5501 to 5550 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 5501 to 5550
The isoelectric pH of albumin is:
- a) 3.6
- b) 4.7
- c) 5.0
- d) 6.1
Explanation:
The isoelectric point (pI) of serum albumin is approximately 4.7. At this pH, the protein carries no net electrical charge.
Why other options are incorrect:
Why other options are incorrect:
- • 3.6: This is significantly more acidic than the isoelectric point of serum albumin.
- • 5.0: While close, 4.7 is the scientifically accepted standard value for serum albumin.
- • 6.1: This value is near the pKa of certain buffers (like bicarbonate), but is not the isoelectric point of albumin.
Ninhydrin reaction gives a purple colour and evolves CO2 with:
- a) Peptide bonds
- b) Histamine
- c) Ergothioneine
- d) Aspargine
Explanation:
The Ninhydrin reaction is specific to free alpha-amino groups (found in amino acids like Aspargine). The reaction involves oxidative deamination and decarboxylation, resulting in the production of CO2 and a blue-purple colored complex (Ruhemann’s purple).
Why other options are incorrect:
Why other options are incorrect:
- • Peptide bonds: These do not contain a free alpha-amino group and therefore do not react with Ninhydrin in this manner.
- • Histamine: While it contains amino groups, it lacks the alpha-amino acid structure required for the classic purple color and CO2 evolution.
- • Ergothioneine: This is a sulfur-containing derivative of histidine and does not undergo the standard Ninhydrin reaction.
Denaturation of proteins involves breakdown of
- a) Secondary structure
- b) Tertiary structure
- c) Quarternary structure
- d) All of these
Explanation:
Protein denaturation causes disruption of the higher-order structures of proteins, including secondary, tertiary, and quaternary structures. The primary structure, consisting of peptide bonds, generally remains intact during denaturation.
Why other options are incorrect:
Why other options are incorrect:
- • Secondary structure: It can be disrupted during denaturation, but it is not the only structure affected.
- • Tertiary structure: It can be disrupted, but denaturation may also affect secondary and quaternary structures.
- • Quaternary structure: It can be disrupted in proteins composed of multiple subunits, but it is not the only structure affected.
In denaturation of proteins, the bond which is not broken:
- a) Disulphide bond
- b) Peptide bond
- c) Hydrogen bond
- d) Ionic bond
Explanation:
During protein denaturation, the peptide bonds that form the primary structure are generally not broken. Denaturation disrupts the higher-order structures while leaving the amino acid sequence intact.
Why other options are incorrect:
Why other options are incorrect:
- • Disulphide bond: May be disrupted under certain strong denaturing or reducing conditions.
- • Hydrogen bond: Is commonly disrupted during denaturation, affecting secondary structure.
- • Ionic bond: Salt bridges can be disrupted during denaturation, affecting protein folding.
The purity of an isolated protein can be tested by employing various methods.
- a) Solubility curve
- b) Molecular weight
- c) Ultra Centrifugation
- d) Immuno Ractivity
- e) All of these
Explanation:
The purity of an isolated protein can be assessed using several methods, including solubility curves, molecular weight determination, ultracentrifugation, and immunoreactivity. Therefore, the correct answer is All of these.
Why other options are incorrect:
Why other options are incorrect:
- • Solubility curve: Can provide information about the homogeneity and purity of a protein preparation.
- • Molecular weight: Determination of molecular weight can help assess whether the isolated protein corresponds to the expected protein.
- • Ultracentrifugation: Can be used to assess protein homogeneity based on sedimentation behavior.
- • Immunoreactivity: Specific antibodies can help confirm the identity and purity of a protein preparation.
More than one break in the line or in saturation curve indicates the following quality of protein.
- a) Non homogenity
- b) Purity
- c) Homogeneity
- d) None of these
Explanation:
More than one break or discontinuity in a saturation curve indicates that the protein preparation contains more than one component with different properties. This demonstrates non-homogeneity of the protein sample.
Why other options are incorrect:
Why other options are incorrect:
- • Purity: A pure protein generally produces a single, consistent saturation behavior.
- • Homogeneity: Homogeneous protein preparations are expected to show a single break or consistent curve.
- • None of these: Incorrect because multiple breaks indicate non-homogeneity.
A sharp moving boundary is obtained between the pure solvent and solute containing layer in:
- a) Chromatography
- b) Immuno Reactivity
- c) Ultra Centrifugation
- d) Solubility curve
Explanation:
The moving boundary method is a classic technique used in ultracentrifugation (specifically analytical ultracentrifugation). As the centrifugal force is applied, the protein molecules sediment, creating a sharp boundary between the sedimenting solute and the pure solvent, which can be monitored optically.
