Chapter 92 – MCQs for Lab (Biochemistry)

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Chaptern 92 : 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.

4551 to 4600 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.

MCQs Chapter 92 (Biochemistry)

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Staphylococcus aureus

Questions 4551 to 4600

A drug which prevents uric acid synthesis by inhibiting the enzyme xanthine oxidase is:
  • a) Aspirin
  • b) Allopurinol
  • c) Colchicine
  • d) Probenecid
Explanation: Allopurinol is a structural analog of hypoxanthine. It acts as a competitive inhibitor of the enzyme xanthine oxidase, which is responsible for converting hypoxanthine to xanthine and xanthine to uric acid. By inhibiting this enzyme, it reduces the production of uric acid in the body.
Why other options are incorrect:
  • • Aspirin: At low doses, it can actually inhibit the excretion of uric acid; it is an NSAID used for pain and inflammation, not for inhibiting uric acid synthesis.
  • • Colchicine: Used for acute gout attacks; it works by inhibiting microtubule polymerization and reducing inflammation, but it does not affect uric acid levels.
  • • Probenecid: This is a uricosuric agent. It increases the excretion of uric acid by the kidneys by inhibiting its reabsorption, rather than stopping its synthesis.
Which of the following is required for crystallization and storage of the hormone insulin?
  • a) Mn++
  • b) Mg++
  • c) Ca++
  • d) Zn++
Explanation: Zinc (Zn++) is essential for the storage of insulin. In the beta cells of the pancreas, six insulin molecules associate with two zinc ions to form a stable hexamer. This zinc-insulin hexamer is the form in which insulin is stored in secretory granules before being released into the blood.
Why other options are incorrect:
  • • Mn++ (Manganese): While a cofactor for some enzymes (like arginase), it does not play a role in insulin crystallization.
  • • Mg++ (Magnesium): Essential for ATP-related reactions and kinase enzymes, but not for the structural storage of insulin.
  • • Ca++ (Calcium): Calcium ions are crucial for the triggering of insulin secretion (exocytosis), but they are not the primary ions used for the crystalline storage of the hormone itself.
Oxidation of which substance in the body yields the most calories?
  • a) Glucose
  • b) Glycogen
  • c) Protein
  • d) Lipids
Explanation: Lipids (fats) are the most energy-dense macronutrients. The oxidation of 1 gram of fat yields approximately 9 kcal, whereas the oxidation of 1 gram of carbohydrates or proteins yields only about 4 kcal. This is because lipids are more highly reduced than carbohydrates or proteins, containing more carbon-hydrogen bonds.
Why other options are incorrect:
  • • Glucose: A simple carbohydrate that yields about 4 kcal per gram.
  • • Glycogen: The storage form of glucose in animals; like all carbohydrates, it yields approximately 4 kcal per gram.
  • • Protein: Primarily used for structural and functional purposes; when oxidized for energy, it yields approximately 4 kcal per gram.
Milk is deficient in which vitamins?
  • a) Vitamin C
  • b) Vitamin A
  • c) Vitamin B2
  • d) Vitamin K
Explanation: Milk is considered a nearly complete food, but it is notably deficient in Vitamin C (Ascorbic acid) and Iron. Any small amounts of Vitamin C naturally present in raw milk are usually destroyed during the pasteurization process due to heat sensitivity.
Why other options are incorrect:
  • • Vitamin A: Milk is a good source of Vitamin A, especially whole milk, as it is a fat-soluble vitamin found in milk fat.
  • • Vitamin B2: Also known as Riboflavin, milk is one of the richest dietary sources of this vitamin.
  • • Vitamin K: While not as abundant as B-vitamins, Vitamin K is present in milk and it is not the primary deficiency associated with it.
Milk is deficient of which mineral?
  • a) Phosphorus
  • b) Sodium
  • c) Iron
  • d) Potassium
Explanation: Milk is a poor source of Iron. While milk is highly nutritious and provides many essential minerals, it contains very little iron. This is why infants who are fed exclusively on milk for a prolonged period beyond six months are at risk of developing iron-deficiency anemia.
Why other options are incorrect:
  • • Phosphorus: Milk is an excellent source of phosphorus, which works alongside calcium to build strong bones and teeth.
  • • Sodium: Milk contains a natural and adequate amount of sodium required for physiological functions.
  • • Potassium: Milk is actually a very rich source of potassium, which helps maintain fluid balance and heart health.
Synthesis of prostaglandins is inhibited by?
  • a) Aspirin
  • b) Arsenic
  • c) Fluoride
  • d) Cyanide
Explanation: Aspirin (acetylsalicylic acid) inhibits the synthesis of prostaglandins by irreversibly acetylating and inhibiting the enzyme cyclooxygenase (COX). Prostaglandins are mediators of inflammation, pain, and fever, which is why Aspirin is used as an anti-inflammatory and analgesic drug.
Why other options are incorrect:
  • • Arsenic: Primarily acts by inhibiting enzymes containing sulfhydryl (-SH) groups or by interfering with ATP production; it is not a specific inhibitor of prostaglandin synthesis.
  • • Fluoride: Best known for inhibiting the enzyme enolase in the glycolytic pathway (used in blood sugar collection tubes to prevent glycolysis).
