1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 06 Metabolism: Fueling Cell Growth  Two fundamental tasks needed to grow.  Synthesis of macromolecules  Metabolism  Important to humans  Food, medicine, energy, research

 Biologists had noticed that in vats of grape juice, alcohol and CO 2 are produced while yeast cells increase in number  Biologists concluded that multiplying cells were converting sugar in the juice to alcohol and CO 2  But idea not widely accepted Mocked by influential chemists and others  In 1850s, Louis Pasteur set out to determine how alcohol develops from grape juice Simplified setup: clear solution of sugar, ammonia, mineral salts, trace elements Added a few yeast cells—as they grew, sugar decreased, alcohol level increased Strongly supported idea, but Pasteur failed to extract something from inside the cells that would convert sugar  In 1897, Eduard Buchner, a German chemist, showed that crushed yeast cells could convert sugar to ethanol and CO 2 ; awarded Nobel Prize in 1907 Enzymes were extracted….. A Glimpse of History

 All cells need to accomplish two fundamental tasks 1)Synthesize new parts Cell walls, membranes, ribosomes, nucleic acids 2)Harvest energy to power reactions Sum total of these is called metabolism Human implications Used to make biofuels Used to produce food Important in laboratory Invaluable models for study Unique pathways potential drug targets Microbial Metabolism

 Can separate metabolism into two parts 1)Catabolism Processes that degrade compounds to release energy Cells capture to make ATP 2)Anabolism/Biosynthesis Biosynthetic processes Assemble subunits of macromolecules Use ATP to drive reactions Processes intimately linked 6.1. Principles of Metabolism

 Energy is the capacity to do work  Two types of energy 1)Potential: stored energy (e.g., chemical bonds, rock on hill, water behind dam) 2)Kinetic: energy of movement (e.g., moving water)  Energy in universe cannot be created or destroyed, but it can be converted between forms Harvesting Energy

 Photosynthetic organisms harvest energy in sunlight Power synthesis of organic compounds from CO 2 Convert kinetic energy of photons to potential energy of chemical bonds  Chemoorganotrophs obtain energy from organic compounds Depend on activities of photosynthetic organisms Harvesting Energy

 Free energy - is energy available to do work after a chemical reaction has occured E.g., energy released when chemical bond is broken Compare free energy of reactants to free energy of products 1)Exergonic reactions: reactants have more free energy Energy is released in reaction 2)Endergonic reactions: products have more free energy Reaction requires input of energy Harvesting Energy

 Role of Enzymes (Proteins) – suffix “ase”… Biological catalysts: accelerate conversion of substrate into product by lowering activation energy Highly specific: one at each step Reactions would occur without, but extremely slowly Components of Metabolic Pathways

 Role of ATP Adenosine triphospate (ATP) is energy currency Composed of ribose, adenine, three phosphate groups Adenosine diphospate (ADP) acceptor of free energy Cells produce ATP by adding P i to ADP using energy Release energy from ATP to yield ADP and P i Components of Metabolic Pathways

 Precursor metabolites are intermediates of catabolism that can be used in anabolism Serve as carbon skeletons for building macromolecules E.g., pyruvate can be converted into amino acids alanine, leucine, or valine Precursor Metabolites

6.2. Enzymes  Environmental Factors Influencing Enzyme Activity Enzymes have narrow range of optimal conditions Temperature, pH, salt concentration 10°C increase doubles speed of enzymatic reaction up until maximum Proteins denature at higher temperatures Low salt, neutral pH usually optimal

6.5. Fermentation  Fermentation used when respiration not an option E. coli is facultative anaerobe Aerobic respiration, anaerobic respiration, and fermentation Streptococcus pneumoniae Fermentation only option  Fermentation end products varied; helpful in identification, commercially useful Lactic acid Ethanol Butyric acid Propionic acid 2,3-Butanediol Mixed acids

6.8. Photosynthesis  Photosynthesis Plants, algae, several groups of bacteria General reaction is where X indicates element such as oxygen or sulfur Can be considered in two distinct stages Light reactions (light-dependent reactions) –Capture energy and convert it to ATP Light-independent reactions (dark reactions) –Use ATP to synthesize organic compounds –Involves carbon fixation 6 CO H 2 X C 6 H 12 O X + 6 H 2 O Light Energy

14 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 06 Metabolism: Fueling Cell Growth  Two fundamental tasks needed to grow.  Synthesis of macromolecules  Metabolism  Important to humans  Food, medicine, energy, research