5251 to 5300 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 5251 to 5300
Haematuria can occur in all of the following except
- a) Acute glomerulonephritis
- b) Cancer of urinary tract
- c) Stone in urinary tract
- d) Mismatched blood transfusion
Explanation:
Haematuria (blood in urine) commonly occurs in diseases affecting the kidneys or urinary tract, such as acute glomerulonephritis, urinary tract cancers, and urinary stones. Mismatched blood transfusion causes acute hemolysis and haemoglobinuria rather than true haematuria.
Why other options are incorrect:
Why other options are incorrect:
- • Acute glomerulonephritis: Can cause haematuria due to glomerular inflammation and damage.
- • Cancer of urinary tract: Haematuria is a common presenting feature of urinary tract malignancies.
- • Stone in urinary tract: Urinary stones can injure the urinary tract lining and cause haematuria.
- • Mismatched blood transfusion: Causes intravascular haemolysis and haemoglobinuria, not true haematuria.
Chyluria can be detected by addition of the following to the urine:
- a) Sulphosalicylic acid
- b) Nitric acid
- c) Acetic anhydride
- d) Chloroform
Explanation:
Chloroform is used in the detection of chyluria. When chloroform is added to chyluric urine and shaken, it dissolves the fat present in the urine, causing the milky, turbid appearance to clear up.
Why other options are incorrect:
Why other options are incorrect:
- • Sulphosalicylic acid: Used primarily to detect protein (albumin) in the urine.
- • Nitric acid: Typically used in Heller’s test for detecting protein.
- • Acetic anhydride: Commonly used in chemical synthesis and lipid analysis (like the Liebermann-Burchard test), but not for the diagnostic clarification of chyluric urine.
Normal range of serum urea is
- a) 0.6–1.5 mg/dl
- b) 9–11 mg/dl
- c) 20–45 mg/dl
- d) 60–100 mg/dl
Explanation:
The normal range for serum urea (also known as Blood Urea Nitrogen or BUN expressed as urea) in a healthy adult is typically 20–45 mg/dl. Values may vary slightly depending on the specific laboratory reference ranges.
Why other options are incorrect:
Why other options are incorrect:
- • 0.6–1.5 mg/dl: This is the standard reference range for serum creatinine in adults.
- • 9–11 mg/dl: This is the typical reference range for serum calcium.
- • 60–100 mg/dl: These values are significantly elevated (azotemia) and indicate potential renal impairment or other metabolic issues.
Normal range of serum creatinine is
- a) 0.6–1.5 mg/dl
- b) 9–11 mg/dl
- c) 20–45 mg/dl
- d) 60–100 mg/dl
Explanation:
The normal range for serum creatinine in healthy adults is approximately 0.6 to 1.5 mg/dl. Creatinine is a waste product from muscle breakdown, and its levels are used as a primary indicator of kidney function.
Why other options are incorrect:
Why other options are incorrect:
- • 9–11 mg/dl: This is the normal reference range for serum calcium.
- • 20–45 mg/dl: This is the normal reference range for serum urea.
- • 60–100 mg/dl: This range is not a standard physiological marker for these specific blood tests and would likely indicate pathological abnormalities.
Standard urea clearance is
- a) 54 ml/min
- b) 75 ml/min
- c) 110 ml/min
- d) 130 ml/min
Explanation:
Standard urea clearance refers to the rate when the urine flow is less than 2 ml/min (specifically at 1 ml/min). In this state, the normal clearance value is approximately 54 ml/min.
Why other options are incorrect:
Why other options are incorrect:
- • 75 ml/min: This is the value often associated with “maximal” urea clearance (when urine flow is 2 ml/min or more).
- • 110–130 ml/min: These values represent the normal range for Glomerular Filtration Rate (GFR) or creatinine clearance in a healthy adult.
Maximum urea clearance is
- a) 54 ml/min
- b) 75 ml/min
- c) 110 ml/min
- d) 130 ml/min
Explanation:
Maximal urea clearance occurs when the urine flow rate is 2 ml/min or greater. Under these conditions, the kidneys clear urea at a rate of approximately 75 ml/min.
Why other options are incorrect:
Why other options are incorrect:
- • 54 ml/min: This is the “standard” urea clearance value, observed when urine flow is less than 2 ml/min.
- • 110–130 ml/min: These represent the normal glomerular filtration rate (GFR) or creatinine clearance, which is higher than urea clearance because urea is partially reabsorbed by the renal tubules.
