An amino acid yielding acetyl CoA during catabolism is

The correct answer is ketogenic.

To understand why this is the correct answer, let's break down the metabolic classification of amino acids based on their catabolic pathways and products.

1. What are Ketogenic Amino Acids?
Ketogenic amino acids are those whose carbon skeletons are broken down directly into acetyl CoA or acetoacetyl CoA (which is subsequently converted into acetyl CoA or ketone bodies). Because the conversion of acetyl CoA to pyruvate is irreversible in animals, acetyl CoA cannot be used for the net synthesis of glucose (gluconeogenesis). Instead, these products are used to generate ketone bodies or fatty acids, or they enter the citric acid cycle for energy production.

2. What are Glucogenic Amino Acids?
Glucogenic amino acids are degraded to pyruvate or one of the intermediates of the citric acid cycle (such as succinyl CoA, fumarate, malate, or oxaloacetate). These intermediates can be converted into oxaloacetate, which is the direct precursor for the synthesis of glucose via gluconeogenesis.

3. Amino Acids yielding Acetyl CoA
When an amino acid yields acetyl CoA during catabolism, it enters the ketogenic pathway. The amino acids leucine and lysine are exclusively ketogenic because their catabolism produces acetyl CoA or acetoacetate without producing any glucogenic intermediates. Other amino acids (like isoleucine, phenylalanine, tryptophan, and tyrosine) are both glucogenic and ketogenic because their breakdown yields both acetyl CoA and glucogenic precursors (like succinyl CoA or fumarate). However, any amino acid that specifically yields acetyl CoA is classified under the ketogenic category (either exclusively ketogenic or containing a ketogenic component).

Therefore, an amino acid that yields acetyl CoA during catabolism is classified as ketogenic.