5201 to 5250 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 5201 to 5250
Consumption of raw eggs can cause deficiency of:
- a) Calcium
- b) Lipoic acid
- c) Biotin
- d) Vitamin A
Explanation:
Raw egg whites contain a protein called avidin. Avidin binds very tightly to Biotin (Vitamin B7) in the digestive tract, preventing its absorption. When eggs are cooked, avidin is denatured (neutralized), allowing the biotin to be absorbed normally.
Why other options are incorrect:
Why other options are incorrect:
- • Calcium: Raw eggs do not contain inhibitors that specifically cause calcium deficiency.
- • Lipoic acid: While it is a co-factor in metabolism, it is not the primary nutrient blocked by raw egg consumption.
- • Vitamin A: Egg yolks are actually a good source of Vitamin A, and raw consumption does not interfere with its absorption.
Egg is poor in:
- a) Essential amino acids
- b) Carbohydrates
- c) Avidin
- d) Biotin
Explanation:
Eggs are essentially a protein and fat-based food. They contain trace amounts of carbohydrates (less than 1 gram per egg), making them a “poor” source of carbs compared to their high protein and vitamin content.
Why other options are incorrect:
Why other options are incorrect:
- • Essential amino acids: Eggs are a “complete protein” source, containing all essential amino acids in high amounts.
- • Avidin: This is a protein naturally present in egg whites; therefore, eggs are not poor in it.
- • Biotin: Egg yolks are actually one of the richest natural dietary sources of Biotin (Vitamin B7).
Cholesterol is present in all the following except:
- a) Milk
- b) Fish
- c) Egg white
- d) Egg yolk
Explanation:
Cholesterol is an animal sterol found in animal fats and cell membranes. While animal products generally contain it, egg white is composed almost entirely of water and protein (albumin) and contains virtually zero fat or cholesterol.
Why other options are incorrect:
Why other options are incorrect:
- • Milk: Contains animal fat which naturally includes cholesterol.
- • Fish: As an animal source, fish contains cholesterol in its tissues and oils.
- • Egg yolk: This is the part of the egg where almost all the fat and cholesterol (approx. 186mg per large egg) are concentrated.
Meat is rich in all of the following except:
- a) Iron
- b) Fluorine
- c) Copper
- d) Zinc
Explanation:
Meat is an excellent source of various minerals, but it is poor in Fluorine. Fluorine is primarily found in drinking water, sea fish, and tea leaves rather than animal muscle tissue.
Why other options are incorrect:
Why other options are incorrect:
- • Iron: Red meat is one of the best sources of heme iron, which is easily absorbed by the body.
- • Copper: Meat, especially organ meats like liver, contains significant amounts of copper.
- • Zinc: Animal meats are a primary dietary source of highly bioavailable zinc.
Kwashiorkor occurs when the diet is severely deficient in:
- a) Iron
- b) Calories
- c) Proteins
- d) Essential fatty acids
Explanation:
Kwashiorkor is a form of severe protein-energy malnutrition (PEM) caused specifically by a deficiency in protein, even if calorie intake is adequate. It is often characterized by edema (swelling), an enlarged liver, and a “pot-bellied” appearance.
Why other options are incorrect:
Why other options are incorrect:
- • Iron: Iron deficiency causes anemia, not the structural wasting and edema associated with Kwashiorkor.
- • Calories: A severe deficiency of total calories leads to Marasmus, where the body appears extremely thin and wasted.
- • Essential fatty acids: Deficiency in fatty acids generally leads to skin issues (like phrynoderma) and poor wound healing.
Clinical features of Kwashiorkor include all of the following except:
- a) Mental retardation
- b) Muscle wasting
- c) Oedema
- d) Anaemia
Explanation:
While children with Kwashiorkor exhibit mental changes like apathy and irritability, Mental retardation (permanent cognitive impairment) is not a primary clinical diagnostic feature of the condition.
Why other options are incorrect:
Why other options are incorrect:
- • Muscle wasting: This occurs in Kwashiorkor, though it may sometimes be masked by the presence of edema.
- • Oedema: This is the hallmark clinical feature of Kwashiorkor, usually starting in the feet and lower legs.
- • Anaemia: Most children with PEM (Protein-Energy Malnutrition) suffer from concurrent nutritional anemias due to lack of iron, protein, and vitamins.
Kwashiorkor usually occurs in:
- a) The post-weaning period
- b) Pregnancy
- c) Lactation
- d) Old age
Explanation:
Kwashiorkor typically affects children between the ages of 1 and 4 years during the post-weaning period. The name itself means “the sickness the baby gets when the new baby comes,” referring to the first child being weaned off protein-rich breast milk and onto a high-starch, low-protein diet.
Why other options are incorrect:
Why other options are incorrect:
- • Pregnancy: While nutritional needs increase, deficiency here usually results in maternal anemia or low birth weight, not Kwashiorkor.
- • Lactation: Similar to pregnancy, the mother needs more nutrients, but Kwashiorkor is a pediatric clinical syndrome.
- • Old age: Malnutrition in the elderly typically manifests as general wasting or sarcopenia rather than the specific oedematous features of Kwashiorkor.