Average creatinine clearance in an adult man is about
- a) 54 ml/min
- b) 75 ml/min
- c) 110 ml/min
- d) 130 ml/min
Explanation:
The average creatinine clearance in a healthy adult man is approximately 110 ml/min, which is used as an estimate of the glomerular filtration rate (GFR).
Why other options are incorrect:
Why other options are incorrect:
- • 54 ml/min: Considerably below the normal adult range.
- • 75 ml/min: Lower than the average normal value in a healthy adult man.
- • 110 ml/min: This is the approximate average creatinine clearance in an adult man.
- • 130 ml/min: Higher than the commonly cited average value.
Inulin clearance in an average adult man is about
- a) 54 ml/min
- b) 75 ml/min
- c) 110 ml/min
- d) 130 ml/min
Explanation:
Inulin clearance is considered the “gold standard” for measuring Glomerular Filtration Rate (GFR) because it is freely filtered by the glomeruli and is neither reabsorbed nor secreted by the renal tubules. In an average healthy adult man, this value is approximately 125–130 ml/min.
Why other options are incorrect:
Why other options are incorrect:
- • 54 ml/min: This is the value for standard urea clearance.
- • 75 ml/min: This is the value for maximal urea clearance.
- • 110 ml/min: This value is closer to the average GFR for an adult woman.
Among the following, a test of tubular function is
- a) Creatinine clearance
- b) Inulin clearance
- c) PAH clearance
- d) PSP excretion test
Explanation:
The Phenolsulfonphthalein (PSP) excretion test is a classical clinical test used to assess the secretory function of the renal tubules. The rate at which the dye is excreted in the urine is a measure of the effective renal tubular function.
Why other options are incorrect:
Why other options are incorrect:
- • Creatinine clearance & Inulin clearance: These are primarily used to measure the Glomerular Filtration Rate (GFR).
- • PAH clearance: Para-aminohippuric acid (PAH) clearance is used to measure Effective Renal Plasma Flow (ERPF). While it is secreted by tubules, it is primarily used as a measurement of blood flow rather than a direct test of tubular secretory capacity.
A simple way to assess tubular function is to withhold food and water for 12 hours and, then, measure
- a) Serum urea
- b) Serum creatinine
- c) Urine output in one hour
- d) Specific gravity of urine
Explanation:
This is a concentration test (also known as the Fishberg concentration test). Withholding fluids forces the kidneys to conserve water by producing concentrated urine. In a healthy kidney, the renal tubules will concentrate urine, resulting in a specific gravity of 1.025 or higher. If the tubules are damaged, they lose the ability to concentrate urine.
Why other options are incorrect:
Why other options are incorrect:
- • Serum urea & Creatinine: These are primarily markers of glomerular filtration function, not tubular concentration ability.
- • Urine output in one hour: While output decreases during dehydration, the volume itself is less informative than the ability to concentrate solutes (specific gravity).
Among the following, the most sensitive indicator of glomerular function is
- a) Serum urea
- b) Serum creatinine
- c) Urea clearance
- d) Creatinine clearance
Explanation:
Creatinine clearance is a more sensitive and reliable indicator of Glomerular Filtration Rate (GFR) compared to serum levels or urea clearance. Because creatinine is produced at a relatively constant rate and is primarily excreted via glomerular filtration, its clearance rate provides a direct measurement of renal efficiency.
Why other options are incorrect:
Why other options are incorrect:
- • Serum urea: Levels can be influenced by diet, hydration status, and protein metabolism, making it less specific.
- • Serum creatinine: While useful, it is a marker of status rather than a clearance rate, and levels may not rise significantly until a large portion of kidney function is already lost.
- • Urea clearance: Less sensitive because urea is subject to passive tubular reabsorption, which fluctuates based on urine flow.
All the following statements about inulin are correct except
- a) It is completely non-toxic
- b) It is completely filtered by glomeruli
- c) It is not reabsorbed by tubular cells
- d) It is secreted by tubular cells
Explanation:
Inulin is not secreted by tubular cells. It is freely filtered by the glomeruli and is neither reabsorbed nor secreted by the renal tubules. This unique property makes inulin clearance an accurate measure of the glomerular filtration rate (GFR).
Why other options are incorrect:
Why other options are incorrect:
- • It is completely non-toxic: Inulin is considered safe and biologically inert when used for measuring GFR.
- • It is completely filtered by glomeruli: Inulin is freely filtered across the glomerular membrane.
- • It is not reabsorbed by tubular cells: Correct property of inulin; none of the filtered inulin is normally reabsorbed.
- • It is secreted by tubular cells: Incorrect. Inulin is neither secreted nor reabsorbed by renal tubules.
