MHT CET 2024 30 April Shift 2 Question Paper : Download PCB Question Paper with Answers PDF

Trypsinogen is an inactive enzyme (zymogen) secreted by the pancreas into the small intestine. Its activation into trypsin is mediated by enterokinase, an enzyme secreted by the duodenal cells. Enterokinase specifically cleaves a peptide bond in trypsinogen, converting it into its active form, trypsin. Trypsin then catalyzes the activation of other zymogens like chymotrypsinogen, playing a crucial role in protein digestion.

Other options are incorrect because:

• Pepsin is active in the stomach, not involved in trypsinogen activation.
• Amylase breaks down carbohydrates, not proteins.
• Lipase digests fats and has no role in trypsinogen activation.

Conclusion: Enterokinase is the enzyme that converts trypsinogen into trypsin.

Polymerase Chain Reaction (PCR) is a technique used to amplify DNA. In each cycle of PCR, the DNA quantity doubles. If we start with a single DNA molecule, the number of DNA copies after n cycles is given by the formula:

Number of DNA copies = 2^n

For n = 5:

Number of DNA copies = 2^5 = 32

Thus, after five cycles of PCR, 32 DNA copies are produced.

Other options are incorrect because:

• 2^4 = 16 corresponds to four cycles.
• 2^6 = 64 corresponds to six cycles.
• 2^7 = 128 corresponds to seven cycles.

Conclusion: After five cycles, PCR produces 32 DNA copies.

The hypothalamus is a small but critical region of the brain located below the thalamus. Its primary role is maintaining homeostasis, which involves regulating vital physiological processes such as:

• Body temperature
• Hunger and thirst
• Sleep-wake cycles
• Hormonal balance through the pituitary gland

Other options are incorrect because:

• Memory formation is primarily managed by the hippocampus.
• Visual processing is controlled by the occipital lobe of the brain.
• Motor coordination is a function of the cerebellum and motor cortex.

Conclusion: The hypothalamus is responsible for regulating homeostasis, making option (A) the correct answer.

Cerebrospinal fluid (CSF) serves multiple critical functions:

• Cushioning the brain and spinal cord: CSF acts as a protective buffer to prevent mechanical injuries.
• Removing metabolic waste: CSF helps in clearing waste products from the brain.
• Transporting nutrients to the brain: CSF facilitates the delivery of essential nutrients to brain cells.

However, CSF does not transmit nerve impulses. Nerve impulses are carried by neurons using electrical and chemical signaling mechanisms.

Conclusion: The incorrect use of CSF is transmitting nerve impulses, which is the function of neurons.

The relationship between sea anemones and clownfish is mutualistic, where both organisms benefit:

Clownfish receive protection from predators by living among the sea anemones' stinging tentacles, which deter predators. Sea anemones benefit from the cleaning of their tentacles by clownfish and nutrients provided by the fish's waste.

Other options are incorrect because:

Predation: One organism eats another, which does not describe this relationship.

Parasitism: One organism benefits at the expense of the other, which is not the case here.

Competition: Both organisms do not compete for resources.

Conclusion: The relationship between sea anemones and clownfish is mutualistic.

Cellophane tubes were used in early hemodialysis machines due to their semipermeable properties.

These tubes allowed waste products like urea and creatinine to pass through while retaining essential components like proteins and blood cells. This selective filtration was critical for removing toxins from the blood while maintaining its composition.

Other options are incorrect because cellophane tubes were not designed for structural support, delivering medication, or directly filtering blood cells.

Conclusion: The historical use of cellophane tubes in hemodialysis was due to their semipermeable nature.

The pharynx and larynx serve important roles in the respiratory and digestive systems:

The pharynx serves as a pathway for both food and air. It connects the nasal cavity to the esophagus and trachea.

The larynx is involved in the production of sound. It contains the vocal cords, which vibrate to produce sound.

The vocal cords are located in the larynx, not the pharynx, making statement (C) incorrect.

The larynx prevents food from entering the trachea. The epiglottis, a flap of tissue, closes over the trachea during swallowing.

Conclusion: Statements 1, 2, and 4 are correct.