Marasmus occurs from deficient intake of:
- a) Essential amino acids
- b) Essential fatty acids
- c) Calories
- d) Zinc
Explanation:
Marasmus is a severe form of protein-energy malnutrition (PEM) caused by a chronic deficiency of total calories (energy). Unlike Kwashiorkor, which is primarily a protein deficiency, Marasmus involves a lack of almost all nutrients, leading to extreme wasting of muscles and subcutaneous fat.
Why other options are incorrect:
Why other options are incorrect:
- • Essential amino acids: While protein intake is low in Marasmus, a specific deficiency in protein with relatively adequate calorie intake leads to Kwashiorkor instead.
- • Essential fatty acids: Deficiency here leads to skin problems (like phrynoderma) and growth retardation, but not the total body wasting seen in Marasmus.
- • Zinc: Zinc deficiency causes growth failure, skin lesions, and impaired immunity, but it is not the primary driver of Marasmus.
Marasmus differs from Kwashiorkor in which of the following respect?
- a) Mental retardation occurs in kwashiorkor but not in marasmus
- b) Growth is retarded in kwashiorkor but not in marasmus
- c) Muscle wasting occurs in marasmus but not kwashiorkor
- d) Subcutaneous fat disappears in marasmus but not in kwashiorkor
Explanation:
The disappearance of subcutaneous fat is a hallmark of Marasmus because the body utilizes its fat stores for energy due to total calorie starvation. In Kwashiorkor, subcutaneous fat is often preserved, but the child appears swollen due to oedema (fluid retention) caused by protein deficiency.
Why other options are incorrect:
Why other options are incorrect:
- • Mental changes: While apathy and irritability are more common in Kwashiorkor, “mental retardation” is not a standard differentiating clinical feature used to distinguish the two.
- • Growth retardation: This is a common feature found in both Kwashiorkor and Marasmus; children with either condition fail to grow at a normal rate.
- • Muscle wasting: Muscle wasting occurs in both conditions. In Kwashiorkor, it may be masked by oedema, but the underlying wasting is present in both forms of PEM.
Energy reserves of an average well-fed adult man are about:
- a) 50,000 kcal
- b) 100,000 kcal
- c) 200,000 kcal
- d) 300,000 kcal
Explanation:
An average 70 kg man has energy reserves of approximately 100,000 to 160,000 kcal. The vast majority of this (about 85%) is stored as triglycerides in adipose tissue. The rest is stored as protein (mostly in muscle) and a small amount as glycogen in the liver and muscles.
Why other options are incorrect:
Why other options are incorrect:
- • 50,000 kcal: This is too low for a “well-fed” adult; this amount would suggest a significantly underweight individual or very low body fat percentage.
- • 200,000 kcal: This level of energy reserve is more characteristic of individuals with higher body fat percentages or mild obesity.
- • 300,000 kcal: This represents a very high amount of energy storage, typically found in individuals suffering from clinical obesity.
During starvation, the first reserve nutrient to be depleted is:
- a) Glycogen
- b) Proteins
- c) Triglycerides
- d) Cholesterol
Explanation:
Glycogen (stored primarily in the liver and muscles) is the body’s immediate reserve of glucose. During the early stages of starvation or fasting, the body first breaks down liver glycogen to maintain blood sugar levels. These stores are typically exhausted within 12 to 24 hours.
Why other options are incorrect:
Why other options are incorrect:
- • Proteins: The body tries to “spare” protein as long as possible. Significant protein breakdown (from muscles) usually accelerates only after glycogen is depleted and fat stores are being utilized.
- • Triglycerides: These are stored in adipose tissue and serve as the long-term energy reserve. They are mobilized after glycogen levels drop, but because the supply is so large, they are not the “first” to be depleted.
- • Cholesterol: Cholesterol is a structural component of cell membranes and a precursor for hormones; it is not used by the body as a fuel source for energy production.
Synthesis of the following enzymes is increased during starvation:
- a) Digestive enzymes
- b) Gluconeogenic enzymes
- c) Urea cycle enzymes
- d) Glucokinase
Explanation:
During starvation, blood glucose levels drop, triggering the secretion of glucagon. To maintain glucose supply for the brain, the liver increases gluconeogenesis (creating glucose from non-carbohydrate sources). Consequently, the synthesis of key gluconeogenic enzymes like PEPCK and Glucose-6-phosphatase is significantly increased.
Why other options are incorrect:
Why other options are incorrect:
- • Digestive enzymes: These decrease during starvation as the gastrointestinal tract becomes less active due to the absence of food.
- • Urea cycle enzymes: While there is an initial increase in protein breakdown, the metabolic priority is the up-regulation of glucose-producing pathways.
- • Glucokinase: This is a glycolytic enzyme active in the “fed” state. In starvation, its synthesis is suppressed to prevent the liver from consuming the glucose it is trying to produce.
In hypoparathyroidism, which of the following is observed?
- a) Plasma calcium and inorganic phosphorous are low
- b) Plasma calcium and inorganic phosphorous are high
- c) Plasma calcium is low and inorganic phosphorous high
- d) Plasma calcium is high and inorganic phosphorous low
Explanation:
Parathyroid Hormone (PTH) normally increases blood calcium and decreases blood phosphorous (by promoting its excretion in the urine). In hypoparathyroidism, the lack of PTH leads to decreased calcium mobilization from bone and decreased renal phosphorous excretion, resulting in low plasma calcium (hypocalcemia) and high inorganic phosphorous (hyperphosphatemia).
