All Free Biology MCQs with Answers

• A. Glucose and fructose
• B. Nucleosides and nucleic acid
• C. Nucleotides and nucleic acid
• D. Purines and pyrimidines

Explanation: The correct answer is Option C: Nucleotides and nucleic acid. Nucleotides are the monomeric units that polymerize to form nucleic acids, just as amino acids polymerize to form proteins. Each nucleotide consists of a nitrogenous base, a sugar, and one or more phosphate groups, allowing them to link together to form the long chains characteristic of DNA and RNA. Other options, such as glucose and fructose, or purines and pyrimidines, do not represent a similar building block-to-polymer relationship.

• A. Ascorbic acid
• B. Collagen
• C. Cellulose
• D. Galactose

Explanation: Collagen is the correct answer because it is a protein, and proteins are made up of amino acids, which are their building blocks. Ascorbic acid is a vitamin, cellulose is a carbohydrate, and galactose is a sugar. None of these contain amino acids. Only proteins, such as collagen, are constructed from amino acids.

• A. Option A
• B. Option B
• C. Option C
• D. Option D

Explanation: The question requires identifying how cellulose and sucrose are correctly characterized. Both are non-reducing sugars, due to the types of glycosidic bonds they possess. Cellulose is a polysaccharide consisting of glucose units linked by β-1,4-glycosidic bonds, providing structural support in plants. Sucrose, on the other hand, is a disaccharide formed from glucose and fructose with an α-1,β-2-glycosidic bond. Option D correctly captures these differences and similarities, while the other options either lack specificity or provide incorrect groupings.

• A. ATP
• B. DNA
• C. Collagen
• D. Maltose

Explanation: Peptide bonds are a defining feature of proteins, linking amino acids in a chain. Collagen, being a structural protein, contains many peptide bonds, making it the correct answer.ATP is involved in energy transfer and contains phosphate bonds, not peptide bonds. DNA is composed of nucleotides held together by phosphodiester bonds, not peptide bonds. Maltose is a sugar, consisting of glucose units linked by glycosidic bonds, not peptide bonds.

• A. Amylose
• B. Myoglobin
• C. Collagen
• D. Glycogen

Explanation: The correct answer is Glycogen. It is a polysaccharide stored in human muscles, playing a vital role in energy storage. Glycogen can be quickly converted to glucose, providing a readily available energy source during physical exertion.Amylose is incorrect because it is a plant-based polysaccharide found in starch, not in human muscles. Myoglobin and Collagen are not carbohydrates; Myoglobin is a protein involved in oxygen transport within muscles, and Collagen is a structural protein found in connective tissues.

• A. Amylase
• B. Haemoglobin
• C. Collagen
• D. Keratin
• E. C and D

Explanation: The correct answer is Option E: C and D, as both Collagen and Keratin are fibrous proteins. Collagen is crucial for the structural integrity of connective tissues, providing strength and support. Keratin, on the other hand, is essential for the protection and durability of skin, hair, and nails. These proteins have fibrous structures that are fundamentally different from the globular structures seen in proteins like Amylase and Haemoglobin. Amylase, a globular enzyme, functions in starch digestion, while Haemoglobin, another globular protein, efficiently carries oxygen in the blood.

• A. Cellulose is a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units
• B. Cellulose is a branched polysaccharide that serves as a storage form of energy in animals
• C. Cellulose is a protein that acts as an enzyme to break down starch
• D. Cellulose consists of α(1→4) linked glucose units, similar to amylose starch

Explanation: Cellulose is a complex carbohydrate or polysaccharide that consists of long chains of β(1→4) linked D-glucose units, forming an unbranched, linear structure. It provides mechanical strength and rigidity to plant cell walls, which is crucial for maintaining plant structure. The β-glycosidic linkages in cellulose make it indigestible to most animals, as they lack the enzyme cellulase needed to break these bonds. Unlike cellulose, starch is a storage polysaccharide composed of α(1→4) linked glucose units, which can be either branched (amylopectin) or unbranched (amylose). This structural difference in glycosidic linkage type between cellulose and starch determines their different roles in biological systems. Option A accurately describes cellulose, while options B, C, and D incorrectly describe its structure and function.

• A. Fatty acids, Polysaccharides
• B. Proteins, Amino acids
• C. Lipids, Glucose
• D. None of these

Explanation: In catabolic reactions, proteins are broken down into amino acids. Proteins are large biomolecules consisting of one or more long chains of amino acid residues. During catabolism, these proteins are degraded into their constituent amino acids, which can then be used in various metabolic processes or for synthesis of new proteins. This makes Option B the correct answer.Option A is incorrect because fatty acids are not released from polysaccharides; rather, polysaccharides are broken down into simple sugars like glucose. Option C is incorrect because lipids are broken down into fatty acids and glycerol, not glucose. Option D is incorrect as there is a correct answer present.

• A. Oxygen
• B. Carbon
• C. Hydrogen
• D. All of these

Explanation: Carbon is the fundamental element found in all organic compounds. Its ability to form four covalent bonds allows for the creation of complex and diverse organic molecules. Unlike carbon, oxygen and hydrogen, although crucial to life, do not define organic compounds. Oxygen is involved in respiration, and hydrogen is abundant and significant in forming compounds, but neither is the basic element of organic compounds. Therefore, option B, carbon, is the correct answer.

• A. 774 Kcal/kg
• B. 874 Kcal/kg
• C. 574 Kcal/kg
• D. 674 Kcal/kg

Explanation: The specific heat of vaporization of water is 574 kcal/kg, representing the energy needed to convert liquid water into vapor without changing its temperature. This high value reflects the strong hydrogen bonds that require significant energy to break.