5401 to 5450 MCQs for Lab Technician and Technologist Exam Preparation
5000 Plus MCQs for Lab Technician and Technologists are designed to test the knowledge and proficiency of laboratory professionals who work in the field of clinical laboratory science. These questions cover a wide range of topics related to laboratory science, including anatomy, physiology, microbiology, chemistry, and hematology.
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Questions 5401 to 5450
Which one of the following is an essential amino acid?
- a) Arginine
- b) Tyrosine
- c) Phenylalanine
- d) Proline
Explanation:
Phenylalanine is an essential amino acid because the human body cannot synthesize it; it must be obtained through the diet.
Why other options are incorrect:
Why other options are incorrect:
- • Arginine: Considered a conditionally essential amino acid (the body can usually produce enough).
- • Tyrosine: A non-essential amino acid that can be synthesized in the body from phenylalanine.
- • Proline: A non-essential amino acid that the body can synthesize from glutamic acid.
One of the following amino acid is solely ketogenic:
- a) Lysine
- b) Alanine
- c) Valine
- d) Glutamate
Explanation:
Lysine (along with Leucine) is one of the only two strictly ketogenic amino acids in humans. They are converted into acetyl-CoA or acetoacetyl-CoA rather than being used for gluconeogenesis.
Why other options are incorrect:
Why other options are incorrect:
- • Alanine: A major glucogenic amino acid that can be converted to pyruvate.
- • Valine: A branched-chain amino acid that is primarily glucogenic.
- • Glutamate: A glucogenic amino acid that enters the Krebs cycle as alpha-ketoglutarate.
Along with CO2, NH3 and ATP, the amino acid that is needed in urea cycle is
- a) Alanine
- b) Isoleucine
- c) Aspartate
- d) Glycine
Explanation:
In the urea cycle, the nitrogen atoms are derived from two sources: one from free ammonia (NH3) and the other from the amino group of Aspartate.
Why other options are incorrect:
Why other options are incorrect:
- • Alanine: Primarily acts as a carrier of nitrogen from muscles to the liver, but is not a direct participant in the urea cycle reactions.
- • Isoleucine: A branched-chain amino acid that is catabolized to produce acetyl-CoA and succinyl-CoA.
- • Glycine: Used in the synthesis of heme, purines, and creatine, but not a direct nitrogen donor in the urea cycle.
Isoelectric pH of an amino acid is that pH at which it has a
- a) Positive charge
- b) Negative charge
- c) No charge
- d) None of these
Explanation:
The isoelectric point (pI) is the pH at which an amino acid carries no net electrical charge. In this state, the molecule exists as a zwitterion, where the positive and negative charges cancel each other out.
Why other options are incorrect:
Why other options are incorrect:
- • Positive charge: Occurs when the pH is below the pI (the amino group is protonated).
- • Negative charge: Occurs when the pH is above the pI (the carboxyl group is deprotonated).
- • None of these: Incorrect because “No charge” accurately describes the net electrical state at the isoelectric point.
Which of the following contributes nitrogen atoms to both purine and pyrimidine rings?
- a) Aspartate
- b) Carbamoyl phosphate
- c) CO2
- d) Glutamine
Explanation:
Glutamine acts as a primary nitrogen donor in the biosynthesis of both purines (providing N3 and N9) and pyrimidines (providing the N3 of the ring).
Why other options are incorrect:
Why other options are incorrect:
- • Aspartate: Contributes nitrogen to purines and pyrimidines, but Glutamine is the classic answer for a broader amide nitrogen donor in these pathways.
- • Carbamoyl phosphate: Provides the nitrogen for the pyrimidine ring but is not a direct precursor for the purine ring.
- • CO2: Provides carbon atoms to the rings, not nitrogen atoms.
Which amino acid is a lipotropic factor?
- a) Lysine
- b) Leucine
- c) Tryptophan
- d) Methionine
Explanation:
Methionine is considered a lipotropic factor because it acts as a methyl donor (in the form of S-adenosylmethionine) for the synthesis of choline, which is essential for the transport and metabolism of fats in the liver.
Why other options are incorrect:
Why other options are incorrect:
- • Lysine: An essential amino acid involved in protein synthesis and carnitine production, but not a primary lipotropic factor.
- • Leucine: A branched-chain amino acid involved in protein synthesis and mTOR pathway activation.
- • Tryptophan: A precursor for serotonin and niacin, not involved in lipid mobilization in the liver.
Which of the following protein is rich in cysteine?
- a) Elastine
- b) Collagen
- c) Fibrin
- d) Keratin
Explanation:
Keratin is a structural protein found in hair, nails, and skin. It is exceptionally rich in cysteine, which allows for the formation of numerous disulfide bonds, providing the protein with its characteristic strength and rigidity.
