OM 1012 – Molecular and Cellular Mechanisms: Amino Acid Metabolism and Urea Cycle (Fill-in-the-Blank Flashcards)

A set of fill-in-the-blank flashcards covering key concepts from amino acid metabolism, glucogenic vs ketogenic classifications, nitrogen handling, and the urea cycle as presented in the lecture notes.

The amino acids that must be acquired through the diet are __.

essential amino acids

Leucine and lysine are the only exclusively __ amino acids found in proteins.

ketogenic

Amino acids whose catabolism yields pyruvate or other TCA cycle intermediates are classified as __.

glucogenic

Amino acids whose catabolism yields acetoacetate or its precursors (Ac-CoA or acetoacetyl-CoA) are called __.

ketogenic

The first step of the urea cycle, forming carbamoyl phosphate, is catalyzed by __ and occurs in the mitochondria and is the rate-limiting step.

carbamoyl phosphate synthetase I (CPS I)

CPS I requires ATP and is located in the .

two; mitochondria

CPS II, located in the cytosol, produces carbamoyl phosphate for pyrimidine synthesis using nitrogen from __.

glutamine

Ornithine transcarbamoylase (OTC) forms citrulline from ornithine and __ in mitochondria.

carbamoyl phosphate

Citrulline combines with __ to form argininosuccinate via argininosuccinate synthetase.

aspartate

Argininosuccinate lyase splits argininosuccinate into __ and fumarate.

arginine

Arginase cleaves arginine to yield one molecule of __ and ornithine.

urea

In the fasted state, amino acids become a major energy source and can contribute to glucose and __ production.

ketone bodies

The major transport form of ammonia in the blood is __.

glutamine

In the kidney, glutamine is converted to __, releasing NH3 (ammonia) into the urine.

glutamate

The urea cycle occurs in the liver, with carbamoyl phosphate synthetase I located in mitochondria and carbamoyl phosphate synthetase II located in the __.

cytosol

The enzyme that converts ammonium and bicarbonate to carbamoyl phosphate is __.

carbamoyl phosphate synthetase I (CPS I)

OTC deficiency leads to accumulation of __ in mitochondria that can be shunted into pyrimidine synthesis.

carbamoyl phosphate

In OTC deficiency, excess carbamoyl phosphate can lead to excretion of __ in the urine.

orotic acid (orotate)

Urease hydrolyzes urea to __ and carbon dioxide.

ammonia and carbon dioxide

The nine essential amino acids for humans include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and __.

valine

Phenylketonuria is caused by deficiency of __, leading to elevated phenylalanine.

phenylalanine hydroxylase

Foods that contain all nine essential amino acids are referred to as __ proteins.

complete

The liver uses transamination to remove amino groups from amino acids, with the coenzyme required being __.

pyridoxal phosphate (vitamin B6)

The urea cycle takes place in the __, with most steps in the cytosol and the initial step in the mitochondria.

liver

The transporter form of ammonia that travels from tissues to the liver is __.

glutamine