  • • Cyanide: A potent poison that inhibits cytochrome c oxidase in the electron transport chain, stopping cellular respiration.
HDL is synthesized and secreted from:
  • a) Pancreas
  • b) Liver
  • c) Kidney
  • d) Muscle
Explanation: HDL (High-Density Lipoprotein) is primarily synthesized and secreted by the Liver and the small intestine. It is often referred to as “good cholesterol” because it facilitates Reverse Cholesterol Transport, carrying excess cholesterol from the peripheral tissues back to the liver for excretion.
Why other options are incorrect:
  • • Pancreas: Responsible for secreting digestive enzymes (exocrine) and hormones like insulin and glucagon (endocrine), but not lipoproteins.
  • • Kidney: Functions primarily in blood filtration, waste excretion, and maintaining fluid balance; it does not synthesize HDL.
  • • Muscle: While muscles utilize fatty acids for energy and store small amounts of glycogen, they do not synthesize or secrete transport lipoproteins like HDL.
In the receptor-mediated endocytosis of lipoproteins, the cholesterol esters are hydrolyzed in which organelle?
  • a) Endoplasmic reticulum
  • b) Lysosomes
  • c) Plasma membrane receptor
  • d) Mitochondria
Explanation: When lipoproteins (such as LDL) enter a cell via receptor-mediated endocytosis, they are internalized into vesicles that eventually fuse with lysosomes. Inside the lysosomes, the enzyme lysosomal acid lipase hydrolyzes the cholesterol esters into free cholesterol and fatty acids for use by the cell.
Why other options are incorrect:
  • • Endoplasmic reticulum: This is the site where cholesterol is synthesized and where excess cholesterol is re-esterified by the enzyme ACAT, but it is not where the initial hydrolysis of imported esters occurs.
  • • Plasma membrane receptor: The receptor (e.g., LDL receptor) is responsible for binding and bringing the lipoprotein into the cell, but it does not perform the chemical hydrolysis.
  • • Mitochondria: While mitochondria are involved in steroid hormone synthesis from cholesterol in specific cells, they are not the site for the hydrolysis of endocytosed cholesterol esters.
Which of the following phospholipids is localized to a greater extent in the outer leaflet of the membrane lipid bilayer?
  • a) Choline phosphoglycerides
  • b) Ethanolamine phosphoglycerides
  • c) Inositol phosphoglycerides
  • d) Serine phosphoglycerides
Explanation: The plasma membrane lipid bilayer is asymmetric. Choline phosphoglycerides (Phosphatidylcholine) and Sphingomyelin are primarily localized in the outer leaflet (extracellular side). This asymmetry is maintained by enzymes called flippases, floppases, and scramblases.
Why other options are incorrect:
  • • Ethanolamine phosphoglycerides: Primarily found in the inner (cytosolic) leaflet of the plasma membrane.
  • • Inositol phosphoglycerides: Almost exclusively located in the inner leaflet, where they play a major role in cell signaling (e.g., PIP2).
  • • Serine phosphoglycerides: Strictly localized to the inner leaflet. If Phosphatidylserine appears on the outer leaflet, it serves as a signal for apoptosis (programmed cell death) for macrophages to engulf the cell.
All the following processes occur rapidly in the membrane lipid bilayer except:
  • a) Flexing of fatty acyl chains
  • b) Lateral diffusion of phospholipids
  • c) Transbilayer diffusion of phospholipids
  • d) Rotation of phospholipids around their long axes
Explanation: Transbilayer diffusion (also known as “flip-flop”) is an extremely slow process. This is because it requires the hydrophilic (polar) head group of the phospholipid to pass through the hydrophobic core of the membrane, which is energetically unfavorable. Without the help of specific enzymes like flippases or scramblases, this can take hours or even days.
Why other options are incorrect:
  • • Flexing of fatty acyl chains: The hydrocarbon tails of phospholipids are in constant, rapid motion, flexing and bending billions of times per second.
  • • Lateral diffusion: Phospholipids move sideways within the same leaflet very rapidly, allowing them to travel the length of a bacterial cell in just a few seconds.
  • • Rotation: Phospholipids rotate very rapidly around their long (vertical) axes, contributing to the overall fluidity of the membrane.
Which of the following statements is correct about membrane cholesterol?
  • a) The hydroxyl group is located near the centre of the lipid layer
  • b) Most of the cholesterol is in the form of a cholesterol ester
  • c) The steroid nucleus forms a rigid, planar structure
  • d) The hydrocarbon chain of cholesterol projects into the extracellular fluid
Explanation: The steroid nucleus of cholesterol (the four-ring system) is a rigid and planar structure. This allows it to pack tightly between the fatty acid tails of phospholipids in the membrane, where it helps regulate membrane fluidity and provides structural stability.
Why other options are incorrect:
  • • Option a: The hydroxyl (-OH) group is polar and is located near the surface of the bilayer (interacting with water and phospholipid head groups), not the center.
  • • Option b: Cholesterol in the plasma membrane is almost entirely unesterified (free). Cholesterol esters are stored in lipid droplets or transported in lipoproteins.
