Question

indicate whether each statement is true or false:

1. in oxidative deamination, the carboxylic acid group is removed from an amino acid, leaving ammonia and a keto acid.

(click to select)

1. the ammonia produced by oxidative deamination is converted to urea by the liver, which is carried to the kidneys for elimination.

(click to select)

1. some amino acids are directly converted into keto acid that can enter the citric acid cycle (click to select)

true
false

Explanation:

1. In oxidative deamination, it is the amino group (-NH₂) that is removed from an amino acid, not the carboxylic acid group (-COOH). The general reaction is: Amino acid + NAD⁺ + H₂O → Keto - acid + NH₃ + NADH + H⁺.
2. The liver has the urea cycle. Ammonia (NH₃) produced by oxidative deamination (and other sources) is toxic. The liver converts it to urea (a less toxic compound) through the urea cycle. Urea is then carried by the blood to the kidneys, where it is filtered out and excreted in urine.
3. Some amino acids (glucogenic amino acids like alanine, aspartate) can be converted into keto - acids (e.g., pyruvate, oxaloacetate) that can enter the citric acid cycle. For example, alanine can be transaminated to form pyruvate.

Answer:

1. False
2. True
3. True