CUET PG 2026 Medical Laboratory Technology Question Paper with Solutions

Concept:
Staphylococcus species are Gram-positive cocci that commonly occur in clusters. To identify and differentiate species within this genus, several biochemical tests are used.

The most important distinguishing test is the Coagulase Test, which detects the presence of the enzyme coagulase. This enzyme converts fibrinogen to fibrin, leading to clot formation.

Step 1: Identify the test that differentiates \textit{Staphylococcus aureus.


Catalase Test – Differentiates \textit{Staphylococcus (catalase positive) from \textit{Streptococcus (catalase negative).
Coagulase Test – Differentiates \textit{Staphylococcus aureus (coagulase positive) from other \textit{Staphylococcus species.
Oxidase Test – Used for identifying certain Gram-negative bacteria.
Indole Test – Used to detect tryptophan metabolism in bacteria.


Thus, the correct test used to differentiate \textit{Staphylococcus aureus is the Coagulase Test. Quick Tip: \textbf{Coagulase-positive Staphylococcus = Staphylococcus aureus.
Most other Staphylococcus species are \textbf{coagulase-negative}.

Concept:
A cryostat is a device used in histology to cut thin sections of frozen tissue for rapid microscopic examination. These frozen sections require quick fixation to preserve cellular structure and prevent tissue degradation.

Acetone is commonly used as a fixative for cryostat sections because it acts rapidly and preserves antigenicity, which is important for immunohistochemistry.

Step 1: Identify the fixative suitable for frozen sections.


Formalin – Common fixative for routine paraffin sections.
Alcohol – Used in cytology and some histological preparations.
Acetone – Ideal rapid fixative for cryostat (frozen) sections.
Bouin's Fixative – Used for specific histological tissues but not frozen sections.


Therefore, the correct answer is Acetone. Quick Tip: \textbf{Acetone} is commonly used for \textbf{cryostat (frozen) tissue sections} because it fixes tissue rapidly and preserves antigenic structures.

Concept:
Hemoglobin estimation is an important laboratory test used to measure the concentration of hemoglobin in blood. Different methods are based on converting hemoglobin into specific derivatives that can be measured colorimetrically.

In the Haldane Method, hemoglobin combines with carbon monoxide to form carboxyhemoglobin, which produces a stable color that can be measured.

Step 1: Identify the method where hemoglobin forms carboxyhemoglobin.


Sahli's Method – Converts hemoglobin to acid hematin.
Cyanmethemoglobin Method – Converts hemoglobin to cyanmethemoglobin.
Haldane Method – Converts hemoglobin to carboxyhemoglobin.
Tallqvist Method – Visual color comparison method.


Thus, the method in which hemoglobin is converted into carboxyhemoglobin is the Haldane Method. Quick Tip: \textbf{Haldane Method} – Hemoglobin forms \textbf{carboxyhemoglobin}.
\textbf{Sahli Method} – Hemoglobin forms \textbf{acid hematin}.
\textbf{Cyanmethemoglobin Method} – Most accurate modern Hb estimation technique.

Concept:
Heme synthesis is a multi-step biochemical pathway that occurs partly in the mitochondria and partly in the cytoplasm of cells. Heme is an essential component of hemoglobin, myoglobin, and certain enzymes.

The final step of heme synthesis involves the insertion of ferrous iron (Fe\(^{2+}\)) into protoporphyrin IX.

Step 1: Identify the enzyme responsible for inserting iron into protoporphyrin IX.


Ferrochelatase – Catalyzes insertion of iron into protoporphyrin IX to form heme.
ALA Synthase – Catalyzes the first step in heme synthesis.
Porphobilinogen Deaminase – Involved in intermediate steps of porphyrin synthesis.
Uroporphyrinogen Decarboxylase – Catalyzes conversion of uroporphyrinogen in the pathway.


Thus, the enzyme responsible for inserting iron into protoporphyrin IX is Ferrochelatase. Quick Tip: \textbf{Ferrochelatase} catalyzes the \textbf{final step of heme synthesis} by inserting Fe\(^{2+}\) into protoporphyrin IX to form heme.

Concept:
The total erythrocyte count (RBC count) is commonly performed using a hemocytometer. To make counting possible, blood must be diluted with an RBC diluting fluid such as Hayem's fluid or Dacie's fluid.

This dilution helps prevent cell clumping and ensures proper distribution of RBCs in the counting chamber.

Step 1: Identify the dilution used for RBC counting.

In manual RBC counting:

Blood is diluted with RBC diluting fluid.
The standard dilution used is 1:200.


