5451 to 5500 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 5451 to 5500
The metabolism of protein is integrated with that of carbohydrate and fat through
- a) Oxaloacetate
- b) Citrate
- c) Isocitrate
- d) Malate
Explanation:
Protein metabolism is integrated with carbohydrate and fat metabolism through Oxaloacetate, an important intermediate of the citric acid cycle. Amino acids can be converted into intermediates such as oxaloacetate, which connects amino acid metabolism with glucose and fatty acid metabolism.
Why other options are incorrect:
Why other options are incorrect:
- • Citrate: It participates in the citric acid cycle but is not the primary connecting intermediate intended here.
- • Isocitrate: It is a citric acid cycle intermediate but does not serve as the principal link for protein metabolism in this context.
- • Malate: It is also a citric acid cycle intermediate, but oxaloacetate is the key connecting point.
The building up and breaking down of protoplasm are concerned with the metabolism of
- a) Carbohydrate
- b) Lipid
- c) Protein
- d) Minerals
Explanation:
Protoplasm is primarily composed of proteins, which are the fundamental structural and functional components of living cells. Protein metabolism (anabolism and catabolism) is directly responsible for the synthesis and maintenance of protoplasmic structures.
Why other options are incorrect:
Why other options are incorrect:
- • Carbohydrate: Primarily used for short-term energy storage and structural support (like cellulose), rather than the main building block of protoplasm.
- • Lipid: While essential for membranes, lipids do not form the bulk of the metabolic turnover associated with protoplasm synthesis.
- • Minerals: These act as cofactors and regulators in metabolic processes but do not constitute the primary mass that is “built up” or “broken down” as protoplasm.
The amino acids abstracted from the liver are not utilized for repair or special synthesis but are broken down to
- a) Keto acids
- b) Sulphur dioxide
- c) Water
- d) Ammonia
Explanation:
When amino acids are not needed for protein synthesis, they undergo deamination in the liver. The amino group is removed, and the remaining carbon skeleton is converted into alpha-keto acids, which can enter the Krebs cycle to produce energy.
Why other options are incorrect:
Why other options are incorrect:
- • Sulphur dioxide: This is an atmospheric pollutant and is not a product of human amino acid metabolism.
- • Water: While water is a byproduct of cellular respiration, it is not the primary breakdown product of the amino acid carbon skeleton.
- • Ammonia: Although ammonia is released during the deamination process, it is a byproduct of the nitrogenous group, not the primary “keto acid” structure that remains after the transformation.
The unwanted amino acids abstracted from the tissues are either used up by the tissue or in the liver converted into
- a) Ammonia
- b) Urea
- c) Ammonium salts
- d) Uric acid
Explanation:
In the liver, the toxic ammonia produced from the deamination of excess amino acids is processed through the Urea Cycle and converted into Urea, which is a less toxic substance that can be safely excreted by the kidneys.
Why other options are incorrect:
Why other options are incorrect:
- • Ammonia: This is a highly toxic intermediate formed during deamination; the liver converts it into urea to prevent poisoning.
- • Ammonium salts: While ammonia can form salts, they are not the primary metabolic product for excretion in humans.
- • Uric acid: This is the end product of purine (nucleotide) metabolism, not the primary end product of protein/amino acid metabolism in humans.
The metabolism of all proteins ingested over and above the essential requirements is called
- a) Exogenous metabolism
- b) Endogenous metabolism
- c) Both (Exogenous metabolism) and (Endogenous metabolism)
- d) None of these
Explanation:
Exogenous metabolism refers to the breakdown and utilization of proteins that are obtained from external dietary sources (ingested proteins). When protein intake exceeds the body’s requirement for tissue repair and maintenance, the excess is metabolized exogenously.
Why other options are incorrect:
Why other options are incorrect:
- • Endogenous metabolism: This refers to the breakdown of proteins that are already part of the body’s own tissues (internal protein turnover).
- • Both: These are distinct processes; the metabolism of dietary protein specifically falls under exogenous metabolism.
- • None of these: Since “Exogenous metabolism” is the correct scientific term for dietary protein breakdown, this is incorrect.
Sulphur containing amino acids after catabolism produces a substance which is excreted:
- a) SO2
- b) HNO3
- c) H2SO4
- d) H3PO4
Explanation:
The catabolism of sulfur-containing amino acids (such as methionine and cysteine) results in the oxidation of the sulfur atom. This process produces sulfate ions, which are excreted in the urine, primarily as inorganic sulfates (H2SO4 or salts thereof).
