5351 to 5400 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 5351 to 5400
All the standard amino acids except the following have one chiral ‘c’ atom:
- a) Threonine, Isoleucine
- b) Isoleucine, Alanine
- c) Threonine, Alanine
- d) Alanine, Glutamine
Explanation:
Most standard amino acids have only one chiral center (the alpha-carbon). However, Threonine and Isoleucine each have two chiral centers because they possess an additional chiral carbon in their side chains.
Why other options are incorrect:
Why other options are incorrect:
- • Alanine: Contains only one chiral center (the alpha-carbon).
- • Glutamine: Contains only one chiral center (the alpha-carbon).
The role of complement proteins:
- a) Defense
- b) Helps immunity of the body
- c) Not predicatable
- d) None of these
Explanation:
The complement system is a part of the immune system that enhances (complements) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, thereby promoting inflammation and attacking the pathogen’s cell membrane.
Why other options are incorrect:
Why other options are incorrect:
- • Defense: While true, “Helps immunity of the body” is a more comprehensive and accurate description of its biological function.
- • Not predictable: The complement system follows highly specific and regulated enzymatic pathways.
- • None of these: Since option (b) correctly describes the role, this option is invalid.
Optical isomers that are mirror images and non superimposable are called:
- a) Diastereomers
- b) Enantiomers
- c) dl isomers
- d) Stereomers
Explanation:
Enantiomers are a pair of stereoisomers that are non-superimposable mirror images of each other. They possess identical physical properties except for their interaction with plane-polarized light.
Why other options are incorrect:
Why other options are incorrect:
- • Diastereomers: These are stereoisomers that are NOT mirror images of each other.
- • dl isomers: This refers to a racemic mixture (a 50:50 mixture of two enantiomers) or a general notation, not the specific definition of the molecules themselves.
- • Stereomers: This is a broad category (stereoisomers) that includes both enantiomers and diastereomers, but is not the specific term for mirror-image pairs.
Living cells have the unique ability to synthesize only the ______ form of optical isomer due to ________.
- a) ‘d’ form, stereospecific enzymes
- b) ‘l’ form, stereospecific enzymes
- c) ‘d’ form, DNA
- d) ‘L’ form, DNA
Explanation:
Living systems primarily utilize the ‘L’ (levorotatory) form of amino acids to build proteins. This selectivity is governed by the presence of highly stereospecific enzymes, which act as catalysts that can distinguish between different optical isomers and ensure only the correct form is incorporated into biological molecules.
Why other options are incorrect:
Why other options are incorrect:
- • ‘d’ form: While D-amino acids exist in nature (e.g., in some bacterial cell walls), the vast majority of biological proteins are composed of L-amino acids.
- • DNA: While DNA carries the genetic code, it is the enzymes (proteins) produced based on that code that perform the stereospecific chemical synthesis.
Isoelectric pH of an amino acid is that pH at which it has a:
- a) Positive charge
- b) Negative charge
- c) No net charge
- d) All of these
Explanation:
The isoelectric point (pI) is the specific pH at which an amino acid molecule carries no net electrical charge. At this point, the amino acid exists primarily as a zwitterion, where the number of positive charges equals the number of negative charges.
Why other options are incorrect:
Why other options are incorrect:
- • Positive charge: This occurs when the pH is below the pI (the amino acid becomes protonated).
- • Negative charge: This occurs when the pH is above the pI (the amino acid loses protons).
- • All of these: Since the amino acid only has “no net charge” at the specific isoelectric pH, this option is incorrect.
Albuminoids are similar to:
- a) Albumin
- b) Globulin
- c) Both Albumin and Globulin
- d) None of these
Explanation:
Albuminoids are fibrous proteins that resemble albumin and globulin in their
chemical composition and properties. They are also known as scleroproteins and
include proteins such as collagen and keratin.
Why other options are incorrect:
Why other options are incorrect:
- • Albumin: Albuminoids are not identical to albumin; they are a separate class of proteins.
- • Globulin: Albuminoids are not identical to globulins; they have different structural and functional characteristics.
- • None of these: Incorrect because albuminoids share properties with both albumin and globulin.
Abnormal chain of amino acids in sickle cells anaemia is:
- a) Alpha chain
- b) Beta chain
- c) Gama chain
- d) Delta chain
Explanation:
Sickle cell anaemia is caused by a mutation in the HBB gene, which leads to the substitution of glutamic acid with valine at the sixth position of the beta-globin chain of the hemoglobin molecule (forming HbS).
