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In biochemistry, a metabolic pathway is a series of chemical reactions occurring within a cell, catalyzed by enzymes, and resulting in either the formation of a metabolic product to be used or stored by the cell ( metabolic sink ), or the initiation of another metabolic pathway (then called a flux generating step).1 Overview
Most metabolic pathways have these common properties:
- They are irreversible, usually because the first step is a committed step that only runs in one direction.
- The pathways are regulated, usually by feedback inhibition .
- Anabolic and catabolic pathways in eukaryotes are separated by either compartmentation or by the use of different enzymes and cofactors.
2 Major metabolic pathways
2.1 Cellular respiration
Main article: Cellular respiration
Several distinct but linked metabolic pathways are used by cells to transfer the energy released by breakdown of fuel molecules to ATP:
- Glycolysis
- Anaerobic respiration
- Krebs' cycle
- Oxidative phosphorylation
2.2 Other pathways
- Fatty acid oxidationIt all happens when we eat Fats, let's say you just ate a Big Mac! what's going to happen to all that fat? well, the digestive system will break down the complex fat into single fat molecules (triglicerides)through the process of hydrolisis. then those si (beta oxidation)
- GluconeogenesisGluconeogenesis is the generation of new glucose molecules from other substrates, as opposed to its generation from glycogen breakdown. Like many metabolic pathways it happens mostly in the liver, and is triggered by the action of glucagon. The kidney can
- HMG-CoA reductase pathwayThe HMG-CoA reductase pathway is an important cellular metabolic pathway present in virtually all organisms. It forms hydrophobic molecules for tasks as diverse as cell membrane maintenance, hormones, protein anchoring and N glycosylation. Reactions Acety ( cholesterolCholesterol is a steroid lipid, found in the cell membranes of all body tissues, and transported in the blood plasma, of all animals. Most cholesterol is produced internally, not dietary in origin. It is present in higher concentrations in tissues which e, isopreneIsoprene is the chemical 2-methyl-1,3-butadiene. It is a common structural motif in biological systems. The terpenes (for example, the carotenes are tetraterpenes) are derived from isoprene, as are the terpenoids and coenzyme Q. Also derived from isoprene prenylation chains)
- Pentose phosphate pathway (hexose monophosphate shunt)
- Porphyrin synthesisA porphyrin is a heterocyclic macrocycle made from 4 pyrrole subunits linked on opposite sides through 4 methine bridges. The macrocycle, therefore, is completely aromatic, unlike the related corrins or chlorins. Types of porphyrins Porphyrins combine rea (or hemeA haem or heme is a metal-containing cofactor that consists of an iron atom contained in the center of a large heterocyclic organic ring called a porphyrin''. Although porphyrins do not necessarily contain iron, a substantial fraction of porphyrin-contain synthesis) pathway
- Urea cycleThe Urea Cycle is a cycle of biochemical reactions occurring in many animal organisms that produces urea from ammonia. This cycle, also known as ornithine cycle, was the first metabolic cycle discovered (Krebs and Hensenleit, 1932) Urea is much less toxic
3 See also