  • • Option d: The hydrophobic hydrocarbon chain projects into the hydrophobic interior (the core) of the lipid bilayer, not into the aqueous extracellular fluid.
Which one is the heaviest particulate component of the cell?
  • a) Nucleus
  • b) Mitochondria
  • c) Cytoplasm
  • d) Golgi apparatus
Explanation: The Nucleus is the largest, densest, and heaviest organelle within a eukaryotic cell. In the laboratory technique of differential centrifugation, the nucleus is the first particulate component to sediment (settle at the bottom) at the lowest centrifugal speeds (approx. 600–1,000 x g).
Why other options are incorrect:
  • • Mitochondria: These are much smaller and lighter than the nucleus; they require higher speeds (approx. 10,000–15,000 x g) to sediment.
  • • Cytoplasm: This is the fluid medium (cytosol) containing the organelles; it is not a “particulate component” itself but rather the substance in which particulates are suspended.
  • • Golgi apparatus: This is part of the microsomal fraction (along with the ER) and is much lighter than both the nucleus and mitochondria, requiring very high speeds to isolate.
Which one is the largest particulate of the cytoplasm?
  • a) Lysosomes
  • b) Mitochondria
  • c) Golgi apparatus
  • d) Endoplasmic reticulum
Explanation: Excluding the nucleus (which is the largest organelle in the cell overall), Mitochondria are generally considered the largest discrete particulate organelles within the cytoplasm. They are large enough to be seen under a high-power light microscope and have a complex double-membrane structure.
Why other options are incorrect:
  • • Lysosomes: These are much smaller, simple spherical vesicles (approx. 0.1 to 1.2 micrometers).
  • • Golgi apparatus: While it can be large in secretory cells, it consists of a series of flattened sacs (cisternae) and is generally considered smaller in total volume/density than the mitochondrial network.
  • • Endoplasmic reticulum: Although it is an extensive network of membranes that can occupy a lot of space, it is characterized as a continuous membrane system rather than a “particulate” body in the context of cell fractionation.
The degradative processes are categorized under the heading of:
  • a) Anabolism
  • b) Catabolism
  • c) Metabolism
  • d) None of the above
Explanation: Catabolism refers to the set of metabolic pathways that break down large, complex molecules (like carbohydrates, lipids, and proteins) into smaller, simpler units. These degradative processes usually release energy, which the body captures in the form of ATP.
Why other options are incorrect:
  • • Anabolism: This is the opposite of catabolism. It involves biosynthetic processes that build complex molecules from simpler ones, requiring an input of energy.
  • • Metabolism: This is the broad term that encompasses both anabolism and catabolism. While degradative processes are part of metabolism, they are specifically categorized as catabolic.
  • • None of the above: This is incorrect because “Catabolism” is the standard scientific term for degradative metabolism.
The exchange of material takes place:
  • a) Only by diffusion
  • b) Only by active transport
  • c) Only by pinocytosis
  • d) All of these
Explanation: The exchange of materials across the biological membrane occurs through several distinct mechanisms depending on the size, charge, and concentration gradient of the molecules. Diffusion handles gases and small molecules; Active transport moves ions against gradients using ATP; and Pinocytosis (a form of endocytosis) allows the cell to take in fluids and dissolved solutes.
Why other options are incorrect:
  • • Only by diffusion: Incorrect because diffusion is a passive process and cannot move substances against a concentration gradient or transport large bulk materials.
  • • Only by active transport: Incorrect because many essential substances (like Oxygen and Carbon Dioxide) move freely via passive diffusion without needing energy.
  • • Only by pinocytosis: Incorrect because pinocytosis is a specialized form of bulk transport; it is not the primary way small ions or individual molecules enter the cell.
The average pH of Urine is:
  • a) 7.0
  • b) 6.0
  • c) 8.0
  • d) 0.0
Explanation: The average pH of human urine is approximately 6.0, which is slightly acidic. Although the normal range can vary significantly from 4.5 to 8.0 depending on diet and health status, a typical mixed diet results in the production of metabolic acids that lower the pH below neutral.
Why other options are incorrect:
  • • 7.0: This is a neutral pH. While urine can be neutral, it is not the typical average for most individuals.
  • • 8.0: This is an alkaline (basic) pH. Urine may reach this level after a strictly vegetarian diet or due to certain urinary tract infections, but it is not the average.
  • • 0.0: This is extremely acidic (equivalent to battery acid). A biological fluid at this pH would cause severe tissue damage and is not possible in a living human.
The pH of blood is 7.4 when the ratio between H2CO3 and NaHCO3 is:
  • a) 1 : 10
  • b) 1 : 20
  • c) 1 : 25
  • d) 1 : 30
Explanation: According to the Henderson-Hasselbalch equation, the pH of a buffer system depends on the pKa and the log of the ratio of salt (base) to acid. For the bicarbonate buffer system in human blood, the pKa is 6.1. To maintain a physiological pH of 7.4, the ratio of bicarbonate (base) to carbonic acid (acid) must be 20:1. Therefore, the ratio of H2CO3 to NaHCO3 is 1 : 20.
Why other options are incorrect:
  • • 1 : 10: This ratio would result in a lower (more acidic) blood pH, leading to acidosis.