Why other options are incorrect:
Why other options are incorrect:
- • Chromatography: Separates components based on differential partitioning, not by creating a moving sedimenting boundary.
- • Immuno Reactivity: Based on specific binding between antigens and antibodies.
- • Solubility curve: Deals with the amount of solute that dissolves in a solvent, not the movement of boundaries under force.
The antibodies raised against a pure protein will show only one sharp spike on this technique:
- a) Solubility curve
- b) Solvent precipitation
- c) Molecular weight determination
- d) Immuno electrophoresis
Explanation:
Immuno electrophoresis is a powerful technique that combines electrophoresis with immunodiffusion. When antibodies are reacted with a pure protein, a single, distinct precipitin arc (or spike) forms where the antibody and antigen meet at optimal concentrations. Multiple spikes would indicate the presence of multiple different proteins (impurities).
Why other options are incorrect:
Why other options are incorrect:
- • Solubility curve: This measures physical solubility, not antibody-antigen interaction.
- • Solvent precipitation: This is a fractionation technique used to concentrate or purify proteins, not an analytical detection method for antibody specificity.
- • Molecular weight determination: This provides data on the size of molecules, but does not utilize antibody-antigen specificity to visualize purity.
This technique takes the advantage of the fact that each protein has different pH at which it is electrically neutral i.e., its isoelectric pH:
- a) Isoelectric focussing
- b) Immuno electrophoresis
- c) Chromatography
- d) HPLC
Explanation:
Isoelectric focusing (IEF) is a specialized form of electrophoresis where proteins are separated based on their isoelectric point (pI). Proteins migrate through a pH gradient in an electric field until they reach a position where the pH of the gel equals their pI; at this point, they carry no net charge and cease to migrate, resulting in sharp, focused bands.
Why other options are incorrect:
Why other options are incorrect:
- • Immuno electrophoresis: Primarily relies on antigen-antibody precipitation in an electric field.
- • Chromatography/HPLC: Generally separate proteins based on physical properties like size, charge, or affinity, rather than focusing them specifically at their neutral point.
The following technique makes use of the difference in net charges of proteins at a given pH:
- a) Thin layer chromatography
- b) Ion exchange chromatography
- c) High performance liquid chromatography
- d) Paper chromatography
Explanation:
Ion exchange chromatography separates proteins according to differences in their net electrical charges at a given pH. Proteins bind differently to charged groups on the ion-exchange resin and can therefore be separated.
Why other options are incorrect:
Why other options are incorrect:
- • Thin layer chromatography: Separates substances mainly according to their adsorption and partition properties.
- • High performance liquid chromatography: Is a general separation technique that can use several different separation principles.
- • Paper chromatography: Primarily separates substances based on their differential partition between the stationary paper phase and the mobile solvent.
The ratio of the distance moved by a compound to the distance moved by the solvent front is known as its:
- a) PI value
- b) Linking number
- c) Rf value
- d) Gold number
Explanation:
The Rf value (Retardation factor or Retention factor) is a quantitative measure used in chromatography. It is calculated as:
Rf = (Distance traveled by the compound) / (Distance traveled by the solvent front).
Why other options are incorrect:
Rf = (Distance traveled by the compound) / (Distance traveled by the solvent front).
Why other options are incorrect:
- • PI value: Refers to the isoelectric point of a protein.
- • Linking number: Refers to the topological property of DNA (supercoiling).
- • Gold number: A measure of the protective power of a colloid.
The movement of charged particles towards one of the electrodes under the influence of electrical current is:
- a) Gel filtration
- b) Molecular sieving
- c) Gas liquid chromatography
- d) Electrophoresis
Explanation:
Electrophoresis is the technique that utilizes an electric field to separate charged particles (such as proteins or nucleic acids). Depending on their net charge, these molecules migrate toward either the anode (positive electrode) or the cathode (negative electrode).
Why other options are incorrect:
Why other options are incorrect:
- • Gel filtration/Molecular sieving: These techniques separate molecules based on their size and shape rather than electrical charge.
- • Gas liquid chromatography: This is a technique for separating volatile compounds based on their partitioning between a gaseous mobile phase and a liquid stationary phase.
An anion exchange resin linked to cellulose backbone is:
- a) DEAE cellulose
- b) CM cellulose
- c) Sephadex
- d) None of these
Explanation:
DEAE (Diethylaminoethyl) cellulose is a positively charged resin used in ion-exchange chromatography to bind negatively charged molecules (anions). Since it attracts anions, it is classified as an anion exchange resin.