Why other options are incorrect:
Why other options are incorrect:
- • Alpha chain: This chain is unaffected in the primary mutation that causes sickle cell disease.
- • Gamma chain: These are typically part of fetal hemoglobin (HbF).
- • Delta chain: These are found in small amounts in adult hemoglobin (HbA2) and are not involved in sickle cell pathophysiology.
In prehepatic jaundice, protein flocculation test is:
- a) Normal/weekly positive
- b) Usually positive
- c) Negative
- d) None of these
Explanation:
Protein flocculation tests (such as the thymol turbidity or zinc sulfate turbidity tests) are used to detect changes in serum proteins, particularly an increase in gamma-globulins or decrease in albumin, often seen in liver disease. In prehepatic jaundice (which is caused by excessive hemolysis), the liver function itself is usually normal, so the flocculation test is typically negative.
Why other options are incorrect:
Why other options are incorrect:
- • Usually positive: Positive results are characteristic of hepatocellular jaundice where liver proteins are altered.
- • Normal/weekly positive: This is generally associated with conditions where there is slight hepatic impairment, not pure prehepatic hemolysis.
Side chains of all amino acids contain aromatic rings except:
- a) Pheynl alanine
- b) Alanine
- c) Tyrosine
- d) Tryptophan
Explanation:
Phenylalanine, Tyrosine, and Tryptophan are the three standard amino acids that contain aromatic rings in their side chains. Alanine, on the other hand, has a simple methyl (-CH3) group as its side chain, which is aliphatic and not aromatic.
Why other options are incorrect:
Why other options are incorrect:
- • Phenylalanine: Contains a benzene ring.
- • Tyrosine: Contains a phenol group (a benzene ring with a hydroxyl group).
- • Tryptophan: Contains an indole ring system (a bicyclic structure).
In Nitroprusside test, amino acid cysteine produces:
- a) Blue colour complex
- b) Red colour
- c) Yellow colour
- d) Purple colour
Explanation:
The Nitroprusside test is a specific chemical test used to detect the presence of sulfhydryl (-SH) groups. When sodium nitroprusside reacts with cysteine (which contains a free sulfhydryl group) in the presence of ammonia, it forms a characteristic purple/red-violet color complex.
Why other options are incorrect:
Why other options are incorrect:
- • Blue/Yellow/Red: These colors do not represent the specific chelation reaction between the nitroprusside reagent and the thiol group of cysteine.
Bonds that are formed between two cysteine residues is:
- a) Disulfide
- b) Peptide
- c) Electrostatic
- d) Hydrophobic
Explanation:
Cysteine residues contain a sulfhydryl (-SH) group in their side chain. When two cysteine residues undergo oxidation, they form a covalent disulfide bond (-S-S-), which is crucial for the stability and folding of protein structures.
Why other options are incorrect:
Why other options are incorrect:
- • Peptide: These are the bonds that link the carboxyl group of one amino acid to the amino group of another in the primary protein chain.
- • Electrostatic: These occur between oppositely charged amino acid side chains (e.g., salt bridges).
- • Hydrophobic: These are non-covalent interactions between non-polar side chains.
The acid amide of Aspartic acid is:
- a) Glutamine
- b) Arginine
- c) Aspargine
- d) Ornithine
Explanation:
Asparagine is the amide derivative of aspartic acid. In this conversion, the carboxyl group (-COOH) of the aspartic acid side chain is replaced by an amide group (-CONH₂).
Why other options are incorrect:
Why other options are incorrect:
- • Glutamine: This is the acid amide of Glutamic acid, not Aspartic acid.
- • Arginine: A basic amino acid containing a guanidino group.
- • Ornithine: A non-proteinogenic amino acid involved in the urea cycle.
It is the only amino acid having an ionizing ‘R’ group with a pK’ near 7 and is important in the active site of some enzymes:
- a) Arginine
- b) Cystein
- c) Cystine
- d) Histidine
Explanation:
Histidine contains an imidazole side chain with a pKa of approximately 6.0. Because this pKa is close to physiological pH (7.4), the imidazole group can easily switch between protonated and deprotonated states. This makes Histidine exceptionally valuable in the active sites of enzymes for acid-base catalysis.