Why other options are incorrect:
Why other options are incorrect:
- • Option A & B: Calcium and phosphorous usually have an inverse relationship in the blood; it is rare for both to move in the same direction in simple parathyroid disorders.
- • Option D: This is the classic profile for Hyperparathyroidism, where excess PTH causes high calcium and low phosphorous.
The number of amino acid residues in calcitonin is:
- a) 9
- b) 32
- c) 51
- d) 84
Explanation:
Calcitonin is a linear polypeptide hormone secreted by the parafollicular cells (C-cells) of the thyroid gland. It consists of a single chain of 32 amino acids with a molecular weight of approximately 3,400 Daltons.
Why other options are incorrect:
Why other options are incorrect:
- • 9: This is the number of amino acid residues found in hormones like Oxytocin and Vasopressin (ADH).
- • 51: This is the total number of amino acids in Insulin (composed of an A-chain of 21 and a B-chain of 30).
- • 84: This is the number of amino acid residues in Parathyroid Hormone (PTH).
Calcitonin is synthesised in:
- a) Parathyroid glands
- b) Thyroid gland
- c) Pars intermedia of pituitary
- d) Adrenal cortex
Explanation:
Calcitonin is synthesized and secreted by the parafollicular cells (also known as C-cells) of the thyroid gland. Its primary role is to lower blood calcium levels by inhibiting the activity of osteoclasts (cells that break down bone).
Why other options are incorrect:
Why other options are incorrect:
- • Parathyroid glands: These glands produce Parathyroid Hormone (PTH), which works in opposition to calcitonin to increase blood calcium levels.
- • Pars intermedia: This part of the pituitary gland primarily secretes Melanocyte-Stimulating Hormone (MSH).
- • Adrenal cortex: This produces steroid hormones such as cortisol, aldosterone, and androgens.
Plasma calcium is lowered by:
- a) Parathormone
- b) Calcitonin
- c) Aldosterone
- d) Deoxycorticosterone
Explanation:
Calcitonin is a hormone produced by the C-cells of the thyroid gland. Its primary function is to lower plasma calcium levels by inhibiting the activity of osteoclasts (cells that break down bone) and by decreasing the reabsorption of calcium in the kidneys.
Why other options are incorrect:
Why other options are incorrect:
- • Parathormone (PTH): This hormone acts in direct opposition to calcitonin; its main role is to increase plasma calcium levels.
- • Aldosterone: This is a mineralocorticoid primarily involved in regulating sodium and potassium levels and blood pressure, not calcium.
- • Deoxycorticosterone: Similar to aldosterone, this is a steroid hormone that influences mineral balance (sodium/potassium) rather than calcium metabolism.
α Cells of Islets of Langerhans secrete:
- a) Insulin
- b) Glucagon
- c) Somatostatin
- d) Cholecystokinin
Explanation:
The Islets of Langerhans in the pancreas contain different types of endocrine cells. The Alpha (α) cells are responsible for the synthesis and secretion of Glucagon, which raises blood glucose levels by promoting glycogenolysis and gluconeogenesis in the liver.
Why other options are incorrect:
Why other options are incorrect:
- • Insulin: This is secreted by the Beta (β) cells of the Islets of Langerhans.
- • Somatostatin: This is secreted by the Delta (δ) cells of the Islets of Langerhans.
- • Cholecystokinin (CCK): This hormone is primarily secreted by the “I” cells in the mucosal epithelium of the small intestine, not the pancreas.
A/G ratio is:
- a) Strength of proteins
- b) ratio of serum proteins
- c) ratio of ceruloplasmin
- d) None of these
Explanation:
The A/G ratio stands for the Albumin/Globulin ratio. It is a mathematical comparison of the concentrations of these two primary serum proteins. It is used clinically to help diagnose liver disease, kidney disease, and nutritional status.
Why other options are incorrect:
Why other options are incorrect:
- • Strength of proteins: This is not a clinical or biochemical term. The test measures quantity and concentration, not physical “strength.”
- • ratio of ceruloplasmin: Ceruloplasmin is just one specific type of globulin. The A/G ratio includes the sum of all globulin fractions (Alpha, Beta, and Gamma).
- • None of these: This is incorrect because option (b) accurately defines the ratio.
Insulin is made up of:
- a) A single polypeptide chain having 51 amino acid residues
- b) A single polypeptide chain having 84 amino acid residues
- c) A-chain having 21 and B-chain having 30 amino acid residues
- d) A-chain having 30 and B-chain having 21 amino acid residues
Explanation:
Mature human insulin consists of two polypeptide chains: the A-chain (containing 21 amino acids) and the B-chain (containing 30 amino acids), linked together by disulfide bonds.
Why other options are incorrect:
Why other options are incorrect:
- • Option A: While insulin has 51 amino acids in total, it is composed of two separate chains, not a single one.
- • Option B: 84 amino acids refers to Proinsulin, the precursor molecule before the C-peptide is removed to form active insulin.
- • Option D: This incorrectly identifies the lengths; the A-chain is the shorter one (21) and the B-chain is the longer one (30).