Why other options are incorrect:
Why other options are incorrect:
- • SO2: Sulfur dioxide is a gas and is not a physiological end-product of amino acid metabolism in the human body.
- • HNO3: Nitric acid is not produced as an end-product of protein catabolism.
- • H3PO4: Phosphoric acid is derived from the catabolism of phosphorus-containing compounds like nucleic acids and phospholipids, not sulfur-containing amino acids.
Ethereal sulphate is synthesized from the _ amino acid.
- a) Neutral
- b) Acidic
- c) Basic
- d) Sulphur containing
Explanation:
Ethereal sulfates (also known as conjugated sulfates) are formed in the liver through the conjugation of phenols and other toxic compounds with sulfate groups. These sulfate groups are derived from the metabolism of sulfur-containing amino acids, primarily methionine and cysteine.
Why other options are incorrect:
Why other options are incorrect:
- • Neutral, Acidic, and Basic: These categories describe the chemical nature of amino acids based on their side chains, but they do not specifically designate the source of the sulfur required for the synthesis of ethereal sulfates.
The amino acids required for creatine formation:
- a) Glycine
- b) Arginine
- c) Methionine
- d) All of these
Explanation:
The synthesis of creatine is a multi-step process involving three amino acids: Arginine and Glycine combine to form guanidinoacetate, and Methionine (in the form of S-adenosylmethionine) provides the methyl group to convert guanidinoacetate into creatine.
Why other options are incorrect:
Why other options are incorrect:
- • Individual selections (a, b, c): These are each individually correct as components of the pathway, but since all three are required for the final product, “All of these” is the comprehensive answer.
In human and other ureotelic organisms, the end product of amino acid nitrogen metabolism:
- a) Bile acids
- b) Ketone bodies
- c) Urea
- d) Barium sulphate
Explanation:
Ureotelic organisms (such as humans) excrete nitrogenous waste primarily in the form of urea. During the metabolism of amino acids, the nitrogen group is removed (deamination) and converted into toxic ammonia, which the liver then processes into urea through the Urea Cycle for safe excretion.
Why other options are incorrect:
Why other options are incorrect:
- • Bile acids: These are synthesized from cholesterol in the liver and are involved in fat digestion, not nitrogen metabolism.
- • Ketone bodies: These are produced during the metabolism of fatty acids and some amino acids as an alternative energy source, not as the primary nitrogenous waste product.
- • Barium sulphate: This is an inorganic salt used in medical imaging (like barium meals) and has no role in biological nitrogen metabolism.
The end product of amino acid nitrogen metabolism in uricotelic organisms (reptiles and birds) is
- a) Bilirubin
- b) Urea
- c) Uric acid
- d) Biliverdin
Explanation:
Uricotelic organisms, such as birds and reptiles, excrete nitrogenous waste in the form of uric acid. This is an evolutionary adaptation to conserve water, as uric acid is relatively insoluble and can be excreted as a semi-solid paste.
Why other options are incorrect:
Why other options are incorrect:
- • Bilirubin & Biliverdin: These are bile pigments produced from the breakdown of heme (hemoglobin), not nitrogenous waste from amino acids.
- • Urea: This is the primary nitrogenous waste product for ureotelic organisms like mammals, but not for uricotelic organisms.
The transaminase activity needs the coenzyme:
- a) ATP
- b) B6 – PO4
- c) FAD+
- d) NAD+
Explanation:
Transaminase enzymes (also known as aminotransferases) require Pyridoxal Phosphate (PLP), which is the active form of Vitamin B6 (B6 – PO4), as an essential coenzyme. It acts as a carrier of amino groups during the transfer process from an amino acid to an alpha-keto acid.
Why other options are incorrect:
Why other options are incorrect:
- • ATP: Adenosine triphosphate is a source of chemical energy, not a specific cofactor for transamination.
- • FAD+ and NAD+: These are coenzymes involved in oxidation-reduction (redox) reactions, particularly in electron transport and metabolic pathways like the Krebs cycle.
Transamination is a
- a) Irreversible process
- b) Reversible process
- c) Both (Irreversible process) and (Reversible process)
- d) None of these
Explanation:
Transamination is a reversible reaction catalyzed by aminotransferases. The amino group is transferred from an amino acid to an alpha-keto acid, and the reaction can proceed in either direction depending on the relative concentrations of the substrates and products within the cell.
Why other options are incorrect:
Why other options are incorrect:
- • Irreversible process: Many metabolic pathways have irreversible steps, but transamination specifically functions to maintain equilibrium between amino acids and keto acids, making it reversible.
- • Both: A reaction cannot be both fundamentally irreversible and reversible at the same time in this biological context.
