What is the immediate source of chemical energy that can be used by skeletal muscle tissue to allow muscle contraction?

Correct Answer: C

Rationale: ATP (adenosine triphosphate) is the immediate energy source for muscle contraction, directly fueling myosin cross-bridge cycling by hydrolyzing to ADP and phosphate, releasing energy to pull actin filaments. Glucose, a fuel, must be metabolized via glycolysis or respiration to produce ATP, not an instant source. ADP, a product of ATP breakdown, needs rephosphorylation to become usable ATP. AMP, further down the energy chain, isn't a primary energy carrier. ATP's ready availability in muscle cells ensures instant contraction energy, distinguishing it from substrates requiring processing or depleted molecules, critical for rapid muscle action.

Correct Answer: B

Rationale: The masseter, from zygomatic arch to mandible, elevates the jaw, closing it for chewing, a primary masticatory muscle. Swallowing involves pharyngeal muscles (e.g., constrictors). Lip movement uses orbicularis oris. Eye closure is orbicularis oculi's role. Masseter's powerful jaw elevation distinguishes it, key for biting and grinding, unlike swallowing, lip, or eye actions.

Correct Answer: B

Rationale: Gastrocnemius, spanning the calf, is the largest lower leg muscle, plantarflexing the foot with two heads. Soleus, beneath it, assists but is smaller. Tibialis anterior dorsiflexes, smaller and anterior. Tibialis posterior supports the arch, not largest. Gastrocnemius' bulk and power distinguish it, key for walking and jumping.

Correct Answer: B

Rationale: Chloroplasts, organelles containing chlorophyll, enable organisms to perform photosynthesis, converting sunlight, carbon dioxide, and water into glucose. Organisms with chloroplasts, like plants and algae, are autotrophs, producing their own food. Heterotrophs, such as animals, consume others for energy, lacking chloroplasts. Herbivores eat plants but don't photosynthesize, and primary consumers occupy an ecological role, not a metabolic one. Autotrophs' self-sustaining capability, reliant on chloroplasts, sets them apart, aligning with their role as producers in ecosystems and their cellular structure.

Correct Answer: C

Rationale: Work in physics is force times distance. Both lifted identical chairs the same vertical distance, applying equal force against gravity (the chair's weight). Age or strength doesn't alter the chair's mass or height moved, so work done is identical. Without data on differing distances or forces like lifting speed or extra effort both perform equal work. This reflects work's definition, focusing on displacement and force, not individual capacity, making their efforts mechanically equivalent.