Biomolecules and Enzymes MCQs 2026

Maltose is formed by the condensation of two molecules of

1. A Fructose ✓
2. B Galactose ✓
3. C Glucose ✓
4. D Ribose ✓

The bond formed between glycerol and a fatty acid is termed

1. A Ester bond ✓
2. B Peptide bond ✓
3. C Glycosidic bond ✓
4. D Ionic bond ✓

Phospholipids are described as amphipathic because they have

1. A Two hydrophobic ends ✓
2. B A hydrophilic head and hydrophobic tails ✓
3. C Two hydrophilic ends ✓
4. D No polar groups at all ✓

Waxes are chemically formed by combining fatty acids with

1. A Glycerol ✓
2. B Long-chain alcohols ✓
3. C Amino acids ✓
4. D Nitrogenous bases ✓

Unsaturated fatty acids typically exist as liquids at room temperature because

1. A They lack a glycerol backbone ✓
2. B Their double bonds create kinks preventing tight packing ✓
3. C They contain phosphate groups ✓
4. D They are shorter in chain length ✓

The overall three-dimensional folding of a single polypeptide chain describes its

1. A Primary structure ✓
2. B Secondary structure ✓
3. C Tertiary structure ✓
4. D Quaternary structure ✓

Most biological enzymes are chemically composed of

1. A Lipids ✓
2. B Nucleic acids ✓
3. C Proteins ✓
4. D Carbohydrates ✓

The nitrogenous base found in RNA but not in DNA is

1. A Thymine ✓
2. B Cytosine ✓
3. C Guanine ✓
4. D Uracil ✓

Adenine and guanine are classified as

1. A Pyrimidines ✓
2. B Purines ✓
3. C Nucleosides ✓
4. D Phosphate groups ✓

Successive nucleotides in a DNA strand are linked together by

1. A Peptide bonds ✓
2. B Glycosidic bonds ✓
3. C Hydrogen bonds ✓
4. D Phosphodiester bonds ✓

The attraction between the partially positive hydrogen of one water molecule and the partially negative oxygen of another is called a

1. A Hydrogen bond ✓
2. B Ionic bond ✓
3. C Covalent bond ✓
4. D Peptide bond ✓

Water is often called the universal solvent because it can dissolve

1. A Most polar and ionic substances ✓
2. B Only nonpolar lipids ✓
3. C Only gases ✓
4. D Only large proteins ✓

Galactosemia in infants results from an inability to properly metabolize

1. A Fructose ✓
2. B Sucrose ✓
3. C Maltose ✓
4. D Galactose ✓

Disulfide bonds that stabilize protein tertiary structure form between the side chains of

1. A Glycine residues ✓
2. B Cysteine residues ✓
3. C Lysine residues ✓
4. D Proline residues ✓

RNA is generally single-stranded while DNA is typically

1. A Double-stranded ✓
2. B Triple-stranded ✓
3. C Single-stranded ✓
4. D Branched ✓

The pentose sugar present in RNA nucleotides is

1. A Ribose ✓
2. B Deoxyribose ✓
3. C Glucose ✓
4. D Fructose ✓

Sucrose is classified as a non-reducing sugar because its glycosidic bond

1. A Involves both anomeric carbons of glucose and fructose ✓
2. B Only forms in the presence of enzymes ✓
3. C Cannot be hydrolyzed by any acid ✓
4. D Occurs only in animal tissues ✓

Water is described as a polar molecule because

1. A It has no charge distribution ✓
2. B Oxygen and hydrogen share electrons equally ✓
3. C Oxygen attracts shared electrons more strongly than hydrogen ✓
4. D It contains only nonpolar covalent bonds ✓

Milk sugar is composed of glucose linked with

1. A Fructose ✓
2. B Galactose ✓
3. C Ribose ✓
4. D Mannose ✓

Starch differs from cellulose mainly in the type of

1. A Monomer used ✓
2. B Glycosidic linkage ✓
3. C Element composition ✓
4. D Solubility in ethanol ✓

The building blocks of proteins are

1. A Fatty acids ✓
2. B Nucleotides ✓
3. C Amino acids ✓
4. D Monosaccharides ✓

The bond joining two monosaccharide units is called a

1. A Peptide bond ✓
2. B Ester bond ✓
3. C Phosphodiester bond ✓
4. D Glycosidic bond ✓

Which level of protein structure refers to the linear sequence of amino acids

1. A Secondary structure ✓
2. B Primary structure ✓
3. C Tertiary structure ✓
4. D Quaternary structure ✓

Which of the following is a disaccharide

1. A Glucose ✓
2. B Sucrose ✓
3. C Fructose ✓
4. D Galactose ✓

The bond that links two amino acids together is called a

1. A Peptide bond ✓
2. B Glycosidic bond ✓
3. C Phosphodiester bond ✓
4. D Hydrogen bond ✓

Hemoglobin, composed of four polypeptide chains, is an example of which protein structure level