Most amino acids are substrates for transamination except
- a) Alanine
- b) Threonine
- c) Serine
- d) Valine
Explanation:
While most amino acids participate in transamination reactions to funnel nitrogen into metabolic pathways, there are a few exceptions. Threonine, Lysine, and Proline do not undergo transamination. Threonine is instead broken down through direct dehydration or deamination.
Why other options are incorrect:
Why other options are incorrect:
- • Alanine: A classic example of an amino acid that undergoes transamination to form pyruvate.
- • Serine: Can be converted to pyruvate via serine dehydratase, but also participates in other metabolic exchanges.
- • Valine: A branched-chain amino acid that readily undergoes transamination as the first step of its catabolism.
Oxidative conversion of many amino acids to their corresponding α-ketoacids occurs in mammalian:
- a) Liver and kidney
- b) Adipose tissue
- c) Pancreas
- d) Intestine
Explanation:
The liver and kidneys are the primary sites for amino acid catabolism in mammals. These organs possess the necessary enzymes (such as L-amino acid oxidases and various aminotransferases) to facilitate the oxidative deamination and transamination required to convert amino acids into α-ketoacids for energy production or gluconeogenesis.
Why other options are incorrect:
Why other options are incorrect:
- • Adipose tissue: Primarily involved in lipid storage and metabolism, not the bulk oxidative catabolism of amino acids.
- • Pancreas: Functions mainly in producing digestive enzymes and hormones like insulin; it is not a major site for systemic amino acid catabolism.
- • Intestine: Primarily concerned with the absorption of nutrients, though some limited amino acid metabolism occurs here, it is not the main site for the conversion described.
The α-ketoacid is decarboxylated by H2O2 forming a carboxylic acid with one carbon atom less in the absence of the enzyme:
- a) Catalase
- b) Decarboxylase
- c) Deaminase
- d) Phosphatase
Explanation:
The oxidative decarboxylation of α-ketoacids by hydrogen peroxide (H2O2) is a non-enzymatic reaction. In the body, the enzyme Catalase effectively breaks down H2O2 into water and oxygen, preventing it from participating in such uncontrolled non-enzymatic decarboxylation reactions.
Why other options are incorrect:
Why other options are incorrect:
- • Decarboxylase: This is a specific enzyme that facilitates the removal of a carboxyl group in a controlled biological manner, not via H2O2.
- • Deaminase: This enzyme is responsible for removing an amino group from an amino acid, not for oxidative decarboxylation of ketoacids.
- • Phosphatase: This enzyme removes phosphate groups from molecules and is unrelated to this chemical process.
The activity of mammalian L-amino acid oxidase, an FMN – flavo protein, is quite
- a) Slow
- b) Rapid
- c) Both (Slow ) and (Rapid)
- d) None of these
Explanation:
The L-amino acid oxidase found in mammalian tissues exhibits very low (slow) activity compared to other enzymes involved in amino acid metabolism. Because of this, it is not considered the primary pathway for the deamination of L-amino acids in mammals; transamination is the much faster and more efficient pathway.
Why other options are incorrect:
Why other options are incorrect:
- • Rapid: If this enzyme were rapid, it would likely cause excessive production of hydrogen peroxide and rapid breakdown of essential amino acids, which is not the case in mammalian physiology.
- • Both: Biological activity is generally characterized by specific kinetic rates, and this enzyme is specifically noted for its sluggishness in mammalian systems.
From dietary protein as well as from the urea present in fluids secreted into the gastrointestinal tract intestinal bacteria produce
- a) Carbondioxide
- b) Ammonia
- c) Ammonium sulphate
- d) Creatine
Explanation:
Intestinal bacteria contain the enzyme urease, which breaks down the urea secreted into the gut into ammonia and carbon dioxide. Additionally, these bacteria catabolize undigested dietary proteins (via putrefaction) into ammonia, which is then absorbed into the portal circulation and sent to the liver.
Why other options are incorrect:
Why other options are incorrect:
- • Carbondioxide: While produced as a byproduct of urease activity, ammonia is the primary nitrogenous product of concern in this metabolic context.
- • Ammonium sulphate: This is not a direct metabolic product of intestinal bacterial action on protein or urea.
- • Creatine: This is a product of amino acid synthesis in the body, not a byproduct of intestinal bacterial degradation.
