MCQ on Carbohydrates

🟢 Easy Level (1–20)

1. Which of the following is a carbohydrate?
   A) Starch ✅
   B) Protein
   C) Fat
   D) DNA
   Explanation: Starch is a polysaccharide and a storage form of carbohydrate in plants.
2. What are the building blocks of carbohydrates?
   A) Amino acids
   B) Fatty acids
   C) Monosaccharides ✅
   D) Nucleotides
   Explanation: Monosaccharides like glucose are the basic units of carbohydrates.
3. Which of these is a monosaccharide?
   A) Lactose
   B) Sucrose
   C) Glucose ✅
   D) Starch
   Explanation: Glucose is a single sugar unit, a monosaccharide.
4. What is the main function of carbohydrates?
   A) Enzyme production
   B) Genetic coding
   C) Energy supply ✅
   D) Hormone synthesis
   Explanation: Carbohydrates are the body’s primary energy source.
5. Which carbohydrate is commonly called “blood sugar”?
   A) Fructose
   B) Galactose
   C) Glucose ✅
   D) Maltose
   Explanation: Glucose circulates in the blood and is used for energy.
6. Sucrose is made of which two sugars?
   A) Glucose + Galactose
   B) Glucose + Fructose ✅
   C) Glucose + Glucose
   D) Fructose + Galactose
   Explanation: Sucrose is a disaccharide of glucose and fructose.
7. Which of the following is a polysaccharide?
   A) Glucose
   B) Fructose
   C) Cellulose ✅
   D) Sucrose
   Explanation: Cellulose is a complex carbohydrate made of many glucose units.
8. Which sugar is found in milk?
   A) Fructose
   B) Lactose ✅
   C) Sucrose
   D) Maltose
   Explanation: Lactose is a disaccharide found in milk.
9. Which carbohydrate cannot be digested by humans?
   A) Starch
   B) Cellulose ✅
   C) Glycogen
   D) Maltose
   Explanation: Humans lack enzymes to digest cellulose.
10. Which of the following is a storage carbohydrate in animals?
    A) Glycogen ✅
    B) Cellulose
    C) Starch
    D) Maltose
    Explanation: Glycogen is stored in liver and muscles for energy.
11. Which organ stores the most glycogen?
    A) Brain
    B) Liver ✅
    C) Kidney
    D) Stomach
    Explanation: The liver stores glycogen to maintain blood sugar levels.
12. Which enzyme breaks down starch in the mouth?
    A) Lipase
    B) Maltase
    C) Amylase ✅
    D) Lactase
    Explanation: Salivary amylase starts starch digestion in the mouth.
13. The general formula for carbohydrates is:
    A) CnH2nOn ✅
    B) CnH2n+2
    C) CH3COOH
    D) CnH2n-1On
    Explanation: Carbohydrates follow the general formula CnH2nOn.
14. Which of these is a reducing sugar?
    A) Sucrose
    B) Glucose ✅
    C) Starch
    D) Cellulose
    Explanation: Glucose contains a free aldehyde group making it reducing.
15. Which test is used to detect reducing sugars?
    A) Benedict’s test ✅
    B) Biuret test
    C) Sudan III test
    D) Iodine test
    Explanation: Benedict’s solution detects reducing sugars like glucose.
16. Which disaccharide is non-reducing?
    A) Maltose
    B) Lactose
    C) Sucrose ✅
    D) Glucose
    Explanation: Sucrose does not have a free aldehyde or ketone group.
17. Fructose is commonly found in:
    A) Dairy
    B) Vegetables
    C) Fruits ✅
    D) Grains
    Explanation: Fructose is the main sugar in fruits.
18. Carbohydrates are mainly absorbed in:
    A) Mouth
    B) Stomach
    C) Small intestine ✅
    D) Large intestine
    Explanation: The small intestine absorbs most digested carbohydrates.
19. Which of the following is a hexose sugar?
    A) Ribose
    B) Glucose ✅
    C) Deoxyribose
    D) Fructose
    Explanation: Glucose has six carbon atoms, making it a hexose.
20. Which is the sweetest natural sugar?
    A) Glucose
    B) Fructose ✅
    C) Sucrose
    D) Lactose
    Explanation: Fructose is sweeter than other natural sugars.

🟡 Moderate Level (21–40)