1. A Primary structure ✓
2. B Secondary structure ✓
3. C Tertiary structure ✓
4. D Quaternary structure ✓

Loss of a protein's native structure due to heat or extreme pH is called

1. A Denaturation ✓
2. B Hydrolysis ✓
3. C Condensation ✓
4. D Phosphorylation ✓

Alpha-helix and beta-pleated sheet are examples of which level of protein structure

1. A Primary structure ✓
2. B Tertiary structure ✓
3. C Secondary structure ✓
4. D Quaternary structure ✓

In enzyme kinetics, the Michaelis constant (Km) represents the substrate concentration at which reaction velocity is

1. A Zero ✓
2. B Half of the maximum velocity ✓
3. C Equal to maximum velocity ✓
4. D Twice the maximum velocity ✓

The region of an enzyme where the substrate binds is called the

1. A Allosteric site ✓
2. B Active site ✓
3. C Coenzyme site ✓
4. D Regulatory site ✓

The model that describes the enzyme active site changing shape slightly to fit the substrate is the

1. A Lock and key model ✓
2. B Fluid mosaic model ✓
3. C Induced fit model ✓
4. D Michaelis-Menten model ✓

Non-protein organic molecules required for some enzymes to function are called

1. A Coenzymes ✓
2. B Apoenzymes ✓
3. C Zymogens ✓
4. D Isoenzymes ✓

Many vitamins, especially B-complex vitamins, function biologically as

1. A Structural proteins ✓
2. B Hormones ✓
3. C Antibodies ✓
4. D Coenzymes or coenzyme precursors ✓

An inhibitor that binds to the active site and competes with the substrate is called a

1. A Non-competitive inhibitor ✓
2. B Allosteric inhibitor ✓
3. C Competitive inhibitor ✓
4. D Irreversible inhibitor ✓

An inhibitor that binds to a site other than the active site, changing enzyme shape, is called

1. A Competitive inhibitor ✓
2. B Non-competitive inhibitor ✓
3. C Substrate analog ✓
4. D Coenzyme ✓

Beyond the optimum temperature, enzyme activity typically decreases because the enzyme becomes

1. A Denatured ✓
2. B More active ✓
3. C Saturated with substrate ✓
4. D Converted to a coenzyme ✓

Most human enzymes function optimally at a temperature close to

1. A 0 degrees Celsius ✓
2. B 100 degrees Celsius ✓
3. C 37 degrees Celsius ✓
4. D 60 degrees Celsius ✓

Pepsin, an enzyme active in the stomach, works best at a pH that is

1. A Neutral ✓
2. B Strongly alkaline ✓
3. C Slightly alkaline ✓
4. D Strongly acidic ✓

Enzymes primarily function by

1. A Being consumed in the reaction ✓
2. B Changing the equilibrium of a reaction ✓
3. C Providing energy for the reaction ✓
4. D Lowering the activation energy of a reaction ✓

Enzymes are classified based mainly on

1. A The type of reaction they catalyze ✓
2. B Their molecular weight ✓
3. C Their color ✓
4. D Their solubility in water ✓

Enzymes belonging to the oxidoreductase class catalyze

1. A Bond cleavage using water ✓
2. B Transfer of functional groups ✓
3. C Isomerization reactions ✓
4. D Oxidation-reduction reactions ✓

Hydrolase enzymes catalyze reactions that involve

1. A Formation of double bonds ✓
2. B Transfer of phosphate groups ✓
3. C Breaking bonds using water molecules ✓
4. D Joining two molecules using ATP ✓

ATP is often called the energy currency of the cell because it

1. A Cannot be broken down ✓
2. B Releases usable energy when its phosphate bonds are hydrolyzed ✓
3. C Is a structural protein ✓
4. D Is only found in plant cells ✓

The storage form of carbohydrate in animal liver and muscle is

1. A Starch ✓
2. B Cellulose ✓
3. C Glycogen ✓
4. D Chitin ✓

Fats are formed by the combination of glycerol with

1. A Fatty acids ✓
2. B Amino acids ✓
3. C Nucleotides ✓
4. D Monosaccharides ✓

A triglyceride consists of one glycerol molecule bonded to how many fatty acid chains