Why other options are incorrect:
Why other options are incorrect:
- • Arginine: Has a highly basic side chain with a pKa around 12.5.
- • Cysteine: Has a sulfhydryl side chain with a pKa around 8.3.
- • Cystine: A dimer of cysteine formed by a disulfide bond; it does not have an ionizable side chain with a pKa near 7.
A hexa peptide with 5 aspartic acid would have a net charge at pH 7:
- a) Neutral
- b) Positive
- c) Negative
- d) Not predictable
Explanation:
Aspartic acid is an acidic amino acid with a side-chain carboxyl group that has a pKa around 3.9. At pH 7, which is well above its pKa, the carboxyl groups are deprotonated and carry a negative charge. Since 5 out of 6 amino acids in this peptide are aspartic acid, the peptide will have a strong net negative charge.
Why other options are incorrect:
Why other options are incorrect:
- • Neutral/Positive: These are impossible as the abundance of acidic (negatively charged) residues outweighs any potential positive charges from the N-terminus or the single remaining amino acid.
- • Not predictable: Because the pKa values of aspartic acid are well-defined, the ionization state at physiological pH (7.4) is predictable.
In the genetic disorder of cystinuria, the patient excretes large quantities of cystine in their urine and its low solubility causes crystalline cystine to precipitate as stones in kidneys. The remedy involves ingesting NaHCO3. Reaction of this treatment is:
- a) NaHCO3 combines with cystine
- b) NaHCO3 raises the pH above the isoelectric point of cystine
- c) NaHCO3 prevents stone formation by hydrolysis of cystine to cysteine
- d) None of these
Explanation:
Cystine is poorly soluble in acidic or neutral urine. Sodium bicarbonate (NaHCO3) is administered to alkalinize the urine, which raises the urinary pH significantly. By increasing the pH above the isoelectric point of cystine, it increases the solubility of cystine, thereby preventing the formation of kidney stones.
Why other options are incorrect:
Why other options are incorrect:
- • NaHCO3 combines with cystine: The bicarbonate acts as a buffer to change pH; it does not directly conjugate with cystine.
- • Hydrolysis: NaHCO3 does not hydrolyze cystine into cysteine; that would require a reducing agent.
Amino acids excepting histidine are not good buffering agents in cell because:
- a) They exist as zwitter ions
- b) Their pKa is not in the physiological pH of a cell
- c) Only Histidine has pKa of its R group at 6.0 unlike the others which have at a different pH
- d) None of these
Explanation:
A molecule is an effective buffer when its pKa is within ±1 pH unit of the environment’s pH. The physiological pH of a cell is approximately 7.4. Histidine’s imidazole side chain has a pKa of ~6.0, which is close enough to be an effective buffer at physiological pH. Most other amino acids have side chains with pKa values that are either too acidic or too basic to provide effective buffering at neutral cellular pH.
Why other options are incorrect:
Why other options are incorrect:
- • Zwitter ions: While true, this is a property of all amino acids at their isoelectric point and does not explain the specific lack of buffering capacity at pH 7.4.
- • Their pKa not in physiological pH: While this is a factual consequence, option (c) provides the specific biochemical reason *why* histidine is the exception.
The amino acids in which the R groups have a net positive charge at pH 7.0 are:
- a) Lysine, Arginine, Histidine
- b) Lysine, Aspargine
- c) Histidine, Aspargine
- d) Glutamine, Arginine
Explanation:
Lysine, Arginine, and Histidine are classified as basic amino acids. Their side chains (R groups) contain nitrogenous groups that can accept protons. At physiological pH (7.0), these side chains remain predominantly in their protonated, positively charged states.
Why other options are incorrect:
Why other options are incorrect:
- • Asparagine and Glutamine: These are polar, uncharged amino acids; their amide side chains do not carry a charge at pH 7.0.
Apolipoproteins are:
- a) AI
- b) AII
- c) CI
- d) All of these
Explanation:
Apolipoproteins are the protein components of lipoproteins. They are classified into several major families (A, B, C, D, E, etc.). Apo A-I, Apo A-II, and Apo C-I are all well-characterized apolipoproteins that play essential roles in lipid metabolism and transport.
Why other options are correct:
Why other options are correct:
- • Apo A-I: The major protein component of HDL (High-Density Lipoprotein).
- • Apo A-II: The second most abundant protein in HDL.
