All Free Biology MCQs with Answers

• A. Uracil is a pyrimidine
• B. Glycine is a sulfur-containing amino acid
• C. Sucrose is a disaccharide
• D. Cellulose is a polysaccharide

Explanation: Option A: Uracil is a pyrimidine: This statement is correct. Uracil is one of the four nitrogenous bases found in RNA.

• A. Carbon and Sulfur
• B. Phosphorus and Calcium
• C. Sulfur and Magnesium
• D. Magnesium and Sodium

Explanation: The correct answer is Phosphorus and Calcium. In the context of biological molecules, the six elements that make up about 98% of the mass…

• A. Coiled around a common axis
• B. Coiled around each other
• C. Coiled differently
• D. Coiled over protein sheath
• E. Both A and B

Explanation: According to the Watson-­Crick model, the DNA molecule consists of two long, parallel chains which are joined together by short crossbars…

• A. Hormones
• B. Cofactors
• C. Antibodies
• D. Vitamins

Explanation: Many coenzymes are derived from vitamins, which are essential nutrients that organisms need in small amounts.

• A. Heat capacity
• B. Heat of vaporization
• C. Dipole nature
• D. Ionization of water

Explanation: The correct answer is Heat of vaporization. Water's high heat of vaporization allows it to absorb large amounts of heat energy as it…

• A. Primary structure
• B. Tertiary structure
• C. Secondary structure
• D. Quaternary structure

Explanation: The correct answer is the tertiary structure because it represents the complete three-dimensional folding of a single polypeptide chain…

• A. Cluster
• B. Spherical or curled up ball
• C. Flat uncoiled chains
• D. Long strands or fibrils

Explanation: Fibrous proteins are distinguished by their long, thread-like strands or fibrils.

• A. Ionic bond
• B. Peptide bond
• C. Glycosidic linkage
• D. Ester linkage

Explanation: Option D is correct. When an alcohol and an acid react, they undergo an esterification reaction to form an ester bond or linkage.

• A. C18H32O16
• B. C57H110O6
• C. C300H500O250
• D. C42H45O23N17S

Explanation: Option B is correct. The molecular formula C57H110O6 corresponds to triacylglycerol, a lipid composed of three fatty acids linked to a…

• A. tRNA
• B. rRNA
• C. mRNA
• D. RNA Primers

Explanation: Option D is correct. The type of RNA that initiates the process of replication in prokaryotic cells is RNA primase, which synthesizes…

• A. Glycolipids
• B. Nucleoproteins
• C. Glycoproteins
• D. Simple proteins

Explanation: The correct answer is Option D: Simple proteins. Simple proteins do not have any non-protein prosthetic groups and are composed entirely…

• A. They are insoluble
• B. They contain carboxyl and amino groups
• C. They have a low molecular mass
• D. They possess only secondary structure

Explanation: Option B is correct. Proteins act as pH buffers due to their amphoteric nature, meaning they can function as both acids and bases.

• A. Cellulose
• B. Starch
• C. Glycogen
• D. Chitin

Explanation: Option B is correct. The given diagram shows an α-glucose ring structure, identifiable by the downward orientation of the hydroxyl (OH)…

• A. They store a high amount of energy
• B. They are polymers of fatty acids
• C. They play an important role in insulation
• D. They are mostly hydrophobic

Explanation: Option B is correct. Lipids are not polymers of fatty acids because they do not consist of repeating units.

• A. Energy currency of the cell
• B. Contains ribose sugar
• C. Contains three high-energy bonds
• D. Contains three phosphate groups

Explanation: Option C is correct because ATP contains only two high-energy bonds, not three.

• A. Starch
• B. Glycogen
• C. Cellulose
• D. All of them

Explanation: Cellulose yields glucose through a process called hydrolysis, where the bonds between glucose units are broken.

• A. Peptide bonds
• B. Hydrogen bonds
• C. Disulphide bonds
• D. Glycosidic bonds

Explanation: The two chains of insulin are held together by disulphide bonds, which form covalent links between sulfur atoms in cysteine residues of…

• A. Disulphide bonds
• B. Hydrogen bonds
• C. Hydrophobic interactions
• D. Peptide bonds

Explanation: The primary structure of proteins is defined by the linear sequence of amino acids, which are linked by peptide bonds.

• A. Ionic bond
• B. Peptide bond
• C. Hydrogen bond
• D. Disulfide bond

Explanation: The secondary structure of proteins, such as the alpha helix, is stabilized by hydrogen bonds.

• A. Ionic bonds
• B. Hydrogen bonds
• C. Disulfide bonds
• D. Hydrophobic interactions

Explanation: The most stable tertiary configuration in proteins is primarily due to disulfide bonds.