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Free Biological Molecules MCQs with Answers

1,790 Biological Molecules MCQs from Biology, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.

The chapter covers water's polarity and biological roles, carbohydrates, lipids, proteins and nucleic acids, including their monomers, bonds, structures and functions. It also distinguishes RNA from DNA and explains conjugated molecules such as glycoproteins, glycolipids and nucleoproteins, which combine organic molecules with a non-protein component.

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Classification of Biological MoleculesBiological Importance of WaterCarbohydratesProteinsLipidsRibonucleic Acid (RNA)Conjugated MoleculesStructure of DNA
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1,790 questions · page 16 of 90

301. Proteins are made from amino acids by the process of ______________?

  • A. Hydrolysis
  • B. Pinocytosis
  • C. Dehydration synthesis
  • D. Active transport

Explanation: Amino acids join by peptide bonds through dehydration synthesis, in which a molecule of water is removed as the bond forms.

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Correct answer: Dehydration synthesis

302. enzymes are actually composed of ___________?

  • A. Carbohydrates
  • B. Proteins
  • C. Nucleic Acid
  • D. Fats

Explanation: Most enzymes are globular proteins whose specific three-dimensional shapes form active sites for binding substrates and catalysing…

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Correct answer: Proteins

303. Which of the following is a disease caused by deficiency of protein in children?

  • A. Pellagra
  • B. Marasmus
  • C. Beri-Beri
  • D. Rickets

Explanation: Marasmus results from severe deficiency of total calories and protein, producing marked wasting in children.

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Correct answer: Marasmus

304. The plant dye Henna imparts orangered colour to skin and hairs due to its reaction with which of the following?

  • A. Lipids
  • B. Carbohydrates
  • C. Amino acids
  • D. Protein and amino acids

Explanation: Henna contains lawsone, which reacts with proteins and amino groups in keratin of the skin and hair to produce an orange-red stain.

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Correct answer: Protein and amino acids

305. Insulin is a human__________?

  • A. Gene
  • B. Protein
  • C. Glucose
  • D. Diabetes

Explanation: Insulin is a peptide hormone made of amino acids, so it is a protein that regulates blood glucose concentration.

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Correct answer: Protein

306. The simplest amino acid is_________?

  • A. alanine
  • B. glycine
  • C. valine
  • D. phenylalanine

Explanation: Glycine is the simplest amino acid because its side chain is only a hydrogen atom, giving it the smallest possible amino-acid structure.

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Correct answer: glycine

307. Which of the following are proteins in nature?

  • A. Antibodies.
  • B. Interferons
  • C. Antitoxins
  • D. All of these

Explanation: Antibodies, interferons and antitoxins are protein molecules involved in defence, signalling or neutralising toxins.

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Correct answer: All of these

308. helical structure is kept by the formation of _________ bonds among amino acids molecules?

  • A. H bonds
  • B. Disulphide Bond
  • C. Ionic bond
  • D. Hydrophobic bonds

Explanation: An alpha helix is stabilized by hydrogen bonds between the carbonyl oxygen of one peptide bond and the hydrogen of another peptide bond in…

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Correct answer: H bonds

309. Which structural organization is most common in globular proteins____________?

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

Explanation: Globular proteins usually fold into a compact three-dimensional shape formed by interactions among amino acid side chains, which is their…

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Correct answer: Tertiary

310. Antibodies play important role against microorganisms and other pathogens to which type of proteins do they belong________?

  • A. Globular proteins
  • B. Fibrous Proteins
  • C. Both a and b
  • D. None of these

Explanation: Antibodies are immunoglobulins that recognize antigens and help neutralize or remove pathogens.

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Correct answer: Globular proteins

311. In an aqueous environment the most stable tertiary conformation is that in which _________ amino acids are buried inside the conformation?

  • A. Hydrophobic
  • B. Hydrophilic
  • C. Basic
  • D. None of these

Explanation: In water, hydrophobic side chains tend to avoid contact with water and become buried in the interior of a folded protein.

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Correct answer: Hydrophobic

312. Hemoglobin molecule exhibits which structural organization of proteins___________?

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

Explanation: A haemoglobin molecule is made of four polypeptide subunits, usually two alpha and two beta chains, each containing a haem group.

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Correct answer: Quaternary structure

313. Which structure of protein gives information aboutnumber and sequence of amino acids in it_______________?

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

Explanation: The primary structure of a protein is the exact number and sequence of its amino acids joined by peptide bonds.

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Correct answer: Primary structure

314. Total number of amino acids in a hemoglobin molecule are__________?

  • A. 554
  • B. 564
  • C. 574
  • D. 584

Explanation: Adult haemoglobin A has two alpha chains of 141 amino acids each and two beta chains of 146 amino acids each: (2 x 141) + (2 x 146) = 282…

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Correct answer: 574

315. A bond formed by linkage between -OH of carboxyl group of one amino acid and H of amino group of another amino acid which releases water is called__________?

  • A. Phosphodiester linkage
  • B. Glycosidic bond
  • C. Peptide bond
  • D. Hydrogen bond

Explanation: A peptide bond forms when the carboxyl group of one amino acid reacts with the amino group of another, releasing one molecule of water and…

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Correct answer: Peptide bond

316. An insulin molecule consists of _________ polypeptide chains?

  • A. 1
  • B. 2
  • C. 3
  • D. 4

Explanation: Insulin is a protein made of two polypeptide chains, called the A chain and B chain, joined by disulfide bonds.

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Correct answer: 2

317. Proteins are polymers of___________?

  • A. Fatty acids
  • B. Isoprenoid units
  • C. Amino acids
  • D. Nucleotides

Explanation: Proteins are polymers whose monomer units are amino acids, joined in chains by peptide bonds.

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Correct answer: Amino acids

318. Proteins comprise of ___________% of the total dry weight of a cell?

  • A. 40%
  • B. 50%
  • C. 60%
  • D. 70%

Explanation: Proteins make up approximately 50% of the dry mass of a typical cell, reflecting their roles as enzymes, structural materials…

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Correct answer: 50%

319. Peptide bond is_____________?

  • A. C-N link
  • B. C- O lind
  • C. N-H link
  • D. C-H link

Explanation: A peptide bond is the covalent C-N bond formed between the carbonyl carbon of one amino acid and the nitrogen of another during…

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Correct answer: C-N link

320. The one which is not a globular protein__________?

  • A. Anti Rh-antibody
  • B. Enzyme
  • C. Myosin
  • D. Haemoglobin

Explanation: Myosin is a long, filamentous structural and motor protein, so it is classified as a fibrous protein rather than a globular protein.

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Correct answer: Myosin
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