  • • 1 : 25 / 1 : 30: These ratios would result in a higher (more alkaline) blood pH, leading to alkalosis. The 20:1 ratio is specifically required to keep the pH at the homeostatic set point of 7.4.
The phenomenon of osmosis is opposite to that of:
  • a) Diffusion
  • b) Effusion
  • c) Affusion
  • d) Coagulation
Explanation: Osmosis and Diffusion are often compared as opposites in terms of particle movement. In diffusion, solute particles move from an area of higher concentration to lower concentration. In osmosis, it is the solvent (water) that moves from an area of lower solute concentration to higher solute concentration across a semi-permeable membrane.
Why other options are incorrect:
  • • Effusion: This refers specifically to the movement of gas particles through a tiny hole (pinhole) into a vacuum or lower-pressure area.
  • • Affusion: This is a medical or religious term referring to the act of pouring liquid over the body (e.g., in hydrotherapy or baptism).
  • • Coagulation: This is the process by which a liquid (like blood or milk) changes into a solid or semi-solid state; it is a chemical/structural change rather than a transport mechanism.
The surface tension in the intestinal lumen between fat droplets and the aqueous medium is decreased by:
  • a) Bile Salts
  • b) Bile acids
  • c) Conc. H2SO4
  • d) Acetic acid
Explanation: Bile salts (such as sodium glycocholate and sodium taurocholate) act as powerful biological detergents. They possess both a hydrophilic and a hydrophobic side, which allows them to lower the surface tension at the oil-water interface. This process, known as emulsification, breaks large fat globules into tiny droplets, increasing the surface area for digestive enzymes like lipase to work.
Why other options are incorrect:
  • • Bile acids: While bile salts are derived from bile acids, it is the conjugated salt form that is physiologically active in the intestine for lowering surface tension.
  • • Conc. H2SO4: Concentrated sulfuric acid is a highly corrosive mineral acid. It is not found in the digestive system and would cause severe tissue damage.
  • • Acetic acid: This is a weak organic acid (found in vinegar). It does not have the amphipathic structure necessary to act as an emulsifying agent for fats.
Which of the following is located in the mitochondria?
  • a) Cytochrome oxidase
  • b) Succinate dehydrogenase
  • c) Dihydrolipoyl dehydrogenase
  • d) All of these
Explanation: The mitochondria house several key metabolic enzymes. Cytochrome oxidase (Complex IV) and Succinate dehydrogenase (Complex II) are both integral components of the Electron Transport Chain located in the inner mitochondrial membrane. Dihydrolipoyl dehydrogenase is a shared component (E3) of the Pyruvate Dehydrogenase and alpha-ketoglutarate dehydrogenase complexes found in the mitochondrial matrix.
Details on each enzyme:
  • • Cytochrome oxidase: The final enzyme of the ETC that reduces oxygen to water.
  • • Succinate dehydrogenase: The only enzyme that participates in both the Citric Acid Cycle and the Electron Transport Chain.
  • • Dihydrolipoyl dehydrogenase: Essential for the oxidative decarboxylation of pyruvate and alpha-keto acids within the matrix.
The most active site of protein synthesis is the:
  • a) Nucleus
  • b) Ribosome
  • c) Mitochondrion
  • d) Cell sap
Explanation: Ribosomes are known as the “protein factories” of the cell. They are the sites where translation occurs—the process of decoding messenger RNA (mRNA) to assemble amino acids into specific polypeptide chains (proteins). Ribosomes can be found floating freely in the cytosol or attached to the Rough Endoplasmic Reticulum.
Why other options are incorrect:
  • • Nucleus: This is the site of transcription (DNA to mRNA), but actual protein synthesis (translation) does not take place here; the mRNA must first exit the nucleus.
  • • Mitochondrion: While mitochondria have their own ribosomes and produce a very small number of their own proteins, they are not the primary or “most active” site for general cellular protein synthesis.
  • • Cell sap: Also known as cytosol/cytoplasm. While ribosomes are located within the cell sap, the “sap” itself is the fluid medium, not the functional machinery responsible for synthesis.
The fatty acids can be transported into and out of mitochondria through:
  • a) Active transport
  • b) Facilitated transfer
  • c) Non-facilitated transfer
  • d) None of these
Explanation: Long-chain fatty acids cannot cross the inner mitochondrial membrane freely. They require a specialized facilitated transfer mechanism known as the Carnitine Shuttle. In this process, the fatty acyl group is transferred to carnitine by the enzyme CPT-I, transported across the membrane by a translocase, and then released back into the matrix.
Why other options are incorrect:
  • • Active transport: While ATP is used to “activate” fatty acids into Acyl-CoA in the cytosol, the actual translocation across the membrane via the carnitine carrier is a form of facilitated diffusion/transfer rather than primary active transport.
  • • Non-facilitated transfer: Simple diffusion only occurs for very short or medium-chain fatty acids. Long-chain fatty acids, which make up the bulk of dietary fats, are too large and polar to pass without help.
  • • None of these: This is incorrect as “facilitated transfer” accurately describes the carnitine-mediated translocation process.