The number of amino acid residues in preproinsulin is:
- a) 51
- b) 84
- c) 109
- d) 119
Explanation:
Preproinsulin is the primary translation product of the insulin gene. In humans, it consists of a total of 109 (or 110 depending on references) amino acids: the signal peptide (24 amino acids), the B chain (30 amino acids), the C-peptide (31-34 amino acids), and the A chain (21 amino acids).
Why other options are incorrect:
Why other options are incorrect:
- • 51: This is the total number of amino acids in mature, active Insulin (A-chain + B-chain).
- • 84: This is the approximate number of amino acids in Proinsulin (after the signal peptide has been removed).
- • 119: This number exceeds the standard length of the human preproinsulin sequence.
Pre-proinsulin contains a signal sequence having
- a) 9 amino acid residues
- b) 19 amino acid residues
- c) 27 amino acid residues
- d) 33 amino acid residues
Explanation:
Pre-proinsulin contains an N-terminal signal sequence that directs the newly synthesized peptide into the endoplasmic reticulum. In this MCQ, the signal sequence is given as 27 amino acid residues.
Why other options are incorrect:
Why other options are incorrect:
- • 9 amino acid residues: This is not the signal sequence length specified for pre-proinsulin in this question.
- • 19 amino acid residues: This is not the signal sequence length specified for pre-proinsulin.
- • 33 amino acid residues: This is not the signal sequence length specified for pre-proinsulin.
The number of intra-chain disulphide bonds in pro-insulin:
- a) One
- b) Two
- c) Three
- d) Four
Explanation:
Pro-insulin is a single polypeptide chain. It contains a total of three disulphide bonds. Because pro-insulin consists of only one continuous chain (A-chain, C-peptide, and B-chain), all three bonds are technically “intra-chain” bonds.
Key Details:
Key Details:
- • Pro-insulin vs. Insulin: In mature insulin (which has two chains), there are 2 inter-chain bonds and only 1 intra-chain bond (within the A-chain).
- • The Bonds: The three bonds are located at A6–A11, A7–B7, and A20–B19.
- • Conversion: When pro-insulin is converted to insulin, the C-peptide is removed, but the three disulphide bonds remain intact to maintain the structure.
Pentagastrin is a
- a) Naturally occurring form of gastrin
- b) Inactive metabolite of gastrin
- c) Active metabolite of gastrin
- d) Synthetic form of gastrin
Explanation:
Pentagastrin is a synthetic form of gastrin. It contains the biologically active C-terminal pentapeptide sequence of gastrin and has been used to stimulate gastric acid secretion.
Why other options are incorrect:
Why other options are incorrect:
- • Naturally occurring form of gastrin: Incorrect. Pentagastrin is synthetically produced.
- • Inactive metabolite of gastrin: Incorrect. Pentagastrin is biologically active.
- • Active metabolite of gastrin: Incorrect. Pentagastrin is not a natural metabolite of gastrin.
- • Synthetic form of gastrin: Correct. Pentagastrin is a synthetic peptide that mimics the active portion of gastrin.
Secretion of gastrin is evoked by
- a) Entry of food into stomach
- b) Vagal stimulation
- c) Lower aliphatic alcohols
- d) All of these
Explanation:
The correct answer is d) All of these. Gastrin secretion is stimulated by the entry of food into the stomach, vagal stimulation, and certain substances such as lower aliphatic alcohols.
Why other options are incorrect:
Why other options are incorrect:
- • Entry of food into stomach: True. Food distension and the presence of peptides and amino acids stimulate gastrin release.
- • Vagal stimulation: True. Vagal activity stimulates gastrin secretion, mainly through gastrin-releasing peptide (GRP).
- • Lower aliphatic alcohols: True. Lower alcohols can stimulate gastric secretion and gastrin release.
- • All of these: Correct. All three listed factors can evoke gastrin secretion.
Gastrin stimulates
- a) Gastric motility
- b) Gastric secretion
- c) Both (Gastric motility) and (Gastric secretion)
- d) None of these
Explanation:
The correct answer is c) Both (Gastric motility) and (Gastric secretion). Gastrin stimulates gastric acid secretion and increases gastric motility, helping promote digestion in the stomach.
Why other options are incorrect:
Why other options are incorrect:
- • Gastric motility: True. Gastrin increases gastric motility.
- • Gastric secretion: True. Gastrin stimulates gastric acid secretion, mainly by acting on parietal cells and ECL cells.
- • Both (Gastric motility) and (Gastric secretion): Correct. Gastrin stimulates both gastric motility and gastric secretion.
- • None of these: Incorrect. Gastrin has important stimulatory effects on both gastric motility and secretion.
Secretin is made up of
- a) 17 amino acids
- b) 27 amino acids
- c) 37 amino acids
- d) 47 amino acids
Explanation:
Secretin is a gastrointestinal peptide hormone composed of 27 amino acids. It is secreted mainly by S cells of the duodenal mucosa and stimulates bicarbonate-rich pancreatic secretion.
Why other options are incorrect:
Why other options are incorrect:
- • 17 amino acids: Incorrect. Secretin contains 27 amino acids.
- • 27 amino acids: Correct. Secretin is a 27-amino-acid peptide hormone.
- • 37 amino acids: Incorrect. Secretin contains 27 amino acids.
- • 47 amino acids: Incorrect. Secretin contains 27 amino acids.