Thus, the dilution factor used for total erythrocyte count is 1:200. Quick Tip: For manual cell counts:
\textbf{RBC Count Dilution} = 1:200
\textbf{WBC Count Dilution} = 1:20

Concept:
Galactosemia is a genetic metabolic disorder caused by the deficiency of the enzyme galactose-1-phosphate uridyltransferase (GALT). This enzyme is required for the normal metabolism of galactose, a sugar derived from lactose.

When the enzyme is deficient, galactose-1-phosphate accumulates in the body, leading to toxic effects, especially in the liver, brain, and eyes.

Step 1: Identify the disorder caused by deficiency of galactose-1-phosphate uridyltransferase.


Phenylketonuria – Caused by deficiency of phenylalanine hydroxylase.
Galactosemia – Caused by deficiency of galactose-1-phosphate uridyltransferase.
Alkaptonuria – Caused by deficiency of homogentisic acid oxidase.
Maple Syrup Urine Disease – Caused by deficiency of branched-chain ketoacid dehydrogenase.


Therefore, the correct answer is Galactosemia. Quick Tip: \textbf{Galactosemia} results from deficiency of \textbf{galactose-1-phosphate uridyltransferase (GALT)}, leading to accumulation of galactose metabolites in the body.

Concept:
Human Chorionic Gonadotropin (hCG) is a hormone produced by the trophoblastic cells of the placenta during pregnancy. It plays a key role in maintaining the corpus luteum and supporting progesterone production in early pregnancy.

The level of hCG rises rapidly during the first trimester and is commonly used as a marker for pregnancy detection.

Step 1: Identify the period when hCG levels are highest.


4–5 weeks – hCG begins to rise.
8–10 weeks – hCG reaches its peak concentration.
16–18 weeks – hCG levels begin to decline.
24–26 weeks – hCG stabilizes at lower levels.


Therefore, the peak level of hCG occurs around 8–10 weeks of pregnancy. Quick Tip: \textbf{hCG levels rise rapidly in early pregnancy and peak at about 8–10 weeks}, after which they gradually decline.

Concept:
Immunoglobulins (antibodies) are proteins produced by plasma cells that play a crucial role in the immune response. There are five major classes of immunoglobulins: IgG, IgA, IgM, IgD, and IgE.

Among these, IgG is the most abundant immunoglobulin in human serum and body fluids. It plays an important role in long-term immunity and protection against infections.

Step 1: Identify the immunoglobulin with the highest concentration in serum.


IgA – Mainly present in mucosal secretions.
IgG – Most abundant immunoglobulin in serum.
IgM – First antibody produced during primary immune response.
IgE – Involved in allergic reactions and parasitic infections.


Thus, the immunoglobulin with the highest concentration in the human body is IgG. Quick Tip: \textbf{IgG} constitutes about \textbf{70–75% of total serum immunoglobulins} and can cross the placenta to provide passive immunity to the fetus.

Concept:
Frederick Sanger was the first scientist to determine the complete amino acid sequence of a protein, which was insulin, in 1955. His work was a major milestone in biochemistry and earned him the Nobel Prize in Chemistry.

To identify the N-terminal amino acid of insulin, Sanger used a specific chemical reagent called 1-fluoro-2,4-dinitrobenzene (FDNB), also known as Sanger’s reagent.

Step 1: Identify the reagent used by Sanger in studying insulin structure.


Ninhydrin – Used to detect amino acids.
Phenylisothiocyanate – Used in Edman degradation.
Fluorodinitrobenzene – Sanger’s reagent used to identify N-terminal amino acids.
Biuret Reagent – Used to detect peptide bonds.


Therefore, the reagent used by Sanger to study insulin structure was Fluorodinitrobenzene (FDNB). Quick Tip: \textbf{Sanger’s reagent} = \textbf{1-fluoro-2,4-dinitrobenzene (FDNB)}. It is used to identify the \textbf{N-terminal amino acid} of proteins.

Concept:
Pasteurization is a heat treatment process used to destroy pathogenic microorganisms in milk and other liquids. The Holder method of pasteurization involves heating milk to 63°C for 30 minutes.

Among milk-borne pathogens, Coxiella burnetii, the causative agent of Q fever, is one of the most heat-resistant non-spore-forming bacteria. Pasteurization standards were designed specifically to ensure the destruction of this organism.

Step 1: Identify the bacterium associated with resistance to pasteurization.


Mycobacterium tuberculosis – Destroyed by pasteurization.
Coxiella burnetii – Highly heat-resistant and used as the standard for pasteurization effectiveness.
Salmonella typhi – Destroyed by pasteurization.
Brucella abortus – Destroyed by pasteurization.


Thus, the bacterium capable of surviving inadequate Holder pasteurization conditions is Coxiella burnetii. Quick Tip: \textbf{Coxiella burnetii} is the most heat-resistant non-spore-forming pathogen in milk and is used to determine pasteurization standards.

