Free Classification of Proteins MCQs with Answers
62 Classification of Proteins MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Proteins are classified by composition as simple, conjugated and derived proteins, and by shape as fibrous or globular proteins. The topic relates these classes to examples such as albumin, keratin, collagen, haemoglobin and casein, while distinguishing structural proteins from proteins with transport, catalytic or regulatory roles.
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- A. a glycosidic linkage
- B. a peptide linkage, formed by condensation between a carboxyl and an amino group
- C. an ester linkage
- D. a hydrogen bond
Explanation: The carboxyl group of one amino acid condenses with the amino group of the next, releasing water and leaving a CO-NH amide link known as…
Correct answer: a peptide linkage, formed by condensation between a carboxyl and an amino group- A. dissolves only in organic solvents
- B. contains a benzene ring
- C. contains both an acidic carboxyl group and a basic amino group, so it reacts with both acids and bases
- D. has no charge under any conditions
Explanation: The carboxyl group can donate a proton and the amino group can accept one, so an amino acid neutralises both acids and alkalis.
Correct answer: contains both an acidic carboxyl group and a basic amino group, so it reacts with both acids and bases- A. neutral point
- B. isoelectric point
- C. equivalence point
- D. melting point
Explanation: At the isoelectric point the positive and negative charges within the molecule exactly balance, so the net charge is zero and the amino…
Correct answer: isoelectric point- A. insoluble in water and structural in function
- B. soluble in water and catalytic in function
- C. always an enzyme
- D. made of a single amino acid repeated
Explanation: Fibrous proteins consist of long parallel chains held in bundles, which makes them tough, insoluble and suited to structural roles in…
Correct answer: insoluble in water and structural in function- A. peptide bonds between amino acids
- B. ionic bonds between side chains only
- C. hydrogen bonds between the carbonyl and amide groups of the backbone
- D. disulphide bridges only
Explanation: Regular coiling or pleating arises because each carbonyl oxygen hydrogen bonds to an amide hydrogen further along the same chain, giving…
Correct answer: hydrogen bonds between the carbonyl and amide groups of the backbone- A. Protein and glucose
- B. Starch and amino acid
- C. Nucleic acid and fatty acid
- D. Protein and amino acid
Explanation: Proteins are polymers of amino acids, starch and cellulose of glucose, and nucleic acids of nucleotides, while fats are not true polymers…
Correct answer: Protein and amino acid- A. contains a disulphide bridge
- B. is fibrous
- C. consists of two or more polypeptide chains associated together
- D. contains more than one hundred amino acids
Explanation: Quaternary structure describes how separate polypeptide subunits fit together, as in haemoglobin with its two alpha and two beta chains…
Correct answer: consists of two or more polypeptide chains associated together- A. only amino acids
- B. a non protein prosthetic group in addition to the polypeptide
- C. no peptide bonds
- D. two identical chains
Explanation: A conjugated protein is bound to a non protein group, so haemoglobin carries a haem group, glycoproteins carry carbohydrate and…
Correct answer: a non protein prosthetic group in addition to the polypeptide- A. the sequence of amino acids joined by peptide bonds
- B. the coiling of the chain into a helix
- C. the folding of the chain into a globular shape
- D. the association of several chains
Explanation: Primary structure is simply the order of the residues, and it determines every higher level of structure, because the chain folds…
Correct answer: the sequence of amino acids joined by peptide bonds- A. peptide bonds along the backbone
- B. hydrogen bonds between backbone carbonyl and amide groups
- C. disulphide bridges between cysteines
- D. ionic bonds between side chains
Explanation: Regular hydrogen bonding between a carbonyl oxygen and an amide hydrogen four residues further along coils the chain into a helix.
Correct answer: hydrogen bonds between backbone carbonyl and amide groups- A. cysteine residues
- B. glycine residues
- C. lysine residues
- D. serine residues
Explanation: Two sulphydryl groups are oxidised to form a covalent S-S link, the strongest of the interactions holding tertiary structure.
Correct answer: cysteine residues- A. soluble in water and act as enzymes
- B. insoluble in water and serve structural roles
- C. always conjugated
- D. made of a single amino acid
Explanation: Long parallel chains bundled together make fibrous proteins tough and insoluble, which suits keratin in hair, collagen in tendons and…
Correct answer: insoluble in water and serve structural roles- A. carbon dioxide
- B. a molecule of water
- C. ammonia
- D. hydrogen
Explanation: Condensation between the carboxyl group of one residue and the amino group of the next expels water and creates the peptide link.
Correct answer: a molecule of water- A. large molecules built from repeating amino acid units
- B. made of two identical halves
- C. always branched
- D. insoluble in all solvents
Explanation: A polymer is any large molecule assembled from many small repeating units, and in a protein those units are amino acids joined by peptide…
Correct answer: large molecules built from repeating amino acid units- A. 4
- B. 20
- C. 64
- D. 100
Explanation: Twenty amino acids account for almost all natural protein, and their enormous number of possible sequences is what allows such variety of…
Correct answer: 20- A. no charged groups
- B. a positive charge on the amino group and a negative charge on the carboxyl group at the same time
- C. two positive charges
- D. a single negative charge only
Explanation: The carboxyl group donates its proton to the amino group within the same molecule, so the ion has both charges and a net charge of zero at…
Correct answer: a positive charge on the amino group and a negative charge on the carboxyl group at the same time- A. albumin
- B. haemoglobin
- C. keratin
- D. fibroin
Explanation: Haemoglobin carries a non protein haem prosthetic group that does the actual oxygen binding, which makes it conjugated.
Correct answer: haemoglobin- A. Peptide
- B. Enzymes
- C. Primary protein
- D. Secondary proteins
Explanation: Globular proteins fold into compact, roughly spherical structures, and enzymes are the main biological examples because their folded…
Correct answer: Enzymes- A. glumatic acid
- B. lactic acid
- C. aspartic acids
- D. glycine
Explanation: Amino acids contain both an amino group and a carboxyl group, while lactic acid contains a hydroxyl group and a carboxyl group but no…
Correct answer: lactic acid- A. Sweet taste
- B. Bitter taste
- C. Shining appearance
- D. Green colour
Explanation: The name glycine comes from the Greek word glykys, meaning sweet, because glycine has a sweet taste.
Correct answer: Sweet tasteClassification of Proteins MCQs: common questions
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