Deficiency of which vitamin can lead to irritability, loss of appetite, and beriberi?

Correct Answer: C

Rationale: Vitamin deficiencies cause specific symptoms based on their metabolic roles. Beriberi, characterized by muscle weakness, nerve damage, and heart issues, results from insufficient thiamine, a nutrient vital for carbohydrate metabolism and nerve function. Found in whole grains, legumes, and nuts, thiamine deficiency leads to energy deficits, manifesting as irritability and appetite loss. Vitamin K aids clotting, its deficiency causing bleeding, not beriberi. Vitamin B12 supports nerve health and blood formation, with deficiency linked to anemia and neuropathy, not beriberi. Vitamin B6 assists protein metabolism, its lack causing dermatitis or seizures. Thiamine's unique role in energy production and its association with beriberi's distinct symptoms pinpoint it as the correct vitamin.

Correct Answer: D

Rationale: Volume of a cube is edge length cubed. Cube A (10 cm) has a volume of 10 × 10 × 10 = 1000 cm³; Cube B (5 cm) is 5 × 5 × 5 = 125 cm³. Dividing 1000 by 125 yields 8, meaning Cube A's volume is 8 times Cube B's. The edge ratio (10/5 = 2) cubes to 2³ = 8, confirming this. Options 2x, 4x, and 6x miscalculate the exponential relationship, making 8x the correct volumetric comparison.

Correct Answer: C

Rationale: The sarcoplasmic reticulum, a specialized endoplasmic reticulum, stores calcium ions (Ca²⁺) in muscle fibers, releasing them upon T-tubule signals to trigger contraction via troponin binding. T-tubules conduct action potentials, not storing Ca²⁺. Myofibrils, contractile units of actin and myosin, rely on Ca²⁺ but don't store it. Troponin binds Ca²⁺ to shift tropomyosin, not storing it its source is the reticulum. Sarcoplasmic reticulum's storage role ensures rapid, regulated Ca²⁺ availability, distinguishing it from conduction, contraction, or binding structures, critical for muscle activation.

Correct Answer: D

Rationale: Each myosin head uses one ATP molecule, hydrolyzed to ADP and phosphate, to change shape, cocking for the power stroke and detaching post-actin binding, fueling one cycle. Ca²⁺ binds troponin, not myosin, initiating exposure, not shape change. Two ADP or ATP molecules overstate biochemistry confirms one ATP per stroke. Na⁺ drives depolarization, not myosin mechanics. One ATP's energy distinguishes it, critical for efficient contraction, unlike ions or excess molecules.

Correct Answer: A

Rationale: Muscle names may reflect action, movement produced. Adductor longus indicates adduction drawing a limb toward the midline as its primary function, with longus denoting size. Temporalis refers to its temporal bone location, sternocleidomastoid to origin-insertion points, and peroneus longus to its fibular position and length. Only adductor directly names the action, a convention aiding functional understanding, distinguishing it from location- or attachment-based names, essential for predicting muscle roles in movement analysis.