What should elite athletes ideally consume during prolonged high intensity exercise (>2.5 hours)?

Correct Answer: D

Rationale: Elite athletes in prolonged high-intensity exercise (>2.5 hours), like marathons, should consume 90 g of glucose plus fructose per hour. This mix leverages multiple transporters (SGLT1 for glucose, GLUT5 for fructose), maximizing absorption beyond glucose's 60 g/h limit, delivering ~1.5 g/min of energy. Solo 60 g glucose caps at 1 g/min, insufficient for sustained high intensity. Adding fructose to 60 g boosts uptake slightly, but 90 g optimizes fuel, reducing fatigue. Excess glucose alone (90 g) overloads SGLT1, risking GI distress. The dual-carb approach distinguishes it, critical for elite endurance performance.

Correct Answer: B

Rationale: Triceps brachii extends the forearm, straightening the elbow, with its three heads inserting on the ulna. Biceps brachii flexes it. Brachialis flexes beneath biceps. Deltoid abducts the arm, not elbow-focused. Triceps' extension role distinguishes it, essential for pushing, unlike flexors or shoulder movers.

Correct Answer: B

Rationale: Gram-positive bacteria, with thick peptidoglycan walls, secrete potent, soluble proteins known as exotoxins into the bloodstream. These toxins, like tetanus or botulinum toxins, are released during bacterial growth, targeting specific host cells and causing diseases such as diphtheria or food poisoning. Endotoxins, conversely, are lipopolysaccharides from gram-negative bacteria's outer membranes, released upon cell lysis, not secreted. The generic term 'toxin' lacks specificity, and 'none of the above' dismisses the clear distinction. Exotoxins' solubility in plasma and their secretion mechanism highlight their role in pathogenesis, contrasting with endotoxins' structural origin, making them the precise answer for gram-positive bacterial products.

Correct Answer: D

Rationale: Animals are heterotrophs, obtaining nutrients by consuming organic matter. Bread mold, a fungus, also functions heterotrophically, secreting enzymes to break down external organic substrates like bread, absorbing the products. Seaweed, oak trees, and grass are autotrophs, using photosynthesis to synthesize food from sunlight. Bread mold's reliance on external digestion and absorption mirrors animal nutrition, unlike plants' self-production, making it the closest match in nutritive strategy, reflecting shared ecological roles as decomposers or consumers.

Correct Answer: D

Rationale: During pregnancy, the placenta forms from maternal and fetal tissues, connecting the embryo to the uterine wall. It transfers oxygen and nutrients from the mother's blood to the fetus's, removes waste, and produces hormones like progesterone to sustain pregnancy. The amnion encases the fetus in fluid, the yolk sac provides early nutrients in other species, and the fallopian tube transports eggs. The placenta's nourishing role, critical for fetal development, distinguishes it as the key gestational organ in humans.