Here below some basic MCQ’s about “Carbohydrates, proteins, vitamins and nucleic acid” with answer which is explained in details for exam practice. Let’s check one by one.
Q1. Which of the following is a reducing sugar?
(a) Sucrose
(b) Lactose
(c) Starch
(d) Cellulose
Answer: (b) Lactose
Explanation: Reducing sugars are sugars that can donate electrons to other molecules, typically through their free aldehyde or ketone groups. Lactose is a reducing sugar because it has a free anomeric carbon that can reduce other substances. Sucrose is non-reducing because its glycosidic bond involves both anomeric carbons, and starch and cellulose are polysaccharides that do not show reducing properties.
Q2. The basic unit of cellulose is:
(a) Glucose
(b) Fructose
(c) Ribose
(d) Galactose
Answer: (a) Glucose
Explanation: Cellulose is a polysaccharide made of β-D-glucose units. These glucose units are linked by β-1,4-glycosidic bonds, forming long, straight chains, which gives cellulose its structural strength in plants.
Q3. Which of the following is not a function of proteins?
(a) Enzymatic activity
(b) Genetic information storage
(c) Transport of molecules
(d) Structural support
Answer: (b) Genetic information storage
Explanation: Proteins perform many functions in the body, including enzymatic activity (as enzymes), transport of molecules (as in hemoglobin), and providing structural support (as in collagen). However, the storage of genetic information is the function of nucleic acids like DNA, not proteins.
Q4. Which of the following is an essential amino acid?
(a) Glycine
(b) Alanine
(c) Lysine
(d) Proline
Answer: (c) Lysine
Explanation: Essential amino acids are those that cannot be synthesized by the human body and must be obtained from the diet. Lysine is one of these essential amino acids. Glycine, alanine, and proline can be synthesized by the body.
Q5. Deficiency of which vitamin causes night blindness?
(a) Vitamin A
(b) Vitamin D
(c) Vitamin K
(d) Vitamin E
Answer: (a) Vitamin A
Explanation: Vitamin A is crucial for the maintenance of healthy vision. A deficiency in vitamin A impairs the production of rhodopsin, a pigment in the retina, leading to night blindness.
Q6. Vitamin K is essential for:
(a) Vision
(b) Blood clotting
(c) Bone formation
(d) Nerve function
Answer: (b) Blood clotting
Explanation: Vitamin K is necessary for the synthesis of clotting factors in the liver. A deficiency in vitamin K can lead to excessive bleeding due to impaired blood clotting.
Nucleic Acids MCQs
Q7. The bond between two nucleotides in a DNA strand is:
(a) Hydrogen bond
(b) Phosphodiester bond
(c) Glycosidic bond
(d) Ionic bond
Answer: (b) Phosphodiester bond
Explanation: Nucleotides in a DNA strand are connected by phosphodiester bonds, which form between the phosphate group of one nucleotide and the hydroxyl group of another. These bonds create the sugar-phosphate backbone of the DNA strand.
Q8. Which of the following is not a component of RNA?
(a) Adenine
(b) Thymine
(c) Uracil
(d) Guanine
Answer: (b) Thymine
Explanation: RNA contains the nitrogenous bases adenine, uracil, cytosine, and guanine. Thymine is present only in DNA, where it pairs with adenine, whereas uracil replaces thymine in RNA.
Q9. Which form of RNA carries the genetic code from the nucleus to the ribosome for protein synthesis?
(a) tRNA
(b) mRNA
(c) rRNA
(d) snRNA
Answer: (b) mRNA
Explanation: Messenger RNA (mRNA) carries the genetic instructions from DNA in the nucleus to the ribosomes in the cytoplasm, where proteins are synthesized based on the mRNA sequence.
Q10. Glycogen is primarily stored in which of the following tissues?
(a) Liver and skeletal muscles
(b) Adipose tissue
(c) Pancreas
(d) Kidneys
Answer: (a) Liver and skeletal muscles
Explanation: Glycogen is the storage form of glucose in animals. It is primarily stored in the liver, where it helps regulate blood glucose levels, and in skeletal muscles, where it serves as an energy reserve for muscle contraction.
Q11. Which of the following polysaccharides is used as structural material in plants?
(a) Amylopectin
(b) Chitin
(c) Glycogen
(d) Cellulose
Answer: (d) Cellulose
Explanation: Cellulose is a structural polysaccharide found in the cell walls of plants. It is made up of β-glucose units and forms long, straight fibers, providing structural support to the plant cells.