Mitochondrial DNA is:
  • a) Circular double stranded
  • b) Circular single stranded
  • c) Linear double helix
  • d) None of these
Explanation: Mitochondrial DNA (mtDNA) is a small, circular, double-stranded DNA molecule. It is located inside mitochondria and contains genes important for mitochondrial function.
Why other options are incorrect:
  • • Circular single stranded: Mitochondrial DNA consists of two complementary DNA strands.
  • • Linear double helix: Nuclear DNA contains linear chromosomes, whereas mitochondrial DNA is circular.
  • • None of these: Incorrect because mitochondrial DNA is circular and double-stranded.
The absorption of intact protein from the gut in the foetal and newborn animals takes place by:
  • a) Pinocytosis
  • b) Passive diffusion
  • c) Simple diffusion
  • d) Active transport
Explanation: In fetal and newborn animals, the intestinal mucosa is uniquely permeable to large molecules. Pinocytosis (a form of endocytosis) allows these animals to absorb intact immunoglobulins (antibodies) from colostrum directly into their circulation. This provides “passive immunity” until their own immune system and digestive enzymes are fully developed.
Why other options are incorrect:
  • • Passive/Simple diffusion: Proteins are large polymers that cannot pass through the phospholipid bilayer or small pores via a concentration gradient.
  • • Active transport: This mechanism typically involves specific carrier proteins moving small ions or molecules (like amino acids) against a gradient, but it is not used for the bulk intake of whole protein molecules.
The cellular organelles called “suicide bags” are:
  • a) Lysosomes
  • b) Ribosomes
  • c) Nucleolus
  • d) Golgi’s bodies
Explanation: Lysosomes are known as “suicide bags” because they contain powerful hydrolytic enzymes (acid hydrolases) that can break down all types of biological polymers. If the lysosomal membrane ruptures or the cell is severely damaged, these enzymes are released into the cytoplasm and digest the cell itself, a process known as autolysis.
Why other options are incorrect:
  • • Ribosomes: These are the “protein factories” of the cell; they build proteins rather than destroying the cell.
  • • Nucleolus: A structure within the nucleus primarily responsible for the synthesis of ribosomal RNA (rRNA) and the assembly of ribosome subunits.
  • • Golgi’s bodies: Often called the “post office” of the cell, they are involved in modifying, sorting, and packaging proteins and lipids for secretion or delivery to other organelles.
From the biological viewpoint, solutions can be grouped into
  • a) Isotonic solution
  • b) Hypotonic solutions
  • c) Hypertonic solution
  • d) All of these
Explanation: From the biological viewpoint, solutions are classified as isotonic, hypotonic, or hypertonic based on their solute concentration relative to a cell or another solution.
Why other options are incorrect:
  • • Isotonic solution: This is one of the three major biological classifications of solutions.
  • • Hypotonic solutions: These have a lower solute concentration compared with the reference solution and are another major classification.
  • • Hypertonic solution: These have a higher solute concentration compared with the reference solution and are also a major classification.
Bulk transport across cell membrane is accomplished by:
  • a) Phagocytosis
  • b) Pinocytosis
  • c) Extrusion
  • d) All of these
Explanation: Bulk transport involves the movement of large molecules or quantities of substances across the cell membrane via vesicle formation. It includes both endocytosis (Phagocytosis and Pinocytosis) and exocytosis (Extrusion).
Definitions:
  • • Phagocytosis: Often called “cell eating,” it is the process by which a cell engulfs large solid particles.
  • • Pinocytosis: Often called “cell drinking,” it is the process of taking in fluids and dissolved small molecules.
  • • Extrusion (Exocytosis): The process by which the cell expels waste or secretes products like hormones out of the cell membrane.
The ability of the cell membrane to act as a selective barrier depends upon
  • a) The lipid composition of the membrane
  • b) The pores which allows small molecules
  • c) The special mediated transport systems
  • d) All of these
Explanation: The selective barrier function of the cell membrane depends on its lipid composition, membrane pores, and specialized transport systems. Together, these features regulate the movement of substances into and out of the cell.
Why other options are incorrect:
  • • The lipid composition: The lipid bilayer determines which substances can pass through the membrane easily.
  • • The pores: Membrane pores or channels allow selected small molecules and ions to cross.
  • • Special mediated transport systems: Transport proteins selectively move specific substances across the membrane.
Carrier protein can
  • a) Transport only one substance
  • b) Transport more than one substance
  • c) Exchange one substance to another
  • d) Perform all of these functions
Explanation: Carrier proteins can transport a single substance, transport multiple substances together, or exchange one substance for another. Therefore, carrier proteins can perform all of these functions.
Why other options are incorrect:
  • • Transport only one substance: Some carrier proteins transport one type of substance, but this is not their only function.
  • • Transport more than one substance: Cotransporters can transport two or more substances.
  • • Exchange one substance to another: Exchangers (antiporters) exchange one substance for another.
A lipid bilayer is permeable to:
  • a) Urea
  • b) Fructose
  • c) Glucose
  • d) Potassium
Explanation: The pure lipid bilayer is semi-permeable. It allows small, uncharged polar molecules and small non-polar molecules to pass through via simple diffusion. Urea is a small, uncharged molecule that can slowly cross the lipid bilayer.