Why other options are incorrect:
Why other options are incorrect:
- • CM cellulose: Carboxymethyl cellulose is a negatively charged resin used as a cation exchanger.
- • Sephadex: This is a cross-linked dextran gel primarily used for molecular sieve (size exclusion) chromatography, not ion exchange.
A cation exchange resin linked to cellulose backbone is:
- a) CM-cellulose
- b) DEAE cellulose
- c) Starch
- d) Biogel
Explanation:
CM-cellulose (Carboxymethyl cellulose) acts as a cation exchange resin. Because it carries a negative charge (due to the carboxymethyl group), it binds to positively charged proteins (cations) at a pH above their isoelectric point.
Why other options are incorrect:
Why other options are incorrect:
- • DEAE cellulose: This is a positively charged resin used for anion exchange.
- • Starch: A storage polysaccharide, not typically used as an ion-exchange resin.
- • Biogel: A polyacrylamide-based gel used primarily for size-exclusion chromatography.
The sorting out of molecules according to size and shape may be adapted to protein purification in this technique:
- a) Adsorption chromatography
- b) Gel filtration chromatography
- c) Paper chromatography
- d) None of these
Explanation:
Gel filtration chromatography (also known as size-exclusion chromatography) separates molecules based on their hydrodynamic volume (size and shape). Porous beads in the column allow smaller molecules to enter the pores, while larger molecules are excluded and pass through the column faster.
Why other options are incorrect:
Why other options are incorrect:
- • Adsorption chromatography: Separates molecules based on their affinity for the surface of a stationary phase.
- • Paper chromatography: Separates molecules primarily based on differential partitioning (solubility) between a stationary liquid phase (water on paper) and a mobile phase.
Frequently employed materials for the adsorption chromatography of proteins include
- a) High capacity supporting gel
- b) Starch blocks
- c) Calcium phosphate gel, alumina gel and hydroxy apatite
- d) All of these
Explanation:
Adsorption chromatography of proteins uses materials that adsorb proteins through surface interactions. Commonly employed materials include supporting gels, starch blocks, calcium phosphate gel, alumina gel, and hydroxyapatite. Therefore, the correct answer is All of these.
Why other options are incorrect:
Why other options are incorrect:
- • High capacity supporting gel: Can be used as a supporting material, but this is only one category.
- • Starch blocks: May be used as an adsorption medium, but the option is incomplete.
- • Calcium phosphate gel, alumina gel and hydroxy apatite: These are commonly used adsorbents, but this option does not include all the listed materials.
The solubility of most proteins is lowered at high salt concentrations is called as
- a) Salting in process
- b) Salting out process
- c) Isoelectric focussing
- d) None of these
Explanation:
The salting out process refers to the decrease in protein solubility at high salt concentrations. High concentrations of salts compete with proteins for water molecules, reducing protein hydration and causing proteins to precipitate.
Why other options are incorrect:
Why other options are incorrect:
- • Salting in process: At lower salt concentrations, protein solubility may increase rather than decrease.
- • Isoelectric focussing: This is a technique for separating proteins based on their isoelectric points.
- • None of these: Incorrect because the described phenomenon is specifically called salting out.
Phenylalanine, ornithine and methionine are involved in the biogenesis of:
- a) Lysergic acid
- b) Reserpine
- c) L-Hyoscyamine
- d) Papaverine
Explanation:
The biogenesis of Lysergic acid (an ergoline alkaloid) involves specific precursor amino acids including tryptophan, which is related to the phenylalanine pathway, while methionine serves as a methyl donor (methylation) and ornithine is involved in the structural development of the ergoline nucleus.
Why other options are incorrect:
Why other options are incorrect:
- • Reserpine: Derived from the indole alkaloid pathway (tryptamine and secologanin).
- • L-Hyoscyamine: Derived from the tropane alkaloid pathway (ornithine and phenylalanine).
- • Papaverine: Derived from the benzylisoquinoline pathway (tyrosine).
All the following diuretics inhibit the carbonic anhydrase except:
- a) Acetazolamide
- b) Bumetanide
- c) Furosemide
- d) Ethacrynic acid
Explanation:
Acetazolamide is a potent carbonic anhydrase inhibitor. While loop diuretics like Furosemide and Ethacrynic acid also possess minor carbonic anhydrase inhibitory activity, Bumetanide does not possess this property significantly.
Why other options are incorrect:
Why other options are incorrect:
- • Acetazolamide: The classic sulfonamide-based carbonic anhydrase inhibitor used in glaucoma and mountain sickness.
- • Furosemide: A loop diuretic that has a slight secondary effect of inhibiting carbonic anhydrase.
