Question 1

A patient presents with symptoms of bleeding gums and general weakness. Which vitamin deficiency is most likely responsible for these symptoms?

Accepted Answer

Correct Option: C. Solution: Vitamin C deficiency causes scurvy, which is characterized by bleeding gums and weakness.

Question 2

Which statement is true regarding the primary structure of proteins?

Accepted Answer

Correct Option: B. Solution: The primary structure of proteins is the specific sequence of amino acids in a polypeptide chain.

Question 3

What is the main structural difference between amylose and amylopectin?

Accepted Answer

Correct Option: B. Solution: Amylose is a long unbranched chain of glucose units, whereas amylopectin is a branched chain polymer.

Question 4

What type of bond is formed between α-amino acids in proteins?

Accepted Answer

Correct Option: B. Solution: Proteins are polymers of α-amino acids linked by peptide bonds, which are amide bonds formed between –COOH and –NH₂ groups.

Question 5

Which of the following proteins is an example of a fibrous protein?

Accepted Answer

Correct Option: C. Solution: Keratin is a fibrous protein, characterized by its insolubility and structural role in hair and nails.

Question 6

Which enzyme catalyzes the hydrolysis of maltose into glucose?

Accepted Answer

Correct Option: A. Solution: Maltase is the enzyme that specifically catalyzes the hydrolysis of maltose into glucose.

Question 7

What is the implication of glucose forming a cyanohydrin with $HCN$?

Accepted Answer

Correct Option: B. Solution: The formation of a cyanohydrin with $HCN$ indicates the presence of a carbonyl group (>C=O) in glucose.

Question 8

Which of the following polysaccharides is primarily used for energy storage in animals?

Accepted Answer

Correct Option: C. Solution: Glycogen is the storage polysaccharide in animals, similar to amylopectin but more highly branched.

Question 9

Which of the following vitamins is not stored in the body and must be supplied regularly through diet?

Accepted Answer

Correct Option: C. Solution: Vitamin C is a water-soluble vitamin that is not stored in the body and must be consumed regularly.

Question 10

Which of the following reactions confirms the presence of a carbonyl group in glucose?

Accepted Answer

Correct Option: A. Solution: Glucose reacts with hydroxylamine to form an oxime, confirming the presence of a carbonyl group.

Question 11

What condition is caused by an abnormally low level of thyroxine?

Accepted Answer

Correct Option: B. Solution: Hypothyroidism is caused by an abnormally low level of thyroxine, leading to symptoms such as lethargy and obesity.

Question 12

Which vitamin deficiency is linked to the condition known as pernicious anemia?

Accepted Answer

Correct Option: D. Solution: Pernicious anemia is caused by a deficiency of Vitamin B₁₂, which is essential for red blood cell formation.

Question 13

Which carbon in the fructose molecule is involved in the formation of the cyclic furanose structure?

Accepted Answer

Correct Option: C. Solution: The cyclic furanose structure of fructose is formed by the addition of the -OH group at C-5 to the ketonic group at C-2.

Question 14

Which of the following is a structural difference between DNA and RNA?

Accepted Answer

Correct Option: A. Solution: DNA contains thymine and is double-stranded, whereas RNA contains uracil and is usually single-stranded.

Question 15

What role does RNA play in the cell?

Accepted Answer

Correct Option: B. Solution: RNA molecules participate directly in protein synthesis, unlike DNA which stores genetic information.

Question 16

In a hypothetical scenario, a mutation occurs where uracil is incorporated into DNA instead of thymine. What immediate consequence might this have on the DNA structure?

Accepted Answer

Correct Option: B. Solution: Uracil normally pairs with adenine in RNA. If uracil replaces thymine in DNA, it could lead to incorrect base pairing during replication, potentially causing mutations.

Question 17

What is the structural difference between sucrose and maltose that results in sucrose being a non-reducing sugar?

Accepted Answer

Correct Option: A. Solution: In sucrose, the glycosidic linkage between C1 of $ 3b1$-D-glucose and C2 of $ 3b2$-D-fructose involves both reducing groups, making it a non-reducing sugar.

Question 18

What condition can result from iodine deficiency affecting thyroxine production?

Accepted Answer

Correct Option: B. Solution: Iodine deficiency can lead to hypothyroidism and goitre due to insufficient production of thyroxine.

Question 19

Which of the following statements correctly describes the structural difference between DNA and RNA?

Accepted Answer

Correct Option: A. Solution: DNA contains $\beta$-D-2-deoxyribose and bases A, G, C, T, while RNA contains $\beta$-D-ribose and bases A, G, C, U.

Question 20

What type of linkage connects nucleotides in a DNA strand?