The symptom of ammonia intoxication includes
- a) Blurring of vision
- b) Constipation
- c) Mental confusion
- d) Diarrhoea
Explanation:
Ammonia is highly neurotoxic. When the liver is unable to detoxify ammonia into urea (as seen in liver failure), high levels of ammonia accumulate in the blood and enter the brain. This leads to neurological symptoms collectively known as hepatic encephalopathy, characterized prominently by mental confusion, tremors (asterixis), and in severe cases, coma.
Why other options are incorrect:
Why other options are incorrect:
- • Blurring of vision: Not a primary clinical sign of hyperammonemia.
- • Constipation/Diarrhoea: These are gastrointestinal symptoms and are not direct clinical indicators of ammonia poisoning in the central nervous system.
Ammonia intoxication symptoms occur when brain ammonia levels are
- a) Slightly diminished
- b) Highly diminished
- c) Increased
- d) All of these
Explanation:
Ammonia is extremely toxic to the central nervous system. Under normal conditions, the liver converts ammonia to urea. When ammonia levels in the brain increase (hyperammonemia), it disrupts neurotransmitter balance, alters cerebral energy metabolism, and causes astrocyte swelling, leading to clinical symptoms of intoxication.
Why other options are incorrect:
Why other options are incorrect:
- • Diminished levels: A decrease in ammonia does not cause toxicity; rather, it is the accumulation (excess) of ammonia that is pathological.
- • All of these: Since diminished levels do not cause intoxication, this is clearly incorrect.
Ammonia production by the kidney is depressed in
- a) Acidosis
- b) Alkalosis
- c) Both (Acidosis ) and (Alkalosis)
- d) None of these
Explanation:
The kidney produces ammonia to act as a buffer for hydrogen ions, which helps in the excretion of acid. During acidosis, the kidneys significantly increase ammonia production to help restore pH balance. Conversely, during alkalosis (when the blood pH is too high), the body decreases this production to prevent further loss of acid.
Why other options are incorrect:
Why other options are incorrect:
- • Acidosis: In this state, ammonia production is stimulated (increased) to combat the high acidity.
- • Both: Ammonia production is upregulated in acidosis and downregulated in alkalosis, so they are opposites.
Ammonia is excreted as ammonium salts during metabolic acidosis but the majority is excreted as
- a) Phosphates
- b) Creatine
- c) Uric acid
- d) Urea
Explanation:
While the kidneys can produce and excrete ammonium (NH4+) as a mechanism to buffer and remove acid during metabolic acidosis, the vast majority of nitrogenous waste in humans is converted by the liver into urea through the Urea Cycle and then excreted by the kidneys under normal physiological conditions.
Why other options are incorrect:
Why other options are incorrect:
- • Phosphates: These are urinary buffers but are not the nitrogenous end-product of protein metabolism.
- • Creatine: This is a nitrogenous compound, but it is not the primary form in which excreted nitrogenous waste is packaged.
- • Uric acid: This is a minor pathway for nitrogen excretion in humans, typically associated with the breakdown of purines, not the bulk of amino acid nitrogen.
Synthesis of glutamine is accompanied by the hydrolysis of
- a) ATP
- b) ADP
- c) TPP
- d) Creatin phosphate
Explanation:
The synthesis of glutamine from glutamate and ammonia is catalyzed by the enzyme glutamine synthetase. This reaction is endergonic and requires energy, which is provided by the hydrolysis of one molecule of Adenosine Triphosphate (ATP) into ADP and inorganic phosphate.
Why other options are incorrect:
Why other options are incorrect:
- • ADP: This is a product of ATP hydrolysis, not the energy-donating substrate itself.
- • TPP: Thiamine pyrophosphate is a coenzyme used in decarboxylation reactions, not for glutamine synthesis.
- • Creatine phosphate: This acts as a high-energy phosphate reserve for muscle contraction, not for the synthesis of glutamine.
In brain, the major metabolism for removal of ammonia is the formation of
- a) Glutamate
- b) Aspartate
- c) Asparagine
- d) Glutamine
Explanation:
Since the brain lacks a complete urea cycle, it utilizes glutamine synthetase to detoxify ammonia. Ammonia reacts with glutamate in the presence of ATP to form glutamine. This is the primary mechanism for ammonia detoxification in the central nervous system.
Why other options are incorrect:
Why other options are incorrect:
- • Glutamate: This is actually the substrate that combines with ammonia to form glutamine.
- • Aspartate: While involved in the urea cycle, it is not the primary end-product for ammonia removal in the brain.
- • Asparagine: Not the primary detoxification product for ammonia in brain tissue.