Why other options are incorrect:
Why other options are incorrect:
- • Elastin: Primarily rich in glycine, proline, and alanine; it provides elasticity rather than rigidity.
- • Collagen: Characterized by high amounts of glycine, proline, and hydroxyproline, but low in cysteine.
- • Fibrin: Involved in blood clotting and is not noted for a particularly high cysteine content compared to keratin.
Which amino acid is present at 6th position of β-chain of Hbs instead of glutamate in HbA?
- a) Cysteine
- b) Valine
- c) Aspartate
- d) Glutamate
Explanation:
In Sickle Cell Hemoglobin (HbS), a point mutation in the DNA leads to the substitution of the amino acid Valine for Glutamate at the 6th position of the β-globin chain. This replacement creates a “sticky” hydrophobic patch, causing the hemoglobin to polymerize under low oxygen conditions.
Why other options are incorrect:
Why other options are incorrect:
- • Cysteine: Not involved in the classic HbS mutation.
- • Aspartate: Similar in acidic nature to glutamate, but is not the substitution found in HbS.
- • Glutamate: This is the amino acid present in normal adult hemoglobin (HbA), not the mutant HbS.
The amino acid which contains an indole group is
- a) Histidine
- b) Arginine
- c) Cystine
- d) Tryptophan
Explanation:
Tryptophan is the only standard amino acid that contains an indole ring in its side chain. This bicyclic structure consists of a six-membered benzene ring fused to a five-membered nitrogen-containing pyrrole ring.
Why other options are incorrect:
Why other options are incorrect:
- • Histidine: Contains an imidazole group, not an indole group.
- • Arginine: Contains a guanidino group in its side chain.
- • Cystine: Formed by the oxidation of two cysteine molecules to form a disulfide bond (-S-S-).
From two amino acids peptide bond formation involves removal of one molecule of
- a) Water
- b) Ammonia
- c) Carbondioxide
- d) Carboxylic acid
Explanation:
A peptide bond is formed by a dehydration synthesis (condensation) reaction between the alpha-carboxyl group of one amino acid and the alpha-amino group of another, resulting in the release of one water molecule (H2O).
Why other options are incorrect:
Why other options are incorrect:
- • Ammonia: Not a byproduct of standard peptide bond formation.
- • Carbondioxide: Decarboxylation involves the removal of CO2, which is a different biochemical process.
- • Carboxylic acid: This is a functional group that participates in the bond, not a product that is removed.
Polymers of more than 100 amino acids are termed
- a) Proteins
- b) Polypeptides
- c) Both (Proteins) and (Polypeptides)
- d) None of these
Explanation:
While definitions can sometimes overlap, generally, a polypeptide chain exceeding approximately 100 amino acids in length and possessing a defined three-dimensional structure is termed a protein.
Why other options are incorrect:
Why other options are incorrect:
- • Polypeptides: This term is generally used for shorter chains of amino acids (typically less than 100).
- • Both: Incorrect, because the term “Protein” is specifically reserved for longer, complex folded chains.
- • None of these: Incorrect, as “Proteins” is the accepted biological classification for these long polymers.
The example of scleroproteins:
- a) Glutamin
- b) Giladin
- c) Salmine
- d) Elastin
Explanation:
Scleroproteins (also known as fibrous proteins) are structural proteins that are insoluble in water and generally resistant to enzymatic digestion. Examples include elastin, collagen, and keratin.
Why other options are incorrect:
Why other options are incorrect:
- • Glutamin: This is an amino acid (Glutamine), not a protein.
- • Giladin: A prolamin (storage protein) found in wheat, classified differently from scleroproteins.
- • Salmine: A protamine (a type of basic protein) found in the sperm of salmon, not a fibrous structural protein.
The example of phosphoprotein:
- a) Mucin
- b) Ovovitellin
- c) Ovomucoid
- d) Tendomucoid
Explanation:
Phosphoproteins are a group of conjugated proteins containing phosphate groups attached to amino acid residues (like serine). Ovovitellin, found in egg yolk, is a classic example of a phosphoprotein.
Why other options are incorrect:
Why other options are incorrect:
- • Mucin: Classified as a glycoprotein (carbohydrate-rich).
- • Ovomucoid: Also a glycoprotein found in egg white.
- • Tendomucoid: Another example of a glycoprotein found in connective tissue (tendons).
The example of metalloproteins:
- a) Siderophilin
- b) OREES mucoid
- c) Elastin
- d) All of these
Explanation:
Siderophilin (also known as transferrin) is a classic example of a metalloprotein. It is an iron-binding blood plasma glycoprotein that controls the level of free iron in biological fluids.
