Biochemistry also involves the elaborate study of various metabolic pathways of an organism.
Glycolysis, gluconeogenesis and the pentose phosphate pathway- glycolysis is the enzyme catalysed breakdown of six carbon glucose into 2 molecules of 3 C pyruvate with energy conserved as ATP and NADP which takes place in the cell cytoplasm. Gluconeogenesis is a ubiquitious multistep process in which glucose is produced from lactate, pyruvte or oxaloacetate. In mammals, gluconeogenesis in the liver, kidney,and small intestine provides glucose for the use of brain, muscles, and erythrocytes. Pentose phosphate pathway brings about oxidation and decarboxylation at C-1 of glucose 6-phosphate, reducing NADP+ to NADPH and producing pentose phosphates.
The citric acid cycle: The citric acid cycle (Krebs cycle, TCA cycle) is a nearly universal central catabolic pathway in which compounds derived from the breakdown of carbohydrates, fats and proteins are oxidized to CO2, with most of the energy of oxidation temporarily held in the electron carriers FADH2 and NADH. During aerobic metabolism, these electrons are transferred to O2 and the energy of electron flow is trapped as ATP.
Fatty acid catabolism: The chemical steps of fatty acid catabolism take place in the mitochondria. The complete oxidation of fatty acids into CO2 and H2O takes place in three stages: the oxidation of long chain fatty acids to two carbon fragments, in the form of acetyl-CoA (β-oxidation); the oxidation of acetyl CoA to CO2 in the citric acid cycle; and the transfer of electrons from reduced electron carriers to the mitochondrial respiratory chain.
Amino acid oxidation: it is the separation of the amino group from the carbon skeleton. Mostly the amino group is transferred to α-ketoglutarate to form glutamate which is further transported to liver mitochondria, where glutamate dehydrogenase liberates the ammonium ion as NH4+
Lipid biosynthesis: it is the synthesis of long-chain saturated fatty acids from acetyl CoA. Cholesterol is formed from acetyl CoA in a complex series of reaction and the various steroid hormones (glucocorticoids, mineralocorticoids and sex hormones) are produced from cholesterol by alternation of the side chain and introduction of oxygen into the steroid ring system.
DNA and RNA metabolism: DNA metabolism involves the replication which is semiconservative and each strand acts as a template for a new daughter strand, it has three major phases: initiation, elongation and termination, it is catalysed by the enzyme DNA polymerase and form a leading and a lagging strand subsequently. RNA is the only macromolecule known to have a role in the storage and transmission of information and also in catalysis. Formation of RNA is DNA dependent and is catalysed by the enzyme RNA polymerase. During transcription, an enzyme system converts the genetic information from DNA to RNA. The three major kinds of RNA which are produced are messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA).
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