BENG0004 2021 Lecture 15_Metabolism.pdf

BENG0004 Biochemistry and Molecular Biology Emily Kostas Lecture 15 Cells have to eat – Metabolism, the major catabolic pathways An introduction to metabolism  The major metabol...

BENG0004 Biochemistry and Molecular Biology Emily Kostas Lecture 15 Cells have to eat – Metabolism, the major catabolic pathways An introduction to metabolism  The major metabolic pathways Metabolism – all of the reactions within a cell that are used to take in and assimilate food to provide the cell with carbon, nitrogen and all the other components the cell needs. Also all the reactions the cell uses to build up the complex materials that it needs. This includes all the metabolism to build DNA, RNA, proteins and lipids. Metabolism - all of the reactions are catalysed by enzymes. - the intermediate compounds in all these metabolic pathways are called metabolites. - there is a new science called metabolomics which is the cataloguing and analysis of metabolites (we will look at this in a later lecture) - metabolism is divided into the breakdown (catabolism) and the building up (anabolism) of compounds.  An overview of metabolism – catabolism and anabolism From: http://www.nature.com/scitable  The major catabolic pathways Catabolic and catabolism – means the breaking down of foodstuffs into less complex chemical compounds. For two purposes – to get energy and to get building blocks to make other compounds. Prokaryotic cells can build most complex organic compounds from inorganic nitrogen and sulphur compounds using only a carbon source (e.g. glucose) for energy and to provide carbon for the organic compounds. But if a prokaryotic cell doesn't have to build complex material from scratch it won’t. It uses much less energy to take in complex, already-made material e.g. amino acids, vitamins, purines, pyrimidines etc and reshape these and then build them up into proteins, DNA and RNA. Cells also need phosphate for DNA, RNA and phospholipids and ions such as Mg, Na, Ca, K. Then there are the micronutrients that all cells also need: Fe, Co, Mo, Se, Cu, Mn, Zn, B  The major catabolic pathways Eukaryotic cells need to take in carbon, nitrogen and sulphur compounds that are already incorporated into organic compounds. These will be broken down and built into new compounds. Higher eukaryotic cells such as mammalian cells cannot make many amino acids or any vitamins. A media recipe for mammalian cells will include many components for stable growth: Amino acids (both essential ones and non-essential), vitamins, lipids, trace elements and the major elements such as Mg, K, Na. Also proteins (Fe binding proteins, hormones, growth factors) and carbohydrates such as glucose and galactose. Many mammalian cell culture media recipes use serum [fetal calf serum] as a way of providing all these complex nutrients. The move in industry to serum-free media for production has been going on for several years and many companies now use defined serum free media for mammalian cell culture. But mammalian cells cannot build many of the compounds that they need for growth.  The major catabolic pathways What are the major catabolic pathways? We will look at two major ones. Sugars – glucose Glycolysis Lipids – fatty acids b-oxidation The major catabolic pathways Glycolysis b-oxidation