Why other options are incorrect:
Why other options are incorrect:
- • OREES mucoid: This is a glycoprotein, not a metalloprotein.
- • Elastin: This is a scleroprotein (fibrous structural protein), not a metalloprotein.
- • All of these: Incorrect, as the other two options do not contain a metal cofactor as their primary classification feature.
The example of chromoprotein:
- a) Salmine
- b) Catalase
- c) Zein
- d) Gliadin
Explanation:
Chromoproteins are conjugated proteins containing a pigmented (colored) prosthetic group. Catalase is a heme-containing enzyme (a type of chromoprotein) that breaks down hydrogen peroxide into water and oxygen.
Why other options are incorrect:
Why other options are incorrect:
- • Salmine: A protamine, which is a simple basic protein.
- • Zein: A prolamin (storage protein) found in maize; it is not a chromoprotein.
- • Gliadin: Another example of a prolamin storage protein, not a chromoprotein.
Deamination is __ of amino group.
- a) Removal
- b) Addition
- c) Supplementation
- d) None of these
Explanation:
Deamination is the biochemical process involving the removal of an amino group (-NH2) from an amino acid or other compound. This process occurs primarily in the liver and is a crucial step in the breakdown of amino acids.
Why other options are incorrect:
Why other options are incorrect:
- • Addition: This would be referred to as amination, not deamination.
- • Supplementation: This is a nutritional term and not a chemical reaction involved in protein metabolism.
- • None of these: Incorrect, as “Removal” is the definition of deamination.
Proteins produce polypeptides from proteins by
- a) Oxidizing
- b) Reducing
- c) Hydrolyzing
- d) None of these
Explanation:
The breakdown of proteins into smaller polypeptide chains or amino acids is achieved through hydrolysis, a reaction that uses water to break the covalent peptide bonds between amino acid residues.
Why other options are incorrect:
Why other options are incorrect:
- • Oxidizing: Involves the loss of electrons and does not specifically cleave peptide bonds.
- • Reducing: Involves the gain of electrons; often used to break disulfide bonds (e.g., using beta-mercaptoethanol), but not the primary method for peptide bond cleavage.
- • None of these: Incorrect, as hydrolysis is the standard biochemical mechanism for proteolysis.
Proteins react with biuret reagent which is suggestive of 2 or more
- a) Hydrogen bonds
- b) Peptide bonds
- c) Disulphide bonds
- d) Hydrophobic bonds
Explanation:
The Biuret test is a chemical test used for detecting the presence of peptide bonds. In the presence of at least two peptide bonds (which corresponds to a tripeptide or larger), the copper ions in the Biuret reagent form a violet-colored complex with the nitrogen atoms of the peptide bonds.
Why other options are incorrect:
Why other options are incorrect:
- • Hydrogen bonds: These are weak electrostatic attractions that maintain the secondary/tertiary structure of proteins but are not detected by the Biuret reagent.
- • Disulphide bonds: These are covalent bonds between cysteine residues; they are not the target of the Biuret test.
- • Hydrophobic bonds: These drive protein folding but do not react with the copper ions in the Biuret reagent.
The disulphide bond is not broken under the usual conditions of
- a) Filtration
- b) Reduction
- c) Oxidation
- d) Denaturation
Explanation:
Disulfide bonds are strong covalent linkages. Filtration is a physical process used for separating solids from fluids and does not involve the chemical reagents or energy required to break covalent bonds.
Why other options are incorrect:
Why other options are incorrect:
- • Reduction: Commonly used to break disulfide bonds using reagents like beta-mercaptoethanol or DTT.
- • Oxidation: Strong oxidizing agents (like performic acid) can cleave disulfide bonds by converting them into cysteic acid.
- • Denaturation: While mild denaturation might not break them, stronger denaturing conditions (often combined with heat or chemical agents) are frequently used alongside reduction to disrupt the protein structure fully.
Insulin is oxidized to separate the protein molecule into its constituent polypeptide chains without affecting the other part of the molecule by the use of
- a) Performic acid
- b) Oxalic acid
- c) Citric acid
- d) Malic acid
Explanation:
Performic acid is a strong oxidizing agent used in biochemistry to specifically cleave disulfide bonds by converting them into two cysteic acid residues. This allows the separation of polypeptide chains (like those in insulin) without breaking the peptide backbone.
Why other options are incorrect:
Why other options are incorrect:
- • Oxalic acid: A weak dicarboxylic acid used primarily as a chelating agent or cleaner; it cannot cleave disulfide bonds.
- • Citric acid: A weak organic acid commonly found in citrus fruits; it does not possess the oxidizing power to break disulfide bonds.
- • Malic acid: An organic compound involved in the Krebs cycle; it is not used for the chemical cleavage of disulfide bridges in proteins.