- • Apo C-I: A protein involved in the regulation of lipid metabolism enzymes.
The amino acid which has a pK near 4 and thus is negatively charged at pH 7 is:
- a) Alanine
- b) Glutamic acid
- c) Glutamine
- d) Aspargine
Explanation:
Glutamic acid (and Aspartic acid) are acidic amino acids. Their side chains contain a carboxyl group with a pKa of approximately 4.2. Because pH 7 is significantly higher than this pKa, the carboxyl group loses a proton (becomes deprotonated/ionized) and carries a negative charge in the physiological environment.
Why other options are incorrect:
Why other options are incorrect:
- • Alanine: A non-polar amino acid with no ionizable side chain.
- • Glutamine and Asparagine: These are the amide forms of glutamic and aspartic acid; the amide groups are neutral and do not ionize at pH 7.
The side chain of which of the following amino acid contain sulphur atom?
- a) Methionine
- b) Threonine
- c) Leucine
- d) Tryptophan
Explanation:
There are two sulfur-containing amino acids in the standard set: Methionine and Cysteine. Methionine contains a thioether group (-S-CH3) in its side chain, making it the correct answer among the provided choices.
Why other options are incorrect:
Why other options are incorrect:
- • Threonine: Contains a hydroxyl (-OH) group, not sulfur.
- • Leucine: An aliphatic, branched-chain amino acid without sulfur.
- • Tryptophan: An aromatic amino acid with an indole ring; it contains no sulfur.
Which of the following gives a positive test for Ninhydrin?
- a) Reducing sugars
- b) Triglycerides
- c) Alpha amino acids
- d) Esterified Fats
Explanation:
The Ninhydrin test is a chemical test used to detect the presence of ammonia or primary amines. Since alpha amino acids contain a free alpha-amino group, they react with ninhydrin to produce a characteristic deep blue or purple color (Ruhemann’s purple).
Why other options are incorrect:
Why other options are incorrect:
- • Reducing sugars: These are typically detected by tests like Benedict’s or Fehling’s test, not ninhydrin.
- • Triglycerides and Esterified Fats: These are lipids and lack the free amino group required for the ninhydrin reaction.
In glutathione (a tripeptide) is present apart from Glutamic acid and cysteine:
- a) Serine
- b) Glycine
- c) Leucine
- d) Phenyl alanine
Explanation:
Glutathione is a tripeptide consisting of three amino acids: Glutamic acid, Cysteine, and Glycine. It is a vital antioxidant in plants, animals, and fungi, preventing damage to important cellular components caused by reactive oxygen species such as free radicals and peroxides.
Why other options are incorrect:
Why other options are incorrect:
- • Serine, Leucine, and Phenylalanine: These amino acids are not part of the primary structure of the glutathione molecule.
2-Amino 3-OH propanoic acid is
- a) Glycine
- b) Alanine
- c) Valine
- d) Serine
Explanation:
2-Amino-3-hydroxypropanoic acid is the IUPAC name for Serine, a polar amino acid containing a hydroxyl group (-OH) on its side chain.
Why other options are incorrect:
Why other options are incorrect:
- • Glycine: The simplest amino acid (2-aminoethanoic acid) without a side chain.
- • Alanine: An amino acid with a methyl (-CH3) group as its side chain.
- • Valine: A branched-chain amino acid with an isopropyl side chain.
All amino acids have one asymmetric carbon atom, except
- a) Arginine
- b) Aspargine
- c) Histidine
- d) Glycine
Explanation:
Glycine is the only proteinogenic amino acid that is achiral (optically inactive) because its side chain is a simple hydrogen atom. This means the alpha-carbon is bonded to two identical hydrogen atoms, making it symmetric.
Why other options are incorrect:
Why other options are incorrect:
- • Arginine: Contains a complex side chain, making the alpha-carbon asymmetric.
- • Aspargine: The alpha-carbon is attached to four different groups (H, NH2, COOH, and the side chain), creating asymmetry.
- • Histidine: Possesses an imidazole ring side chain, maintaining the asymmetry of the alpha-carbon.
Number of amino acids present in the plant, animal and microbial proteins:
- a) 20
- b) 80
- c) 150
- d) 200
Explanation:
There are 20 standard (proteinogenic) amino acids that are genetically coded and commonly found in the proteins of plants, animals, and microorganisms. These are the building blocks used to synthesize proteins via the ribosome.