Non-protein nitrogenous substances in blood include all of the following except
- a) Urea
- b) Uric acid
- c) Creatinine
- d) Inositol
Explanation:
Non-protein nitrogen (NPN) substances are nitrogen-containing compounds in blood that are not part of proteins. Major NPN substances include urea, uric acid, creatinine, and amino acids. Inositol is a carbohydrate-like cyclic polyol and is not classified as a non-protein nitrogenous substance.
Why other options are incorrect:
Why other options are incorrect:
- • Urea: The major nitrogenous end product of protein metabolism in humans and a major NPN substance.
- • Uric acid: A nitrogen-containing end product of purine metabolism and an NPN substance.
- • Creatinine: A nitrogenous waste product formed from creatine in muscle and an NPN substance.
- • Inositol: Does not contain nitrogen and therefore is not an NPN substance.
Serum amylase is increased in
- a) Acute parotitis
- b) Acute pancreatitis
- c) Pancreatic cancer
- d) All of these
Explanation:
Serum amylase can be increased in acute parotitis, acute pancreatitis, and pancreatic cancer. Therefore, the correct answer is All of these.
Why other options are incorrect:
Why other options are incorrect:
- • Acute parotitis: Salivary gland inflammation can increase serum amylase.
- • Acute pancreatitis: Causes a marked elevation of serum amylase.
- • Pancreatic cancer: May cause elevated serum amylase in some patients.
- • All of these: Correct, because all three conditions can cause increased serum amylase.
Maximum rise in serum amylase occurs in
- a) Acute parotitis
- b) Acute pancreatitis
- c) Chronic pancreatitis
- d) Pancreatic cancer
Explanation:
The maximum rise in serum amylase occurs in acute pancreatitis. Serum amylase usually rises within a few hours of onset and can reach several times the normal upper limit.
Why other options are incorrect:
Why other options are incorrect:
- • Acute parotitis: Can cause an increase in serum amylase, mainly due to salivary gland involvement, but typically less marked.
- • Acute pancreatitis: Correct. It produces a marked elevation of serum amylase.
- • Chronic pancreatitis: Serum amylase is often normal or only mildly elevated.
- • Pancreatic cancer: May occasionally cause elevated amylase, but usually not as markedly as acute pancreatitis.
Serum lipase is increased in:
- a) Acute parotitis
- b) Acute pancreatitis
- c) Infective hepatitis
- d) Biliary obstruction
Explanation:
Serum lipase is highly specific for pancreatic disease. In acute pancreatitis, lipase is released into the blood, and its levels remain elevated for a longer period than serum amylase, making it a more sensitive and specific marker for the condition.
Why other options are incorrect:
Why other options are incorrect:
- • Acute parotitis: Amylase is elevated, but lipase levels typically remain normal because lipase is primarily pancreatic.
- • Infective hepatitis: Primarily involves liver enzymes (AST, ALT), not lipase.
- • Biliary obstruction: Typically leads to elevated alkaline phosphatase and bilirubin levels rather than lipase.
Which one of the following metabolites is not directly produced in the hexose monophosphate pathway?
- a) Fructose-6-phosphate
- b) Dihydroxy acetone phosphate
- c) CO2
- d) Erythrose-4-phosphate
Explanation:
The hexose monophosphate (HMP) pathway, also called the pentose phosphate pathway, directly produces CO2, fructose-6-phosphate, and erythrose-4-phosphate. Dihydroxyacetone phosphate is not a direct product of this pathway.
Why other options are incorrect:
Why other options are incorrect:
- • Fructose-6-phosphate: Produced during the non-oxidative phase of the HMP pathway.
- • Dihydroxy acetone phosphate: Correct. It is an intermediate of glycolysis and is not directly produced in the HMP pathway.
- • CO2: Released during the oxidative phase of the HMP pathway.
- • Erythrose-4-phosphate: Formed during the non-oxidative phase of the HMP pathway.
Which one of the following statements concerning glucose-6-phosphate dehydrogenase (G6PD) deficiency is correct?
- a) Young RBCs, particularly reticulocytes, contain the highest enzyme activity
- b) Glucose-6-P dehydrogenase deficiency leads to dysfunction of many tissues
- c) G-6-PD deficiency is due to a single deletion of a large sequence of DNA in the G-6-PD gene
- d) G-6-PD deficiency is precipitated by ingestion of drugs such as aspirin
Explanation:
G6PD is required for the production of NADPH in red blood cells. Since RBCs lack a nucleus and cannot synthesize new proteins, they rely on the enzyme present at the time of their release from the bone marrow. As RBCs age, the enzyme gradually degrades; therefore, young RBCs (reticulocytes) have the highest enzyme activity.
