Liquid produced during the contraction of muscle due to anaerobic breakdown is

Correct Answer: C

Rationale: During anaerobic muscle contraction, like in intense exercise, glucose breaks down without oxygen, forming lactic acid. This accumulates when oxygen is scarce, causing the burn felt during sprints. Glucose is the starting fuel, not a product. Oxygen drives aerobic respiration, not produced here. Sugar is a vague term for glucose, not the output. Lactic acid's production marks anaerobic metabolism, distinguishing it from aerobic water and carbon dioxide outputs, explaining fatigue and tying to energy shifts in high-demand scenarios, unlike initial substrates or unrelated elements.

Correct Answer: B

Rationale: In the sliding filament theory, calcium ions bind to troponin on thin filaments, causing a conformational shift that moves tropomyosin, exposing actin's myosin-binding sites. This enables cross-bridges to form, initiating contraction. Calcium doesn't bind myosin directly myosin's activation relies on ATP and site exposure. It also doesn't hydrolyze ATP ATP binds myosin for that. 'All of the above' overextends calcium's role. Its specific binding to troponin is pivotal, triggering the cascade for actin-myosin interaction, distinct from myosin's mechanics or ATP's energy role, central to contraction's molecular choreography.

Correct Answer: B

Rationale: Fast-twitch fibers fatigue quickly, relying on anaerobic glycolysis for rapid, powerful contractions, like sprinting, depleting ATP and accumulating lactic acid fast. Slow-twitch fibers, rich in mitochondria and myoglobin, use aerobic respiration for endurance, fatiguing slower, as in marathons. Equal fatigue ignores their metabolic differences. Non-fatiguing fibers don't exist both tire, but at different rates. Fast-twitch's high-energy, low-endurance profile contrasts slow-twitch's sustained capacity, distinguishing their roles in activity duration and fatigue onset.

Correct Answer: D

Rationale: Trapezius adducts the scapula, pulling it toward the spine, and extends the head backward when both sides contract. Buccinator compresses cheeks. Serratus anterior protracts scapula, not adducts. Sternocleidomastoid turns the head. Trapezius' dual role in scapular and neck movement sets it apart, key for posture and head positioning.

Correct Answer: D

Rationale: Iliopsoas flexes the thigh, lifting it toward the torso, as in stepping. Gluteus maximus extends it, straightening the hip, as in standing. Abduction-adduction involves lateral shifts, not their hip-centric actions. Flexion-extension captures their opposing roles, distinct from side movements, essential for thigh positioning.