1. A One ✓
2. B Three ✓
3. C Two ✓
4. D Four ✓

Phospholipids are the major structural component of

1. A Cell walls ✓
2. B Ribosomes ✓
3. C Chromosomes ✓
4. D Cell membranes ✓

Cholesterol belongs to which class of lipids

1. A Triglycerides ✓
2. B Phospholipids ✓
3. C Steroids ✓
4. D Waxes ✓

Saturated fatty acids differ from unsaturated fatty acids in that they

1. A Contain double bonds between carbon atoms ✓
2. B Contain no double bonds between carbon atoms ✓
3. C Are always liquid at room temperature ✓
4. D Cannot be found in animal fats ✓

The monomer unit of nucleic acids is the

1. A Nucleotide ✓
2. B Amino acid ✓
3. C Monosaccharide ✓
4. D Fatty acid ✓

A nucleotide is composed of a nitrogenous base, a sugar, and a

1. A Fatty acid ✓
2. B Amino acid ✓
3. C Glycerol molecule ✓
4. D Phosphate group ✓

In DNA, adenine pairs specifically with

1. A Guanine ✓
2. B Cytosine ✓
3. C Thymine ✓
4. D Uracil ✓

In RNA, adenine pairs with

1. A Thymine ✓
2. B Uracil ✓
3. C Cytosine ✓
4. D Guanine ✓

Cellulose, starch, and glycogen are all examples of

1. A Monosaccharides ✓
2. B Disaccharides ✓
3. C Lipids ✓
4. D Polysaccharides ✓

Guanine pairs with cytosine through how many hydrogen bonds

1. A Three ✓
2. B Two ✓
3. C Four ✓
4. D One ✓

ATP is composed of adenine, ribose sugar, and how many phosphate groups

1. A One ✓
2. B Two ✓
3. C Four ✓
4. D Three ✓

Water's high specific heat capacity, important for living organisms, is largely due to

1. A Extensive hydrogen bonding between water molecules ✓
2. B Its acidic nature ✓
3. C Its high molecular weight ✓
4. D Covalent bonding within water molecules ✓

A solution with a pH of 3 is considered

1. A Strongly alkaline ✓
2. B Neutral ✓
3. C Acidic ✓
4. D Slightly alkaline ✓

Buffers in biological systems function to

1. A Increase reaction rates ✓
2. B Resist changes in pH ✓
3. C Provide energy ✓
4. D Break down proteins ✓

Which biomolecule is most efficient for long-term energy storage due to its high caloric value per gram

1. A Carbohydrate ✓
2. B Protein ✓
3. C Nucleic acid ✓
4. D Lipid ✓

Amino acids are classified as essential when they

1. A Cannot be synthesized by the body and must be obtained from diet ✓
2. B Are synthesized only in the liver ✓
3. C Do not contain nitrogen ✓
4. D Are found only in plant proteins ✓

The unique property allowing an amino acid's side chain (R group) to determine its classification includes being

1. A Always identical across amino acids ✓
2. B Only found in essential amino acids ✓
3. C Polar, nonpolar, acidic, or basic ✓
4. D Always positively charged ✓

The genetic information in DNA is ultimately expressed through the synthesis of

1. A Lipids ✓
2. B Proteins ✓
3. C Polysaccharides ✓
4. D Steroids ✓

Which sugar is found in the backbone of DNA

1. A Ribose ✓
2. B Fructose ✓
3. C Glucose ✓
4. D Deoxyribose ✓

The DNA double helix structure was proposed by

1. A Watson and Crick ✓
2. B Singer and Nicolson ✓
3. C Schleiden and Schwann ✓
4. D Meselson and Stahl ✓

An enzyme's substrate specificity is primarily determined by the

1. A Enzyme's molecular weight ✓
2. B Enzyme's overall size ✓
3. C Three-dimensional shape of its active site ✓
4. D Number of amino acids in the enzyme ✓

Chitin, found in fungal cell walls and insect exoskeletons, is a polymer of

1. A Glucose only ✓
2. B Amino acids ✓
3. C Fatty acids ✓
4. D N-acetylglucosamine ✓

Which vitamin deficiency is linked to the coenzyme NAD, causing the disease pellagra

1. A Vitamin C ✓
2. B Niacin (Vitamin B3) ✓
3. C Vitamin D ✓
4. D Vitamin K ✓

Enzyme activity that increases steadily with substrate concentration until it plateaus indicates

1. A Enzyme denaturation ✓
2. B Competitive inhibition ✓
3. C Saturation of active sites at high substrate concentration ✓
4. D Absence of a cofactor ✓

The overall chemical reactions within a living organism, including both anabolic and catabolic processes, are collectively called

1. A Metabolism ✓
2. B Catabolism only ✓
3. C Anabolism only ✓
4. D Homeostasis ✓