The action potential in neurons is an electrical impulse that enables nerve communication. It occurs in distinct phases:

The correct sequence is: Polarization → Depolarization → Repolarization → Resting Potential

Polarization: The neuron is at its resting potential (~-70 mV) due to the sodium-potassium pump.

Depolarization: Sodium channels open, sodium ions flow in, causing a positive membrane potential.

Repolarization: Potassium channels open, allowing potassium ions to exit the cell, restoring negativity.

Resting Potential: The sodium-potassium pump reestablishes the resting ionic gradients.

Conclusion: The sequence is 3 (Polarization), 1 (Depolarization), 2 (Repolarization), 4 (Resting Potential).

Ethylene is a gaseous plant hormone responsible for processes such as fruit ripening, leaf abscission, and flower wilting. Its primary source is plants, especially ripening fruits, which produce ethylene in significant amounts to accelerate ripening. Ethylene production is commercially harnessed to ripen fruits like bananas and tomatoes during transportation.

Conclusion: Plants, particularly ripening fruits, are the primary source of ethylene.

Geitonogamy is a type of self-pollination where pollen is transferred between flowers of the same plant. It differs from autogamy, which occurs within the same flower, and cross-pollination, which involves different plants.

Conclusion: Geitonogamy involves pollen transfer between flowers of the same plant.

Spermatogenesis is the biological process through which male gametes (sperm cells) are produced in the testes.

The process begins with spermatogonia (germ cells) undergoing mitosis to form primary spermatocytes. The primary spermatocytes undergo meiosis I to produce secondary spermatocytes, which then undergo meiosis II to form spermatids. Finally, spermatids mature into functional sperm cells (spermatozoa) through a process called spermiogenesis.

Conclusion: Spermatogenesis is essential for male fertility and provides sperm cells necessary for reproduction.

Euploidy is the condition in which a cell contains a complete set of chromosomes. Examples include haploid (n), diploid (2n), triploid (3n), and tetraploid (4n).

Aneuploidy is the presence of an abnormal number of chromosomes, such as an extra or missing chromosome. Examples include trisomy 21 (Down syndrome) and Turner syndrome (45, X).

Conclusion: Euploidy maintains the complete set of chromosomes, while aneuploidy results in abnormalities in chromosome numbers.

Chromosomal abnormalities result from changes in chromosome number:

Monosomy: A single copy of a chromosome (e.g., Turner syndrome).

Nullisomy: Absence of a chromosome pair (lethal condition).

Trisomy: Three copies of a chromosome (e.g., Down syndrome, trisomy 21).

Tetrasomy: Four copies of a chromosome (rare condition).

Conclusion: The correct matching of terms with definitions is provided above.

Huntington's Disease is a genetic condition caused by a single copy of a mutated gene on an autosome, making it a dominant autosomal disorder.

Disorders like Cystic Fibrosis and Sickle Cell Anemia are recessive, requiring two copies of the mutated gene to manifest. Hemophilia is an X-linked recessive disorder.

Conclusion: Huntington's Disease is the correct answer because it is inherited in a dominant autosomal manner.

EcoRI is an enzyme that recognizes specific DNA sequences and cleaves the DNA at these sites. It is widely used in molecular biology for DNA manipulation.

DNA polymerase and RNA polymerase synthesize DNA and RNA, respectively, while ligase is involved in joining DNA fragments.

Conclusion: EcoRI is the correct answer as it is a restriction endonuclease.

The early Earth's atmosphere contained carbon dioxide, nitrogen, and ammonia but lacked oxygen.

Oxygen became abundant later due to the photosynthetic activity of organisms like cyanobacteria, which released oxygen as a byproduct.

Conclusion: Oxygen was not present in the early Earth's atmosphere, making it the correct answer.

Plants produce various natural inhibitors, including alkaloids, terpenoids, and glycosides, as defense mechanisms against herbivores and pathogens.

Each of these compounds plays a specific role in plant protection, such as deterring predators, inhibiting microbial growth, or providing toxic effects.

Conclusion: The correct answer is (D) All of the above, as all these compounds are natural inhibitors produced by plants.