Q12. Which of the following carbohydrates is a disaccharide?
(a) Maltose
(b) Glucose
(c) Fructose
(d) Galactose
Answer: (a) Maltose
Explanation: Maltose is a disaccharide composed of two glucose units. Disaccharides are carbohydrates made up of two monosaccharide molecules linked together by a glycosidic bond.
Q13. Which of the following sugars is a pentose sugar found in nucleic acids?
(a) Glucose
(b) Fructose
(c) Ribose
(d) Galactose
Answer: (c) Ribose
Explanation: Ribose is a pentose (five-carbon) sugar that is a component of RNA, while its deoxygenated form, deoxyribose, is found in DNA.
Q14. Which of the following monosaccharides is the most common energy source in living organisms?
(a) Fructose
(b) Galactose
(c) Glucose
(d) Mannose
Answer: (c) Glucose
Explanation: Glucose is the primary energy source for most living organisms. It is metabolized during cellular respiration to produce ATP, the energy currency of the cell.
Q15. The enzyme that breaks down starch into maltose is:
(a) Pepsin
(b) Amylase
(c) Lactase
(d) Trypsin
Answer: (b) Amylase
Explanation: Amylase is an enzyme that catalyzes the hydrolysis of starch into smaller sugar units, primarily maltose. It is secreted by the salivary glands and the pancreas.
Proteins MCQs (Continued)
Q16. Which of the following bonds is responsible for the secondary structure of proteins?
(a) Disulfide bonds
(b) Peptide bonds
(c) Hydrogen bonds
(d) Ionic bonds
Answer: (c) Hydrogen bonds
Explanation: The secondary structure of proteins, such as alpha-helices and beta-pleated sheets, is stabilized primarily by hydrogen bonds between the backbone atoms of the polypeptide chain.
Q17. The primary structure of a protein refers to:
(a) The sequence of amino acids
(b) Alpha-helices and beta-sheets
(c) Three-dimensional folding
(d) The interaction of multiple polypeptide chains
Answer: (a) The sequence of amino acids
Explanation: The primary structure of a protein is the linear sequence of amino acids in the polypeptide chain, which is determined by the gene encoding the protein.
Q18. Denaturation of proteins involves:
(a) Breaking of peptide bonds
(b) Loss of secondary and tertiary structure
(c) Hydrolysis of proteins into amino acids
(d) Formation of new covalent bonds
Answer: (b) Loss of secondary and tertiary structure
Explanation: Denaturation is the process where a protein loses its functional shape (secondary and tertiary structure) due to external stress like heat or pH change, but the primary sequence (peptide bonds) remains intact.
Q19. The fibrous protein responsible for the strength and elasticity of connective tissue, such as tendons and skin, is:
(a) Hemoglobin
(b) Myoglobin
(c) Collagen
(d) Elastin
Answer: (c) Collagen
Explanation: Collagen is the most abundant fibrous protein in the human body and provides tensile strength and structural integrity to connective tissues.
Q20. An example of a conjugated protein is:
(a) Hemoglobin
(b) Albumin
(c) Insulin
(d) Collagen
Answer: (a) Hemoglobin
Explanation: Conjugated proteins contain a non-protein component called a prosthetic group. Hemoglobin is an example, as it consists of a protein component (globin) and a prosthetic group (heme).
Q21. Which of the following vitamins is water-soluble?
(a) Vitamin A
(b) Vitamin C
(c) Vitamin D
(d) Vitamin K
Answer: (b) Vitamin C
Explanation: Vitamin C (ascorbic acid) is water-soluble and is essential for the synthesis of collagen and wound healing. Water-soluble vitamins are not stored in the body and must be replenished regularly.
Q22. Deficiency of Vitamin D leads to:
(a) Scurvy
(b) Rickets
(c) Pellagra
(d) Beriberi
Answer: (b) Rickets
Explanation: Vitamin D deficiency leads to rickets in children, characterized by the softening and weakening of bones due to impaired calcium absorption.
Q23. Which vitamin is essential for the coagulation of blood?
(a) Vitamin A
(b) Vitamin K
(c) Vitamin D
(d) Vitamin B12
Answer: (b) Vitamin K
Explanation: Vitamin K plays a critical role in the synthesis of proteins required for blood clotting. Its deficiency can lead to bleeding disorders.