Why other options are incorrect:
  • • Fructose & Glucose: These are large, polar organic molecules (hexose sugars) that cannot pass through the hydrophobic core of the lipid bilayer without the help of transport proteins.
  • • Potassium (K+): Although small, ions carry a charge. Charged particles are highly excluded by the hydrophobic interior of the membrane and require specific ion channels to cross.
The Golgi complex:
  • a) Synthesizes proteins
  • b) Produces ATP
  • c) Provides a pathway for transporting chemicals
  • d) Forms glycoproteins
Explanation: The Golgi complex (or Golgi apparatus) acts as the “packaging center” of the cell. Its primary role is to modify, sort, and package proteins and lipids that are synthesized in the ER. One of its most important functions is glycosylation, which is the addition of carbohydrate chains to proteins to form glycoproteins.
Why other options are incorrect:
  • • Synthesizes proteins: This is the function of ribosomes (often attached to the Rough ER).
  • • Produces ATP: This is the function of the mitochondria, the powerhouse of the cell.
  • • Pathway for transporting chemicals: This is primarily the function of the Endoplasmic Reticulum (ER).
The following points about microfilaments are true except:
  • a) They form cytoskeleton with microtubules
  • b) They provide support and shape
  • c) They form intracellular conducting channels
  • d) They are involved in muscle cell contraction
Explanation: Microfilaments (mainly composed of actin) are solid, rod-like structures that provide mechanical support and enable movement. However, they do not function as “conducting channels.”
Fact Check:
  • • Cytoskeleton (True): Microfilaments, along with microtubules and intermediate filaments, constitute the cell’s structural framework.
  • • Support and Shape (True): They help maintain the cell’s shape and are responsible for the consistency of the cytoplasm (sol-gel states).
  • • Muscle Contraction (True): Actin microfilaments interact with myosin to produce force and movement in muscle cells.
  • • Conducting Channels (False): Intracellular transport and “pathway” functions are primarily handled by the Endoplasmic Reticulum or microtubules (acting as tracks for motor proteins).
The following substances are cell inclusions except
  • a) Melanin
  • b) Glycogen
  • c) Lipids
  • d) Centrosome
Explanation: The centrosome is a cell organelle involved in organizing microtubules and forming the spindle during cell division. It is not considered a cell inclusion. Melanin, glycogen, and lipids can occur as non-living cytoplasmic inclusions.
Why other options are incorrect:
  • • Melanin: A pigment that can be present as a cytoplasmic inclusion.
  • • Glycogen: A storage carbohydrate found in cells as cytoplasmic granules.
  • • Lipids: Stored in cells as lipid droplets and considered cellular inclusions.
Fatty acids can be transported into and out of cell membrane by:
  • a) Active transport
  • b) Facilitated transport
  • c) Diffusion
  • d) Osmosis
Explanation: Fatty acids are lipid-soluble (non-polar) molecules. Since the cell membrane is primarily composed of a phospholipid bilayer, lipid-soluble substances can dissolve directly into the lipid phase of the membrane and pass through it via simple diffusion.
Why other options are incorrect:
  • • Active transport: This requires ATP and carrier proteins to move substances against a concentration gradient, typically used for ions or large polar molecules.
  • • Facilitated transport: This uses specific carrier proteins or channels for molecules that are not lipid-soluble (like glucose). While some long-chain fatty acids use transporters, the primary general mechanism for fatty acids is simple diffusion.
  • • Osmosis: This term refers specifically to the diffusion of water across a semi-permeable membrane.
Enzymes catalyzing electron transport are present mainly in the:
  • a) Ribosomes
  • b) Endoplasmic reticulum
  • c) Lysosomes
  • d) Inner mitochondrial membrane
Explanation: The Inner Mitochondrial Membrane contains the Electron Transport Chain (ETC), a series of protein complexes and enzymes. These enzymes facilitate the transfer of electrons and the pumping of protons to generate a gradient used for ATP synthesis (Oxidative Phosphorylation).
Why other options are incorrect:
  • • Ribosomes: These are the sites of protein synthesis (translation), not electron transport.
  • • Endoplasmic Reticulum: Involved in lipid synthesis, calcium storage, and protein folding/transport.
  • • Lysosomes: Known as the “suicidal bags” of the cell, they contain hydrolytic enzymes for digesting waste and cellular debris.
Mature erythrocytes do not contain
  • a) Glycolytic enzymes
  • b) HMP shunt enzymes
  • c) Pyridine nucleotide
  • d) ATP
Explanation: Mature erythrocytes lack a nucleus and mitochondria, but they retain glycolytic enzymes, HMP shunt enzymes, pyridine nucleotides, and ATP. Therefore, none of these substances is completely absent. However, if the question requires the best answer among the given choices, it is typically keyed as HMP shunt enzymes in some older MCQ sources.
Why other options are incorrect:
  • • Glycolytic enzymes: Mature RBCs depend on glycolysis for ATP production.
  • • Pyridine nucleotide: NAD/NADH and related cofactors are present and participate in RBC metabolism.
  • • ATP: ATP is produced mainly through anaerobic glycolysis and is essential for RBC membrane functions.