Why other options are incorrect:
Why other options are incorrect:
- • Dysfunction of many tissues: G6PD deficiency is primarily clinically significant in erythrocytes, as other tissues can compensate through alternative pathways or have better enzyme turnover.
- • Single deletion: Most G6PD variants are caused by point mutations rather than large deletions.
- • Aspirin: While aspirin should be used with caution, the classic drugs known to precipitate hemolysis in G6PD deficiency are primaquine, sulfonamides, and antimalarials, rather than aspirin.
The phenomenon of inhibition of glycolysis by O2 is termed as:
- a) Red drop
- b) Pasteur effect
- c) Michaelis effect
- d) Fischer’s effect
Explanation:
The “Pasteur effect” is the observation that the rate of glucose consumption (glycolysis) is significantly higher under anaerobic conditions compared to aerobic conditions. When oxygen is present, cells switch to oxidative phosphorylation, which is more efficient at producing ATP, leading to a down-regulation of glycolytic flux.
Why other options are incorrect:
Why other options are incorrect:
- • Red drop: Refers to a decrease in quantum efficiency of photosynthesis at long wavelengths of light.
- • Michaelis effect: Relates to enzyme kinetics (Michaelis-Menten).
- • Fischer’s effect: Generally refers to work in other biological contexts, such as the Bohr effect or lock-and-key model, but is not the term for aerobic inhibition of glycolysis.
Serotonin is derived in the body from the following amino acid:
- a) Phenylalanine
- b) Histidine
- c) Tryptophan
- d) Serine
Explanation:
Serotonin (5-hydroxytryptamine) is synthesized from the essential amino acid Tryptophan. The process involves two steps: hydroxylation of tryptophan to 5-hydroxytryptophan (by tryptophan hydroxylase) followed by decarboxylation to serotonin (by aromatic L-amino acid decarboxylase).
Why other options are incorrect:
Why other options are incorrect:
- • Phenylalanine: Precursor for tyrosine, dopamine, norepinephrine, and epinephrine.
- • Histidine: Precursor for histamine.
- • Serine: A non-essential amino acid involved in the synthesis of glycine, cysteine, and phospholipids like phosphatidylserine.
Which amino acid is a lipotropic factor?
- a) Lysine
- b) Leucine
- c) Tryptophan
- d) Methionine
Explanation:
Methionine is a classic lipotropic factor. Lipotropic factors are substances that help catalyze the breakdown of fat in the liver and prevent the accumulation of excess fat in the liver (fatty liver). Methionine acts as a methyl donor (in the form of S-adenosylmethionine) for the synthesis of choline, which is essential for the formation of phospholipids like phosphatidylcholine (lecithin) required for fat transport out of the liver.
Why other options are incorrect:
Why other options are incorrect:
- • Lysine & Leucine: These are essential amino acids used primarily for protein synthesis but do not possess lipotropic properties.
- • Tryptophan: An essential amino acid used for the synthesis of proteins, niacin, and serotonin, not involved in lipid transport in this manner.
Which among the following is a nutritionally essential amino acid for man?
- a) Alanine
- b) Glycine
- c) Tyrosine
- d) Tryptophan
Explanation:
Tryptophan is an essential amino acid in humans because it cannot be synthesized by the body in sufficient amounts and must therefore be obtained from the diet.
Why other options are incorrect:
Why other options are incorrect:
- • Alanine: A non-essential amino acid that can be synthesized by the body.
- • Glycine: A non-essential amino acid that can be synthesized in the body.
- • Tyrosine: A conditionally essential amino acid that can be synthesized from phenylalanine.
- • Tryptophan: An essential amino acid that must be supplied through the diet.
The essential amino acids:
- a) Must be supplied in the diet because the organism has lost the capacity to aminate the corresponding ketoacids
- b) Must be supplied in the diet because the human has an impaired ability to synthesize the carbon chain of the corresponding ketoacids
- c) Are identical in all species studied
- d) Are defined as those amino acids which cannot be synthesized by the organism at a rate adequate to meet metabolic requirements
Explanation:
The definition of an essential (or indispensable) amino acid is one that cannot be synthesized by an organism (or cannot be synthesized in sufficient quantities) to support growth and maintain health, and therefore must be supplied in the diet.
Why other options are incorrect:
Why other options are incorrect:
- • (a) and (b): These are too specific. While the inability to synthesize the carbon skeleton is the underlying biological reason, the definition is based on the organism’s overall inability to meet metabolic demand.
