes.
- DNA and RNA are nucleic acids responsible for storing and transmitting genetic information.
- Enzymes are biological catalysts that speed up biochemical reactions.
- Enzyme activity depends on temperature, pH, substrate concentration, and enzyme concentration.
- Vitamins are organic compounds required in small amounts for normal body functions.
- Vitamins B-complex and C are water-soluble, while vitamins A, D, E, and K are fat-soluble.
- Biochemistry plays a vital role in medicine, nutrition, agriculture, biotechnology, and pharmaceutical industries.
Important Definitions
Biochemistry: The branch of chemistry that studies the chemical composition and reactions of living organisms.
Biomolecule: An organic molecule produced by living organisms, such as carbohydrates, proteins, lipids, and nucleic acids.
Enzyme: A biological catalyst that speeds up chemical reactions without being consumed.
Carbohydrate: A biomolecule that serves as the body’s main source of energy.
Protein: A biomolecule composed of amino acids that is essential for growth, repair, and various body functions.
Lipid: A group of biomolecules including fats and oils that store energy and form cell membranes.
Nucleic Acid: A biomolecule (DNA or RNA) responsible for storing and transmitting genetic information.
Vitamin: An organic compound required in small amounts to maintain normal growth, metabolism, and health.
Important Concepts
Applications of biochemistry
Biochemistry
Biomolecules
Carbohydrates
Proteins
Lipids
Nucleic acids
Enzymes
Factors affecting enzyme activity
Vitamins and deficiency diseases
Class 10 Chemistry Chapter 4 – Biochemistry MCQs
1. Which of the following is the main energy source for the body?
- A. Proteins
- B. Carbohydrates ✅
- C. Lipids
- D. Vitamins
Explanation: Carbohydrates are the primary source of energy, broken down into glucose during metabolism.
2. Which is the simplest carbohydrate?
- A. Sucrose
- B. Glucose ✅
- C. Starch
- D. Cellulose
Explanation: Glucose is a monosaccharide, the simplest form of carbohydrate.
3. Proteins are made up of repeating units called:
- A. Fatty acids
- B. Nucleotides
- C. Amino acids ✅
- D. Monosaccharides
Explanation: Proteins are polymers of amino acids linked by peptide bonds.
4. Which of the following is NOT a lipid?
- A. Fats
- B. Oils
- C. Glycogen ✅
- D. Waxes
Explanation: Glycogen is a carbohydrate, not a lipid.
5. The genetic material in cells is made of:
- A. Proteins
- B. Lipids
- C. Nucleic acids ✅
- D. Vitamins
Explanation: DNA and RNA are nucleic acids that store and transmit genetic information.
6. Enzymes act as:
- A. Hormones
- B. Structural molecules
- C. Biological catalysts ✅
- D. Energy storage
Explanation: Enzymes speed up biochemical reactions without being consumed.
7. Which factor does NOT affect enzyme activity?
- A. Temperature
- B. pH
- C. Colour of enzyme ✅
- D. Substrate concentration
Explanation: Enzyme activity depends on temperature, pH, and substrate concentration, not its colour.
8. The enzyme that breaks down starch into maltose is:
- A. Lipase
- B. Amylase ✅
- C. Protease
- D. Catalase
Explanation: Amylase hydrolyzes starch into the disaccharide maltose.
9. Which vitamin is essential for blood clotting?
- A. Vitamin A
- B. Vitamin C
- C. Vitamin K ✅
- D. Vitamin D
Explanation: Vitamin K is necessary for the synthesis of clotting factors in the blood.
10. Vitamin C deficiency causes:
- A. Rickets
- B. Night blindness
- C. Scurvy ✅
- D. Beriberi
Explanation: Scurvy is caused by a lack of vitamin C, affecting collagen synthesis.
11. Which vitamin is produced in the skin when exposed to sunlight?
- A. Vitamin A
- B. Vitamin D ✅
- C. Vitamin E
- D. Vitamin K
Explanation: Sunlight converts cholesterol derivatives in the skin to vitamin D.
12. Which of the following is a disaccharide?
- A. Glucose
- B. Fructose
- C. Sucrose ✅
- D. Galactose
Explanation: Sucrose is made of glucose and fructose linked together.
13. Which lipid serves as an important component of cell membranes?
- A. Triglycerides
- B. Phospholipids ✅
- C. Steroids
- D. Waxes
Explanation: Phospholipids form the bilayer structure of cell membranes.
14. Which nitrogenous base is found only in RNA?
- A. Adenine
- B. Uracil ✅
- C. Thymine
- D. Cytosine
Explanation: Uracil replaces thymine in RNA.
15. Which of the following is a water-soluble vitamin?
- A. Vitamin A
- B. Vitamin D
- C. Vitamin B-complex ✅
- D. Vitamin E
Explanation: Vitamin B-complex and vitamin C are water-soluble vitamins.
16. Which biomolecule stores genetic information?
- A. Proteins
- B. Lipids
- C. DNA ✅
- D. Carbohydrates
Explanation: DNA contains the instructions for the development and functioning of living organisms.
17. Excess intake of vitamin A can cause:
- A. Rickets
- B. Toxicity symptoms like headache and nausea ✅
- C. Scurvy
- D. Pellagra
Explanation: Fat-soluble vitamins like vitamin A can accumulate in the body and cause toxicity.
18. Which enzyme breaks down proteins into peptides?
- A. Amylase
- B. Pepsin ✅
- C. Lipase
- D. Catalase
Explanation: Pepsin hydrolyzes proteins into smaller peptides in the stomach.
19. Which biomolecule is the body’s primary long-term energy storage material?
- A. Carbohydrates
- B. Proteins
- C. Lipids ✅
- D. Vitamins
Explanation: Lipids (fats and oils) store large amounts of energy and serve as the body’s long-term energy reserve.
20. Which field makes extensive use of biochemistry to develop medicines and vaccines?
- A. Astronomy
- B. Geology
- C. Pharmaceutical industry ✅
- D. Civil engineering
Explanation: Biochemistry is essential in the pharmaceutical industry for developing drugs, vaccines, diagnostic tests, and therapeutic products.
Exam Tips
- Memorize the functions and examples of carbohydrates, proteins, lipids, and nucleic acids.
- Learn the names and functions of common enzymes such as amylase, pepsin, and lipase.
- Understand the factors affecting enzyme activity.
- Remember the major vitamins, their sources, functions, and deficiency diseases.
- Differentiate between water-soluble and fat-soluble vitamins.
Common Mistakes
❌ Confusing enzymes with hormones.
❌ Mixing up the functions of carbohydrates and lipids.
❌ Forgetting that DNA stores genetic information while RNA helps in protein synthesis.
❌ Confusing water-soluble and fat-soluble vitamins.
❌ Assuming all vitamins can be stored in the body (water-soluble vitamins are generally not stored in significant amounts).
Conclusion
Biochemistry explains the chemical basis of life by studying biomolecules, enzymes, vitamins, and metabolic processes. Understanding these concepts helps students appreciate how living organisms obtain energy, grow, repair tissues, and maintain normal body functions. Regular practice of these MCQs will strengthen conceptual knowledge and help students perform confidently in board examinations.