In mammalian cells rRNA is produced mainly in the:
  • a) Endoplasmic reticulum
  • b) Ribosome
  • c) Nucleolus
  • d) Nucleus
Explanation: The Nucleolus is a distinct, non-membrane bound structure within the nucleus. Its primary function is the transcription of ribosomal RNA (rRNA) and the assembly of ribosomal subunits.
Why other options are incorrect:
  • • Endoplasmic reticulum: Involved in protein folding and transport, but does not synthesize RNA.
  • • Ribosome: While ribosomes are *made* of rRNA and protein, they are the site where protein synthesis (translation) happens, not where the RNA itself is produced.
  • • Nucleus: While the nucleolus is located *inside* the nucleus, “Nucleolus” is the more specific and correct answer for where rRNA production is concentrated.
Genetic information of nuclear DNA is transmitted to the site of protein synthesis by:
  • a) rRNA
  • b) mRNA
  • c) tRNA
  • d) Polysomes
Explanation: mRNA (messenger RNA) is synthesized in the nucleus during transcription. It carries the genetic “message” from the DNA to the ribosomes in the cytoplasm, where protein synthesis occurs.
Why other options are incorrect:
  • • rRNA: Ribosomal RNA forms the structural and catalytic core of the ribosome, but it does not carry the specific genetic code for a protein.
  • • tRNA: Transfer RNA acts as an adapter molecule that brings specific amino acids to the ribosome; it reads the code on the mRNA but does not carry it from the nucleus.
  • • Polysomes: These are groups of ribosomes bound to a single mRNA molecule. While they are involved in translation, they are a structural complex rather than the transmission molecule itself.
The power house of the cell is:
  • a) Nucleus
  • b) Cell membrane
  • c) Mitochondria
  • d) Lysosomes
Explanation: Mitochondria are known as the “powerhouse of the cell” because they are responsible for producing ATP (Adenosine Triphosphate), the main energy currency of the cell, through cellular respiration.
Why other options are incorrect:
  • • Nucleus: Known as the “brain” or control center of the cell as it contains the genetic material (DNA).
  • • Cell membrane: Acts as a protective barrier and regulates the passage of substances into and out of the cell.
  • • Lysosomes: Known as “suicide bags” because they contain digestive enzymes that break down waste materials and cellular debris.
The digestive enzymes of cellular compounds are confined to:
  • a) Lysosomes
  • b) Ribosomes
  • c) Peroxisomes
  • d) Polysomes
Explanation: Lysosomes are membrane-bound organelles that contain acidic hydrolytic enzymes capable of breaking down all types of biological polymers—proteins, nucleic acids, carbohydrates, and lipids.
Why other options are incorrect:
  • • Ribosomes: These are the sites of protein synthesis (translation), not digestion.
  • • Peroxisomes: These contain oxidative enzymes (like catalase) primarily involved in lipid metabolism and chemical detoxification, rather than general cellular digestion.
  • • Polysomes: These are simply strings of ribosomes attached to a single mRNA molecule to synthesize multiple copies of a protein simultaneously.
The general formula of monosaccharides is:
  • a) CnH2nOn
  • b) C2nH2On
  • c) CnH2O2n
  • d) CnH2nO2n
Explanation: Monosaccharides are simple sugars that follow the general chemical formula (CH2O)n, which is expressed as CnH2nOn. This reflects the 1:2:1 ratio of Carbon, Hydrogen, and Oxygen.
Why other options are incorrect:
  • • C2nH2On: This formula provides an incorrect ratio of carbon to hydrogen and oxygen for a carbohydrate.
  • • CnH2O2n: This would imply a significantly higher amount of oxygen than carbon, which does not match the molecular structure of sugars.
  • • CnH2nO2n: While this includes the 2n hydrogen count, it doubles the required oxygen atoms, making it incorrect for simple monosaccharides.
The general formula of polysaccharides is:
  • a) (C6H10O5)n
  • b) (C6H12O5)n
  • c) (C6H10O6)n
  • d) (C6H10O6)n
Explanation: Polysaccharides like starch and cellulose are polymers of hexose sugars (C6H12O6). When these monomers join via glycosidic bonds, a molecule of water (H2O) is removed for every bond formed. This results in the repeating unit formula (C6H10O5)n.
Why other options are incorrect:
  • • (C6H12O5)n: This formula does not account for the loss of two hydrogen atoms during the dehydration synthesis process.
  • • (C6H10O6)n: This formula suggests that only hydrogen was lost, whereas a water molecule (two hydrogens and one oxygen) must be removed.
  • • (C6H10O6)n: (Duplicate option) Incorrect for the same reason—it fails to reflect the removal of the oxygen atom during bond formation.
Which of the following is an aldose sugar?
  • a) Glycerose
  • b) Ribulose
  • c) Erythrulose
  • d) Dihydroxyacetone
Explanation: An aldose is a monosaccharide that contains an aldehyde group (-CHO). Glycerose (also known as glyceraldehyde) is the simplest aldose sugar.
Why other options are incorrect:
  • • Ribulose: This is a ketose sugar (specifically a ketopentose) used in the Calvin cycle.
  • • Erythrulose: This is a ketose sugar (a ketotetrose) often used in self-tanning cosmetics.
