The word metabolism derives from the Greek word for “change.” Metabolism represents the sum of the chemical changes that convert nutrients, the “raw materials” necessary to nourish living organisms, into energy and the chemically complex finished products of cells. Metabolism consists of literally hundreds of enzymatic reactions organized into discrete pathways. | Chapter 18 Metabolism--an Overview to accompany Biochemistry, 2/e by Reginald Garrett and Charles Grisham All rights reserved. Requests for permission to make copies of any part of the work should be mailed to: Permissions Department, Harcourt Brace & Company, 6277 Sea Harbor Drive, Orlando, Florida 32887-6777 Outline Basic Set of Metabolic Pathways Catabolism and Anabolism Experimental Methods Nutrition SPECIAL FOCUS: Vitamins Metabolism The sum of the chemical changes that convert nutrients into energy and the chemically complex products of cells Hundreds of enzyme reactions organized into discrete pathways Substrates are transformed to products via many specific intermediates Metabolic maps portray the reactions A Common Set of Pathways Organisms show a marked similarity in their major metabolic pathways Evidence that all life descended from a common ancestral form There is also significant diversity Autotrophs use CO2; Heterotrophs use organic carbon; Phototrophs use light; Chemotrophs use Glc, inorganics & S The Sun is Energy for Life Phototrophs use light to drive synthesis of organic molecules Heterotrophs use these as building blocks CO2, O2, and H2O are recycled See Figure Metabolism Metabolism consists of catabolism and anabolism Catabolism: degradative pathways Usually energy-yielding! Anabolism: biosynthetic pathways energy-requiring! Organization in Pathways Pathways consist of sequential steps The enzymes may be separate Or may form a multienzyme complex Or may be a membrane-bound system New research indicates that multienzyme complexes are more common than once thought Catabolism and Anabolism Catabolic pathways converge to a few end products Anabolic pathways diverge to synthesize many biomolecules Some pathways serve both in catabolism and anabolism Such pathways are amphibolic Comparing Pathways Anabolic & catabolic pathways involving the same product are not the same Some steps may be common to both Others must be . | Chapter 18 Metabolism--an Overview to accompany Biochemistry, 2/e by Reginald Garrett and Charles Grisham All rights reserved. Requests for permission to make copies of any part of the work should be mailed to: Permissions Department, Harcourt Brace & Company, 6277 Sea Harbor Drive, Orlando, Florida 32887-6777 Outline Basic Set of Metabolic Pathways Catabolism and Anabolism Experimental Methods Nutrition SPECIAL FOCUS: Vitamins Metabolism The sum of the chemical changes that convert nutrients into energy and the chemically complex products of cells Hundreds of enzyme reactions organized into discrete pathways Substrates are transformed to products via many specific intermediates Metabolic maps portray the reactions A Common Set of Pathways Organisms show a marked similarity in their major metabolic pathways Evidence that all life descended from a common ancestral form There is also significant diversity Autotrophs use CO2; Heterotrophs use organic carbon; .