- • Ethacrynic acid: A phenoxyacetic acid derivative loop diuretic that also exhibits mild carbonic anhydrase inhibitory activity.
Protein is a polymer of:
- a) Sugars
- b) Phenols
- c) Amino acids
- d) Carboxylic acids
Explanation:
Proteins are large, complex molecules (macromolecules) composed of long chains of amino acids linked together by peptide bonds. They are essential for the structure, function, and regulation of the body’s tissues and organs.
Why other options are incorrect:
Why other options are incorrect:
- • Sugars: These are the building blocks of carbohydrates (polysaccharides) like starch and cellulose.
- • Phenols: These are aromatic organic compounds, not the primary units of biological polymers like proteins.
- • Carboxylic acids: While amino acids contain a carboxylic acid group, “carboxylic acids” as a general category are not the structural units of proteins.
All the following amino acids are optically active except:
- a) Tryptophane
- b) Phenylalanine
- c) Valine
- d) Glycine
Explanation:
Optical activity in amino acids is due to the presence of a chiral carbon (alpha-carbon) bonded to four different groups. Glycine is the simplest amino acid; its side chain is a hydrogen atom (-H). Since it has two hydrogen atoms attached to the alpha-carbon, it is achiral and therefore optically inactive.
Why other options are incorrect:
Why other options are incorrect:
- • Tryptophane: Contains a chiral alpha-carbon with four distinct groups.
- • Phenylalanine: Contains a chiral alpha-carbon with four distinct groups.
- • Valine: Contains a chiral alpha-carbon with four distinct groups.
Proteinous substances which catalyze biochemical reactions are known as:
- a) Activators
- b) Catalysts
- c) Enzymes
- d) Hormones
Explanation:
Enzymes are biological catalysts, almost all of which are proteins. They accelerate chemical reactions in living organisms by lowering the activation energy required for the reaction to proceed.
Why other options are incorrect:
Why other options are incorrect:
- • Activators: These are molecules that increase the activity of an enzyme, rather than being the catalytic proteins themselves.
- • Catalysts: A general term for any substance that increases the rate of a reaction; while enzymes are catalysts, not all catalysts are proteinous.
- • Hormones: These are chemical messengers produced by glands that regulate physiological processes, not primarily catalysts.
Insulin is a protein which controls:
- a) Blood clotting
- b) Metabolic pathway
- c) Digestion
- d) Kreb’s cycle
Explanation:
Insulin is a polypeptide hormone that plays a central role in the regulation of carbohydrate and fat metabolism. It facilitates the uptake of glucose into cells, thereby controlling glucose metabolic pathways.
Why other options are incorrect:
Why other options are incorrect:
- • Blood clotting: Regulated by proteins like fibrinogen and prothrombin.
- • Digestion: Primarily regulated by digestive enzymes (like pepsin and trypsin) and hormones like gastrin.
- • Kreb’s cycle: A series of chemical reactions used by all aerobic organisms to release stored energy; while insulin influences metabolism overall, it is not the direct controller of the cycle itself.
Proteins which are responsible for defence mechanism are called:
- a) Antimetabolites
- b) Antibodies
- c) Antimycins
- d) Apoproteins
Explanation:
Antibodies (also known as immunoglobulins) are specialized Y-shaped proteins produced by the immune system (specifically B cells) to identify and neutralize foreign objects like bacteria and viruses.
Why other options are incorrect:
Why other options are incorrect:
- • Antimetabolites: Chemicals that inhibit the use of a metabolite, often used in cancer chemotherapy.
- • Antimycins: A group of antibiotics produced by Streptomyces bacteria that inhibit the electron transport chain.
- • Apoproteins: The protein portion of a conjugated protein, such as the protein component of a lipoprotein.
When the net charge on an amino acid is zero, the pH is maintained as?
- a) 4.5
- b) 11.2
- c) 7.0
- d) 9.1
Explanation:
The pH at which an amino acid exists as a zwitterion (net charge of zero) is known as the isoelectric point (pI). For many simple/neutral amino acids, this point is close to neutral pH (approx 6-7). At this pH, the molecule is electrically neutral and least soluble in water.
Why other options are incorrect:
Why other options are incorrect:
- • 4.5: This is generally too acidic for the isoelectric point of most common amino acids.
- • 11.2 & 9.1: These values are alkaline and would typically correspond to basic amino acids (like Arginine or Lysine) rather than the standard state for the general group.
Isoelectric point of amino acids is used for:
- a) Crystallisation
- b) Precipitation
- c) Solubility
- d) Reactivity
Explanation:
At the isoelectric point (pI), an amino acid or protein carries a net charge of zero. Because the molecules lack a net electrical charge, they do not repel each other, which leads to minimal solubility and results in the precipitation of the substance from the solution.