Each hydrogen bond is quite
- a) Weak
- b) Strong
- c) Both (Weak ) and (Strong)
- d) None of these
Explanation:
An individual hydrogen bond is relatively weak compared to covalent or ionic bonds. However, their cumulative effect when present in large numbers (as seen in the double helix of DNA or the structure of proteins) provides significant stability to biological molecules.
Why other options are incorrect:
Why other options are incorrect:
- • Strong: On an individual basis, hydrogen bonds are far weaker than the covalent bonds that form the backbone of biological macromolecules.
- • Both: This is a contradictory classification; while the collective force is strong, the individual bond is defined as weak.
- • None of these: Incorrect, as “Weak” is the standard scientific description for the strength of a single hydrogen bond.
A coiled structure in which peptide bonds are folded in regular manner by
- a) Globular proteins
- b) Fibrous proteins
- c) Both (Globular proteins ) and (Fibrous proteins)
- d) None of these
Explanation:
Fibrous proteins, such as alpha-keratin, are characterized by highly regular, coiled secondary structures (like the alpha-helix). This repetitive, folded arrangement allows them to form long fibers that provide structural support to tissues.
Why other options are incorrect:
Why other options are incorrect:
- • Globular proteins: These proteins are generally spherical and have a complex, highly folded tertiary structure, rather than the regular, long-range coiled regularity of fibrous proteins.
- • Both: Incorrect, as globular proteins exhibit a much more intricate and varied folding pattern compared to the consistent coiled structures found in fibrous proteins.
- • None of these: Incorrect, because fibrous proteins are the classic example of such structures.
In many proteins the hydrogen bonding produces a regular coiled arrangement called
- a) α-helix
- b) β-helix
- c) Both (α-helix) and (β-helix)
- d) None of these
Explanation:
The α-helix is the most common secondary structure in proteins, characterized by a regular, right-handed coiled arrangement maintained by hydrogen bonds between the carbonyl oxygen and the amino hydrogen of the peptide backbone.
Why other options are incorrect:
Why other options are incorrect:
- • β-helix: This structure is rare in natural proteins; most sheet-like structures are referred to as β-pleated sheets, not β-helices.
- • Both: Incorrect, as the term specifically describing the common regular coiled secondary structure is the α-helix.
- • None of these: Incorrect, as the α-helix accurately defines the structure mentioned.
Many globular proteins are stable in solution although they lack in
- a) Hydrogen bonds
- b) Salt bonds
- c) Non-polar bonds
- d) Disulphide bonds
Explanation:
While disulfide bonds provide significant stabilization to extracellular proteins (like insulin or immunoglobulins), many intracellular globular proteins are highly stable in solution despite lacking disulfide bonds. Their stability is primarily derived from the hydrophobic effect, hydrogen bonding, and ionic interactions.
Why other options are incorrect:
Why other options are incorrect:
- • Hydrogen bonds: Essential for secondary structure (α-helices, β-sheets).
- • Salt bonds: Important ionic interactions (electrostatic bridges) that contribute to the tertiary stability of many proteins.
- • Non-polar bonds: The “hydrophobic effect” (clustering of non-polar side chains in the core) is the primary driving force for protein folding and stability.
Each turn of α-helix contains the number of amino acids
- a) 2.8
- b) 3.2
- c) 3.4
- d) 3.6
Explanation:
The α-helix is a right-handed coil. Each turn of the helix corresponds to a height of 0.54 nm and contains 3.6 amino acid residues. Each amino acid residue advances the helix by 0.15 nm along its axis.
Why other options are incorrect:
Why other options are incorrect:
- • 2.8, 3.2, and 3.4: These values do not represent the physical geometry of the standard alpha-helix found in natural proteins.
The distance travelled per turn of α-helix in nm is
- a) 0.34
- b) 0.44
- c) 0.54
- d) 0.64
Explanation:
The pitch (the distance for one complete turn) of an α-helix is 0.54 nm. Since there are 3.6 amino acid residues per turn, and each residue advances the helix by 0.15 nm, the total distance per turn is 3.6 × 0.15 nm = 0.54 nm.
Why other options are incorrect:
Why other options are incorrect:
- • 0.34 nm: This is the distance between adjacent bases in a DNA double helix, not the pitch of an α-helix.
- • 0.44 and 0.64 nm: These values do not correspond to the structural geometry of the α-helix.
α-helix is disrupted by certain amino acids like
- a) Proline
- b) Arginine
- c) Histidine
- d) Lysine
Explanation:
Proline is known as a “helix breaker” because its rigid cyclic structure introduces a kink in the peptide chain, and it lacks the hydrogen atom on the amide nitrogen necessary for hydrogen bonding within the helix.