- • (c): Essential amino acids vary between different species (e.g., what is essential for humans may not be essential for certain microorganisms or rodents).
Which among the following is an essential amino acid?
- a) Cysteine
- b) Leucine
- c) Tyrosine
- d) Aspartic acid
Explanation:
Leucine is a branched-chain essential amino acid that the human body cannot synthesize; it must be obtained through dietary protein sources.
Why other options are incorrect:
Why other options are incorrect:
- • Cysteine: A non-essential amino acid that can be synthesized from the essential amino acid methionine.
- • Tyrosine: A non-essential amino acid that can be synthesized from the essential amino acid phenylalanine.
- • Aspartic acid: A non-essential amino acid that the body can synthesize from oxaloacetate via transamination.
Which among the following is a basic amino acid?
- a) Asparagine
- b) Arginine
- c) Proline
- d) Alanine
Explanation:
Arginine is classified as a basic amino acid. Basic amino acids are those that have a side chain with a positive charge at physiological pH (pH 7.4), primarily due to the presence of an extra amino or guanidino group. Lysine, Arginine, and Histidine are the three basic amino acids.
Why other options are incorrect:
Why other options are incorrect:
- • Asparagine: A polar, uncharged (amide-containing) amino acid.
- • Proline: A non-polar, imino acid.
- • Alanine: A non-polar, aliphatic amino acid.
This amino acid cannot have optical isomers:
- a) Alanine
- b) Histidine
- c) Threonine
- d) Glycine
Explanation:
Glycine is the simplest amino acid and is the only proteinogenic amino acid that does not have an optical isomer. This is because its side chain consists of a single hydrogen atom (-H). As a result, the alpha-carbon is bonded to two identical hydrogen atoms, meaning it lacks a chiral center (it is achiral).
Why other options are incorrect:
Why other options are incorrect:
- • Alanine, Histidine, & Threonine: All of these possess a chiral alpha-carbon atom (bonded to four different groups), allowing them to exist as L- and D-enantiomers.
The amino acid which contains a guanidine group is:
- a) Histidine
- b) Arginine
- c) Citrulline
- d) Ornithine
Explanation:
Arginine contains a guanidino group in its side chain. This group is highly basic and positively charged at physiological pH, which contributes to the basic nature of the amino acid.
Why other options are incorrect:
Why other options are incorrect:
- • Histidine: Contains an imidazole ring.
- • Citrulline: Contains a ureido group (-NH-CO-NH2), but not a guanidine group.
- • Ornithine: An amino acid involved in the urea cycle, but it contains a delta-amino group, not a guanidine group.
GABA (gamma-aminobutyric acid) is:
- a) Post-synaptic excitatory transmitter
- b) Post-synaptic inhibitor transmitter
- c) Activator of glia-cell function
- d) Inhibitor of glia-cell function
Explanation:
GABA is the primary inhibitory neurotransmitter in the central nervous system. It functions by binding to specific receptors (GABA-A and GABA-B) on the post-synaptic membrane, which typically leads to hyperpolarization (often by increasing chloride ion influx), thereby inhibiting the firing of the post-synaptic neuron.
Why other options are incorrect:
Why other options are incorrect:
- • Post-synaptic excitatory transmitter: This describes neurotransmitters like Glutamate, not GABA.
- • Glia-cell function: While GABA receptors are found on glia, GABA’s primary biological classification is as a neuronal inhibitory neurotransmitter.
Sulphur-containing amino acid is:
- a) Glutathione
- b) Chondroitin sulphate
- c) Homocysteine
- d) Tryptophan
Explanation:
Homocysteine is a sulfur-containing amino acid. It is a non-proteinogenic amino acid (an intermediate in the metabolism of methionine and cysteine). The primary proteinogenic sulfur-containing amino acids are methionine and cysteine.
Why other options are incorrect:
Why other options are incorrect:
- • Glutathione: This is a tripeptide (Glu-Cys-Gly), not an individual amino acid.
- • Chondroitin sulphate: This is a glycosaminoglycan (a structural component of cartilage), not an amino acid.
- • Tryptophan: This is an aromatic, heterocyclic amino acid, but it does not contain sulfur.
The useful reagent for detection of amino acids is:
- a) Molisch reagent
- b) Dichlorophenol Indophenol
- c) Ninhydrin
- d) Biuret
Explanation:
Ninhydrin is the standard reagent used to detect amino acids and peptides. When it reacts with the free amino group of an amino acid, it produces a characteristic deep blue or purple color (known as Ruhemann’s purple).
Why other options are incorrect:
Why other options are incorrect:
- • Molisch reagent: Used for the detection of carbohydrates.