Why other options are incorrect:
Why other options are incorrect:
- • Crystallisation: While pI is a factor in purity, it is not the primary purpose of defining the point itself.
- • Solubility: The pI is where solubility is lowest, not a tool used to enhance solubility.
- • Reactivity: The isoelectric point relates to the physical state and charge balance, not the chemical reactivity of the functional groups.
Xanthoproteic test is positive in proteins containing:
- a) Sulphur amino acids
- b) α-Amino acids
- c) Aromatic amino acids
- d) Aliphatic amino acids
Explanation:
The Xanthoproteic test is positive for proteins that contain aromatic amino acids such as tyrosine, tryptophan, and phenylalanine. When heated with concentrated nitric acid, the benzene ring of these amino acids is nitrated to form yellow-colored nitro compounds.
Why other options are incorrect:
Why other options are incorrect:
- • Sulphur amino acids: Detected by the Lead Acetate test, not the Xanthoproteic test.
- • α-Amino acids: A general classification for all standard amino acids; this test is specific to the aromatic ring.
- • Aliphatic amino acids: These lack the aromatic ring required for the nitration reaction that produces the yellow color.
All α-amino acids give positive:
- a) Millon’s test
- b) Biuret test
- c) Xanthoproteic test
- d) Ninhydrin test
Explanation:
The Ninhydrin test is a general chemical test used to detect the presence of α-amino acids. When reacted with ninhydrin, α-amino acids produce a characteristic deep blue or purple color (Ruhemann’s purple).
Why other options are incorrect:
Why other options are incorrect:
- • Millon’s test: Specific for phenolic groups (found in Tyrosine).
- • Biuret test: Specific for peptide bonds; therefore, it gives a positive result for proteins and peptides, but not free amino acids.
- • Xanthoproteic test: Specific for aromatic amino acids (Tyrosine, Tryptophan, Phenylalanine).
N-terminal amino acids of a polypeptide are estimated by
- a) Edmann reaction
- b) Sanger’s reagent
- c) Formaldehyde test
- d) Ninhydrine reaction
Explanation:
The Edman reaction is used to identify and determine the N-terminal amino acid of a polypeptide chain. It sequentially removes the N-terminal amino acid as a phenylthiohydantoin (PTH) derivative.
Why other options are incorrect:
Why other options are incorrect:
- • Sanger’s reagent: FDNB can identify the N-terminal amino acid but is not used for sequential N-terminal sequencing.
- • Formaldehyde test: It is used for the estimation of amino nitrogen, not specifically for identifying the N-terminal amino acid.
- • Ninhydrine reaction: It is mainly used for detecting amino acids and estimating amino nitrogen.
Millon’s test is positive for:
- a) Phenylalanine
- b) Glycine
- c) Tyrosine
- d) Proline
Explanation:
Millon’s test is specific for the phenolic group (-OH group attached to a benzene ring). Among the options, Tyrosine is the only amino acid that contains a phenolic group, which reacts with Millon’s reagent (mercuric sulfate in sulfuric acid) to produce a red color.
Why other options are incorrect:
Why other options are incorrect:
- • Phenylalanine: An aromatic amino acid but lacks the phenolic hydroxyl group necessary for a positive Millon’s test.
- • Glycine: The simplest aliphatic amino acid; it contains no aromatic or phenolic groups.
- • Proline: A cyclic imino acid that does not contain a phenolic group.
Indole group of tryptophan responses positively to:
- a) Glyoxylic acid
- b) Schiff’s reagent
- c) Biuret test
- d) Resorcinol test
Explanation:
The Hopkins-Cole test uses glyoxylic acid in the presence of concentrated sulfuric acid to detect the indole ring of tryptophan. A positive result is indicated by the formation of a violet ring at the junction of the two liquids.
Why other options are incorrect:
Why other options are incorrect:
- • Schiff’s reagent: Used primarily for the detection of aldehydes.
- • Biuret test: Used to detect peptide bonds in proteins/peptides.
- • Resorcinol test: Primarily used (Seliwanoff’s test) to distinguish between aldose and ketose sugars.
Guanidine group of arginine gives positive test with:
- a) Lead acetate
- b) Sakaguchi reagent
- c) Trichloroacetic acid
- d) Molisch’s reagent
Explanation:
The Sakaguchi test is a specific colorimetric test used for the detection of the amino acid Arginine. It reacts with the guanidine group present in the side chain of arginine to produce a red color in the presence of alpha-naphthol and an oxidizing agent (like sodium hypochlorite or hypobromite).