Why other options are incorrect:
Why other options are incorrect:
- • Arginine: It is a positively charged amino acid that generally favors or is neutral toward alpha-helix formation.
- • Histidine: While it carries a charge depending on pH, it is commonly found in helical structures.
- • Lysine: Being a polar, positively charged amino acid, it is frequently found in alpha-helical segments of proteins.
α-helix is stabilized by
- a) Hydrogen bonds
- b) Disulphide bonds
- c) Salt bonds
- d) Non-polar bonds
Explanation:
The α-helix is primarily stabilized by hydrogen bonds formed between the carbonyl oxygen (-C=O) of one amino acid residue and the amide hydrogen (-N-H) of the amino acid located four residues ahead in the polypeptide chain.
Why other options are incorrect:
Why other options are incorrect:
- • Disulphide bonds: These are covalent bonds between cysteine residues that typically stabilize the tertiary or quaternary structure, not the secondary α-helix.
- • Salt bonds: Also known as ionic interactions, these usually contribute to the tertiary structure of proteins.
- • Non-polar bonds: Hydrophobic interactions (non-polar) are generally involved in the folding of the entire protein structure (tertiary), rather than defining the α-helix itself.
Foetal haemoglobin contains
- a) Two α and two γ chains
- b) Two β and two γ chains
- c) Both (Two α and two γ chains) and (Two β and two γ chains)
- d) None of these
Explanation:
Foetal haemoglobin (HbF) is the primary form of haemoglobin in the developing foetus. Its tetrameric structure consists of two alpha (α) globin chains and two gamma (γ) globin chains (α₂γ₂).
Why other options are incorrect:
Why other options are incorrect:
- • Two β and two γ chains: This combination does not exist in nature. The beta chain replaces the gamma chain after birth.
- • Both: Since only the α₂γ₂ combination is correct for HbF, this option is false.
- • None of these: Incorrect, as option (a) accurately describes the structure of foetal haemoglobin.
When haemoglobin takes up oxygen there is a change in the structure due to the moving closer together of
- a) β-chains
- b) α-chains
- c) γ-chains
- d) α and γ chains
Explanation:
When oxygen binds to the iron atom in the haem group of adult haemoglobin (HbA), the iron atom moves into the plane of the porphyrin ring. This pulls the proximal histidine and its attached helix, causing the beta-chains to move closer together, shifting the haemoglobin from the “T” (tense) state to the “R” (relaxed) state.
Why other options are incorrect:
Why other options are incorrect:
- • α-chains: While the entire tetramer undergoes a conformational shift, the most significant relative movement involves the beta-chains.
- • γ-chains: These are found in foetal haemoglobin and are not the primary chains involved in the structural shift of adult haemoglobin.
- • α and γ chains: This combination is specific to foetal haemoglobin and is not the focus of the structural explanation regarding standard oxygen-induced shifts in HbA.
The hydrogen bonds in the secondary and tertiary structure of proteins are directly attacked by
- a) Salts
- b) Alkalies
- c) Detergents
- d) All of these
Explanation:
Hydrogen bonds are relatively weak interactions that maintain the structural integrity of proteins. Various agents can disrupt these bonds: salts (by altering ionic strength), alkalies (by changing pH), and detergents (by interacting with hydrophobic regions and disrupting the internal structure), all leading to protein denaturation.
Why other options are correct:
Why other options are correct:
- • Salts: High concentrations of salts (salting out) or specific ions can interfere with the hydrogen bonding network.
- • Alkalies: Extremes in pH disrupt the protonation states of amino acid side chains, breaking the hydrogen bonds that stabilize the protein structure.
- • Detergents: Detergents have both hydrophobic and hydrophilic parts; they penetrate the protein structure and disrupt the H-bonds and hydrophobic interactions holding the protein together.
The hydrogen bonds between peptide linkages are interfered by
- a) Guanidine
- b) Uric acid
- c) Salicylic acid
- d) Oxalic acid
Explanation:
Guanidine (often used as guanidine hydrochloride) is a powerful protein denaturant. It works by forming strong hydrogen bonds with the peptide backbone, effectively competing with the existing hydrogen bonds that maintain the protein’s secondary structure (like α-helices and β-sheets).
Why other options are incorrect:
Why other options are incorrect:
- • Uric acid: A metabolic waste product that does not function as a protein denaturant.
- • Salicylic acid: While it can affect proteins at high concentrations, it is not primarily known for disrupting peptide hydrogen bonds in the same manner as chaotropic agents like guanidine.
- • Oxalic acid: Primarily acts as a chelating agent for calcium and does not act as a standard denaturant for breaking backbone hydrogen bonds in proteins.
