Mammalian dive capacity is largely constrained by the total oxygen stored in muscle tissue… — LSAT

Mammalian dive capacity is largely constrained by the total oxygen stored in muscle tissue, which depends directly on the concentration of the oxygen-binding protein myoglobin. In non-diving terrestrial mammals, excessively high intracellular concentrations of myoglobin lead to fatal electrostatic self-association and precipitation, causing severe muscle necrosis. However, evolutionary genomic analyses of deep-diving aquatic mammals, such as sperm whales and hooded seals, reveal that their myoglobin molecules possess an unusually high positive net surface electrical charge compared to those of terrestrial mammals. These positive charges generate mutual electrostatic repulsion, preventing adjacent myoglobin molecules from aggregating even at cellular concentrations nearly ten times greater than the lethal threshold of terrestrial species. Crucially, while this surface adaptation permits substantially higher total muscular oxygen storage, it leaves the intrinsic oxygen-binding affinity ( $P_{50}$ ) of the individual heme pockets unaltered, nor does it suppress the accumulation of metabolic lactic acid once cellular oxygen reserves are completely exhausted.

Based on the passage, which of the following statements about myoglobin and dive capacity are logically supported? (Select all that apply.)

Terrestrial mammals are unable to safely maintain the elevated myoglobin concentrations found in diving mammals because their myoglobin molecules lack sufficient mutual electrostatic repulsion to prevent damaging cellular aggregation.Cevap
B
The biochemical adaptations of myoglobin in diving mammals enable their muscle tissue to continue aerobic metabolic performance without producing lactic acid after oxygen reserves have been fully consumed.
The evolutionary adaptation that expands muscular oxygen storage in diving mammals does so without altering the baseline chemical affinity for oxygen within the protein's individual heme binding sites.Cevap
D
Deep-diving aquatic mammals withstand prolonged submersion primarily because their individual myoglobin molecules bind oxygen more tightly than those of terrestrial mammals.
E
Sperm whales and hooded seals manage lactic acid accumulation during dives by maintaining lower average core muscle temperatures than terrestrial mammals.

Cevap

The supported statements are the one explaining that terrestrial mammals cannot maintain elevated myoglobin levels due to insufficient electrostatic repulsion to prevent aggregation, and the one stating that the adaptation expands total oxygen storage without altering individual heme oxygen-binding affinity.

The passage establishes two clear textual facts: (1) terrestrial mammals cannot safely hold high myoglobin concentrations because lack of repulsive surface charge leads to aggregation and necrosis, and (2) diving mammals increase oxygen storage purely via higher protein density made possible by repulsive charges, while leaving the intrinsic oxygen-binding affinity (

P_{50}

) of individual heme pockets completely unchanged.

Adım Adım Çözüm

Analyze the passage premises regarding myoglobin charge and protein aggregation.

The passage demonstrates that high positive net surface charge creates electrostatic repulsion preventing aggregation at high density, whereas terrestrial mammals lack this and suffer necrosis from aggregation at high concentrations.

This confirms the statement attributing terrestrial limits to insufficient electrostatic repulsion.

Analyze the passage premises regarding oxygen binding affinity and lactic acid.

The text states that higher storage is achieved without modifying intrinsic heme affinity (

P_{50}

) and without preventing lactic acid accumulation once oxygen runs out.

This confirms the statement regarding unaltered baseline binding affinity and disproves statements claiming tighter binding affinity or absence of lactic acid.

Evaluate remaining options against textual evidence.

Claims regarding thermoregulation/temperature and altered binding affinity represent unsupported leaps or extraneous information.

LSAT inference requires strict entailment derived solely from the provided text.

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Drawing precise deductive inferences from explicit textual mechanisms without adding outside facts or assuming changes in unmentioned variables.

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