Why other options are incorrect:
Why other options are incorrect:
- • Lead acetate: Used to detect sulfur-containing amino acids (like cysteine).
- • Trichloroacetic acid: Primarily used for the precipitation of proteins from a solution.
- • Molisch’s reagent: A general test for the presence of carbohydrates.
Thiol group of cysteine gives red colour with:
- a) Sodium acetate
- b) Lead acetate
- c) Sodium nitroprusside
- d) Barfoed’s reagent
Explanation:
The sodium nitroprusside test is used to detect the presence of free sulfhydryl (-SH) groups in amino acids like cysteine. In an alkaline solution, the thiol group reacts with sodium nitroprusside to produce a characteristic deep red/purple color.
Why other options are incorrect:
Why other options are incorrect:
- • Sodium acetate: Commonly used as a buffer, not a diagnostic reagent for thiol groups.
- • Lead acetate: Used to detect sulfur by forming a black precipitate of lead sulfide (PbS), not a red color.
- • Barfoed’s reagent: Used to distinguish between monosaccharides and disaccharides.
Protein deficiency disease is known as:
- a) Cushing’s disease
- b) Fabry’s disease
- c) Parkinson’s disease
- d) Kwashiorkor and marasmus
Explanation:
Kwashiorkor and Marasmus are the two primary forms of Protein-Energy Malnutrition (PEM). Kwashiorkor is primarily caused by a deficiency of protein, while Marasmus is caused by a severe deficiency of both protein and total calories (energy).
Why other options are incorrect:
Why other options are incorrect:
- • Cushing’s disease: A condition caused by an excess of the hormone cortisol in the body.
- • Fabry’s disease: A rare genetic lysosomal storage disorder.
- • Parkinson’s disease: A progressive nervous system disorder affecting movement, not related to protein dietary deficiency.
A vegetable source of protein is:
- a) Egg plant
- b) Soyabean
- c) Tree of the Heaven
- d) Devil’s dung
Explanation:
Soyabean is one of the richest plant-based sources of high-quality protein. It contains all the essential amino acids required by the human body, making it a “complete” protein source similar to animal proteins.
Why other options are incorrect:
Why other options are incorrect:
- • Egg plant: A vegetable, but it has a very low protein content compared to legumes.
- • Tree of the Heaven (Ailanthus): Used primarily in traditional medicine, not as a dietary protein source.
- • Devil’s dung (Asafoetida/Hing): A resinous gum used primarily as a spice and digestive aid, not as a source of protein.
Oxaloacetate is converted to aspartic acid by:
- a) Reductase
- b) Oxidase
- c) Transaminase
- d) Catalase
Explanation:
The conversion of oxaloacetate to aspartic acid is a classic transamination reaction. The enzyme involved is aspartate aminotransferase (AST/GOT), which transfers an amino group from glutamate to oxaloacetate, resulting in the formation of aspartate (aspartic acid) and alpha-ketoglutarate.
Why other options are incorrect:
Why other options are incorrect:
- • Reductase: Involved in reduction reactions (adding hydrogen/electrons).
- • Oxidase: Involved in oxidation reactions (removing hydrogen/electrons).
- • Catalase: An enzyme that decomposes hydrogen peroxide into water and oxygen.
Deficiency of biotin results in decrease in:
- a) Amino acid synthesis
- b) Lipid synthesis
- c) Kidney
- d) Fatty acid synthesis
Explanation:
Biotin (Vitamin B7) acts as a coenzyme for carboxylase enzymes. One of its most critical roles is as a cofactor for Acetyl-CoA carboxylase, which catalyzes the rate-limiting step in fatty acid synthesis (converting Acetyl-CoA to Malonyl-CoA). Therefore, a deficiency in biotin significantly impairs fatty acid synthesis.
Why other options are incorrect:
Why other options are incorrect:
- • Amino acid synthesis: While biotin is involved in some carboxylations, it is not the primary factor in general amino acid synthesis.
- • Lipid synthesis: This is a broad category; biotin is specifically vital for the fatty acid component of lipid metabolism.
- • Kidney: This is an organ, not a metabolic process affected by vitamin deficiencies in this manner.
The precursor of bile salts, sex hormones and vitamin D is:
- a) Diosgenin
- b) Cholesterol
- c) Campesterol
- d) Ergosterol
Explanation:
Cholesterol is a vital steroid molecule that serves as the biological precursor for several essential compounds in the human body, including bile acids (salts), steroid hormones (sex hormones like estrogen and testosterone), and Vitamin D (synthesized in the skin).
Why other options are incorrect:
Why other options are incorrect:
- • Diosgenin: A plant-derived steroid sapogenin used in the synthesis of steroid drugs, but not the primary precursor in human metabolism.