- • Dichlorophenol Indophenol: Used as an indicator in redox titrations (e.g., for Vitamin C).
- • Biuret: Used for the detection of peptide bonds in proteins (it reacts with proteins to produce a violet color, but does not react with free amino acids).
The amino acid which contains an indole group is:
- a) Histidine
- b) Arginine
- c) Glycine
- d) Tryptophan
Explanation:
Tryptophan is a unique amino acid that contains an indole ring in its side chain. The indole group is a bicyclic structure consisting 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 ring.
- • Arginine: Contains a guanidine group.
- • Glycine: The simplest amino acid with only a hydrogen atom as its side chain.
Sakaguchi reaction is answered by:
- a) Lysine
- b) Ornithine
- c) Arginine
- d) Arginino succinic acid
Explanation:
The Sakaguchi reaction is a specific colorimetric test used for the detection of the guanidino group. Since Arginine is the only proteinogenic amino acid that contains a guanidino group, it gives a positive result in this test, typically producing a red or orange color.
Why other options are incorrect:
Why other options are incorrect:
- • Lysine: Contains an epsilon-amino group, not a guanidino group.
- • Ornithine: A basic amino acid with a delta-amino group.
- • Arginino succinic acid: Although it is an intermediate in the urea cycle involving arginine, the substituted guanidino group in this molecule typically does not produce a positive result in the standard Sakaguchi test.
The pH of an amino acid depends on:
- a) Optical rotation
- b) Dissociation constant
- c) Diffusion coefficient
- d) Chain length
Explanation:
The pH at which an amino acid exists in its zwitterionic form (isoelectric point, pI) is determined by its dissociation constants (pKa values) of the carboxyl and amino groups (and the side chain, if applicable). The pKa reflects the tendency of these ionizable groups to donate or accept protons.
Why other options are incorrect:
Why other options are incorrect:
- • Optical rotation: Relates to the ability of the molecule to rotate plane-polarized light, which is independent of its pH behavior.
- • Diffusion coefficient: Relates to the rate of movement of particles in a medium.
- • Chain length: Refers to the physical structure, whereas ionization behavior (pH) is defined by the chemical properties of the functional groups (pKa).
When amino acids are treated with neutral formaldehyde, the pH of the mixture
- a) Is not altered
- b) Increases
- c) Decreases
- d) First increases then decreases
Explanation:
When amino acids are treated with neutral formaldehyde, the amino group reacts with formaldehyde and loses its basic character. This reduces the zwitterionic/basic buffering effect and results in an increase in acidity, so the pH of the mixture decreases.
Why other options are incorrect:
Why other options are incorrect:
- • Is not altered: Formaldehyde reacts with the amino group and affects the acid-base balance.
- • Increases: The reaction does not make the mixture more alkaline.
- • Decreases: Correct. The amino group’s basic character is blocked by formaldehyde, causing the pH to fall.
- • First increases then decreases: The characteristic effect is a decrease in pH.
Which among the following has an imidazole group?
- a) Histidine
- b) Tryptophan
- c) Proline
- d) Hydroxy proline
Explanation:
Histidine is the only proteinogenic amino acid that contains an imidazole group in its side chain. The imidazole ring is a five-membered aromatic ring containing two nitrogen atoms, which makes histidine uniquely capable of acting as a buffer at physiological pH (near pH 6.0).
Why other options are incorrect:
Why other options are incorrect:
- • Tryptophan: Contains an indole ring.
- • Proline & Hydroxyproline: These contain a pyrrolidine ring (they are imino acids).
The amino acid exist as Zwitter ions when they are in
- a) Solid state
- b) Acidic solution
- c) Alkaline solution
- d) Neutral solution
Explanation:
In the solid state, amino acids exist as dipolar ions (Zwitter ions) due to strong electrostatic forces between the protonated amino group (-NH3⁺) and the deprotonated carboxyl group (-COO⁻).
Why other options are incorrect:
Why other options are incorrect:
- • Acidic solution: In highly acidic conditions, the carboxylate group gets protonated, resulting in a net positive charge.
- • Alkaline solution: In highly alkaline conditions, the amino group loses its proton, resulting in a net negative charge.
- • Neutral solution: While amino acids can exist as Zwitter ions in a neutral aqueous solution at their isoelectric point, the most stable and fundamental state where they *always* exist as Zwitter ions is the solid crystalline state.
Plasma proteins are isolated by:
- a) Salting out
- b) Electrophoresis
- c) Flourimetry
- d) Both (Salting out) and (Electrophoresis)
Explanation:
Plasma proteins can be separated or isolated using various techniques. “Salting out” (using salts like ammonium sulfate) is commonly used for precipitation, and “Electrophoresis” is the standard method for separating proteins based on their charge and size.
Why other options are incorrect:
Why other options are incorrect:
- • Flourimetry: This is a technique used for the measurement of fluorescence, typically used to quantify specific molecules, not for the general isolation of plasma proteins.
After digestion, amino acids:
- a) Are absorbed into portal circulation
- b) Are absorbed into lymph
- c) Are excreted to the extent of 50%
- d) Converted into glucose in the intestine
Explanation:
After protein digestion, the resulting amino acids are absorbed by the enterocytes of the small intestine and transported directly into the hepatic portal vein, which carries them to the liver.
Why other options are incorrect:
Why other options are incorrect:
- • Lymph: Primarily used for the absorption of dietary fats (chylomicrons), not amino acids.
- • Excretion: In a healthy individual, amino acids are efficiently absorbed and are not excreted in large amounts (50%).
- • Conversion: While the liver can convert amino acids into glucose (gluconeogenesis), this does not occur in the intestine as a standard part of absorption.
Cysteine has the formula:
- a) CH3SH
- b) H2N—CH2—COOH
- c) HS—CH2—CH(NH2)—COOH
- d) S—CH2—CH(NH2)—COOH | S—CH2—CH(NH2)—COOH
Explanation:
Cysteine is a sulfur-containing amino acid with the structural formula HS—CH2—CH(NH2)—COOH. The thiol (-SH) group is the defining characteristic of its side chain.
Why other options are incorrect:
Why other options are incorrect:
- • CH3SH: This is Methanethiol, not an amino acid.
- • H2N—CH2—COOH: This is the formula for Glycine, the simplest amino acid.
- • Option d: This represents Cystine (the oxidized dimer formed by two cysteine molecules joined by a disulfide bond).
The compound having the formula H2N—CO—NH—CH2—CH2—CH2—CH(NH2)—COOH is:
- a) Lysine
- b) Glutamine
- c) Serine
- d) Citrulline
Explanation:
The chemical formula represents Citrulline. It contains a ureido group (-NH-CO-NH2) attached to a propyl chain, which is a key intermediate in the Urea Cycle.
Why other options are incorrect:
Why other options are incorrect:
- • Lysine: Has an amino group (-NH2) at the end of its side chain, not a ureido group.
- • Glutamine: Contains an amide group (-CONH2) on a shorter carbon chain.
- • Serine: A much smaller amino acid containing a hydroxyl group (-OH).
An amino acid which contains a disulphide bond is:
- a) Lysine
- b) Methionine
- c) Homocysteine
- d) Cystine
Explanation:
Cystine is the oxidized dimer of two cysteine molecules, connected by a covalent disulfide bond (-S-S-). This bond is crucial for stabilizing the tertiary and quaternary structures of many proteins.
Why other options are incorrect:
Why other options are incorrect:
- • Lysine: A basic amino acid that does not contain sulfur.
- • Methionine: Contains sulfur in a thioether group (-S-CH3), not a disulfide bond.
- • Homocysteine: A sulfhydryl-containing amino acid similar to cysteine, but it exists as a free thiol group, not a disulfide bond.
One of the following has a phenolic group:
- a) Histidine
- b) Hydroxy lysine
- c) Seratonine
- d) Hydroxy proline
Explanation:
Serotonin (5-hydroxytryptamine) contains a phenolic hydroxyl group attached to the 5th position of its indole ring structure.
Why other options are incorrect:
Why other options are incorrect:
- • Histidine: Contains an imidazole ring.
- • Hydroxy lysine: An amino acid derivative containing a hydroxyl group, but it is an aliphatic alcohol, not phenolic.
- • Hydroxy proline: Contains an aliphatic hydroxyl group on the pyrrolidine ring.
An amino acid not containing the usual —COOH group is:
- a) Alanine
- b) Tryptophan
- c) Methionine
- d) Taurine
Explanation:
Taurine (2-aminoethanesulfonic acid) is a derivative of cysteine. Unlike standard amino acids that contain a carboxyl group (–COOH), taurine contains a sulfonic acid group (–SO₃H).
Why other options are incorrect:
Why other options are incorrect:
- • Alanine: A classic alpha-amino acid containing a –COOH group.
- • Tryptophan: Contains a standard carboxylic acid group at the alpha position.
- • Methionine: Like all standard proteinogenic amino acids, it contains a –COOH group at the alpha position.