Q24. Pellagra is caused due to a deficiency of which vitamin?
(a) Vitamin C
(b) Niacin (Vitamin B3)
(c) Riboflavin (Vitamin B2)
(d) Folic acid
Answer: (b) Niacin (Vitamin B3)
Explanation: Pellagra is a disease caused by a deficiency of niacin, characterized by symptoms such as dermatitis, diarrhea, and dementia.
Q25. Which of the following is a fat-soluble vitamin?
(a) Vitamin B12
(b) Vitamin C
(c) Vitamin E
(d) Vitamin B6
Answer: (c) Vitamin E
Explanation: Vitamin E is a fat-soluble vitamin and an important antioxidant that protects cells from oxidative stress. Fat-soluble vitamins are stored in body fat and are not easily excreted.
Q26. The number of hydrogen bonds between adenine and thymine in a DNA molecule is:
(a) One
(b) Two
(c) Three
(d) Four
Answer: (b) Two
Explanation: Adenine and thymine are paired together in DNA through two hydrogen bonds, while cytosine and guanine form three hydrogen bonds.
Q27. The sugar present in DNA is:
(a) Ribose
(b) Glucose
(c) Fructose
(d) Deoxyribose
Answer: (d) Deoxyribose
Explanation: DNA contains deoxyribose, a five-carbon sugar that lacks an oxygen atom on the second carbon, distinguishing it from ribose, which is found in RNA.
Q28. Which enzyme is responsible for adding new nucleotides during DNA replication?
(a) DNA polymerase
(b) RNA polymerase
(c) Helicase
(d) Ligase
Answer: (a) DNA polymerase
Explanation: DNA polymerase is the enzyme that synthesizes new DNA strands by adding nucleotides to a growing DNA chain during replication.
Q29. Which of the following is an example of a polysaccharide?
(a) Ribose
(b) Maltose
(c) Glycogen
(d) Galactose
Answer: (c) Glycogen
Explanation: Glycogen is a polysaccharide that serves as the primary storage form of glucose in animals. It is stored mainly in the liver and muscle tissues.
Q30. The test used to detect the presence of starch is:
(a) Benedict’s test
(b) Biuret test
(c) Iodine test
(d) Fehling’s test
Answer: (c) Iodine test
Explanation: The iodine test is used to detect the presence of starch. When iodine is added to a starch solution, a blue-black color appears, indicating a positive result.
Q31. Which of the following sugars is a ketose sugar?
(a) Glucose
(b) Galactose
(c) Fructose
(d) Maltose
Answer: (c) Fructose
Explanation: Fructose is a ketose sugar because it contains a ketone group (-C=O) at the second carbon atom, whereas glucose and galactose are aldoses (containing an aldehyde group).
Proteins MCQs (Continued)
Q32. The bond formed between amino acids in a protein is called:
(a) Hydrogen bond
(b) Peptide bond
(c) Ionic bond
(d) Glycosidic bond
Answer: (b) Peptide bond
Explanation: A peptide bond is a covalent bond formed between the carboxyl group of one amino acid and the amino group of another. It is the key bond linking amino acids in proteins.
Q33. Which of the following proteins is involved in oxygen transport?
(a) Hemoglobin
(b) Collagen
(c) Keratin
(d) Actin
Answer: (a) Hemoglobin
Explanation: Hemoglobin is the oxygen-carrying protein in red blood cells. It binds to oxygen in the lungs and transports it to tissues throughout the body.
Q34. Enzymes are composed of:
(a) Nucleotides
(b) Fatty acids
(c) Proteins
(d) Carbohydrates
Answer: (c) Proteins
Explanation: Most enzymes are proteins. They act as biological catalysts, speeding up chemical reactions in the body without being consumed in the process.
Q35. The primary structure of a protein is stabilized by:
(a) Hydrogen bonds
(b) Peptide bonds
(c) Disulfide bonds
(d) Ionic bonds
Answer: (b) Peptide bonds
Explanation: The primary structure of a protein, which is the sequence of amino acids, is stabilized by peptide bonds between adjacent amino acids.
Q36. An enzyme’s activity is affected by:
(a) Temperature
(b) pH
(c) Substrate concentration
(d) All of the above
Answer: (d) All of the above
Explanation: Enzyme activity can be affected by several factors, including temperature, pH, and substrate concentration. Enzymes have optimal conditions under which they function best.
