Nutrition and Energy Metabolism MCQs

Biochemistry · 31 free questions with answers & explanations.

1. During prolonged fasting (>72 hours), the brain adapts to use ketone bodies as the primary energy substrate. This adaptation involves upregulation of which enzyme in astrocytes and neurons?
2. A malnourished child develops refeeding syndrome after aggressive intravenous glucose administration. The biochemical mechanism underlying hypophosphataemia in refeeding syndrome is:
3. Brown adipose tissue (BAT) mediates non-shivering thermogenesis. The protein responsible for uncoupling the proton gradient from ATP synthesis is:
4. In obesity, adipose tissue macrophage infiltration promotes systemic insulin resistance. The key adipokine that is DECREASED in obesity and has insulin-sensitising, anti-inflammatory and atheroprotective properties is:
5. During prolonged starvation (>72 hours), brain glucose consumption decreases significantly because the brain adapts by utilizing which alternative fuel, synthesized in the liver from fatty acid-derived acetyl-CoA?
6. In obesity, adipose tissue secretes reduced amounts of adiponectin and increased leptin, resistin, and pro-inflammatory cytokines. The net biochemical consequence on hepatic glucose production is:
7. The respiratory quotient (RQ) provides information about the substrate being oxidized. Which metabolic state is associated with RQ < 0.7?
8. AMPK (AMP-activated protein kinase) is the 'cellular energy sensor'. When AMP:ATP ratio rises, AMPK is activated and phosphorylates which target to simultaneously inhibit fatty acid synthesis AND activate fatty acid oxidation?
9. During prolonged starvation (beyond 5–7 days), the brain adapts its fuel utilisation by switching from glucose to ketone bodies. The biochemical signal that initiates hepatic ketogenesis during fasting is:
10. The respiratory quotient (RQ) of pure fat oxidation is approximately 0.7. The physiological basis for this low value compared with carbohydrate (RQ = 1.0) is:
11. Leptin, secreted by white adipose tissue in proportion to fat mass, reduces food intake through which primary central mechanism?
12. A patient recovering from major surgery receives total parenteral nutrition (TPN). After 2 weeks, the patient develops liver steatosis. The MOST likely biochemical reason for TPN-associated steatosis is:
13. During prolonged starvation (>48 hours), the brain adapts to use ketone bodies as its primary fuel. The rate-limiting enzyme for ketone body utilisation by the brain (and heart) is:
14. A clinical researcher measures resting metabolic rate (RMR) by indirect calorimetry. The respiratory quotient (RQ) of a patient on a fat-predominant diet is 0.72. This indicates that per mole of substrate oxidised, the substrate is generating:
15. A severely malnourished patient is started on aggressive parenteral nutrition. On day 3, he develops severe hypophosphataemia, hypokalaemia, and hypomagnesaemia with cardiac arrhythmia. This presentation is consistent with refeeding syndrome. The underlying mechanism involves:
16. AMP-activated protein kinase (AMPK) is called the cellular energy sensor. In conditions of energy depletion, AMPK activation switches on catabolic pathways. Which combination best describes AMPK's actions?
17. During prolonged starvation (>5 days), the brain adapts to use ketone bodies as its primary fuel. The biochemical marker that BEST signals the shift of the brain to ketone utilisation at the enzyme level is:
18. A patient with severe obesity (BMI 45 kg/m2) has undergone Roux-en-Y gastric bypass. Six months post-surgery, she shows dramatic resolution of type 2 diabetes even before significant weight loss. The MOST likely hormonal mechanism is:
19. Respiratory quotient (RQ) measures the ratio of CO2 produced to O2 consumed. In a patient receiving intravenous lipid emulsion as the sole caloric source, the expected RQ and its implication for ventilatory requirement is:
20. AMP-activated protein kinase (AMPK) is activated by a high AMP:ATP ratio. In skeletal muscle during vigorous exercise, AMPK activation leads to which combination of effects?
21. Leptin is secreted by adipocytes in proportion to fat mass. In diet-induced obesity, leptin resistance develops. The PRIMARY intracellular mechanism of leptin resistance involves:
22. During prolonged starvation (>3 weeks), the brain adapts to use ketone bodies as its primary fuel, reducing its glucose requirement. Which enzyme in astrocytes and neurons converts acetoacetate to acetoacetyl-CoA to enter the TCA cycle?
23. AMPK (AMP-activated protein kinase) acts as a cellular energy sensor. Which combination of effects results from AMPK activation under low energy (high AMP/ATP ratio) conditions?
24. A patient has a resting metabolic rate measured by indirect calorimetry. The respiratory quotient (RQ) is found to be 0.7. This value indicates predominant oxidation of which substrate?
25. Leptin is an adipokine secreted proportional to fat mass. A patient with congenital leptin deficiency (Leptin gene mutation) has severe hyperphagia and obesity. The primary receptor through which leptin suppresses appetite is located in which hypothalamic nucleus, and on which type of neurons?
26. During acute fasting (12–24 hours), the liver maintains blood glucose primarily through glycogenolysis. Which allosteric effector activates hepatic glycogen phosphorylase b to phosphorylase a conversion by promoting its phosphorylation?
27. During prolonged starvation (>3 weeks), the brain adapts to use which fuel, thereby reducing protein catabolism?
28. Respiratory quotient (RQ) of 0.7 indicates the body is primarily oxidising:
29. Leptin, secreted by adipocytes, reduces food intake primarily by acting on:
30. A patient admitted with severe protein-energy malnutrition is started on aggressive total parenteral nutrition (TPN). Three days later he develops hypophosphataemia, hypokalaemia, and cardiac arrhythmias. This is called:
31. AMPK (AMP-activated protein kinase) is activated during energy deficit and exerts all of the following effects EXCEPT: