Metabolism, Citric Acid Cycle, and Nitrogen Metabolism

Flashcards for reviewing lecture notes on metabolism, citric acid cycle, and nitrogen metabolism.

Citric Acid Cycle

Also known as the Tricarboxylic Acid Cycle or the Krebs Cycle, this cycle occurs within mitochondria and is a major site of carbon dioxide liberation and energy production.

GTP

Activated molecules that function similarly to ATP, storing energy through high-energy phosphine hydro bonds between elongated phosphate groups.

FADH

Functions similarly to NADH and NADPH, carrying high-energy electrons taken up by nitrogen-containing ring structures.

Citric Acid Cycle as a Common Pathway

Regardless of the energy-yielding nutrient (proteins, carbohydrates, or lipids), this cycle is a common pathway where these nutrients eventually feed into, either directly or indirectly via acetyl CoA.

Oxidation of Pyruvate to Acetyl CoA

A key pathway in metabolism involving an irreversible reaction that commits substrates to oxidation and limits the interchangeability of major energy-yielding nutrients.

Pyruvate Dehydrogenase Complex

A complex of three enzymes that catalyze the oxidation of pyruvate to acetyl CoA, liberating carbon dioxide and energy in the form of NADH.

Citric Acid Cycle Steps

A series of eight steps starting and finishing with oxaloacetate, where two carbons from acetyl CoA enter, and two carbons are released, generating energy.

Ammonia

A toxic intermediate, especially for neurons, that is readily permeable to cell membranes and can lead to decreased citric acid cycle activity and osmotic imbalances.

Ureotelic Organisms

Organisms that excrete urea as the primary form of nitrogen waste.

Urea Cycle

A cycle that brings together amino nitrogen and central carbon from carbamoyl phosphate and amino nitrogen from aspartate to form urea.

Ornithine

A modified amino acid scaffold in the urea cycle that is trafficked through the mitochondrial membrane, coordinated with the movement of citrulline.

Citrullinemia

An inherited disorder in Holstein Friesian cattle caused by a single base substitution in the arginine succinate synthetase gene, leading to hyperammonemia.

Ammoniotelic Organisms

Aquatic animals that excrete ammonia directly into their environment through gas exchange in the gills.