Q37. Which of the following is not an example of a fibrous protein?
(a) Collagen
(b) Keratin
(c) Elastin
(d) Hemoglobin
Answer: (d) Hemoglobin
Explanation: Hemoglobin is a globular protein, not a fibrous protein. Fibrous proteins, like collagen and keratin, have structural roles, while globular proteins, like hemoglobin, have functional roles such as transport.
Q38. The three-dimensional structure of a protein is maintained by:
(a) Peptide bonds
(b) Disulfide bonds
(c) Ionic interactions
(d) All of the above
Answer: (d) All of the above
Explanation: The three-dimensional structure of a protein (tertiary structure) is maintained by various interactions, including disulfide bonds, ionic interactions, hydrophobic interactions, and hydrogen bonds.
Q39. Which of the following vitamins is synthesized by intestinal bacteria?
(a) Vitamin C
(b) Vitamin K
(c) Vitamin D
(d) Vitamin A
Answer: (b) Vitamin K
Explanation: Vitamin K is synthesized by the gut microbiota and is essential for blood clotting. It is also obtained from green leafy vegetables in the diet.
Q40. Which vitamin is involved in the synthesis of collagen?
(a) Vitamin A
(b) Vitamin C
(c) Vitamin D
(d) Vitamin K
Answer: (b) Vitamin C
Explanation: Vitamin C is crucial for the synthesis of collagen, an important structural protein in connective tissues. It acts as a cofactor for enzymes involved in collagen biosynthesis.
Q41. Night blindness is a symptom of deficiency of which vitamin?
(a) Vitamin B12
(b) Vitamin A
(c) Vitamin D
(d) Vitamin K
Answer: (b) Vitamin A
Explanation: Vitamin A deficiency can lead to night blindness, where the ability to see in low light is impaired. This vitamin is essential for the production of rhodopsin, a pigment in the retina.
Q42. Which vitamin is also known as tocopherol?
(a) Vitamin C
(b) Vitamin A
(c) Vitamin E
(d) Vitamin B6
Answer: (c) Vitamin E
Explanation: Vitamin E, also known as tocopherol, is a fat-soluble antioxidant that protects cell membranes from oxidative damage.
Q43. Beriberi is caused by the deficiency of:
(a) Vitamin B1
(b) Vitamin B6
(c) Vitamin B12
(d) Vitamin C
Answer: (a) Vitamin B1
Explanation: Beriberi is caused by a deficiency of Vitamin B1 (thiamine). It affects the cardiovascular and nervous systems, leading to weakness and heart failure in severe cases.
Q44. Which of the following is required for the absorption of calcium in the body?
(a) Vitamin B12
(b) Vitamin D
(c) Vitamin E
(d) Vitamin A
Answer: (b) Vitamin D
Explanation: Vitamin D enhances the absorption of calcium from the gastrointestinal tract, playing a key role in bone formation and maintenance.
Q45. The deficiency of which vitamin can lead to pernicious anemia?
(a) Vitamin B12
(b) Vitamin C
(c) Vitamin B6
(d) Vitamin A
Answer: (a) Vitamin B12
Explanation: Pernicious anemia is caused by a deficiency of Vitamin B12. It leads to impaired red blood cell production and nervous system issues.
Q46. Which of the following is not a purine base found in nucleic acids?
(a) Adenine
(b) Guanine
(c) Cytosine
(d) Thymine
Answer: (c) Cytosine
Explanation: Adenine and guanine are purine bases, while cytosine, thymine (DNA), and uracil (RNA) are pyrimidine bases.
Q47. The process of copying DNA into RNA is known as:
(a) Translation
(b) Transcription
(c) Replication
(d) Transformation
Answer: (b) Transcription
Explanation: Transcription is the process by which the genetic information encoded in DNA is copied into a complementary RNA molecule.
Q48. The sugar present in RNA is:
(a) Deoxyribose
(b) Ribose
(c) Glucose
(d) Sucrose
Answer: (b) Ribose
Explanation: RNA contains ribose, a five-carbon sugar. In contrast, DNA contains deoxyribose, which lacks one oxygen atom.
Q49. Which type of RNA carries amino acids to the ribosome during protein synthesis?