Why other options are incorrect:
Why other options are incorrect:
- • 80, 150, 200: While there are hundreds of non-proteinogenic amino acids found in nature, these numbers do not represent the set of standard amino acids used universally in protein synthesis across these kingdoms.
Immunoglobulins are characterized by their:
- a) Heavy chains
- b) Molecular weight
- c) Light chains
- d) Electrophoretic behaviour
Explanation:
Immunoglobulins are classified primarily according to the type of their
heavy chains. The five major classes—IgG, IgA, IgM, IgD, and IgE—are
distinguished by their different heavy-chain structures.
Why other options are incorrect:
Why other options are incorrect:
- • Molecular weight: Molecular weight varies among immunoglobulins but is not the primary basis for their classification.
- • Light chains: Light chains are either kappa (κ) or lambda (λ) and do not determine the major immunoglobulin classes.
- • Electrophoretic behaviour: Electrophoretic mobility can help identify proteins but is not the defining characteristic of immunoglobulin classes.
The bond in proteins that is not hydrolysed under usual conditions of denaturation:
- a) Hydrophobic bond
- b) Hydrogen bond
- c) Disulphide bond
- d) Peptide bonds
Explanation:
Denaturation involves the unfolding of the tertiary and secondary structure of proteins by breaking weak interactions like hydrogen bonds, hydrophobic interactions, and sometimes disulfide bonds. Peptide bonds, however, constitute the primary structure (the backbone) of the protein and remain intact during typical denaturation processes.
Why other options are incorrect:
Why other options are incorrect:
- • Hydrophobic & Hydrogen bonds: These are weak, non-covalent interactions that are disrupted easily by heat, pH changes, or detergents.
- • Disulphide bond: Although covalent, these can be reduced or disrupted under many common denaturing conditions (like the addition of urea or mercaptoethanol).
If the amino group and a carboxylic group of the amino acid are attached to same carbon atom, the amino acid is called
- a) Alpha
- b) Beta
- c) Gamma
- d) Delta
Explanation:
In alpha-amino acids, the amino group (-NH2) is attached to the alpha-carbon, which is the carbon atom directly adjacent to the carboxyl group (-COOH). Since the alpha-carbon is the one immediately attached to the carboxylic acid group, this configuration is standard for all proteinogenic amino acids.
Why other options are incorrect:
Why other options are incorrect:
- • Beta: In beta-amino acids, the amino group is attached to the beta-carbon (the second carbon from the carboxyl group).
- • Gamma and Delta: These refer to positions further down the carbon chain from the carboxyl group, which are not characteristic of standard protein amino acids.
Zymogen is
- a) An intracellular enzyme
- b) Serum enzyme
- c) A complete extracellular enzyme
- d) An inactivated enzyme
Explanation:
A zymogen (or proenzyme) is an inactive precursor of an enzyme. It requires a biochemical change (such as the hydrolysis of a specific peptide bond or a conformational change) to become an active enzyme. This mechanism prevents enzymes from damaging the cells that produce them (e.g., digestive enzymes like pepsinogen or trypsinogen).
Why other options are incorrect:
Why other options are incorrect:
- • Intracellular/Serum/Extracellular: These terms describe the location or function of enzymes, but do not define the specific biological classification of a zymogen, which is fundamentally defined by its inactive state.
SGOT level in a adult is
- a) 5–40 units/dl
- b) 1–4 units/dl
- c) 5–15 units/dl
- d) 50–100 units/dl
Explanation:
Serum Glutamic-Oxaloacetic Transaminase (SGOT), also known as Aspartate Aminotransferase (AST), typically has a normal reference range in adults of approximately 5–40 units/dl (or IU/L). Elevated levels often indicate damage to cells in the liver, heart, or muscles.
Why other options are incorrect:
Why other options are incorrect:
- • 1–4 units/dl: This range is significantly lower than the standard clinical reference values.
- • 5–15 units/dl: While closer, it is narrower than the generally accepted clinical range.
- • 50–100 units/dl: These values are typically considered elevated and may suggest clinical pathology rather than a normal range.
Activity of ceruloplasmin shown in vitro:
- a) Reductase
- b) Hydrolase
- c) Ligase
- d) Oxidase
Explanation:
Ceruloplasmin is a copper-carrying protein in the blood that possesses ferroxidase activity. In vitro, it demonstrates significant oxidase activity, particularly towards substrates like p-phenylenediamine. It plays a crucial role in converting ferrous iron (Fe2+) to ferric iron (Fe3+), facilitating its binding to transferrin.