The digestability of certain denatured proteins by proteolytic enzymes
- a) Decreases
- b) Increases
- c) Normal
- d) None of these
Explanation:
Denaturation unfolds the compact, globular structure of a protein, exposing the peptide bonds that were previously hidden within the interior. Since proteolytic enzymes require access to these peptide bonds to catalyze hydrolysis, the unfolded (denatured) state makes these bonds more accessible, thereby increasing digestibility.
Why other options are incorrect:
Why other options are incorrect:
- • Decreases: Denaturation actually facilitates digestion by removing the structural barriers that protect the protein from enzymatic attack.
- • Normal: Digestibility is significantly altered, not normal, because the protein’s conformation has changed.
- • None of these: Since “Increases” is the biologically correct phenomenon, this option is incorrect.
The antigenic antibody functions of proteins by denaturation are frequently
- a) Not changed
- b) Changed
- c) Both (Not changed) and (Changed)
- d) None of these
Explanation:
Antigenicity is largely dependent on the three-dimensional conformation (epitopes) of a protein. Denaturation unfolds the protein, destroying its tertiary and secondary structure, which effectively alters or destroys the specific binding sites (epitopes) that antibodies recognize. Therefore, the antigenic function is typically changed or lost.
Why other options are incorrect:
Why other options are incorrect:
- • Not changed: This is incorrect because the loss of the native 3D shape prevents the original antibodies from binding effectively.
- • Both: Antigenicity is not maintained in its original form once the protein is denatured; it is specifically “changed.”
- • None of these: Since “Changed” accurately describes the biological outcome, this option is incorrect.
In case of severe denaturation of protein, there is
- a) Reversible denaturation
- b) Moderate reversible denaturation
- c) Irreversible denaturation
- d) None of these
Explanation:
While some proteins can undergo renaturation if the denaturing agent is removed (reversible denaturation), “severe” denaturation—often caused by extreme heat, strong acids/bases, or heavy metals—causes the protein to aggregate or precipitate. This process permanently disrupts the protein’s native structure, making the denaturation irreversible.
Why other options are incorrect:
Why other options are incorrect:
- • Reversible denaturation: This typically occurs only under mild conditions where the protein can refold once the stressor is removed.
- • Moderate reversible denaturation: This describes mild scenarios, not “severe” cases.
- • None of these: “Irreversible denaturation” is the standard biochemical term for severe protein structural collapse.
When egg albumin is heated till it is coagulated, the secondary and tertiary structures of the proteins are completely lost resulting in a mixture of randomly arranged
- a) Dipeptide chains
- b) Tripeptide chains
- c) Polypeptide chains
- d) All of these
Explanation:
Heat-induced coagulation of egg albumin (an example of irreversible denaturation) causes the protein to unfold. The primary structure (the sequence of amino acids linked by peptide bonds) remains intact, but the protein chains become randomly arranged, unfolded long chains known as polypeptide chains.
Why other options are incorrect:
Why other options are incorrect:
- • Dipeptide/Tripeptide chains: Denaturation breaks non-covalent bonds (hydrogen, hydrophobic, ionic), but it does not break the strong covalent peptide bonds that hold the amino acids together. Therefore, the protein does not break down into small di- or tri-peptides.
- • All of these: Since the denaturation process does not hydrolyze the protein into short di- or tri-peptides, this option is incorrect.
In glycoproteins the carbohydrate is in the form of disaccharide units, the number of units are
- a) 50–100
- b) 200–300
- c) 400–500
- d) 600–700
Explanation:
In glycoproteins, carbohydrate components may occur as oligosaccharide chains composed of repeating disaccharide units. The number of such units is commonly given as approximately 50–100.
Why other options are incorrect:
Why other options are incorrect:
- • 200–300: This is considerably higher than the typical number stated.
- • 400–500: This range is much higher than the expected number of units.
- • 600–700: This is far above the usual number of carbohydrate units.
The milk protein in the stomach of the infants is digested by
- a) Pepsin
- b) Trypsin
- c) Chymotrypsin
- d) Rennin
Explanation:
Rennin (also known as chymosin) is a specialized enzyme present in the gastric juice of infants. It specifically acts on casein (milk protein) to curdle it, transforming it into paracasein. This prevents the rapid passage of milk out of the stomach, allowing pepsin to digest it more effectively.
Why other options are incorrect:
Why other options are incorrect:
- • Pepsin: While it digests proteins generally, it is not the specialized enzyme responsible for the initial coagulation of milk in infants.
- • Trypsin & Chymotrypsin: These are proteolytic enzymes secreted by the pancreas into the small intestine, not the stomach.