(a) mRNA
(b) tRNA
(c) rRNA
(d) snRNA
Answer: (b) tRNA
Explanation: Transfer RNA (tRNA) carries specific amino acids to the ribosome during protein synthesis, where the amino acids are added to the growing polypeptide chain.
Q50. The major storage form of carbohydrates in plants is:
(a) Glycogen
(b) Starch
(c) Cellulose
(d) Sucrose
Answer: (b) Starch
Explanation: Starch is the primary storage form of carbohydrates in plants. It is composed of two polysaccharides: amylose and amylopectin.
Q51. The enzyme involved in the hydrolysis of lactose is:
(a) Lactase
(b) Sucrase
(c) Amylase
(d) Maltase
Answer: (a) Lactase
Explanation: Lactase is the enzyme that breaks down lactose, a disaccharide, into its monosaccharide components, glucose and galactose.
Q52. Which of the following polysaccharides is used as an energy source in fungi?
(a) Glycogen
(b) Cellulose
(c) Chitin
(d) Amylose
Answer: (a) Glycogen
Explanation: Fungi store energy in the form of glycogen, just like animals. Glycogen is a branched polysaccharide that serves as a short-term energy reserve.
Q53. Which of the following amino acids contains sulfur?
(a) Glycine
(b) Serine
(c) Methionine
(d) Alanine
Answer: (c) Methionine
Explanation: Methionine is an essential amino acid that contains sulfur in its side chain, making it important for protein synthesis and methylation reactions.
Q54. Which of the following proteins functions as an enzyme inhibitor?
(a) Collagen
(b) Trypsin
(c) Pepsin
(d) Antitrypsin
Answer: (d) Antitrypsin
Explanation: Antitrypsin is a protein that inhibits the enzyme trypsin and other proteases, preventing tissue damage during inflammation.
Q55. The protein responsible for muscle contraction is:
(a) Actin
(b) Hemoglobin
(c) Albumin
(d) Fibrinogen
Answer: (a) Actin
Explanation: Actin, along with myosin, is responsible for muscle contraction. These proteins interact to cause the shortening of muscle fibers.
Q56. Which of the following is not a property of enzymes?
(a) They are proteins.
(b) They are catalysts.
(c) They are consumed during reactions.
(d) They are specific to substrates.
Answer: (c) They are consumed during reactions.
Explanation: Enzymes are not consumed in the reactions they catalyze. They facilitate reactions and can be used repeatedly.
Q57. The deficiency of which amino acid causes pellagra?
(a) Lysine
(b) Tryptophan
(c) Glycine
(d) Leucine
Answer: (b) Tryptophan
Explanation: Pellagra is caused by a deficiency in niacin (Vitamin B3), which can also result from a deficiency of tryptophan, as tryptophan is a precursor for niacin synthesis.
Q58. Which of the following vitamins plays a major role in calcium metabolism?
(a) Vitamin K
(b) Vitamin B12
(c) Vitamin D
(d) Vitamin A
Answer: (c) Vitamin D
Explanation: Vitamin D facilitates calcium absorption in the intestines and is essential for maintaining proper bone health.
Q59. Vitamin C deficiency leads to which of the following conditions?
(a) Scurvy
(b) Rickets
(c) Anemia
(d) Pellagra
Answer: (a) Scurvy
Explanation: Scurvy is caused by a deficiency of Vitamin C, leading to symptoms such as bleeding gums, poor wound healing, and joint pain.
Q60. Which vitamin is essential for vision and the proper functioning of the immune system?
(a) Vitamin A
(b) Vitamin C
(c) Vitamin E
(d) Vitamin D
Answer: (a) Vitamin A
Explanation: Vitamin A is essential for maintaining healthy vision (especially in low light) and is also involved in immune function and cellular communication.
Q61. Which of the following vitamins acts as an antioxidant?
(a) Vitamin D
(b) Vitamin K
(c) Vitamin E
(d) Vitamin B6
Answer: (c) Vitamin E
Explanation: Vitamin E is a powerful antioxidant that protects cells from oxidative damage caused by free radicals.
Q62. The deficiency of folic acid during pregnancy can lead to:
(a) Neural tube defects
(b) Beriberi
(c) Rickets
(d) Night blindness
Answer: (a) Neural tube defects
Explanation: Folic acid (Vitamin B9) is crucial during early pregnancy for the development of the neural tube in the fetus. Its deficiency can result in neural tube defects like spina bifida.