Secretin causes all of the following except
- a) Secretion of pancreatic juice
- b) Secretion of bile
- c) Inhibition of gastric secretion
- d) Stimulation of intestinal motility
Explanation:
The correct answer is d) Stimulation of intestinal motility. Secretin primarily stimulates bicarbonate-rich pancreatic secretion and promotes bile secretion. It also inhibits gastric acid secretion and gastric emptying. It does not significantly stimulate intestinal motility.
Why other options are incorrect:
Why other options are incorrect:
- • Secretion of pancreatic juice: True. Secretin stimulates the pancreas to secrete bicarbonate-rich pancreatic juice.
- • Secretion of bile: True. Secretin promotes bile secretion, particularly bicarbonate-rich secretion from the bile ducts.
- • Inhibition of gastric secretion: True. Secretin inhibits gastric acid secretion.
- • Stimulation of intestinal motility: Incorrect. Secretin does not primarily stimulate intestinal motility.
All of the following statements about cholecystokinin pancreozymin are true except
- a) It is secreted by mucosa of small intestine
- b) It stimulates secretion of pancreatic juice rich in enzymes
- c) It stimulates contraction of gall bladder
- d) It inhibits gastric motility
Explanation:
The correct answer is d) It inhibits gastric motility. Cholecystokinin (CCK, formerly called pancreozymin) is secreted mainly by I cells of the duodenal and jejunal mucosa. It stimulates pancreatic enzyme secretion and gallbladder contraction. CCK generally inhibits gastric emptying rather than simply being described as inhibiting gastric motility.
Why other options are incorrect:
Why other options are incorrect:
- • It is secreted by mucosa of small intestine: True. CCK is secreted mainly by I cells in the duodenal and jejunal mucosa.
- • It stimulates secretion of pancreatic juice rich in enzymes: True. CCK strongly stimulates pancreatic acinar cells to release digestive enzymes.
- • It stimulates contraction of gall bladder: True. CCK causes gallbladder contraction and promotes bile delivery into the duodenum.
- • It inhibits gastric motility: Incorrect in the context of this MCQ. CCK primarily delays gastric emptying; it does not directly act as a general inhibitor of gastric motility.
All of the following statements about pancreatic somatostatin are true except
- a) It is secreted by δ cells of islets of Langerhans
- b) It stimulates the secretion of gastrin
- c) It inhibits the secretion of secretin
- d) It inhibits the secretion of cholecystokinin pancreozymin
Explanation:
The correct answer is b) It stimulates the secretion of gastrin. Somatostatin generally has an inhibitory effect on gastrointestinal hormones and secretions, including gastrin.
Why other options are incorrect:
Why other options are incorrect:
- • It is secreted by δ cells of islets of Langerhans: True. Pancreatic somatostatin is produced by δ (delta) cells.
- • It stimulates the secretion of gastrin: Incorrect. Somatostatin inhibits gastrin secretion.
- • It inhibits the secretion of secretin: True. Somatostatin inhibits the release of several gastrointestinal hormones, including secretin.
- • It inhibits the secretion of cholecystokinin pancreozymin: True. Somatostatin inhibits CCK (cholecystokinin) secretion.
Histidine is converted into histamine by
- a) Carboxylation
- b) Decarboxylation
- c) Methylation
- d) Hydroxylation
Explanation:
Histidine is converted into histamine by decarboxylation. The reaction is catalysed by the enzyme histidine decarboxylase and requires pyridoxal phosphate (vitamin B6) as a cofactor.
Why other options are incorrect:
Why other options are incorrect:
- • Carboxylation: This adds a carboxyl group and does not produce histamine from histidine.
- • Decarboxylation: Correct. Removal of the carboxyl group from histidine produces histamine.
- • Methylation: This involves addition of a methyl group and is not the pathway for histamine synthesis.
- • Hydroxylation: This adds a hydroxyl group and does not convert histidine into histamine.
Histamine is synthesised in
- a) Brain
- b) Mast cells
- c) Basophils
- d) All of these
Explanation:
The correct answer is d) All of these. Histamine is synthesised from the amino acid histidine by the enzyme histidine decarboxylase. It is produced and stored in several tissues, including the brain, mast cells, and basophils.
Why other options are incorrect:
Why other options are incorrect:
- • Brain: Histamine is synthesised by neurons in the brain and functions as a neurotransmitter.
- • Mast cells: Mast cells synthesise and store large amounts of histamine in their granules.
- • Basophils: Basophils also synthesise and store histamine.
- • All of these: Correct, because histamine synthesis occurs in all three listed sites.
Histamine causes all the following except
- a) Stimulation of gastric secretion
- b) Vasoconstriction
- c) Pruritus
- d) Increase in capillary permeability
Explanation:
The correct answer is b) Vasoconstriction. Histamine primarily causes vasodilatation, along with increased capillary permeability, pruritus, and stimulation of gastric acid secretion.
Why other options are incorrect:
Why other options are incorrect:
- • Stimulation of gastric secretion: True. Histamine stimulates gastric acid secretion through H₂ receptors.
- • Vasoconstriction: Incorrect. Histamine generally causes vasodilatation, especially through H₁ and H₂ receptors.
- • Pruritus: True. Histamine stimulates sensory nerve endings and produces itching.
- • Increase in capillary permeability: True. Histamine increases vascular permeability, causing edema.