Branched chain amino acids are:
- a) Cysteine and cystine
- b) Tyrosine and Tryptophan
- c) Glycine and Serine
- d) Valine, Leucine and Isoleucine
Explanation:
Valine, Leucine, and Isoleucine are known as Branched-Chain Amino Acids (BCAAs) because their side chains contain a carbon branch (a central carbon atom bound to three or more carbon atoms).
Why other options are incorrect:
Why other options are incorrect:
- • Cysteine/Cystine: These are sulfur-containing amino acids.
- • Tyrosine/Tryptophan: These are aromatic amino acids.
- • Glycine/Serine: These are polar, uncharged, or small amino acids, not branched-chain.
A Zwitter ion is one which has in aqueous solution:
- a) One positive charge and one negative charge
- b) Two positive charges and one negative charge
- c) Two negative charges and one positive charge
- d) No electrical charges at all
Explanation:
A zwitterion is a dipolar ion. In amino acids, this occurs at the isoelectric point where the carboxyl group loses a proton (becoming -COO⁻) and the amino group gains a proton (becoming -NH₃⁺), resulting in a net charge of zero.
Why other options are incorrect:
Why other options are incorrect:
- • Multiple charges (b & c): These would create a net positive or net negative charge, not a typical zwitterion state.
- • No charge (d): While the net charge is zero, it is not “uncharged”; it is a dipolar ion with both positive and negative centers.
The amino acid which gives yellow colour with Ninhydrin in paper chromatography is:
- a) Tyrosine
- b) Proline
- c) Tryptophan
- d) Alanine
Explanation:
Proline is an imino acid (it contains a secondary amine group). Unlike standard alpha-amino acids that react with ninhydrin to form a purple color, proline reacts to form a yellow-colored complex.
Why other options are incorrect:
Why other options are incorrect:
- • Tyrosine, Tryptophan, and Alanine: These are primary amino acids that produce the characteristic purple/blue color when reacting with ninhydrin.
Hydroxylation of Proline and Lysine in a protein is effected by:
- a) Vitamin B1
- b) Vitamin B2
- c) Vitamin B6
- d) Vitamin C
Explanation:
Vitamin C (Ascorbic acid) is essential for the activity of prolyl hydroxylase and lysyl hydroxylase enzymes. These enzymes hydroxylate proline and lysine residues in collagen, which is critical for the formation of stable collagen triple helices. A deficiency in Vitamin C leads to scurvy, characterized by defective collagen synthesis.
Why other options are incorrect:
Why other options are incorrect:
- • Vitamin B1 (Thiamine): Functions primarily in carbohydrate metabolism as a coenzyme.
- • Vitamin B2 (Riboflavin): Serves as a precursor for FAD and FMN in redox reactions.
- • Vitamin B6 (Pyridoxine): Primarily acts as a coenzyme in amino acid metabolism (e.g., transamination).
Millon’s test is for identification of:
- a) Tyrosine
- b) Tryptophan
- c) Proline
- d) Arginine
Explanation:
Millon’s test is positive for compounds containing a phenolic group. Among the amino acids, Tyrosine is the only one that contains a hydroxyphenyl 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:
- • Tryptophan: Identified by Hopkins-Cole test (indole ring).
- • Proline: Identified by the Ninhydrin test (producing a yellow color).
- • Arginine: Identified by the Sakaguchi test (guanidino group).
Hopkins-Cole test is for identification of:
- a) Tyrosine
- b) Tryptophan
- c) Arginine
- d) Cysteine
Explanation:
The Hopkins-Cole test is used to detect the presence of the indole ring of the amino acid Tryptophan. It involves the reaction of the indole ring with glyoxylic acid in the presence of concentrated sulfuric acid to produce a violet ring at the interface.
Why other options are incorrect:
Why other options are incorrect:
- • Tyrosine: Identified by Millon’s test (phenolic group).
- • Arginine: Identified by the Sakaguchi test (guanidino group).
- • Cysteine: Identified by the Lead sulfide test (sulfur group).
Collagen is very rich in:
- a) Glycine
- b) Serine
- c) Aspartic acid
- d) Glutamic acid
Explanation:
Collagen is characterized by a repeating sequence of (Glycine-X-Y)n, where X and Y are often Proline and Hydroxyproline. Glycine, being the smallest amino acid (having only a hydrogen atom as a side chain), is the only one small enough to occupy the crowded central position of the collagen triple helix.
Why other options are incorrect:
Why other options are incorrect:
- • Serine, Aspartic acid, and Glutamic acid: While present in collagen, they do not hold the structural significance of glycine and are not the primary amino acids defining the triple-helical structure.
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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