Q63. Which of the following nitrogenous bases is present in RNA but not in DNA?
(a) Thymine
(b) Guanine
(c) Uracil
(d) Adenine
Answer: (c) Uracil
Explanation: In RNA, uracil replaces thymine as one of the pyrimidine bases, pairing with adenine during transcription.
Q64. DNA replication occurs during which phase of the cell cycle?
(a) G1 phase
(b) G2 phase
(c) S phase
(d) M phase
Answer: (c) S phase
Explanation: DNA replication occurs during the S phase (Synthesis phase) of the cell cycle, ensuring that each daughter cell receives a complete set of chromosomes.
Q65. Which enzyme is responsible for unwinding the DNA double helix during replication?
(a) DNA polymerase
(b) Helicase
(c) Ligase
(d) Primase
Answer: (b) Helicase
Explanation: Helicase unwinds the DNA double helix, creating replication forks where the DNA strands are separated to allow replication.
Q66. Which type of RNA serves as the template for protein synthesis?
(a) mRNA
(b) tRNA
(c) rRNA
(d) snRNA
Answer: (a) mRNA
Explanation: Messenger RNA (mRNA) carries the genetic information from DNA to the ribosome, where it serves as a template for protein synthesis.
Q67. The process of synthesizing a protein from mRNA is called:
(a) Replication
(b) Transcription
(c) Translation
(d) Mutation
Answer: (c) Translation
Explanation: Translation is the process in which the mRNA sequence is used by ribosomes to assemble amino acids into a polypeptide, forming a protein.
Q68. The structural backbone of DNA consists of:
(a) Sugar-phosphate units
(b) Nitrogenous bases
(c) Amino acids
(d) Fatty acids
Answer: (a) Sugar-phosphate units
Explanation: The DNA backbone is made of alternating sugar (deoxyribose) and phosphate groups. The nitrogenous bases are attached to the sugar molecules.
Q69. Which enzyme is responsible for joining Okazaki fragments during DNA replication?
(a) DNA polymerase
(b) Helicase
(c) Ligase
(d) Primase
Answer: (c) Ligase
Explanation: DNA ligase seals the nicks between Okazaki fragments on the lagging strand during DNA replication, creating a continuous DNA strand.
Q70. Which of the following nitrogenous bases pairs with cytosine in DNA?
(a) Adenine
(b) Thymine
(c) Guanine
(d) Uracil
Answer: (c) Guanine
Explanation: In DNA, cytosine pairs with guanine through three hydrogen bonds, maintaining the structure of the double helix.
Q71. Which of the following carbohydrates is a pentose sugar?
(a) Glucose
(b) Fructose
(c) Ribose
(d) Galactose
Answer: (c) Ribose
Explanation: Ribose is a pentose sugar (five-carbon sugar) found in RNA. Glucose, fructose, and galactose are hexose sugars (six-carbon sugars).
Q72. Which of the following is a reducing sugar?
(a) Sucrose
(b) Glucose
(c) Starch
(d) Cellulose
Answer: (b) Glucose
Explanation: Glucose is a reducing sugar, as it has a free aldehyde group that can donate electrons and reduce other substances. Sucrose is a non-reducing sugar because its glycosidic bond prevents it from having a free aldehyde or ketone group.
Q73. The main component of plant cell walls is:
(a) Glycogen
(b) Cellulose
(c) Chitin
(d) Starch
Answer: (b) Cellulose
Explanation: Cellulose is a polysaccharide that provides structural support to plant cell walls. It is composed of β-glucose units linked by β-1,4 glycosidic bonds.
Q74. The process of converting glucose into pyruvate in the cytoplasm is called:
(a) Glycolysis
(b) Gluconeogenesis
(c) Glycogenesis
(d) Glycogenolysis
Answer: (a) Glycolysis
Explanation: Glycolysis is the metabolic pathway that breaks down glucose into two molecules of pyruvate, producing ATP and NADH in the process. It occurs in the cytoplasm of cells.
Proteins MCQs (Continued)
Q75. Which level of protein structure involves α-helices and β-pleated sheets?
(a) Primary structure
(b) Secondary structure
(c) Tertiary structure
(d) Quaternary structure
Answer: (b) Secondary structure
Explanation: The secondary structure of a protein involves the folding of the polypeptide chain into α-helices and β-pleated sheets, which are stabilized by hydrogen bonds.
