DUHS MDCAT 2023 past paper, Code A

Answer: A. Lacking envelope

The correct answer is A because

Answer: C. Middle lamella

The middle lamella is the outermost layer of the plant cell wall, rich in pectin, and acts as a glue to hold adjacent cells together. The primary and secondary walls are internal to the middle lamella, and the cell membrane is inside the cell wall.

Answer: B. Domestication

Artificial selection is the process where humans selectively breed organisms for desired traits, leading to changes in their characteristics over generations. This is essentially domestication, where we have modified plants and animals from their wild ancestors for our use. Vestigial organs (A) are remnants of structures that were functional in ancestors but are no longer used. Mutation (C) is a change in DNA sequence, which is the raw material for evolution but not the definition of artificial selection. Homology (D) refers to similar structures in different species due to common ancestry, a different type of evolutionary evidence.

Answer: A. Synovial

The correct answer is **A) Synovial**. Synovial cavities are specifically found in synovial joints and are lined with a membrane that produces synovial fluid, which lubricates the joint. **C) Acetabulum** is a specific part of the hip joint socket, not a cavity containing lubricating fluid.

Answer: D. Number of protons

The number of protons defines the element, and since the atomic numbers (Z) are different for sodium, magnesium, and aluminum, their atoms will have different numbers of protons. Options A, B, and C are incorrect because these ions are isoelectronic, meaning they have the same number of electrons and thus the same electronic configuration and number of shells.

Answer: B. Open chain and closed chain compound

Organic compounds are fundamentally defined by the presence of carbon. However, their classification goes beyond simply carbon-containing versus non-carbon-containing. Instead, the primary classification is based on the structure of the carbon skeleton, distinguishing between compounds with open, continuous chains of carbon atoms (open chain) and those with closed rings of carbon atoms (closed chain). While other options like homocyclic, heterocyclic, and aromatic are valid ways to categorize *some* organic compounds, they represent sub-classifications and not the broadest, initial division.

Answer: B. ΔE + PΔV

The first law of thermodynamics states that the change in internal energy ($\Delta E$) of a system is equal to the heat added to the system ($q$) minus the work done by the system ($w$), i.e., $\Delta E = q - w$. At constant pressure, the work done by the system is given by $w = P\Delta V$. Therefore, $q = \Delta E + P\Delta V$. If we consider heat at constant pressure as $\Delta H$, then $\Delta H = \Delta E + P\Delta V$. Option A is incorrect because it represents the negative of the heat added.

Answer: C. Coulomb's law

Coulomb's law directly quantifies the electrostatic force between two point charges, establishing a relationship where the force is proportional to the product of the charges and inversely proportional to the square of the distance between them. Ohm's law relates voltage, current, and resistance in a circuit, while Lenz's law describes the direction of induced current, and Ampere's law deals with the magnetic field produced by electric currents.

Answer: C. 3.6 MJ

A kilowatt-hour is a unit of energy. To convert it to joules, we convert kilowatts to watts (1 kW = 1000 W) and hours to seconds (1 hour = 3600 s). Thus, 1 kWh = 1000 W * 3600 s = 3,600,000 J, which is equal to 3.6 MJ. Option A is incorrect because it's too small a value, and Option D is too large.

Answer: A. She usually goes for jogging in evening.

Option A is correct because it follows the standard English sentence structure of Subject-Verb-Object/Complement, with adverbs placed appropriately. The phrase "in the evening" functions as an adverbial phrase indicating time, which correctly follows the main clause. Option D is tempting because "usually" is correctly placed at the beginning, but the rest of the sentence structure is incorrect.