H2-receptors are blocked by:
- a) Diphenhydramine
- b) Mepayramine
- c) Pyrilamine
- d) Cimetidine
Explanation:
Cimetidine is a classic H2-receptor antagonist. These drugs specifically block the histamine H2-receptors located on the parietal cells in the stomach, thereby reducing the production of gastric acid.
Why other options are incorrect:
Why other options are incorrect:
- • Diphenhydramine: A first-generation H1-receptor antagonist used primarily for allergies and as a sedative.
- • Mepayramine (Mepyramine): Also known as pyrilamine, it is a first-generation H1-receptor antagonist.
- • Pyrilamine: An H1-receptor blocker commonly used in over-the-counter cold and allergy medications.
Serotonin is synthesised from:
- a) Serine
- b) Phenylalanine
- c) Tyrosine
- d) Tryptophan
Explanation:
Serotonin (also known as 5-hydroxytryptamine or 5-HT) is synthesized from the essential amino acid Tryptophan. The synthesis occurs in two steps: first, Tryptophan is hydroxylated to 5-hydroxytryptophan, and then it is decarboxylated to form Serotonin.
Why other options are incorrect:
Why other options are incorrect:
- • Serine: Involved in the synthesis of phospholipids and cysteine, but not serotonin.
- • Phenylalanine: An essential amino acid that serves as the precursor to Tyrosine.
- • Tyrosine: The precursor for Catecholamines (Dopamine, Norepinephrine, and Epinephrine), as well as Thyroid hormones and Melanin.
All the following statements about serotonin are true except
- a) It causes vasodilatation
- b) It causes bronchoconstriction
- c) It is metabolized by monoamine oxidase
- d) Its metabolite is 5-hydroxyindole acetic acid
Explanation:
The correct answer is a) It causes vasodilatation. Serotonin (5-hydroxytryptamine, 5-HT) generally causes vasoconstriction, although its vascular effects can vary depending on the vascular bed and receptor subtype.
Why other options are incorrect:
Why other options are incorrect:
- • It causes bronchoconstriction: True. Serotonin can cause contraction of bronchial smooth muscle.
- • It is metabolized by monoamine oxidase: True. Serotonin is metabolized mainly by monoamine oxidase (MAO).
- • Its metabolite is 5-hydroxyindole acetic acid: True. Serotonin is metabolized to 5-hydroxyindoleacetic acid (5-HIAA).
All the following statements about angiotensin are true except
- a) Its precursor is an α2-globulin
- b) Its active form is an octapeptide
- c) It is a vasodilator
- d) It increases the secretion of aldosterone
Explanation:
The correct answer is c) It is a vasodilator. Angiotensin II is a potent vasoconstrictor, not a vasodilator. It also stimulates aldosterone secretion from the adrenal cortex.
Why other options are incorrect:
Why other options are incorrect:
- • Its precursor is an α2-globulin: True. Angiotensinogen is an α2-globulin produced mainly by the liver.
- • Its active form is an octapeptide: True. Angiotensin II is an octapeptide and the principal active form.
- • It is a vasodilator: Incorrect. Angiotensin II causes powerful vasoconstriction.
- • It increases the secretion of aldosterone: True. Angiotensin II stimulates aldosterone secretion from the adrenal cortex.
Methyl dopa decreases blood pressure by:
- a) Inhibiting the synthesis of catecholamines
- b) Antagonising the action of aldosterone
- c) Stimulating the release of renin
- d) Inhibiting the breakdown of angiotensin
Explanation:
Methyldopa is a centrally acting antihypertensive. It acts as a competitive inhibitor of the enzyme DOPA decarboxylase, which is responsible for converting L-DOPA into dopamine, thereby inhibiting the synthesis of catecholamines (Norepinephrine and Epinephrine). Its active metabolite also stimulates central alpha-2 adrenergic receptors.
Why other options are incorrect:
Why other options are incorrect:
- • Aldosterone Antagonism: This is the mechanism of Potassium-sparing diuretics like Spironolactone.
- • Renin Release: Methyldopa actually tends to decrease renin activity via its central effect, not stimulate it.
- • Angiotensin: ACE inhibitors prevent the synthesis of Angiotensin II, while ARBs block its receptors. Methyldopa does not interfere with angiotensin breakdown.
Binding of gamma-aminobutyric acid (GABA) to its receptors in the brain increases the permeability of the cell membrane to:
- a) Cl–
- b) Na+
- c) K+
- d) Ca++
Explanation:
GABA is the primary inhibitory neurotransmitter in the central nervous system. When it binds to GABAA receptors, it opens ligand-gated ion channels, specifically allowing Chloride ions (Cl–) to flow into the neuron. This leads to hyperpolarization, making the neuron less likely to fire an action potential.
Why other options are incorrect:
Why other options are incorrect:
- • Na+ (Sodium): Increased permeability to Na+ causes depolarization and excitation (common with Glutamate receptors), which is the opposite of GABA’s function.
- • K+ (Potassium): While GABAB receptors can affect K+ channels, the classic rapid increase in membrane permeability associated with GABA receptor binding refers to the Cl– channel.
- • Ca++ (Calcium): Calcium influx is generally associated with excitatory signals or the release of neurotransmitters, not the inhibitory effect of GABA.