Why other options are incorrect:
Why other options are incorrect:
- • Reductase: Ceruloplasmin is an oxidizer, not a reducer.
- • Hydrolase: This class of enzymes catalyzes the hydrolysis of chemical bonds; ceruloplasmin does not belong to this group.
- • Ligase: Ligases catalyze the joining of two molecules; this is not the primary function of ceruloplasmin.
Increased serum alanine during fasting is due to
- a) Breakdown of muscle proteins
- b) Decreased utilization of non essential amino acids
- c) Leakage of aminoacids to plasma
- d) Impaired renal function
Explanation:
During fasting, the body breaks down muscle proteins to provide amino acids for gluconeogenesis. The carbon skeletons of these amino acids are converted to pyruvate in the muscle, which is then transaminated to alanine. This alanine is released into the blood and transported to the liver, where it serves as a primary substrate for glucose production (the Glucose-Alanine Cycle).
Why other options are incorrect:
Why other options are incorrect:
- • Decreased utilization: Alanine utilization actually increases in the liver for gluconeogenesis during fasting.
- • Leakage/Renal function: These do not represent the physiological mechanism behind the Glucose-Alanine cycle during a metabolic fast.
The following 4 amino acids are required for completion of urea cycle except
- a) Aspartic acid
- b) Arginine
- c) Ornithine
- d) Glycine
Explanation:
The Urea Cycle involves Ornithine, Citrulline, Argininosuccinate, Arginine, and Aspartic acid.
Why other options are incorrect:
- Ornithine: Acts as a carrier.
- Aspartic acid: Provides the second nitrogen atom for the urea molecule.
- Arginine: Acts as an intermediate and is cleaved to release urea.
Why other options are incorrect:
- • Aspartic acid, Arginine, and Ornithine: These are essential components or intermediates that facilitate the cycle, unlike glycine.
Number of amino acids present in the dietary proteins:
- a) 22
- b) 23
- c) 20
- d) 19
Explanation:
There are 20 standard (proteinogenic) amino acids that are genetically encoded and commonly found in dietary proteins. These are the building blocks required by the body to synthesize its own proteins.
Why other options are incorrect:
Why other options are incorrect:
- • 22, 23, 19: While rare amino acids like selenocysteine and pyrrolysine exist, the standard set of amino acids universally recognized as the components of dietary protein is 20.
Urea synthesis takes place in
- a) Blood
- b) Liver
- c) Kidney
- d) Heart
Explanation:
The urea cycle (ornithine cycle) takes place almost exclusively in the liver. It is the metabolic pathway by which the body converts toxic ammonia (a byproduct of amino acid metabolism) into urea, which is then transported to the kidneys for excretion.
Why other options are incorrect:
Why other options are incorrect:
- • Blood: Acts only as a transport medium for urea to reach the kidneys.
- • Kidney: The site where urea is filtered and excreted, not where it is synthesized.
- • Heart: Does not play a role in the metabolic synthesis of urea.
All followings are ketogenic aminoacids except
- a) Leucine
- b) Isoleucine
- c) Phenyl alanine
- d) Glycine
Explanation:
Glycine is a purely glucogenic amino acid. It is degraded into pyruvate or carbon dioxide and ammonia, which can then be used for glucose synthesis via gluconeogenesis. It cannot be converted into acetyl-CoA or acetoacetate, which are the precursors for ketone bodies.
Why other options are incorrect:
Why other options are incorrect:
- • Leucine: Strictly ketogenic; it is converted solely to acetyl-CoA and acetoacetate.
- • Isoleucine and Phenylalanine: These are both glucogenic and ketogenic (amphibolic), meaning they can provide precursors for both glucose and ketone bodies.
The amino acid containing an indole ring:
- a) Tryptophan
- b) Arginine
- c) Threonine
- d) Phenylalanine
Explanation:
Tryptophan is the only standard amino acid that contains an indole ring (a bicyclic structure consisting of a six-membered benzene ring fused to a five-membered nitrogen-containing pyrrole ring) as part of its side chain.
Why other options are incorrect:
Why other options are incorrect:
- • Arginine: Contains a guanidino group.
- • Threonine: Contains a hydroxyl group and is an aliphatic amino acid.