21. Which enzyme breaks down lactose?
    A) Maltase
    B) Sucrase
    C) Lactase ✅
    D) Amylase
    Explanation: Lactase breaks lactose into glucose and galactose.
22. Which of these carbohydrates is found in plant cell walls?
    A) Glycogen
    B) Cellulose ✅
    C) Sucrose
    D) Glucose
    Explanation: Cellulose forms structural support in plant cell walls.
23. Which of the following has alpha-1,4 glycosidic bonds?
    A) Cellulose
    B) Starch ✅
    C) Chitin
    D) Lactose
    Explanation: Starch consists of alpha-1,4 linked glucose units.
24. Chitin is a structural carbohydrate found in:
    A) Fungi and arthropods ✅
    B) Plants
    C) Bacteria
    D) Mammals
    Explanation: Chitin forms exoskeletons in arthropods and walls in fungi.
25. Which is an example of a ketose sugar?
    A) Glucose
    B) Fructose ✅
    C) Galactose
    D) Maltose
    Explanation: Fructose contains a ketone group.
26. Which bond connects two monosaccharides?
    A) Peptide bond
    B) Ester bond
    C) Glycosidic bond ✅
    D) Hydrogen bond
    Explanation: Glycosidic bonds form between sugar molecules.
27. Which carbohydrate gives a positive iodine test?
    A) Cellulose
    B) Starch ✅
    C) Glucose
    D) Fructose
    Explanation: Iodine turns blue-black in presence of starch.
28. Which form of starch is highly branched?
    A) Amylose
    B) Amylopectin ✅
    C) Cellulose
    D) Glycogen
    Explanation: Amylopectin has branched chains of glucose.
29. What is the main difference between cellulose and starch?
    A) Type of sugar
    B) Glycosidic bond ✅
    C) Molecular weight
    D) Number of units
    Explanation: Starch has alpha bonds, cellulose has beta bonds.
30. The storage form of carbohydrates in plants is:
    A) Glycogen
    B) Sucrose
    C) Cellulose
    D) Starch ✅
    Explanation: Plants store glucose as starch.
31. The term “saccharide” refers to:
    A) Proteins
    B) Sugars ✅
    C) Fats
    D) Hormones
    Explanation: Saccharides are sugar molecules—mono-, di-, or polysaccharides.
32. Which of the following is a trisaccharide?
    A) Raffinose ✅
    B) Glucose
    C) Lactose
    D) Sucrose
    Explanation: Raffinose is composed of three monosaccharides.
33. The glycemic index measures:
    A) Fat content
    B) Vitamin level
    C) Effect of carbohydrate on blood glucose ✅
    D) Fiber content
    Explanation: It ranks carbs based on their impact on blood sugar.
34. Which carbohydrate helps in cell signaling?
    A) Glycogen
    B) Glycoproteins ✅
    C) Cellulose
    D) Maltose
    Explanation: Glycoproteins play roles in cell recognition and communication.
35. In humans, excess glucose is stored as:
    A) Starch
    B) Glycogen ✅
    C) Lactose
    D) Sucrose
    Explanation: Glucose is converted to glycogen for storage.
36. Which polysaccharide is used in bacterial cell walls?
    A) Glycogen
    B) Peptidoglycan ✅
    C) Cellulose
    D) Chitin
    Explanation: Peptidoglycan is a structural component in bacteria.
37. Which of the following carbohydrates is found in DNA?
    A) Ribose
    B) Deoxyribose ✅
    C) Glucose
    D) Fructose
    Explanation: DNA contains deoxyribose sugar.
38. Which sugar is the sweetest?
    A) Maltose
    B) Fructose ✅
    C) Glucose
    D) Sucrose
    Explanation: Fructose is naturally the sweetest carbohydrate.
39. Which sugar is used in intravenous therapy?
    A) Lactose
    B) Fructose
    C) Glucose ✅
    D) Sucrose
    Explanation: Glucose is administered in IV fluids for energy.
40. The functional group in glucose includes:
    A) Ketone
    B) Aldehyde ✅
    C) Amine
    D) Carboxyl
    Explanation: Glucose contains an aldehyde group, making it an aldose.

🔴 Hard Level (41–50)

41. Which of the following is a non-reducing sugar?
    A) Glucose
    B) Fructose
    C) Sucrose ✅
    D) Maltose
    Explanation: Sucrose lacks a free aldehyde/ketone group.
42. Beta-glycosidic bonds are found in:
    A) Glycogen
    B) Amylose
    C) Cellulose ✅
    D) Maltose
    Explanation: Cellulose consists of β-1,4 glycosidic bonds.
43. Which sugar alcohol is used in sugar-free products?
    A) Lactose
    B) Sorbitol ✅
    C) Sucrose
    D) Glucose
    Explanation: Sorbitol is a sugar alcohol used in low-calorie foods.
44. Glycogen is structurally similar to:
    A) Amylose
    B) Cellulose
    C) Amylopectin ✅
    D) Raffinose
    Explanation: Both glycogen and amylopectin are branched polymers.
45. Which test identifies starch?
    A) Fehling’s test
    B) Iodine test ✅
    C) Benedict’s test
    D) Biuret test
    Explanation: Iodine binds with starch, giving a blue-black color.
46. Lactose intolerance results from lack of:
    A) Glucose
    B) Lactase ✅
    C) Amylase
    D) Sucrase
    Explanation: Lactase deficiency causes lactose intolerance.
47. The cyclic form of glucose is called:
    A) Hemiketal
    B) Hemiacetal ✅
    C) Ketose
    D) Anomer
    Explanation: The cyclic glucose forms a hemiacetal structure.
48. Which enzyme catalyzes glycogen breakdown?
    A) Glycogen synthase
    B) Amylase
    C) Glycogen phosphorylase ✅
    D) Maltase
    Explanation: Glycogen phosphorylase breaks glycogen into glucose-1-phosphate.
49. What is the carbon number in fructose?
    A) 4
    B) 5
    C) 6 ✅
    D) 7
    Explanation: Fructose is a 6-carbon ketose sugar.
50. Which vitamin is required for carbohydrate metabolism?
    A) Vitamin C
    B) Vitamin D
    C) Thiamine (B1) ✅
    D) Vitamin K
    Explanation: Thiamine is essential for carbohydrate enzymatic reactions.