Carbamoyl phosphate synthetase structure is marked by change in the presence of
- a) N-Acetyl glutamate
- b) N-Acetyl Aspartate
- c) Neuraminic acid
- d) Oxalate
Explanation:
Carbamoyl phosphate synthetase I (CPS I), the rate-limiting enzyme of the urea cycle, requires N-Acetylglutamate (NAG) as an essential allosteric activator. NAG binds to the enzyme, causing a conformational change that increases its activity, thereby linking the urea cycle rate to the availability of amino acids.
Why other options are incorrect:
Why other options are incorrect:
- • N-Acetyl Aspartate: Found in the brain, but it is not the regulator for urea cycle enzymes.
- • Neuraminic acid: A component of glycoproteins and glycolipids, not involved in urea cycle regulation.
- • Oxalate: A metabolic end-product often associated with kidney stones; it has no regulatory role in carbamoyl phosphate synthesis.
The biosynthesis of Urea occurs mainly in the Liver:
- a) Cytosol
- b) Microsomes
- c) Nucleus
- d) Mitochondria
Explanation:
The Urea cycle is a compartmentalized process. The first two steps—the formation of carbamoyl phosphate and the synthesis of citrulline—occur inside the mitochondria of the liver cells. The remaining steps of the cycle take place in the cytosol. Because the initial and rate-limiting step occurs here, the mitochondria are the primary site for the start of urea biosynthesis.
Why other options are incorrect:
Why other options are incorrect:
- • Cytosol: While the cycle is completed here, the process cannot begin without the mitochondrial steps.
- • Microsomes: These are involved in protein synthesis and detoxification (like cytochrome P450), not the urea cycle.
- • Nucleus: The nucleus is the site of genetic material storage and transcription, not metabolic cycles like urea synthesis.
One mol. of Urea is synthesized at the expense of the _ mols. of ATP.
- a) 2
- b) 3
- c) 4
- d) 5
Explanation:
The synthesis of one molecule of urea through the urea cycle consumes 4 high-energy phosphate bonds. Three ATP molecules are used, but one ATP is converted to AMP and therefore consumes two high-energy phosphate bonds, making the total energy cost equivalent to 4 ATP.
Why other options are incorrect:
Why other options are incorrect:
- • 2: Fewer than the actual high-energy phosphate bonds required.
- • 3: Three ATP molecules are consumed, but the energy expenditure is equivalent to 4 ATP high-energy phosphate bonds.
- • 5: More energy than required for one urea molecule.
The normal daily output of Urea through urine in grams:
- a) 10 to 20
- b) 15 to 25
- c) 20 to 30
- d) 25 to 35
Explanation:
The amount of urea excreted in the urine is the primary reflection of protein intake and metabolic turnover. In a healthy adult with a normal protein intake, the average daily urinary urea excretion typically ranges from 20 to 30 grams.
Why other options are incorrect:
Why other options are incorrect:
- • 10 to 20: This range is generally considered low, often seen in individuals with restricted protein intake or certain renal conditions.
- • 15 to 25: While closer to the average, it sits on the lower end for a standard healthy adult diet.
- • 25 to 35: This is a slightly higher range; while possible, it is not the standard “normal” clinical average compared to the 20-30g window.
In severe acidosis, the output of urea is
- a) Decreased
- b) Slightly increased
- c) Highly increased
- d) Moderately increased
Explanation:
In states of severe acidosis, the kidneys prioritize the excretion of hydrogen ions (H+). To facilitate this, the kidney increases the production of ammonia (NH3) to act as a buffer, which is excreted as ammonium (NH4+). Because more nitrogen is diverted toward ammonia/ammonium production to manage acidity, the liver’s conversion of ammonia into urea is correspondingly decreased.
Why other options are incorrect:
Why other options are incorrect:
- • Increased (Slightly/Moderately/Highly): If urea output increased, it would imply the body is effectively processing nitrogenous waste normally, whereas in acidosis, the metabolic pathway for nitrogen is shifted toward buffering (ammonia/ammonium) rather than urea synthesis.
Uremia occurs in
- a) Cirrhosis of the liver
- b) Nephritis
- c) Diabetes mellitus
- d) Coronary thrombosis
Explanation:
Uremia refers to the clinical syndrome resulting from the accumulation of nitrogenous waste products (primarily urea) in the blood due to inadequate renal (kidney) function. Nephritis, which involves inflammation of the kidneys, leads to renal failure and is a classic cause of uremia.
Why other options are incorrect:
Why other options are incorrect:
- • Cirrhosis of the liver: This primarily affects the liver’s ability to produce urea from ammonia; it often leads to hyperammonemia, not uremia.
- • Diabetes mellitus: Primarily a disorder of glucose metabolism.
