Ans. c (RBCs). (Ref. Harper's Biochemistry 26th ed. 124, 180)In liver, fatty acid and amino acids are metabolized to acetoacetate and b-hydroxybutyrate (to be used in muscle and brain). In prolonged starvation and diabetic ketoacidosis, oxaloacetate is depleted for gluconeogenesis. In alcoholism, excess NADH shunts oxaloacetate to malate. Both processes stall the TCA cycle, which shunts glucose and FFA to ketone bodies. Excreted in urine. Made from HMG-CoA. Ketone bodies are metabolized by the brain to 2 molecules of acetyl-CoA. Urine test for ketones does not detect b-hydroxybutyrate (favored by high redox state).ORGAN METABOLISMORGANPROPERTIESBrain# Uses glucose as chief energy source.# Can use ketone bodies only after a few days without food.Erythrocytes# Can use only glucose for metabolism.# Lack mitochondria, and release lactic acid into the circulation.Intestine# Release digested carbohydrate into the portal vein.# Release alanine, citrulline, proline, and lactate derived from amino acids.# Can use glutamine for energy production, and releases alanine derived from glutamine.# Forms chylomicrons for triglyceride and cholesterol uptake.Kidney# Uses glutamine for ammonia production.# Uses glutamine for gluconeogenesis after a few days of fasting.Liver# Maintains blood glucose by glycogenolysis and gluconeogenesis.# Contains glucose 6-phosphatase that enables it to release glucose into the circulation.# Active in triglyceride, cholesterol, bile acid production.# Exports cholesterol and triglyceride as VLDL.# Takes up HDL during reverse cholesterol transport0# Liver-derived proteins are albumin, transport proteins and blood clotting factors.# Insulin-responsive organ, except for glucose transport. 0# Forms, but dos not utilize the ketone bodies.# Synthesizes urea.0Muscle# Insulin-responsive glucose and amino acid transport systems.# Uses fatty acids and ketone bodies for energy.# Can perform anaerobic glycolysis for energy production.# Take up and transaminates branched-chain amino acids.#Release lactate, alanine, and glutamine.#Lactate and alanine are used for hepatic gluconeogenesis.Heart# Uses free fatty acids, lactate, ketone bodies, VLDL, TAGs and some glucose for energy.