  • • Dihydroxyacetone: This is the simplest ketose sugar; it contains a ketone group rather than an aldehyde group.
A triose sugar is:
  • a) Glycerose
  • b) Ribose
  • c) Erythrose
  • d) Fructose
Explanation: A triose is a monosaccharide containing three carbon atoms. Glycerose (glyceraldehyde) and dihydroxyacetone are the two simplest triose sugars.
Why other options are incorrect:
  • • Ribose: This is a pentose sugar, meaning it contains five carbon atoms.
  • • Erythrose: This is a tetrose sugar, meaning it contains four carbon atoms.
  • • Fructose: This is a hexose sugar, meaning it contains six carbon atoms.
A pentose sugar is:
  • a) Dihydroxyacetone
  • b) Ribulose
  • c) Erythrose
  • d) Glucose
Explanation: A pentose is a monosaccharide that contains five carbon atoms. Ribulose is a ketopentose that plays a vital role in the photosynthesis process (specifically the Calvin cycle).
Why other options are incorrect:
  • • Dihydroxyacetone: This is a triose sugar, containing only three carbon atoms.
  • • Erythrose: This is a tetrose sugar, containing four carbon atoms.
  • • Glucose: This is a hexose sugar, containing six carbon atoms.
The pentose sugar present mainly in the heart muscle is:
  • a) Lyxose
  • b) Ribose
  • c) Arabinose
  • d) Xylose
Explanation: Ribose is a vital pentose sugar used by the body to synthesize RNA and ATP (Adenosine Triphosphate). Since the heart muscle has extremely high energy demands and requires a constant supply of ATP to function, ribose plays a critical role in myocardial energy metabolism.
Why other options are incorrect:
  • • Lyxose: While sometimes found in trace amounts in the heart as part of lyxoflavins, it is not the primary functional pentose sugar like ribose.
  • • Arabinose: This pentose is typically found in plant gums and pectin, rather than being a structural or functional component of human muscle tissue.
  • • Xylose: Often referred to as “wood sugar,” it is found in plant materials and is not a major component of animal heart tissue.
Polysaccharides are:
  • a) Polymers
  • b) Acids
  • c) Proteins
  • d) Oils
Explanation: Polysaccharides are complex carbohydrates formed by the polymerization of a large number of monosaccharide units (monomers) joined together by glycosidic bonds. Examples include starch, glycogen, and cellulose.
Why other options are incorrect:
  • • Acids: While some polysaccharides can have acidic groups (like hyaluronic acid), they are primarily classified as complex sugars/carbohydrates, not simple acids.
  • • Proteins: Proteins are polymers, but they are made of amino acids, whereas polysaccharides are made of monosaccharides.
  • • Oils: Oils are a type of lipid (triglycerides) and are hydrophobic molecules, not carbohydrate polymers.
The number of isomers of glucose is:
  • a) 2
  • b) 4
  • c) 8
  • d) 16
Explanation: The number of optical isomers is calculated using the formula 2n, where n is the number of asymmetric (chiral) carbon atoms. In its open-chain form, glucose has 4 chiral centers, so 24 = 16 isomers.
Why other options are incorrect:
  • • 2: This would be the number of isomers for a molecule with only 1 chiral center (like glyceraldehyde).
  • • 4: This would be the number of isomers for a molecule with 2 chiral centers.
  • • 8: This would be the number of isomers for a molecule with 3 chiral centers (like ribose).
Two sugars which differ from one another only in configuration around a single carbon atom are termed:
  • a) Epimers
  • b) Anomers
  • c) Optical isomers
  • d) Stereoisomers
Explanation: Epimers are diastereomers that differ in configuration at only one specific chiral carbon atom. For example, Glucose and Galactose are epimers because they differ only at the C-4 position.
Why other options are incorrect:
  • • Anomers: These are a specific type of epimer that differ in configuration only at the hemiacetal or hemiketal carbon (the anomeric carbon) when the sugar forms a ring.
  • • Optical isomers: This is a broad category of compounds that can rotate plane-polarized light; it includes enantiomers and all diastereomers.
  • • Stereoisomers: This is the general term for all isomers that have the same molecular formula but differ in the spatial arrangement of atoms.
Isomers differing as a result of variations in configuration of the —OH and —H on carbon atoms 2, 3 and 4 of glucose are known as:
  • a) Epimers
  • b) Anomers
  • c) Enantiomers
  • d) Optical isomers
Explanation: Epimers are a type of diastereomer that differ in configuration around only one specific chiral carbon. In the case of glucose, mannose is the C-2 epimer and galactose is the C-4 epimer.
Why other options are incorrect:
  • • Anomers: These isomers differ specifically at the anomeric carbon (C-1 for glucose) only when the sugar is in its cyclic/ring form (e.g., alpha vs. beta glucose).
  • • Enantiomers: These are non-superimposable mirror images of the entire molecule (e.g., D-glucose vs. L-glucose).
  • • Optical isomers: This is a broad term for any isomers that can rotate plane-polarized light, including epimers, anomers, and enantiomers.

Answer Key Summary

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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.

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One Comment

  1. Dasharath Mahanta says:

    Please continue the Mock test chapter 91 onwards

    Reply

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