- • Coronary thrombosis: A cardiovascular condition (heart attack) that does not directly cause the retention of nitrogenous wastes in the blood.
Clinical symptom in urea cycle disorder is
- a) Mental retardation
- b) Drowsiness
- c) Diarrhoea
- d) Oedema
Explanation:
Urea cycle disorders result in the inability to detoxify ammonia, leading to chronic or recurrent hyperammonemia. This is highly neurotoxic, and if left untreated, it causes irreversible brain damage, resulting in developmental delays and mental retardation.
Why other options are incorrect:
Why other options are incorrect:
- • Drowsiness: This is a symptom of acute hyperammonemic episodes, but “mental retardation” is the classic developmental clinical outcome of the disorder.
- • Diarrhoea/Oedema: These are not specific or primary clinical features of urea cycle metabolic defects.
The sparing action of methionine is
- a) Tyrosine
- b) Cystine
- c) Arginine
- d) Tryptophan
Explanation:
Methionine is a sulfur-containing essential amino acid. The body can convert methionine to cysteine (which forms cystine). Therefore, if a diet provides an adequate amount of cystine, the requirement for methionine is reduced because the body no longer needs to break down as much methionine to produce the cysteine it requires. This is known as the “sparing action.”
Why other options are incorrect:
Why other options are incorrect:
- • Tyrosine: This amino acid spares phenylalanine, not methionine.
- • Arginine/Tryptophan: These amino acids have different metabolic pathways and do not have a direct sparing relationship with the sulfur-containing methionine/cystine pool.
NH4+ aminates glutamate to form glutamine requiring ATP and
- a) K+
- b) Na+
- c) Ca++
- d) Mg++
Explanation:
The synthesis of glutamine from glutamate and ammonia is catalyzed by the enzyme glutamine synthetase. This reaction is ATP-dependent and requires divalent metal ions, typically Magnesium (Mg++) or Manganese (Mn++), as cofactors to facilitate the transfer of the phosphate group from ATP.
Why other options are incorrect:
Why other options are incorrect:
- • K+ and Na+: Monovalent cations like potassium and sodium are not the specific enzymatic cofactors required for the glutamine synthetase reaction mechanism.
- • Ca++: Calcium ions often act as secondary messengers in cellular signaling but are not the catalytic cofactors for this specific metabolic step.
Glutathione is a
- a) Dipeptide
- b) Tripeptide
- c) Polypeptide
- d) None of these
Explanation:
Glutathione is a tripeptide composed of three amino acids: Glutamate, Cysteine, and Glycine. It plays a crucial role as an antioxidant in the body, protecting cells from oxidative stress and damage by neutralizing free radicals.
Why other options are incorrect:
Why other options are incorrect:
- • Dipeptide: This would imply only two amino acids, which is incorrect for glutathione.
- • Polypeptide: While it is technically a short peptide, the term “tripeptide” is the specific and correct classification for its three-residue structure.
All following are conjugated proteins except
- a) Nucleoproteins
- b) Proteoses
- c) Metalloproteins
- d) Flavoproteins
Explanation:
Conjugated proteins are proteins that contain a non-protein component (prosthetic group) attached to the polypeptide chain. Nucleoproteins, Metalloproteins, and Flavoproteins all possess specific prosthetic groups. Proteoses, however, are intermediate breakdown products (derived proteins) formed during the hydrolysis of proteins, not conjugated proteins.
Why other options are incorrect:
Why other options are incorrect:
- • Nucleoproteins: Contain nucleic acids as the prosthetic group.
- • Metalloproteins: Contain metal ions as the prosthetic group.
- • Flavoproteins: Contain flavin nucleotides (FAD/FMN) as the prosthetic group.
All α-amino acids have one asymmetric carbon atom except:
- a) Arginine
- b) Glycine
- c) Aspartic acid
- d) Histidine
Explanation:
Glycine is the simplest amino acid with the formula NH₂-CH₂-COOH. Its α-carbon atom is attached to two identical hydrogen atoms, which makes it achiral (optically inactive). All other α-amino acids have at least one chiral center.
Why other options are incorrect:
Why other options are incorrect:
- • Arginine: Contains a chiral α-carbon atom and is optically active.
- • Aspartic acid: Contains a chiral α-carbon atom and is optically active.
- • Histidine: Contains a chiral α-carbon atom and is optically active.
Number of amino acids present in plants, animals and microbial proteins:
- a) 20
- b) 80
- c) 150
- d) 200
Explanation:
There are 20 standard amino acids that serve as the building blocks for proteins in virtually all living organisms, including plants, animals, and microorganisms.
