KMU MDCAT 2024 past paper, Code B

Answer: B. Bacteria

The peptidoglycan cell wall is a unique structural component found exclusively in bacteria, providing them with shape and protection. While amoeba and protozoa are eukaryotes and lack cell walls, viruses are not cellular organisms and do not possess cell walls of any kind.

Answer: B. Atrichious

Bacteria lacking flagella are described as atrichious. Amphitrichous, lophotrichous, and peritrichous all refer to bacteria that *do* have flagella, but arranged in different patterns.

Answer: D. Fermentation

The breakdown of glucose by microorganisms can occur through various pathways. While lactic acid fermentation and alcoholic fermentation are specific types of this breakdown, and cellular respiration is a more complete breakdown, "fermentation" is the overarching term that encompasses all anaerobic processes where glucose is broken down without oxygen. Therefore, it is the most accurate and general description.

Answer: B. Excrete

Viruses are not living organisms and lack the cellular machinery for metabolic processes like excretion. They can, however, undergo crystallization, infect other organisms including bacteria (bacteriophages), and possess genetic material that mutates. Option C, infecting bacteria, is a tempting distractor as some viruses do infect bacteria, but viruses can infect a wide range of hosts, not just bacteria.

Answer: B. 450

This is a reversible exothermic reaction. While lower temperatures favor product formation in exothermic reactions according to Le Chatelier's principle, very low temperatures would significantly slow down the reaction rate. Therefore, a moderately high temperature like 450°C is chosen to achieve a reasonable rate of ammonia production while still maintaining a favorable equilibrium position. Option C (5000°C) is excessively high and would likely cause decomposition of ammonia.

Answer: C. Oxygen

Oxygen cannot be detected directly in an organic compound because it is usually present in a combined state, making its isolation and direct detection difficult without breaking down the compound. While chlorine, nitrogen, and phosphorus can be detected using specific qualitative tests like Lassaigne's test or by their characteristic reactions, oxygen's detection requires more sophisticated methods.

Answer: C. 4

The central atom in water is oxygen. Oxygen has 6 valence electrons. Two of these electrons are used to form single bonds with the two hydrogen atoms, leaving 4 non-bonding electrons. These 4 non-bonding electrons form two lone pairs, meaning there are a total of 4 electron pairs (2 bonding + 2 lone pairs) in the valence shell of the central oxygen atom.

Answer: D. zero

The electric potential at the midpoint is the sum of the potentials due to each charge. The potential due to the +5μC charge is positive, and the potential due to the -5μC charge is negative and equal in magnitude. Therefore, the net potential at the midpoint is zero. Option B is tempting because it represents the potential due to a single charge at that distance, but it incorrectly ignores the contribution from the other charge.

Answer: A. Below the threshold frequency

The photoelectric effect only occurs when

Answer: B. The teacher asked, "Did you complete your homework?"

Option B is correct because it correctly punctuates a direct question within quotation marks. The opening quotation mark, capitalized "Did," question mark at the end, and closing quotation mark are all necessary for proper direct quotation. Option A is incorrect because it doesn't use quotation marks for the direct speech. Option C incorrectly starts the quoted question with a lowercase letter and lacks a closing quotation mark and question mark. Option D is incorrect for similar reasons to A and C, lacking proper quotation marks and capitalization.