Achylia gastrica is said to be when absence of
- a) Pepsin only
- b) Both pepsin and HCl
- c) HCl only
- d) All of these
Explanation:
Achylia gastrica is a clinical condition characterized by the complete absence of both gastric hydrochloric acid (HCl) and the proteolytic enzyme pepsin in the stomach secretions.
Why other options are incorrect:
Why other options are incorrect:
- • Pepsin only: This condition is referred to as achylia with respect to enzymes, but Achylia gastrica specifically includes the absence of acid as well.
- • HCl only: The absence of only HCl is referred to as achlorhydria.
- • All of these: Since the condition is defined specifically by the absence of both pepsin and HCl, “All of these” is not the correct clinical definition.
The pH of gastric juice become low in
- a) Hemolytic anemia
- b) Pernicious anemia
- c) Both (Hemolytic anemia) and (Pernicious anemia)
- d) None of these
Explanation:
The pH of gastric juice is typically low (acidic) in a healthy individual. In conditions like pernicious anemia, the parietal cells of the stomach are often damaged or destroyed (autoimmune gastritis), leading to achlorhydria (absence of HCl), which actually results in an increase in pH (making it less acidic/more alkaline). Therefore, none of these conditions are characterized by a “low” (more acidic) gastric pH.
Why other options are incorrect:
Why other options are incorrect:
- • Pernicious anemia: Associated with chronic atrophic gastritis, which leads to a lack of acid production (higher pH).
- • Hemolytic anemia: This is a blood disorder characterized by the destruction of red blood cells and does not directly cause hypersecretion of gastric acid.
- • Both: Since neither condition is associated with a decrease in pH, this is incorrect.
In small intestine trypsin hydrolyzes peptide linkages containing
- a) Arginine
- b) Histidine
- c) Serine
- d) Aspartate
Explanation:
Trypsin is a serine protease that exhibits high specificity for peptide bonds where the carboxyl group is provided by basic amino acids, specifically Arginine and Lysine.
Why other options are incorrect:
Why other options are incorrect:
- • Histidine: While basic, it is not a primary target for trypsin cleavage.
- • Serine: A polar uncharged amino acid; trypsin does not target peptide bonds involving serine.
- • Aspartate: An acidic amino acid. Proteases like V8 protease or others have specificity for acidic residues, but trypsin does not.
Chymotrypsin in the small intestine hydrolyzes peptide linkages containing
- a) Alanine
- b) Phenylalanine
- c) Valine
- d) Methionine
Explanation:
Chymotrypsin is a digestive enzyme that specifically hydrolyzes peptide bonds on the carboxyl side of aromatic amino acids, such as Phenylalanine, Tyrosine, and Tryptophan.
Why other options are incorrect:
Why other options are incorrect:
- • Alanine & Valine: These are small non-polar amino acids and are not the primary targets for chymotrypsin’s specific active site.
- • Methionine: While chymotrypsin can sometimes show activity toward large hydrophobic residues, its primary and most efficient targets are aromatic amino acids.
Carboxy peptidase B in the small intestine hydrolyzes peptides containing
- a) Leucine
- b) Isoleucine
- c) Arginine
- d) Cysteine
Explanation:
Carboxypeptidase B is an exopeptidase that specifically cleaves the C-terminal peptide bond of amino acids with basic side chains, namely Arginine and Lysine.
Why other options are incorrect:
Why other options are incorrect:
- • Leucine & Isoleucine: These are non-polar, hydrophobic amino acids. They are typically cleaved by Carboxypeptidase A, which prefers aromatic or branched-chain aliphatic amino acids at the C-terminus.
- • Cysteine: This is a sulfur-containing amino acid and is not a specific target for Carboxypeptidase B.
The third active process for amino acids transport involves
- a) Acidic amino acids
- b) Basic amino acids
- c) Neutral amino acids
- d) Sulphur containing amino acids
Explanation:
There are specific transport systems for different groups of amino acids. The primary active transport systems are categorized for acidic, basic, and neutral amino acids. The transport of neutral amino acids is generally considered the third major classification in this transport mechanism.
Why other options are incorrect:
Why other options are incorrect:
- • Acidic amino acids: These have their own distinct transport system (often the first group identified).
- • Basic amino acids: These are transported via a separate specific system, typically categorized differently from the neutral group.
- • Sulphur containing amino acids: These are usually transported via the systems meant for neutral amino acids, rather than having a unique “third” active transport process of their own.
The neutral amino acids for absorption need
- a) TPP
- b) B6 – PO4 (Pyridoxal phosphate)
- c) NAD+
- d) NADP+
Explanation:
The absorption of amino acids, particularly neutral amino acids, across the intestinal brush border involves a transport system that is dependent on Pyridoxal phosphate (B6–PO4). This vitamin B6 derivative acts as a coenzyme in the transport mechanism, facilitating the movement of amino acids into the intestinal epithelial cells.