Why other options are incorrect:
Why other options are incorrect:
- • 80, 150, and 200: These figures do not represent the set of standard proteinogenic amino acids found across different biological kingdoms. While many non-proteinogenic amino acids exist in nature, only 20 are universally coded by DNA to form proteins.
Hydrated density of (HD) lipoproteins is:
- a) 0.94 gm/ml
- b) 0.94-1.006 gm/ml
- c) 1.006-1.063 gm/ml
- d) 1.063-1.21 gm/ml
Explanation:
High-Density Lipoproteins (HDL) are characterized by their high protein-to-lipid ratio, which results in a higher density compared to other lipoproteins, typically ranging between 1.063 and 1.21 gm/ml.
Why other options are incorrect:
Why other options are incorrect:
- • 0.94 gm/ml: This is characteristic of Chylomicrons (the least dense).
- • 0.94-1.006 gm/ml: This range corresponds to Very Low-Density Lipoproteins (VLDL).
- • 1.006-1.063 gm/ml: This range corresponds to Low-Density Lipoproteins (LDL).
The bond in proteins that is not broken 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 structures of a protein. Peptide bonds, which constitute the primary structure (the sequence of amino acids), remain intact during standard denaturation processes.
Why other options are incorrect:
Why other options are incorrect:
- • Hydrophobic bond: These weak interactions are disrupted by heat and organic solvents.
- • Hydrogen bond: These are easily broken by heat, pH changes, and urea.
- • Disulphide bond: While stronger, these can be broken by specific reducing agents or high-intensity denaturation, unlike the stable backbone peptide bond.
Plasma proteins act as
- a) Buffers
- b) Immunoglobulins
- c) Reserve proteins
- d) All of these
Explanation:
Plasma proteins perform several important functions. They act as buffers to help maintain blood pH, include immunoglobulins that provide immune defense, and can serve as a reserve source of amino acids/protein. Therefore, all of these are correct.
Why other options are incomplete:
Why other options are incomplete:
- • Buffers: Plasma proteins help maintain the acid–base balance of blood.
- • Immunoglobulins: These plasma proteins function as antibodies in immune responses.
- • Reserve proteins: Plasma proteins can act as a circulating protein reserve.
Group that reacts in the Biuret test:
- a) Peptide
- b) Amino group
- c) Carboxylic group
- d) Aldehyde group
Explanation:
The Biuret test detects peptide bonds present in proteins and peptides. In an alkaline solution, copper ions react with peptide bonds to produce a violet or purple-colored complex.
Why other options are incorrect:
Why other options are incorrect:
- • Amino group: The Biuret test does not specifically detect free amino groups.
- • Carboxylic group: Carboxyl groups are not responsible for the Biuret reaction.
- • Aldehyde group: Aldehyde groups are not detected by the Biuret test.
In nitroprusside test, amino acid cysteine produces a:
- a) Red colour
- b) Blue colour
- c) Yellow colour
- d) Purple colour
Explanation:
In the nitroprusside test, cysteine gives a purple colour due to the reaction of its sulfhydryl (-SH) group with sodium nitroprusside under alkaline conditions.
Why other options are incorrect:
Why other options are incorrect:
- • Red colour: Cysteine does not produce a red colour in the nitroprusside test.
- • Blue colour: Blue is not the characteristic colour produced by cysteine in this test.
- • Yellow colour: Yellow is not the positive reaction colour for cysteine in the nitroprusside test.
Protein present in hemoglobin has the structure known as:
- a) Primary
- b) Secondary
- c) Tertiary
- d) Quaternary
Explanation:
Hemoglobin has a quaternary structure because it consists of four
polypeptide subunits: two α (alpha) chains and two β (beta) chains.
These subunits work together to form functional hemoglobin.
Why other options are incorrect:
Why other options are incorrect:
- • Primary: Refers to the linear sequence of amino acids in a polypeptide chain.
- • Secondary: Refers mainly to local structures such as α-helices and β-sheets.
- • Tertiary: Refers to the three-dimensional structure of a single polypeptide chain.
Isoelectric pH of an amino acid is that pH at which it has a:
- a) Positive charge
- b) Negative charge
- c) Nil net charge
- d) None of these
Explanation:
The isoelectric point (pI) is the pH at which an amino acid exists
predominantly as a zwitterion and has a net electrical charge of zero.
At this pH, the positive and negative charges balance each other.
Why other options are incorrect:
Why other options are incorrect:
- • Positive charge: This occurs at pH values below the isoelectric point.
- • Negative charge: This occurs at pH values above the isoelectric point.