Accepted Answer

Correct Option: C. Solution: Nucleotides in a DNA strand are connected by phosphodiester linkages between the 5' and 3' carbon atoms of the pentose sugar.

Question 21

Which reaction confirms the presence of an aldehydic group in glucose?

Accepted Answer

Correct Option: C. Solution: The oxidation of glucose to gluconic acid with bromine water confirms the presence of an aldehydic group.

Question 22

What is the primary function of DNA in living organisms?

Accepted Answer

Correct Option: B. Solution: DNA is the chemical basis of heredity and acts as the reserve of genetic information, maintaining the identity of different species.

Question 23

Which of the following statements best describes the role of enzymes in biochemical reactions?

Accepted Answer

Correct Option: B. Solution: Enzymes act as biocatalysts by lowering the activation energy required for biochemical reactions, thereby increasing the rate of the reactions.

Question 24

Which of the following monosaccharides is classified as a ketose?

Accepted Answer

Correct Option: B. Solution: Fructose is a ketohexose, meaning it is a ketose with six carbon atoms. Glucose and galactose are aldoses, while ribose is an aldopentose.

Question 25

Which of the following bases is found in RNA but not in DNA?

Accepted Answer

Correct Option: D. Solution: RNA contains uracil instead of thymine, which is found in DNA.

Question 26

Which of the following disaccharides is composed of two glucose units linked by a glycosidic bond between C1 of one glucose and C4 of another, and is a reducing sugar?

Accepted Answer

Correct Option: B. Solution: Maltose is composed of two $b1$-D-glucose units linked through C1–C4 and is a reducing sugar.

Question 27

Which of the following is a characteristic of monosaccharides?

Accepted Answer

Correct Option: D. Solution: Monosaccharides cannot be hydrolyzed to simpler carbohydrates as they are the simplest form of carbohydrates.

Question 28

Which structural feature distinguishes cellulose from starch?

Accepted Answer

Correct Option: A. Solution: Cellulose is a straight-chain polymer of $\beta$-D-glucose units linked by C1-C4 glycosidic bonds, making it distinct from starch which is composed of $\alpha$-D-glucose.

Question 29

In an aqueous solution, amino acids exist as zwitterions. What is the significance of this form?

Accepted Answer

Correct Option: C. Solution: In their zwitterionic form, amino acids can react with both acids and bases, showing amphoteric behavior.

Question 30

In the enzyme-catalyzed hydrolysis of sucrose, which enzyme is responsible for reducing the activation energy?

Accepted Answer

Correct Option: B. Solution: Sucrase is the enzyme that catalyzes the hydrolysis of sucrose into glucose and fructose, reducing the activation energy required for the reaction.

Question 31

During the denaturation of proteins, which bonds are primarily disrupted?

Accepted Answer

Correct Option: B. Solution: Denaturation primarily disrupts hydrogen bonds, leading to the loss of secondary and tertiary structures.

Question 32

What is the structural form of fructose when it forms a cyclic structure?

Accepted Answer

Correct Option: B. Solution: Fructose forms a five-membered cyclic furanose structure through the addition of the -OH group at C-5 to the ketonic group.

Question 33

Which vitamin is essential for blood clotting and its deficiency leads to increased blood clotting time?

Accepted Answer

Correct Option: B. Solution: Vitamin K is essential for the synthesis of proteins required for blood clotting, and its deficiency increases clotting time.

Question 34

Which of the following is a non-reducing sugar?

Accepted Answer

Correct Option: C. Solution: Sucrose is a non-reducing sugar because its glycosidic bond involves the reducing groups of glucose and fructose.

Question 35

A polypeptide chain consisting of 150 amino acids is considered a protein. Which of the following best explains why?

Accepted Answer

Correct Option: A. Solution: A polypeptide with more than about 100 amino acid residues and a molecular mass above 10,000 u is generally termed a protein.

Question 36

Which structural feature of glucose is responsible for its classification as an aldohexose?

Accepted Answer

Correct Option: B. Solution: Glucose is classified as an aldohexose because it contains an aldehyde group at carbon 1 and has six carbon atoms.

Question 37

Which sugar is present in the backbone of RNA?

Accepted Answer

Correct Option: B. Solution: RNA contains $\beta$-D-ribose as its sugar component, whereas DNA contains $\beta$-D-2-deoxyribose.

Question 38

Which of the following statements about peptide bonds is true?

Accepted Answer

Correct Option: A. Solution: A peptide bond is an amide linkage formed by the condensation reaction between the carboxyl group of one amino acid and the amino group of another, releasing a molecule of water.

Question 39

Which type of RNA is primarily responsible for carrying the genetic code from DNA to the ribosome for protein synthesis?

