Which of these substances is a product of cellular respiration in animals?

Correct Answer: A

Rationale: Cellular respiration in animals breaks down glucose with oxygen to produce energy. This process glycolysis, Krebs cycle, and electron transport chain yields ATP, the cell's energy currency, powering functions like muscle movement. Oxygen is a reactant, not a product, while RNA and DNA are genetic molecules, not respiration outputs. ATP's role as the direct energy product, formed via oxidative phosphorylation, marks it as the primary outcome, essential for cellular work and distinguishing it from structural or input substances.

Correct Answer: D

Rationale: Muscle names encode specific traits. Quadriceps femoris combines quadriceps, indicating four origins four distinct attachment points on the pelvis or femur with femoris, pinpointing its location on the thigh's femur bone. Action (e.g., extension) isn't specified, nor are insertion points (tibia via patella) or fibre direction (e.g., rectus). Location and origin count align with naming conventions, as seen in biceps or triceps, where number denotes origins and the second term locates it. This reflects skeletal muscle nomenclature's focus on anatomical anchors, distinguishing it from action-based or directional terms, crucial for identifying muscles in clinical and educational contexts.

Correct Answer: D

Rationale: Contraction begins with a neural signal. Calcium release from the sarcoplasmic reticulum into the cytoplasm is the first intracellular step, triggered by sarcolemma depolarization. This calcium binds troponin, exposing actin sites, followed by ATP binding and hydrolysis to drive myosin movement. ADP detachment occurs later in the cycle. Calcium's release initiates the cascade, distinct from subsequent biochemical steps, ensuring contraction aligns with nerve input, a critical sequence in muscle physiology.

Correct Answer: A

Rationale: Biceps brachii encodes two origins ( bi- ) two tendon heads on the scapula and location ( brachii ) on the arm's humerus. Action (flexion) isn't specified, nor is size (e.g., maximus) or shape (e.g., deltoid). This origin-location naming, common in muscles like triceps, aids anatomical mapping, distinguishing it from action- or shape-based names, reflecting skeletal muscle's attachment-based classification.

Correct Answer: B

Rationale: Sternocleidomastoid names origin (sternum, clavicle) and insertion (mastoid process), not just location, unlike biceps brachii (arm), rectus abdominus (abdomen), and flexor carpi radialis (wrist). Its attachment-based name distinguishes it from purely locational terms, aiding precise anatomical identification over regional descriptors.