- • None of these: Incorrect because the amino acid has a nil net charge at its isoelectric pH.
Albuminoids are similar to:
- a) Albumin
- b) Globulin
- c) Both (Albumin) and (Globulin)
- d) None of these
Explanation:
Albuminoids, also called scleroproteins, are fibrous proteins that have
properties similar to both albumins and globulins in certain chemical
characteristics. Examples include collagen, elastin, and keratin.
Why other options are incorrect:
Why other options are incorrect:
- • Albumin: Albuminoids are a distinct class of proteins, although they share some properties with albumin.
- • Globulin: Albuminoids are not classified as globulins, although they share certain properties with them.
- • None of these: Incorrect because albuminoids have similarities with both albumin and globulin.
Optical isomers of all amino acids exist except
- a) Glycine
- b) Arginine
- c) Alanine
- d) Hydroxy proline
Explanation:
Glycine is the only standard amino acid that does not have optical isomers because its side chain is a hydrogen atom. Therefore, glycine has no chiral center and is optically inactive.
Why other options are incorrect:
Why other options are incorrect:
- • Arginine: Has a chiral α-carbon and therefore exists as optical isomers.
- • Alanine: Has a chiral α-carbon because its side chain is a methyl group.
- • Hydroxyproline: Has a chiral center and therefore exhibits optical activity.
Proteins that constitute keratin, collagen and elastin in body are
- a) Protamines
- b) Phosphol proteins
- c) Scleroproteins
- d) Metaproteins
Explanation:
Scleroproteins, also called fibrous proteins, are structural proteins that provide strength and support to body tissues. Keratin, collagen, and elastin are important examples of scleroproteins.
Why other options are incorrect:
Why other options are incorrect:
- • Protamines: These are small, strongly basic proteins associated mainly with nucleic acids in sperm cells.
- • Phosphol proteins: These are not the structural protein group that includes keratin, collagen, and elastin.
- • Metaproteins: These are denatured protein derivatives formed by the action of acids or bases.
Systematic name of lysine is
- a) Amino acetic acid
- b) 2,6-Diaminohexanoic acid
- c) Aminosuccinic acid
- d) 2-Aminopropanoic acid
Explanation:
The systematic name of lysine is 2,6-diaminohexanoic acid. It contains two amino groups, one at the α-carbon (carbon 2) and another at the ε-carbon (carbon 6).
Why other options are incorrect:
Why other options are incorrect:
- • Amino acetic acid: This is the systematic name of glycine.
- • Aminosuccinic acid: This refers to aspartic acid.
- • 2-Aminopropanoic acid: This is the systematic name of alanine.
Side chains of all following amino acids contain aromatic rings except
- a) Phenylalanine
- b) Alanine
- c) Tyrosine
- d) Tryptophan
Explanation:
Alanine is the correct answer because its side chain is a simple methyl group (-CH₃), which does not contain an aromatic ring. In contrast, phenylalanine, tyrosine, and tryptophan all contain aromatic rings in their side chains.
Why other options are incorrect:
Why other options are incorrect:
- • Phenylalanine: Contains a benzyl group with a phenyl aromatic ring.
- • Tyrosine: Contains a phenyl ring with a hydroxyl (-OH) group.
- • Tryptophan: Contains an indole ring system, which is aromatic.
Abnormal chain of amino acids in sickle cell anaemia is
- a) Alpha chain
- b) Beta chain
- c) Delta chain
- d) Gamma chain
Explanation:
In sickle cell anaemia, the abnormality occurs in the β (beta) chain of hemoglobin. A single amino acid substitution occurs in which valine replaces glutamic acid at the sixth position of the β-globin chain.
Why other options are incorrect:
Why other options are incorrect:
- • Alpha chain: The α-globin chain is not the site of the characteristic mutation in sickle cell anaemia.
- • Delta chain: The δ-globin chain is not affected by the characteristic sickle cell mutation.
- • Gamma chain: The γ-globin chain is mainly associated with fetal hemoglobin (HbF), not the typical sickle cell mutation.
Number of chains in globin part of normal Hb:
- a) 1
- b) 2
- c) 3
- d) 4
Explanation:
The globin part of normal adult hemoglobin (HbA) consists of four polypeptide chains: two α (alpha) chains and two β (beta) chains. Therefore, the number of globin chains is 4.
Why other options are incorrect:
Why other options are incorrect:
- • 1: Hemoglobin does not contain a single globin chain.
- • 2: Two chains would not represent the complete globin portion of normal HbA.
- • 3: Normal adult hemoglobin contains four globin chains, not three.
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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