Concept:
During intense physical activity, skeletal muscles require rapid energy production. The body uses stored carbohydrates in the form of glycogen to generate energy quickly through glycolysis.

Glycogen stored in muscle tissue is broken down into glucose, which is rapidly metabolized to produce ATP.

Step 1: Identify the main energy source during intense muscle activity.


Fatty acids – Used mainly during prolonged, low-intensity exercise.
Glycogen – Primary and rapid energy source during intense activity.
Ketone bodies – Used during prolonged fasting.
Amino acids – Used minimally for energy.


Therefore, the primary energy source for skeletal muscle during intense activity is Glycogen. Quick Tip: \textbf{Muscle glycogen} is the main fuel for \textbf{high-intensity exercise}, as it can rapidly produce ATP through glycolysis.

Concept:
A microtome is an instrument used in histology to cut extremely thin sections of tissue for microscopic examination. Different types of microtomes use different blades depending on the type of section required.

The rocking microtome, also known as the Cambridge microtome, commonly uses a double concave knife. This knife shape allows smooth and precise sectioning of paraffin-embedded tissues.

Step 1: Identify the microtome that uses a double concave knife.


Rotary Microtome – Commonly used for routine paraffin sections.
Rocking Microtome – Uses a double concave knife.
Freezing Microtome – Used for frozen sections.
Sledge Microtome – Used for cutting large or hard tissue blocks.


Thus, the microtome that requires a double concave knife is the Rocking Microtome. Quick Tip: \textbf{Rocking (Cambridge) microtome} commonly uses a \textbf{double concave knife} for cutting paraffin-embedded tissue sections.

Concept:
Milk contains the protein caseinogen, which is soluble in milk. In infants, digestion of milk involves an enzyme called rennin (also known as chymosin).

Rennin converts caseinogen into paracaseinogen, which then combines with calcium ions to form calcium paracaseinate. This reaction causes milk to curdle, allowing easier digestion of milk proteins.

Step 1: Identify the enzyme responsible for milk curdling.


Pepsin – Digests proteins in the stomach.
Rennin – Converts caseinogen into paracaseinogen causing milk curdling.
Trypsin – Pancreatic enzyme for protein digestion.
Lipase – Digests fats.


Therefore, the enzyme responsible for curdling milk is Rennin. Quick Tip: \textbf{Rennin (Chymosin)} converts \textbf{caseinogen → paracaseinogen}, causing milk coagulation in infants.

Concept:
Cellulose is a structural polysaccharide found in plant cell walls. It is composed of repeating units of glucose molecules.

These glucose units are connected by \(\beta\)-1,4 glycosidic linkages. Humans lack the enzyme cellulase, which is required to break this type of bond.

As a result, cellulose cannot be digested in the human digestive system and functions mainly as dietary fiber.

Step 1: Identify the linkage responsible for cellulose indigestibility.


\(\alpha\)-1,4 linkage – Present in starch and digestible by humans.
\(\alpha\)-1,6 linkage – Found in glycogen and starch branching.
\(\beta\)-1,4 linkage – Present in cellulose and indigestible for humans.
\(\beta\)-1,6 linkage – Not characteristic of cellulose structure.


Thus, the linkage responsible for the indigestibility of cellulose is the \(\beta\)-1,4 glycosidic linkage. Quick Tip: \textbf{Starch} → \(\alpha\)-1,4 linkage (digestible)
\textbf{Cellulose} → \(\beta\)-1,4 linkage (indigestible in humans).

Concept:
Streptococcus agalactiae (Group B Streptococcus) is an important pathogen, particularly in neonatal infections.

The CAMP test is used to identify this bacterium. It is based on the synergistic hemolysis produced when the CAMP factor secreted by \textit{S. agalactiae interacts with the \(\beta\)-hemolysin of \textit{Staphylococcus aureus. This interaction produces a characteristic arrowhead-shaped zone of enhanced hemolysis on blood agar.

Step 1: Identify the test used to detect enhanced hemolysis in \textit{S. agalactiae.


CAMP Test – Detects enhanced hemolysis and identifies \textit{Streptococcus agalactiae.
Catalase Test – Differentiates \textit{Staphylococcus from \textit{Streptococcus.
Coagulase Test – Identifies \textit{Staphylococcus aureus.
Oxidase Test – Used mainly for Gram-negative bacteria.


Thus, the biochemical test used to identify \textit{Streptococcus agalactiae is the CAMP Test. Quick Tip: \textbf{CAMP Test produces an \textbf{arrowhead-shaped enhanced hemolysis} with Staphylococcus aureus, indicating Streptococcus agalactiae.