Why other options are incorrect:
Why other options are incorrect:
- • TPP (Thiamine pyrophosphate): A coenzyme for decarboxylation reactions, not involved in amino acid transport.
- • NAD+ / NADP+: These are coenzymes involved in oxidation-reduction (redox) reactions in metabolism, not in membrane transport processes.
If one amino acid is fed excess, the absorption of another is
- a) Slightly accelerated
- b) Moderately accelerated
- c) Highly accelerated
- d) Retarded
Explanation:
Since amino acids of the same group share the same transport carriers, feeding one amino acid in large excess leads to “competitive inhibition.” The excess amino acid saturates the available carriers, thereby retarding the absorption of other amino acids that rely on those same carriers.
Why other options are incorrect:
Why other options are incorrect:
- • Slightly/Moderately/Highly accelerated: These options are incorrect because the presence of an excess of one substrate for a shared transport protein acts as a competitive inhibitor, which slows down (retards) rather than accelerates the transport of other substrates.
Under normal conditions, food proteins are generally readily digested upto the present
- a) 67 to 73
- b) 74 to 81
- c) 82 to 89
- d) 90 to 97
Explanation:
Under normal physiological conditions, the human digestive system is highly efficient. Most dietary proteins (especially those from animal sources and well-cooked plant sources) are digested and absorbed with an efficiency of approximately 90% to 97%.
Why other options are incorrect:
Why other options are incorrect:
- • 67-73%, 74-81%, 82-89%: These ranges underestimate the typical biological efficiency of the human gastrointestinal tract for protein digestion, which is typically higher than 90% in healthy individuals.
By overheating the nutritional value of cereal proteins is
- a) Increased
- b) Decreased
- c) Unchanged
- d) None of these
Explanation:
Overheating (excessive heat) causes the Maillard reaction, where amino acids—particularly lysine—react with reducing sugars. This reaction makes the amino acids biologically unavailable for digestion and absorption, thereby decreasing the overall nutritional value of the protein.
Why other options are incorrect:
Why other options are incorrect:
- • Increased: Heat can denature proteins (which might help digestion), but “overheating” leads to chemical damage that reduces nutritional quality.
- • Unchanged: High-temperature processing significantly alters the chemical structure of proteins, so the value does not remain unchanged.
- • None of these: Since the nutritional value is indeed negatively affected, “Decreased” is the correct classification.
More than half of the protein of the liver and intestinal mucosa are broken down and resynthesised in
- a) 10 days
- b) 12 days
- c) 15 days
- d) 18 days
Explanation:
The proteins in the liver and intestinal mucosa have a very high “turnover rate” compared to other body tissues like muscle or collagen. Studies indicate that more than half of the protein content in these highly active metabolic tissues is degraded and resynthesized within a period of approximately 10 days.
Why other options are incorrect:
Why other options are incorrect:
- • 12, 15, and 18 days: While these timeframes might apply to the turnover rates of other tissues with slower metabolic activity, they do not accurately reflect the rapid protein turnover cycle characteristic of the liver and intestinal mucosa.
Protein anabolism is stimulated by
- a) ACTH
- b) Testosterone
- c) Glucagon
- d) Epinephrine
Explanation:
Testosterone is a major anabolic steroid hormone. It promotes protein synthesis (anabolism), particularly in skeletal muscle, which leads to increased muscle mass and strength.
Why other options are incorrect:
Why other options are incorrect:
- • ACTH: Stimulates the release of glucocorticoids, which are generally catabolic (promoting protein breakdown).
- • Glucagon: A catabolic hormone that promotes gluconeogenesis and the breakdown of glycogen and proteins to increase blood glucose.
- • Epinephrine: Primarily involved in the “fight or flight” response, it promotes glycogenolysis and lipolysis, not protein anabolism.
Answer Key Summary
The questions are typically designed to assess the technical skills and knowledge required for the laboratory profession, including the ability to analyze laboratory test results, perform laboratory procedures, and maintain laboratory equipment.
To prepare for these MCQs, candidates should have a thorough understanding of the key concepts and principles of laboratory science. They should also be familiar with common laboratory equipment and procedures, as well as laboratory safety protocols.
Candidates may also benefit from studying specific laboratory science textbooks or taking online courses that cover the material tested in the MCQs. Additionally, practicing sample MCQs and reviewing the answers can help candidates identify areas where they may need to improve their knowledge or skills.
Overall, the MCQs for lab technologists are designed to be challenging and comprehensive, requiring candidates to demonstrate a high level of proficiency in the field of laboratory science.
📚 This article may have been prepared using trusted medical literature, clinical guidelines, textbooks, and peer-reviewed sources.
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