Binding of acetylcholine to its receptors increases the permeability of the cell membrane to:
- a) Ca++
- b) Na+
- c) K+
- d) Na+ and K+
Explanation:
When acetylcholine (ACh) binds to nicotinic receptors (ligand-gated ion channels), the channel opens and becomes permeable to small cations. Specifically, it allows the simultaneous movement of Na+ (influx) and K+ (efflux), which leads to depolarization of the cell membrane.
Why other options are incorrect:
Why other options are incorrect:
- • Ca++: While some nicotinic receptors have a slight permeability to Calcium, the primary effect at the neuromuscular junction and synapses involves monovalent cations.
- • Na+ only: Although the influx of Sodium is the dominant force for depolarization, the channel is technically permeable to Potassium as well.
- • K+ only: Increasing only Potassium permeability would usually lead to hyperpolarization (inhibitory), whereas ACh is primarily excitatory at nicotinic sites.
All of the following are glycoproteins except:
- a) Collagen
- b) Albumin
- c) Transferrin
- d) IgM
Explanation:
Albumin is considered a simple protein, not a glycoprotein, because it does not have carbohydrate groups attached to its polypeptide chain. It is the most abundant plasma protein and is synthesized in the liver.
Why other options are incorrect:
Why other options are incorrect:
- • Collagen: It is a structural glycoprotein containing glucose and galactose units attached to hydroxylysine residues.
- • Transferrin: This is a plasma glycoprotein responsible for the transport of iron in the blood.
- • IgM: All immunoglobulins (antibodies), including IgM, are glycoproteins containing varying amounts of carbohydrates.
Sialic acids are present in:
- a) Proteoglycans
- b) Glycoproteins
- c) Both (Proteoglycans) and (Glycoproteins)
- d) None of these
Explanation:
Sialic acids (such as N-acetylneuraminic acid or NANA) are a family of 9-carbon sugar derivatives. They are typically found at the terminal ends of sugar chains attached to both glycoproteins and proteoglycans. They play a crucial role in cell-to-cell recognition and maintaining the negative charge of the cell surface.
Why other options are incorrect:
Why other options are incorrect:
- • Proteoglycans: While they contain sialic acid, selecting this alone ignores their heavy presence in glycoproteins.
- • Glycoproteins: While they are major carriers of sialic acid, many proteoglycans also contain these residues.
- • None of these: Incorrect, as sialic acids are fundamental components of these glycoconjugates.
Hyaluronidase hydrolyses:
- a) Hyaluronic acid
- b) Chondroitin sulphate
- c) Heparin
- d) Hyaluronic acid and chondroitin sulphate
Explanation:
Hyaluronidase is an enzyme that primarily degrades hyaluronic acid. However, most hyaluronidases (especially testicular hyaluronidase) are not strictly specific; they can also hydrolyze Chondroitin 4-sulphate and Chondroitin 6-sulphate because these molecules share similar β-1,4-glycosidic linkages in their structure.
Why other options are incorrect:
Why other options are incorrect:
- • Hyaluronic acid: While this is the primary substrate, selecting only this ignores the enzyme’s ability to act on chondroitin sulphates.
- • Chondroitin sulphate: Similarly, while it is hydrolyzed by the enzyme, it is not the only substrate.
- • Heparin: Heparin has a different chemical structure and linkage pattern; it is degraded by a specific enzyme called heparinase, not hyaluronidase.
The most abundant protein in bones is:
- a) Collagen type I
- b) Collagen type II
- c) Collagen type III
- d) Non-collagen proteins
Explanation:
Collagen Type I is the most abundant protein in bone, accounting for approximately 90% to 95% of the organic matrix. It provides the structural framework and tensile strength necessary for the deposition of calcium hydroxyapatite crystals during mineralization.
Why other options are incorrect:
Why other options are incorrect:
- • Collagen type II: This type is primarily found in hyaline and elastic cartilage, not in bone.
- • Collagen type III: This is common in extensible connective tissues like skin, lungs, and the vascular system (granulation tissue).
- • Non-collagen proteins: While bones contain proteins like osteocalcin, osteopontin, and osteonectin, these only make up about 5-10% of the organic matrix.
The most abundant collagen in cartilages is:
- a) Type I
- b) Type II
- c) Type III
- d) Type IV
Explanation:
Collagen Type II is the primary structural component of cartilage, particularly hyaline and elastic cartilage. It makes up approximately 85% to 90% of the total collagen content in cartilage, providing the necessary tensile strength to withstand pressure.
Why other options are incorrect:
Why other options are incorrect:
- • Type I: Predominantly found in bones, skin, tendons, and fibrocartilage (like the intervertebral discs), but not the main collagen of hyaline cartilage.
- • Type III: Also known as reticular fiber; it is found in the skin, blood vessels, and internal organs.
- • Type IV: This type is a major component of the basal lamina (basement membrane) and does not form large fibers like the other types.
Collagen and elastin have the following similarity:
- a) Both are triple helices
- b) Both have hydroxyproline residues
- c) Both have hydroxylysine residues
- d) Both are glycoproteins
Explanation:
Both collagen and elastin are structural proteins that contain the modified amino acid hydroxyproline. While collagen contains a high amount of it, elastin contains a much smaller amount. Both also share a high glycine and proline content.