Accepted Answer

Correct Option: C. Solution: Messenger RNA (mRNA) is responsible for carrying the genetic code from DNA to the ribosome, where it serves as a template for protein synthesis.

Question 40

Which structural level of proteins is affected during denaturation by heat or pH change?

Accepted Answer

Correct Option: D. Solution: Denaturation affects the secondary and tertiary structures of proteins, leaving the primary structure intact.

Question 41

Which of the following is a primary function of DNA in living organisms?

Accepted Answer

Correct Option: B. Solution: DNA is the chemical basis of heredity and is responsible for maintaining the identity of different species of organisms over millions of years.

Question 42

What is the structural difference between α-D-glucose and β-D-glucose?

Accepted Answer

Correct Option: A. Solution: The structural difference between α-D-glucose and β-D-glucose is the position of the hydroxyl group at the anomeric carbon (C1).

Question 43

What type of linkage is formed between amino acids in a polypeptide chain?

Accepted Answer

Correct Option: B. Solution: A peptide linkage, also known as an amide bond, is formed between the carboxyl group of one amino acid and the amino group of another.

Question 44

Which of the following correctly describes the structure of lactose?

Accepted Answer

Correct Option: C. Solution: Lactose is a disaccharide composed of β-D-galactose and β-D-glucose linked by a glycosidic bond. It is a reducing sugar because it has a free aldehyde group at C-1 of the glucose unit.

Question 45

Which of the following statements correctly differentiates DNA from RNA?

Accepted Answer

Correct Option: B. Solution: DNA is typically double-stranded, forming a double helix, while RNA is usually single-stranded. DNA contains deoxyribose sugar and thymine, whereas RNA contains ribose sugar and uracil.

Question 46

Which of the following is an example of a fibrous protein?

Accepted Answer

Correct Option: C. Solution: Keratin is an example of a fibrous protein, characterized by its insolubility in water and structural role.

Question 47

Which hormone is responsible for increasing the blood glucose level?

Accepted Answer

Correct Option: B. Solution: Glucagon is the hormone that increases blood glucose levels by promoting the conversion of glycogen to glucose in the liver.

Question 48

Which of the following statements about lactose is correct?

Accepted Answer

Correct Option: C. Solution: Lactose is composed of $\beta$-D-galactose and $\beta$-D-glucose linked through C1–C4, making it a reducing sugar.

Question 49

Which of the following structural levels of proteins is affected during denaturation?

Accepted Answer

Correct Option: D. Solution: Denaturation affects the secondary and tertiary structures of proteins, while the primary structure remains intact.

Question 50

What is the primary source of Vitamin C?

Accepted Answer

Correct Option: B. Solution: Citrus fruits are a primary source of Vitamin C.

Question 51

Which vitamin is associated with increased blood clotting time when deficient?

Accepted Answer

Correct Option: B. Solution: Vitamin K deficiency leads to increased blood clotting time.

Question 52

Which of the following is a characteristic of amylopectin?

Accepted Answer

Correct Option: C. Solution: Amylopectin is a branched polymer of α-D-glucose units and contains both α(1→4) and α(1→6) glycosidic bonds, allowing branching.

Question 53

Which hormone is responsible for lowering blood glucose levels?

Accepted Answer

Correct Option: B. Solution: Insulin is responsible for lowering blood glucose levels by facilitating the uptake of glucose into cells.

Question 54

What is the primary function of thyroxine in the body?

Accepted Answer

Correct Option: B. Solution: Thyroxine regulates metabolism in the body and is produced by the thyroid gland.

Question 55

Which type of protein structure is characterized by the arrangement of multiple polypeptide subunits?

Accepted Answer

Correct Option: D. Solution: The quaternary structure of proteins involves the spatial arrangement of multiple polypeptide subunits.

Question 56

Which of the following is a characteristic of reducing sugars?

Accepted Answer

Correct Option: A. Solution: Reducing sugars contain a free aldehyde or ketone group, allowing them to reduce Fehling's solution or Tollens' reagent. Not all disaccharides are reducing sugars.

Question 57

What is the primary role of enzymes in biochemical reactions?

Accepted Answer

Correct Option: B. Solution: Enzymes act as biocatalysts that reduce the activation energy required for biochemical reactions, allowing them to proceed under mild conditions.

Question 58

Which of the following statements accurately describes the classification of carbohydrates?

Accepted Answer

Correct Option: B. Solution: Oligosaccharides are carbohydrates that yield two to ten monosaccharide units upon hydrolysis. Monosaccharides cannot be hydrolyzed further, polysaccharides are not sweet in taste, and not all carbohydrates fit the formula $C_x(H_2O)_y$.

Question 59

In what way does glycogen differ from amylopectin?