- • Phenylalanine: Contains a phenyl ring (a simple benzene ring attached to the alanine backbone).
Histidine is converted to histamine through the process of
- a) Transamination
- b) Decarboxylation
- c) Oxidative deamination
- d) Urea cycle
Explanation:
The conversion of histidine to histamine is catalyzed by the enzyme histidine decarboxylase. This process involves the removal of a carboxyl group (-COOH) from the histidine molecule, releasing carbon dioxide and producing the biogenic amine histamine.
Why other options are incorrect:
Why other options are incorrect:
- • Transamination: Involves transferring an amino group, not removing a carboxyl group.
- • Oxidative deamination: Involves the removal of an amino group, typically producing ammonia and a keto acid.
- • Urea cycle: A pathway for nitrogen excretion, unrelated to histamine synthesis.
Physiologically active configuration of amino acids:
- a) L
- b) D
- c) For some amino acids it is either of two
- d) Neither L nor D
Explanation:
The naturally occurring amino acids found in proteins and used by living organisms for protein synthesis are almost exclusively in the L-configuration (L-amino acids).
Why other options are incorrect:
Why other options are incorrect:
- • D-configuration: While D-amino acids exist (often found in bacterial cell walls or some antibiotics), they are not the physiologically active forms used for protein synthesis in humans and higher organisms.
- • Either/Neither: Biological systems are highly stereospecific, favoring the L-isomer for essential metabolic functions involving protein structures.
Cystine is synthesized from
- a) Cysteine
- b) Methionine
- c) Arginine
- d) Leucine
Explanation:
Cystine is the oxidized dimer of the amino acid cysteine. It is formed by the oxidation of the sulfhydryl (-SH) group of two cysteine molecules, resulting in the formation of a covalent disulfide bond (-S-S-).
Why other options are incorrect:
Why other options are incorrect:
- • Methionine: While methionine is a precursor for the synthesis of cysteine (via the transsulfuration pathway), cystine itself is formed directly from the oxidation of cysteine.
- • Arginine and Leucine: These are unrelated to the structural formation of cystine.
The major constituent of the proteins of hair and keratin of skin:
- a) Arginine
- b) Cysteine
- c) Glycine
- d) Aspartic Acid
Explanation:
Keratin is a structural protein characterized by a very high content of Cysteine. The disulfide bonds formed between cysteine residues provide the structural rigidity, strength, and insolubility characteristic of hair, nails, and skin.
Why other options are incorrect:
Why other options are incorrect:
- • Arginine: A basic amino acid that is part of many proteins but is not the key structural feature of keratin.
- • Glycine: Although abundant in collagen, it is not the primary amino acid responsible for the properties of keratin.
NH3 is removed from brain mainly by
- a) Creatinine formation
- b) Uric acid production
- c) Urea formation
- d) Glutamine formation
Explanation:
The brain does not have a functional urea cycle to dispose of ammonia. Instead, it uses the enzyme glutamine synthetase to combine ammonia with glutamate to form glutamine. This reaction is the primary mechanism for detoxifying ammonia in the brain and transporting it safely to the liver or kidneys.
Why other options are incorrect:
Why other options are incorrect:
- • Urea formation: Occurs primarily in the liver.
- • Uric acid/Creatinine: These are metabolic waste products related to purine and muscle metabolism, respectively, not pathways for ammonia detoxification.
Mechanism by which NH3 is removed from the kidneys is
- a) Urea formation
- b) Uric acid formation
- c) Creatinine formation
- d) None of these
Explanation:
The kidney removes ammonia primarily by excreting it as ammonium ions (NH4+). This occurs through the process of ammoniagenesis (mainly from glutamine), which helps regulate acid-base balance by buffering hydrogen ions in the renal tubules. None of the options listed (urea, uric acid, or creatinine formation) are the primary mechanisms for renal ammonia excretion.
Why other options are incorrect:
Why other options are incorrect:
- • Urea formation: Occurs in the liver.
- • Uric acid: A byproduct of purine metabolism.
- • Creatinine: A breakdown product of creatine phosphate in muscle.
Low density plasma proteins (LDL) are rich in
- a) Chylomicrons
- b) Cholesterol
- c) Triglycerides
- d) Phospholipids
Explanation:
Low-density lipoproteins (LDL), often referred to as “bad cholesterol,” are primarily responsible for transporting cholesterol from the liver to the tissues. Consequently, their core is highly concentrated with cholesterol and cholesteryl esters.