- • Campesterol: A phytosterol that is structurally similar to cholesterol but is not a precursor for human hormones.
- • Ergosterol: A sterol found in fungi; while it is a precursor to Vitamin D2, it is not the precursor for human sex hormones or bile salts.
Unsaturated fatty acids are known as:
- a) Non-essential fatty acids
- b) Essential fatty acids
- c) Cerebrosides
- d) Phospholipids
Explanation:
Many polyunsaturated fatty acids (such as Linoleic and Linolenic acid) cannot be synthesized by the human body and must be obtained through the diet. These are commonly referred to as Essential Fatty Acids (EFAs).
Why other options are incorrect:
Why other options are incorrect:
- • Non-essential fatty acids: These are fatty acids that the body can synthesize on its own.
- • Cerebrosides: These are a type of glycosphingolipid, not a category of fatty acids.
- • Phospholipids: These are a class of lipids containing a phosphate group, not a category of fatty acids.
Biuret test is specific for:
- a) Two peptide linkage
- b) Phenolic group
- c) Imidazole ring
- d) None of these
Explanation:
The Biuret test is a chemical test used to detect the presence of peptide bonds. It is positive for compounds containing at least two peptide bonds (which means a minimum of three amino acids or a tripeptide), as these bonds coordinate with copper (II) ions in an alkaline solution to form a violet-colored complex.
Why other options are incorrect:
Why other options are incorrect:
- • Phenolic group: This is detected by the Millon’s test (specifically for Tyrosine).
- • Imidazole ring: This is characteristic of Histidine and is detected by the Pauly’s test.
Most of calcium is present in bone, but 2% present in soft tissue and the blood is called
- a) Calcinated blood
- b) Solidified blood
- c) Physiological blood
- d) Colloidal blood
Explanation:
The calcium present in the soft tissues and blood, in contrast to the large amount stored in bones, is referred to as physiological calcium. It plays important roles in blood clotting, muscle contraction, nerve transmission, and other physiological functions.
Why other options are incorrect:
Why other options are incorrect:
- • Calcinated blood: This is not the standard term for calcium present in blood and soft tissues.
- • Solidified blood: Refers to coagulated or clotted blood, not calcium distribution.
- • Colloidal blood: This is not the appropriate term for physiologically active calcium in blood.
Calcium present with protein is known as bound while in salt form is called as:
- a) Bound
- b) Precipitated
- c) Solid
- d) Polymorphs
Explanation:
Blood calcium is classified into three fractions: 1) Ionized (free) calcium, which is physiologically active; 2) Protein-bound calcium (usually to albumin); and 3) Complexed (or salt-bound) calcium, which is bound to anions like phosphate, citrate, and bicarbonate. Both protein-bound and complexed forms are collectively referred to as “bound” or non-diffusible calcium.
Why other options are incorrect:
Why other options are incorrect:
- • Precipitated: Calcium in blood is dissolved; if it were precipitated, it would form stones or calcification.
- • Solid: Calcium in the blood is maintained in a dissolved, ionic, or complexed state, not in a solid state.
- • Polymorphs: This term refers to different crystalline forms of a substance, which is not applicable to the physiological state of blood calcium.
The following ions help in enzymatic transfer of phosphate from ATP to pyruvic acid:
- a) Sodium
- b) Calcium
- c) Magnesium
- d) Potassium
Explanation:
Magnesium ions (Mg²⁺) are essential cofactors for almost all enzymes that involve ATP. In the transfer of a phosphate group from ATP to substrates (such as the phosphorylation of phosphoenolpyruvate or similar reactions in glycolysis), Mg²⁺ acts to stabilize the negative charges on the phosphate groups of ATP, facilitating the nucleophilic attack.
Why other options are incorrect:
Why other options are incorrect:
- • Sodium: Primarily involved in maintaining osmotic pressure and nerve impulse transmission.
- • Calcium: Involved in signaling, muscle contraction, and structural roles, but not the primary cofactor for ATP-dependent kinases.
- • Potassium: Primarily involved in intracellular osmotic balance and membrane potential.
International enzyme commission classifies enzymes into:
- a) Three classes
- b) Six classes
- c) Four classes
- d) Ten classes
Explanation:
The International Union of Biochemistry and Molecular Biology (IUBMB) classifies all enzymes into six major classes based on the type of chemical reaction they catalyze:
1. Oxidoreductases, 2. Transferases, 3. Hydrolases, 4. Lyases, 5. Isomerases, and 6. Ligases.
Why other options are incorrect:
Why other options are incorrect:
- • Three/Four/Ten classes: These numbers do not correspond to the internationally accepted systematic classification system established by the IUBMB.
