Answer: Uncoupled mitochondrial respiration via UCP1 (uncoupling protein), dissipating proton gradient as heat instead of making ATP.
- A Coupled oxidative phosphorylation that maximizes ATP yield from fatty acid oxidation within mitochondria themselves as frequently described
- B Uncoupled mitochondrial respiration via UCP1 (uncoupling protein), dissipating proton gradient as heat instead of making ATP
- C Rhythmic skeletal muscle contraction driven by repeated motor neuron stimulation, as occurs in shivering in most textbook accounts
- D Conversion of stored triglycerides into glycogen, releasing heat during rapid glycolysis breakdown during normal conditions
Correct answer: B. Uncoupled mitochondrial respiration via UCP1 (uncoupling protein), dissipating proton gradient as heat instead of making ATP
Explanation: BAT thermogenesis: UCP1 (thermogenin) in inner mitochondrial membrane creates a proton leak, bypassing ATP synthase. Proton gradient energy released as heat instead of ATP.
The hypothalamus releases hormones that direct the pituitary, which releases its own trophic hormone to a target gland; that gland's hormone output then feeds back (dashed lines) to suppress both the pituitary and hypothalamus once levels are sufficient - a self-correcting loop running the entire endocrine system.
Concept context
The endocrine glands, hormone classification and mechanism of action, and negative feedback regulation.