UHS MDCAT 2024 past paper, Code A

Answer: A. Adenovirus

Adenoviruses are known for their icosahedral (polyhedral) capsid structure, which is composed of 252 capsomeres. This specific number and arrangement are characteristic features of adenoviruses. While bacteriophages can have complex polyhedral heads, their overall structure is more intricate than a simple polyhedral capsid and they are not primarily defined by having 252 capsomeres.

Answer: A. Chromatin

The nucleus stains readily because it contains chromatin, which is composed of DNA and proteins. These molecules have a strong affinity for acidic dyes. Lipids (B) are generally not stained by common nuclear dyes, and thylakoids (D) are found in chloroplasts, not the nucleus.

Answer: C. Spirochete

The endosymbiotic theory proposes that certain organelles within eukaryotic cells originated from free-living prokaryotes. Spirochetes, with their characteristic helical shape and motility, are considered a plausible ancestral candidate for flagella due to their structural and functional similarities to the proposed mechanism of flagellar development. While aerobic bacteria were important for the origin of mitochondria, and amoeboid prokaryotes and spirilla don't have the specific structural features of flagella, spirochetes offer the best resemblance.

Answer: C. Rheumatoid arthritis

Rheumatoid arthritis is an autoimmune disorder where the body's immune system mistakenly attacks its own joints, causing inflammation and damage. Sciatica is nerve pain, spondylosis is age-related degeneration of the spine, and rickets is a vitamin D deficiency. While these conditions affect the skeletal system or nerves, they are not autoimmune in nature.

Answer: D. Hydrocarbon

Hydrocarbons consist only of carbon and hydrogen atoms, which have a very small electronegativity difference. This lack of significant electronegativity difference means they cannot form the strong dipole moments necessary for hydrogen bonding. Ammonia, ethyl alcohol, and carboxylic acid all contain highly electronegative atoms (nitrogen and oxygen) bonded to hydrogen, enabling them to participate in hydrogen bonding.

Answer: B. S

Atomic radius generally decreases across a period due to an increase in effective nuclear charge, which pulls valence electrons closer to the nucleus. Sulfur (S) is furthest to the right among the given elements in the same period (Period 3), experiencing the strongest pull. Sodium (Na) is the most tempting incorrect answer because it is on the far left of the period, exhibiting the largest atomic radius.

Answer: B. Phenol is less acidic than carboxylic acid

The correct answer is B because carboxylic acids are significantly more acidic than phenol. This is due to the greater resonance stabilization of the carboxylate anion compared to the phenoxide anion. Option D is tempting because both are weak acids, but the aromatic ring in phenol allows for better delocalization of the negative charge than the alkyl group in ethanol, making phenol more acidic than ethanol.

Answer: C. Two waves of unequal amplitude

Stationary waves are formed by the superposition of two waves with equal frequency, speed, and amplitude traveling in opposite directions. Option C is correct because if the amplitudes of the two waves are unequal, the resultant wave will not be a perfect stationary wave; there will be some residual displacement. Options A, B, and D are all necessary conditions for the formation of stationary waves.

Answer: B. 1

The emf induced in an AC generator is given by the formula $E = E_{max} \sin(\omega t)$. The maximum value of emf ($E_{max}$) occurs when the sine function is at its maximum value. The maximum value of $\sin(\omega t)$ is 1. Therefore, the emf will be maximum when $\sin(\omega t) = 1$.

Answer: B. Tastes

The sentence uses "soup" as a singular noun, requiring a singular verb. "Tastes" is the correct singular present tense form of the verb "to taste" used to describe a sensory quality. "Taste" is the plural form and would be used with a plural subject.