Accepted Answer

Correct Option: B. Solution: Glycogen is more highly branched compared to amylopectin, which allows for rapid release of glucose when needed by the body.

Question 60

How does the primary structure of a protein differ from its secondary structure?

Accepted Answer

Correct Option: B. Solution: The primary structure of a protein is the specific sequence of amino acids, whereas the secondary structure refers to local folding patterns such as α-helices and β-pleated sheets, stabilized by hydrogen bonds.

Question 61

Which hormone is primarily responsible for the development of secondary male characteristics?

Accepted Answer

Correct Option: B. Solution: Testosterone is the major male sex hormone responsible for the development of secondary male characteristics such as deep voice and facial hair.

Question 62

Which of the following statements is true about amino acids?

Accepted Answer

Correct Option: B. Solution: Glycine is the only naturally occurring $B1$-amino acid that is not optically active because it does not have a chiral center.

Question 63

Which of the following best describes the amphoteric nature of amino acids?

Accepted Answer

Correct Option: C. Solution: Amino acids are amphoteric because they contain both acidic (carboxyl group) and basic (amino group) functional groups, allowing them to act as both acids and bases.

Question 64

Which of the following statements correctly describes a polypeptide?

Accepted Answer

Correct Option: C. Solution: A polypeptide is a polymer of amino acids linked by peptide bonds, which are formed by the condensation of the carboxyl group of one amino acid with the amino group of another.

Biomolecules

Learning Objectives

Revision Notes & Summary

Notes on Biomolecules

10.1 Carbohydrates

10.2 Proteins

10.3 Nucleic Acids

10.4 Vitamins

10.5 Hormones

10.6 Key Concepts

Exam Tips & Common Mistakes

Common Mistakes and Exam Tips

Common Pitfalls

Exam Tips

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Multiple Choice Questions

Q1.A patient presents with symptoms of bleeding gums and general weakness. Which vitamin deficiency is most likely responsible for these symptoms?

Correct Answer: C

Q2.Which statement is true regarding the primary structure of proteins?

Correct Answer: B

Q3.What is the main structural difference between amylose and amylopectin?

Correct Answer: B

Q4.What type of bond is formed between α-amino acids in proteins?

Correct Answer: B

Q5.Which of the following proteins is an example of a fibrous protein?

Correct Answer: C

Q6.Which enzyme catalyzes the hydrolysis of maltose into glucose?

Correct Answer: A

Q7.What is the implication of glucose forming a cyanohydrin with HCNHCNHCN?

Correct Answer: B

Q8.Which of the following polysaccharides is primarily used for energy storage in animals?

Correct Answer: C

Q9.Which of the following vitamins is not stored in the body and must be supplied regularly through diet?

Correct Answer: C

Q10.Which of the following reactions confirms the presence of a carbonyl group in glucose?

Correct Answer: A

Q11.What condition is caused by an abnormally low level of thyroxine?

Correct Answer: B

Q12.Which vitamin deficiency is linked to the condition known as pernicious anemia?

Correct Answer: D

Q13.Which carbon in the fructose molecule is involved in the formation of the cyclic furanose structure?

Correct Answer: C

Q14.Which of the following is a structural difference between DNA and RNA?

Correct Answer: A

Q15.What role does RNA play in the cell?

Correct Answer: B

Q16.In a hypothetical scenario, a mutation occurs where uracil is incorporated into DNA instead of thymine. What immediate consequence might this have on the DNA structure?

Correct Answer: B

Q17.What is the structural difference between sucrose and maltose that results in sucrose being a non-reducing sugar?

Correct Answer: A

Q18.What condition can result from iodine deficiency affecting thyroxine production?

Correct Answer: B

Q19.Which of the following statements correctly describes the structural difference between DNA and RNA?

Correct Answer: A

Q20.What type of linkage connects nucleotides in a DNA strand?

Correct Answer: C

Q21.Which reaction confirms the presence of an aldehydic group in glucose?

Correct Answer: C

Q22.What is the primary function of DNA in living organisms?

Correct Answer: B

Q23.Which of the following statements best describes the role of enzymes in biochemical reactions?

Correct Answer: B

Q24.Which of the following monosaccharides is classified as a ketose?

Correct Answer: B

Q25.Which of the following bases is found in RNA but not in DNA?

Correct Answer: D

Q26.Which of the following disaccharides is composed of two glucose units linked by a glycosidic bond between C1 of one glucose and C4 of another, and is a reducing sugar?

Correct Answer: B

Q27.Which of the following is a characteristic of monosaccharides?

Correct Answer: D

Q28.Which structural feature distinguishes cellulose from starch?

Correct Answer: A

Q29.In an aqueous solution, amino acids exist as zwitterions. What is the significance of this form?

Correct Answer: C