Why other options are incorrect:
Why other options are incorrect:
- • Both are triple helices: Only collagen forms a triple helix structure. Elastin has a more random, coiled structure that allows for stretching.
- • Both have hydroxylysine residues: Hydroxylysine is unique to collagen; it is virtually absent in elastin.
- • Both are glycoproteins: Collagen is a glycoprotein (contains carbohydrate chains), whereas elastin is generally not glycosylated.
Abnormal collagen structure is seen in all of the following except:
- a) I-cell disease
- b) Osteogenesis imperfecta
- c) Menke’s disease
- d) Ehlers-Danlos syndrome
Explanation:
I-cell disease (Inclusion cell disease) is a lysosomal storage disorder caused by a deficiency in the enzyme N-acetylglucosaminyl-1-phosphotransferase. It affects the protein-tagging mechanism (Mannose-6-phosphate) required to send enzymes to the lysosome, rather than the primary structure of collagen.
Why other options are incorrect:
Why other options are incorrect:
- • Osteogenesis imperfecta: Caused by mutations in Type I collagen genes, leading to “brittle bone disease.”
- • Menke’s disease: A copper transport disorder. Since the enzyme lysyl oxidase (which cross-links collagen) requires copper, collagen structure becomes weak and abnormal.
- • Ehlers-Danlos syndrome: A group of genetic disorders that specifically affect the synthesis and processing of collagen, leading to hypermobile joints and skin elasticity.
I-cell disease results from the absence of the following from lysosomal enzymes:
- a) Signal sequence
- b) Mannose-6-phosphate
- c) Sialic acid
- d) A serine residue
Explanation:
Mannose-6-phosphate (M6P) is the essential chemical “tag” added to acid hydrolases in the Golgi apparatus. This tag acts as a signal to transport these enzymes to the lysosomes. In I-cell disease, the enzyme responsible for adding this tag is defective, causing the lysosomal enzymes to be secreted out of the cell instead of being sent to the lysosomes.
Why other options are incorrect:
Why other options are incorrect:
- • Signal sequence: This is a sequence of amino acids that directs proteins to the Endoplasmic Reticulum (ER). It is usually present in I-cell disease; the failure occurs later in the Golgi.
- • Sialic acid: While found in many glycoproteins, it is not the primary targeting signal for lysosomal enzyme trafficking.
- • A serine residue: Serine residues are involved in O-linked glycosylation, but the M6P tag is added to N-linked oligosaccharides on asparagine residues.
In I-cell disease, lysosomal enzymes:
- a) Are not synthesised
- b) Are inactive
- c) Lack signal sequence
- d) Cannot reach lysosomes
Explanation:
In I-cell disease, the protein synthesis machinery works correctly, but the Golgi apparatus fails to add the Mannose-6-Phosphate “tag” to the enzymes. Because this “address label” is missing, the enzymes cannot reach the lysosomes and are instead secreted out of the cell into the blood and extracellular fluid.
Why other options are incorrect:
Why other options are incorrect:
- • Are not synthesised: The enzymes are synthesized normally in the Rough ER; the defect is in post-translational modification.
- • Are inactive: The enzymes are actually fully functional, but they are located in the wrong place (found at high levels in the blood).
- • Lack signal sequence: The initial N-terminal signal sequence (which directs them to the ER) is present; it is the Golgi-specific targeting signal (M6P) that is missing.
Renal glycosuria occurs due to:
- a) Increased filtration of glucose in glomeruli
- b) Increased secretion of glucose by renal tubular cells
- c) Decreased reabsorption of glucose by renal tubular cells
- d) Increased conversion of glycogen into glucose in tubular cells
Explanation:
Renal glycosuria is a condition where glucose is excreted in the urine despite having normal blood glucose levels. This happens because of a defect in the renal tubular reabsorption process (specifically in the proximal convoluted tubule), lowering the “renal threshold” for glucose.
Why other options are incorrect:
Why other options are incorrect:
- • Increased filtration: Glomerular filtration of glucose depends on its concentration in the blood. In renal glycosuria, blood glucose is usually normal, so filtration is normal.
- • Increased secretion: Glucose is not actively secreted by the renal tubules; it is only filtered and then reabsorbed.
- • Increased conversion of glycogen: While the kidneys can perform gluconeogenesis, the presence of glucose in urine is a transport failure (reabsorption), not a result of metabolic overproduction within the tubular cells.
Haematuria can occur in:
- a) Haemolytic anaemia
- b) Mismatched blood transfusion
- c) Yellow fever
- d) Stone in urinary tract
Explanation:
Haematuria refers to the presence of intact red blood cells in the urine. This is commonly caused by physical trauma to the urinary tract, such as a stone (calculus) scraping the lining of the kidney, ureter, or bladder, causing direct bleeding.
Why other options are incorrect:
Why other options are incorrect:
- • Haemolytic anaemia: This causes haemoglobinuria (free haemoglobin in urine) due to the breakdown of RBCs within the blood vessels, not intact RBCs.
- • Mismatched blood transfusion: Similar to haemolytic anaemia, this leads to massive intravascular lysis of RBCs, resulting in haemoglobinuria.
- • Yellow fever: While severe cases can cause bleeding, it is more characteristically associated with “black vomit” and jaundice; if blood appears in the urine, it is often due to systemic breakdown (haemoglobinuria) rather than localized urinary tract bleeding.
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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