SZABMU MDCAT 2022 past paper, Code A

Answer: B. 25 - 50

The correct answer is B because a granum is a stack of flattened sacs called thylakoids, and this stack typically contains between 25 and 50 individual thylakoids. Option A is tempting as it falls within a similar range, but the more precise and commonly cited range is 25-50.

Answer: B. Activation energy

Enzymes speed up reactions by reducing the amount of energy required to initiate the reaction, which is known as the activation energy. Option A is incorrect because enzymes do not lower kinetic energy; rather, they help more molecules reach the necessary activation energy. Option D is incorrect as enzymes do not alter the potential energy of the reactants or products.

Answer: D. Providing insulation against heat loss

Proteins are crucial for structural support (like collagen), catalyzing reactions as enzymes, and transporting substances across membranes. While fats and other molecules provide insulation, proteins do not have this primary function. Option A, B, and C are all well-established roles of proteins in the body.

Answer: A. Follicle development

FSH, or Follicle-Stimulating Hormone, is crucial in the early stages of the menstrual cycle. It specifically targets the ovaries, stimulating the growth and maturation of ovarian follicles, which contain the eggs. Option B is incorrect because LH (Luteinizing Hormone) triggers ovulation, not FSH.

Answer: B. 20 KHz

Ultrasonic waves are defined as sound waves with frequencies exceeding the upper limit of human hearing. This limit is generally accepted to be around 20 kilohertz (20,000 Hz). Option B, 20 KHz, directly represents this threshold. Option A and C are well within the audible range, and while 2000 KHz is above the audible range, the defining characteristic of ultrasound is its frequency *higher than* 20 KHz, making B the most precise and correct answer.

Answer: B. 130 kmh⁻¹

When two objects move in opposite directions, their relative velocity is the sum of their individual velocities. Therefore, the relative velocity of the two cars is 70 kmh⁻¹ + 60 kmh⁻¹ = 130 kmh⁻¹. Option A is tempting because it represents the difference in velocities, which is used when objects move in the same direction.

Answer: B. 8 days

The half-life of Iodine-131 is 8 days. This is a commonly known value for this radioisotope, often encountered in nuclear medicine and physics. While other isotopes of iodine exist with different half-lives, Iodine-131 specifically has this decay period.

Answer: A. Enthalpy

Enthalpy (H) is defined as the total heat content of a system, including its internal energy (U) and the energy due to pressure-volume work (PV). At constant pressure, any heat added to the system directly increases its enthalpy. Internal energy (U) represents only the kinetic and potential energies of the molecules within the system, not including pressure-volume work.

Answer: C. Hund's rule

Hund's rule states that electrons will singly occupy orbitals within a subshell before pairing up. This process of filling degenerate orbitals one electron at a time, with parallel spins, ensures the lowest energy state, thus explaining the electronic configuration for degenerate orbitals. The Aufbau principle describes the filling order of orbitals in general, and the n+l rule helps determine that order, but neither specifically addresses the distribution of electrons within degenerate orbitals. The Pauli exclusion principle dictates that no two electrons in an atom can have the same four quantum numbers, which is a fundamental rule for filling any orbital, but not specific to degenerate ones.

Answer: A. Hormonal protein

Thyroxin is a hormone that regulates metabolism and is secreted by the thyroid gland. Hormonal proteins are signaling molecules that control various physiological processes. While structural proteins provide support, transport proteins carry substances, and genetic proteins are involved in DNA replication and repair, thyroxin's primary role aligns with the definition of a hormonal protein.