Fatty acid beta-oxidation produces acetyl-CoA for TCA cycle or ketogenesis, not glycolysis or gluconeogenesis.

Statement I correctly describes beta-oxidation products entering citric acid cycle or forming ketone bodies, while Statement II wrongly claims entry into glycolysis or glucose formation.

Question Breakdown

Beta-oxidation breaks fatty acids into acetyl-CoA units in mitochondria. Statement I is true: acetyl-CoA fuels TCA cycle (Krebs) for ATP or condenses to ketone bodies (acetoacetate, beta-hydroxybutyrate) in liver during fasting. Statement II is false: acetyl-CoA cannot convert to pyruvate (irreversible pyruvate dehydrogenase), blocking glycolysis entry or net glucose synthesis from fatty acids.

Option Analysis

• Both true: Incorrect. II violates carbon flow.

• Both false: Wrong. I accurate.

• Statement I true, Statement II false: Correct. Classic biochemistry distinction.

• Statement I false, Statement II true: False. Even-chain fatty acids yield only acetyl-CoA.

Correct Answer

Statement I is true but Statement II is false.

Beta-Oxidation Pathway

Fatty acids undergo beta-oxidation yielding acetyl-CoA every 2 carbons. Products enter citric acid cycle (producing NADH/FADH2 → ATP) or combine to form ketone bodies in liver ketogenesis during starvation/diabetes. No reversal to glycolysis exists.

Statement I: Correct Pathway

Acetyl-CoA + oxaloacetate → citrate in TCA; excess acetyl-CoA → HMG-CoA → ketones for brain/heart fuel. Liver lacks glucose-6-phosphatase, preventing fatty acid gluconeogenesis despite glycerol contribution.

Statement II: Metabolic Block

Fatty acids beta-oxidation products cannot enter glycolysis—pyruvate → acetyl-CoA irreversible (no pyruvate carboxylase bypass for fats). Glycerol enters gluconeogenesis, but fatty acyl chains (90% mass) trapped as acetyl-CoA.

Exam Strategy

GATE/NEET trap: “Fat burning = weight loss” ignores acetyl-CoA fate. Mnemonic: “Fats Make Ketones, Carbs Make Glucose”. Statement I textbook; II tests gluconeogenic exceptions.