Michaelis–Menten equation is used to explain the effect of substrate concentration on:
- a) Carbohydrate
- b) Enzyme
- c) Lipid
- d) Protein
Explanation:
The Michaelis–Menten equation is a foundational model in biochemistry that describes the rate of enzymatic reactions. It relates the reaction velocity (v) to the substrate concentration [S], helping to determine kinetic parameters like Vmax (maximum velocity) and Km (Michaelis constant) for an enzyme.
Why other options are incorrect:
Why other options are incorrect:
- • Carbohydrate/Lipid/Protein: While these are substrates for enzymes, the equation itself characterizes the catalytic behavior of the enzyme, not the molecules themselves.
The pH at which an enzyme has maximum activity is known as:
- a) Isoelectric pH
- b) Optimum pH
- c) Low pH
- d) High pH
Explanation:
Every enzyme has an “optimum pH” at which its tertiary structure is most stable and its active site is in the correct configuration for catalysis. Deviations from this pH value can lead to denaturation or loss of catalytic efficiency.
Why other options are incorrect:
Why other options are incorrect:
- • Isoelectric pH: This is the pH at which a molecule carries no net electrical charge; it is not necessarily the point of maximum enzymatic activity.
- • Low/High pH: These are relative terms for acidic or alkaline environments, respectively, and are not specific values for enzyme optimization.
Degradation of proteins to amino acids, glucose from carbohydrates and fatty acids from lipids is known as:
- a) Anabolism
- b) Metabolism
- c) Catabolism
- d) Cretinism
Explanation:
Catabolism is the set of metabolic pathways that break down complex molecules into smaller units (such as proteins to amino acids, polysaccharides to monosaccharides, and lipids to fatty acids). This process releases energy.
Why other options are incorrect:
Why other options are incorrect:
- • Anabolism: The process of building complex molecules from simpler ones, which requires energy.
- • Metabolism: A general term covering both catabolism and anabolism.
- • Cretinism: A medical condition resulting from untreated congenital deficiency of thyroid hormone.
During glycolysis of glucose, the energy liberated in the absence of oxygen is known as:
- a) Oxygenesis
- b) Glyconeogenesis
- c) Glycogenolysis
- d) Anaerobic fermentation
Explanation:
In the absence of oxygen (anaerobic conditions), the pyruvate produced during glycolysis is further processed into end-products like ethanol or lactic acid. This process, which allows for the regeneration of NAD+ to keep glycolysis running, is referred to as anaerobic fermentation.
Why other options are incorrect:
Why other options are incorrect:
- • Oxygenesis: This is not a biological metabolic term.
- • Glyconeogenesis: The process of synthesizing glucose from non-carbohydrate sources (e.g., amino acids, glycerol).
- • Glycogenolysis: The biochemical pathway for the breakdown of glycogen into glucose.
Deficiency of urea cycle enzymes results in the accumulation of citrulline, argininosuccinate, or arginine in the liver, leading to an increasing concentration of …….. in the blood.
- a) Calcium
- b) Sodium
- c) Ammonia
- d) Lipid
Explanation:
The urea cycle is the primary pathway for the body to dispose of toxic ammonia, a byproduct of amino acid metabolism, by converting it into urea for excretion. If any of the enzymes in this cycle are deficient, the cycle cannot function, causing toxic levels of ammonia (hyperammonemia) to build up in the blood.
Why other options are incorrect:
Why other options are incorrect:
- • Calcium/Sodium: These are electrolytes and are not directly produced or regulated by the urea cycle.
- • Lipid: Lipids are macronutrients and their metabolism is separate from the urea cycle pathway.
Accumulation (or malabsorption/wasting) of tryptophan in the system is associated with:
- a) Pompe’s disease
- b) Wilson’s disease
- c) Wolman’s disease
- d) Hartnup’s disease
Explanation:
Hartnup’s disease is a rare genetic metabolic disorder characterized by the body’s inability to absorb certain amino acids, particularly tryptophan, from the small intestine and kidneys. The lack of tryptophan prevents the body from synthesizing sufficient niacin (vitamin B3), leading to pellagra-like symptoms.
Why other options are incorrect:
Why other options are incorrect:
- • Pompe’s disease: A lysosomal storage disorder caused by a deficiency of acid alpha-glucosidase.
- • Wilson’s disease: A genetic disorder that causes copper to accumulate in the liver, brain, and other vital organs.
- • Wolman’s disease: A rare lysosomal storage disease resulting in the accumulation of cholesterol esters and triglycerides.
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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