Q76. Which amino acid is commonly found at the active sites of enzymes because of its ability to form covalent bonds with substrates?
(a) Glycine
(b) Serine
(c) Proline
(d) Tyrosine
Answer: (b) Serine
Explanation: Serine is often found in the active sites of enzymes due to its reactive hydroxyl group (-OH), which can form covalent bonds with substrates during catalysis.
Q77. The three-dimensional shape of a protein is determined by its:
(a) Primary structure
(b) Secondary structure
(c) Tertiary structure
(d) Quaternary structure
Answer: (c) Tertiary structure
Explanation: The tertiary structure of a protein is its three-dimensional shape, formed by the interactions between the side chains (R-groups) of amino acids, including hydrophobic interactions, hydrogen bonds, ionic bonds, and disulfide bridges.
Q78. Hemoglobin consists of how many polypeptide chains?
(a) 1
(b) 2
(c) 3
(d) 4
Answer: (d) 4
Explanation: Hemoglobin is a tetramer consisting of four polypeptide chains—two alpha chains and two beta chains—that work together to carry oxygen in the blood.
Q79. Which of the following proteins has a fibrous structure?
(a) Hemoglobin
(b) Myoglobin
(c) Collagen
(d) Insulin
Answer: (c) Collagen
Explanation: Collagen is a fibrous protein that provides structural support to connective tissues such as skin, tendons, and ligaments. It is the most abundant protein in the human body.
Q80. Which vitamin is essential for blood clotting?
(a) Vitamin A
(b) Vitamin D
(c) Vitamin E
(d) Vitamin K
Answer: (d) Vitamin K
Explanation: Vitamin K plays a crucial role in the blood clotting process by helping in the synthesis of clotting factors, which are proteins involved in the formation of blood clots.
Q81. Which of the following vitamins is water-soluble?
(a) Vitamin A
(b) Vitamin D
(c) Vitamin C
(d) Vitamin E
Answer: (c) Vitamin C
Explanation: Vitamin C is a water-soluble vitamin that is important for the synthesis of collagen, the immune system, and as an antioxidant. Vitamins A, D, and E are fat-soluble.
Q82. The deficiency of Vitamin D in children leads to:
(a) Scurvy
(b) Pellagra
(c) Beriberi
(d) Rickets
Answer: (d) Rickets
Explanation: Rickets is a condition caused by Vitamin D deficiency in children, leading to soft and weak bones, which can result in skeletal deformities.
Q83. Which of the following is the chemical name of Vitamin B12?
(a) Thiamine
(b) Riboflavin
(c) Cobalamin
(d) Niacin
Answer: (c) Cobalamin
Explanation: Cobalamin is the chemical name of Vitamin B12. It plays a crucial role in red blood cell formation, neurological function, and DNA synthesis.
Q84. Vitamin A is stored in the body mainly in the:
(a) Liver
(b) Kidneys
(c) Skin
(d) Bones
Answer: (a) Liver
Explanation: Vitamin A is primarily stored in the liver, where it can be mobilized as needed for vision, immune function, and cell differentiation.
Q85. Which of the following vitamins helps in the synthesis of nucleic acids and the maturation of red blood cells?
(a) Vitamin D
(b) Vitamin K
(c) Folic acid
(d) Vitamin E
Answer: (c) Folic acid
Explanation: Folic acid (Vitamin B9) is essential for the synthesis of nucleic acids (DNA and RNA) and plays a critical role in the maturation of red blood cells, especially during pregnancy.
Q86. Which of the following is a pyrimidine base found in DNA?
(a) Adenine
(b) Thymine
(c) Guanine
(d) Uracil
Answer: (b) Thymine
Explanation: Thymine is a pyrimidine base found in DNA that pairs with adenine through two hydrogen bonds. Uracil is a pyrimidine found in RNA, replacing thymine.
Q87. The enzyme that catalyzes the synthesis of the RNA primer during DNA replication is:
(a) DNA polymerase
(b) Primase
(c) Helicase
(d) Ligase
Answer: (b) Primase
Explanation: Primase is the enzyme that synthesizes a short RNA primer, which provides a starting point for DNA polymerase to begin DNA replication.
Q88. The region of a gene where RNA polymerase binds to initiate transcription is called:
(a) Operator
(b) Promoter
(c) Enhancer
(d) Terminator
Answer: (b) Promoter
Explanation: The promoter is a specific DNA sequence located near the start of a gene where RNA polymerase binds to initiate the process of transcription.