Why other options are incorrect:
Why other options are incorrect:
- • Chylomicrons: These are distinct particles that transport dietary lipids, not a component of LDL.
- • Triglycerides: These are the primary component of VLDL (Very Low-Density Lipoproteins) and Chylomicrons.
- • Phospholipids: While present, they form the outer shell of all lipoproteins, whereas cholesterol is the defining cargo of LDL.
Transcortins are
- a) Mucoproteins
- b) Glycoproteins
- c) Metalloproteins
- d) Lipoproteins
Explanation:
Transcortin, also known as Corticosteroid-Binding Globulin (CBG), is a glycoprotein produced in the liver. It is responsible for the transport of cortisol and other corticosteroids in the blood.
Why other options are incorrect:
Why other options are incorrect:
- • Mucoproteins: These are proteins heavily glycosylated with mucopolysaccharides.
- • Metalloproteins: Proteins that contain a metal ion cofactor.
- • Lipoproteins: Complexes of lipids and proteins used for lipid transport; transcortin does not transport lipids.
Proteins that carries Iron into different tissues is
- a) Ceruloplasmin
- b) Transferrin
- c) Mucoproteins
- d) Glycoproteins
Explanation:
Transferrin is a blood plasma glycoprotein that plays a central role in iron metabolism. It binds iron tightly and transports it through the blood to various tissues, such as the bone marrow (for erythropoiesis) and other cells.
Why other options are incorrect:
Why other options are incorrect:
- • Ceruloplasmin: Primarily a copper-carrying protein, though it aids in iron oxidation.
- • Mucoproteins & Glycoproteins: These are broad classifications of proteins based on their composition, not specific iron-transporting proteins.
Naturally occurring amino acids have
- a) L-Configuration
- b) D-Configuration
- c) DL-Configuration
- d) None of these
Explanation:
Almost all naturally occurring amino acids found in proteins (proteinogenic amino acids) exist in the L-configuration. This refers to the arrangement of groups around the alpha-carbon atom, which corresponds to the L-glyceraldehyde reference standard.
Why other options are incorrect:
Why other options are incorrect:
- • D-Configuration: While D-amino acids are found in some specialized biological contexts (like bacterial cell walls), they are not the building blocks of human proteins.
- • DL-Configuration: This represents a racemic mixture, which is not the standard biological configuration in living systems.
Abnormal chain of aminoacids in sickle cell anemia is
- a) β-chain
- b) α-chain
- c) γ-chain
- d) δ-chain
Explanation:
Sickle cell anemia is caused by a point mutation in the gene coding for the beta-globin chain of hemoglobin. This mutation results in the substitution of glutamic acid with valine at the 6th position, leading to the formation of abnormal hemoglobin S (HbS).
Why other options are incorrect:
Why other options are incorrect:
- • α-chain: Not the primary site of mutation in sickle cell anemia.
- • γ-chain: Associated with Fetal Hemoglobin (HbF), not sickle cell disease.
- • δ-chain: Associated with Hemoglobin A2, unrelated to the sickle cell mutation.
A dietary deficiency of tryptophan and nicotinate leads to
- a) Beri Beri
- b) Xerophthalmia
- c) Anemia
- d) Pellagra
Explanation:
Pellagra is caused by a deficiency of Niacin (Vitamin B3) or its precursor, the amino acid Tryptophan. Since the body can synthesize niacin from tryptophan, a lack of both leads to the classic symptoms of Pellagra (the “3 Ds”: Dermatitis, Diarrhea, and Dementia).
Why other options are incorrect:
Why other options are incorrect:
- • Beri Beri: Caused by a deficiency of Vitamin B1 (Thiamine).
- • Xerophthalmia: Caused by a deficiency of Vitamin A.
- • Anemia: Generally associated with deficiencies in iron, Vitamin B12, or Folate.
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, meaning it cannot be synthesized by the human body and must be obtained through the diet.
Why other options are incorrect:
Why other options are incorrect:
- • Arginine: Considered semi-essential or conditionally essential, as the body can synthesize it, but sometimes not in sufficient amounts.
- • Tyrosine: A non-essential amino acid that is synthesized in the body from phenylalanine.
- • Proline: A non-essential amino acid that the body can synthesize on its own.
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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