Q89. Which of the following is a type of RNA that forms the structural and functional core of the ribosome?
(a) mRNA
(b) tRNA
(c) rRNA
(d) snRNA
Answer: (c) rRNA
Explanation: Ribosomal RNA (rRNA) forms the structural and functional core of ribosomes, which are the sites of protein synthesis in the cell.
Q90. DNA replication is described as:
(a) Conservative
(b) Dispersive
(c) Semiconservative
(d) Non-conservative
Answer: (c) Semiconservative
Explanation: DNA replication is semiconservative because each newly synthesized DNA molecule consists of one original (parental) strand and one new (daughter) strand.
Q91. Which of the following enzymes is responsible for synthesizing the leading strand during DNA replication?
(a) Helicase
(b) Ligase
(c) DNA polymerase
(d) Primase
Answer: (c) DNA polymerase
Explanation: DNA polymerase synthesizes the leading strand continuously in the 5′ to 3′ direction during DNA replication.
Q92. Which of the following is true for RNA but not for DNA?
(a) It is double-stranded.
(b) It contains deoxyribose.
(c) It contains uracil.
(d) It contains thymine.
Answer: (c) It contains uracil.
Explanation: RNA contains uracil instead of thymine, which is found in DNA. Additionally, RNA contains the sugar ribose, while DNA contains deoxyribose.
Q93. The process of copying a gene’s DNA sequence into an mRNA sequence is called:
(a) Translation
(b) Transcription
(c) Replication
(d) Mutation
Answer: (b) Transcription
Explanation: Transcription is the process by which a gene’s DNA sequence is copied into messenger RNA (mRNA), which is then used for protein synthesis.
Q94. Which of the following nitrogenous bases pairs with adenine in RNA?
(a) Thymine
(b) Cytosine
(c) Guanine
(d) Uracil
Answer: (d) Uracil
Explanation: In RNA, uracil pairs with adenine, replacing thymine, which is found in DNA.
Q95. Which of the following processes occurs in the nucleus of eukaryotic cells?
(a) Translation
(b) Transcription
(c) Protein synthesis
(d) Glycolysis
Answer: (b) Transcription
Explanation: Transcription occurs in the nucleus of eukaryotic cells, where the DNA is located. Translation and protein synthesis occur in the cytoplasm.
Q96. What is the function of tRNA in protein synthesis?
(a) Carry genetic information
(b) Synthesize ribosomes
(c) Transport amino acids
(d) Catalyze peptide bond formation
Answer: (c) Transport amino acids
Explanation: Transfer RNA (tRNA) carries amino acids to the ribosome, where they are added to the growing polypeptide chain during protein synthesis.
Q97. The bonds that link nucleotides together in a nucleic acid strand are called:
(a) Peptide bonds
(b) Glycosidic bonds
(c) Phosphodiester bonds
(d) Hydrogen bonds
Answer: (c) Phosphodiester bonds
Explanation: Phosphodiester bonds link nucleotides together in the sugar-phosphate backbone of nucleic acid strands (DNA and RNA).
Q98. Which of the following statements about DNA and RNA is false?
(a) DNA is double-stranded; RNA is single-stranded.
(b) DNA contains deoxyribose; RNA contains ribose.
(c) DNA uses thymine; RNA uses uracil.
(d) Both DNA and RNA are involved in protein synthesis.
Answer: (d) Both DNA and RNA are involved in protein synthesis.
Explanation: While DNA contains the instructions for protein synthesis, it is not directly involved in the process. Only RNA (mRNA, tRNA, and rRNA) directly participates in protein synthesis.
Q99. The site where translation occurs in a eukaryotic cell is:
(a) Nucleus
(b) Ribosome
(c) Mitochondria
(d) Golgi apparatus
Answer: (b) Ribosome
Explanation: Translation occurs at the ribosome, where mRNA is used as a template to assemble amino acids into proteins.
Q100. The function of RNA polymerase is to:
(a) Synthesize RNA from a DNA template
(b) Synthesize DNA from an RNA template
(c) Synthesize proteins from RNA
(d) Break down RNA
Answer: (a) Synthesize RNA from a DNA template
Explanation: RNA polymerase is the enzyme responsible for synthesizing RNA from a DNA template during the process of transcription
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