Microbial Metabolism

Microbial Metabolism Kathy Huschle Northland Community and Technical College Bacteria on insect carcass

Why study metabolism? • to grow cells must constantly • synthesize new components • harvest energy and convert it to a useable form • the ability to do the above requires complex biochemical reactions

What is metabolism? • metabolism: the sum of all chemical reactions within a living organism • chemical reactions can either release energy or they require stored (potential) energy • metabolism is a balance of those processes

2 Metabolic Components • the 2 components of metabolism include • catabolism • capturing and storing of energy by breaking down complex organic molecules • releases energy • anabolism • use of energy to assemble simple molecules into more complex molecules • requires energy

Catabolism vs. Anabolism Catabolic reactions provide for anabolic reactions. They furnish the energy needed to drive anabolic reactions. ATP generated in catabolism is used in anabolism. Energy used for chemical reactions is stored in ATP. The amount of energy gained by breaking the bonds of a compound is referred to as free energy.

Metabolic Pathway • energy is stored or released from organisms by a series of controlled reactions, not a single burst • this is accomplished as a series of sequential chemical reactions

Metabolic Pathway:can be linear, branching or cyclical

Players in Metabolic Reactions • substrates • end products • intermediates • enzymes • cofactors • energy carriers

Players in Metabolic Reactions • substrate • this is the substance that enters into reactions • end products • substances left at the end of the reaction • intermediates • substances that are formed between the start and the end of the metabolic pathway • enzymes • proteins that act as catalysts along the metabolic pathway • cofactors/coenzymes • molecules that assist enzymes • energy carriers • move or temporarily store energy

Metabolic Pathway • enzymes play a key role in facilitating each step of the metabolic pathway

Enzymes in the Metabolic Pathway • enzymes are proteins that are biological catalysts • a catalyst is a substance that can speed up a chemical reaction without being permanently altered • in other words, they are available to be used again and again

Enzymes • enzymes act very specific as catalysts • accelerate the conversion of one substance (substrate) into another (product) • work by lowering the activation energy, which is the initial energy needed to break chemical bonds • this allows for chemicals to be rearranged Click icon to learn more

Enzymes • enzymes can be influenced by several factors • high temperatures can denature enzymes, allowing them to lose their catalytic abilities • low temperatures slow down the reaction rate

Enzymes • enzymes have optimal pH conditions which produces maximal enzyme reaction • most enzymes function best at a neutral pH of 7 • as substrate concentration increases, so does enzyme activity (within limits)

Cofactor/coenzyme • can be a metal ion • iron, copper, magnesium, manganese, zinc, calcium, cobalt • or a complex organic molecule • NAD+, NADP+, FMN, FAD, or coenzyme A • act in conjunction with enzymes

Energy Carriers • ATP • adenosine triphosphate • energy from glucose breakdown is converted to ATP

Oxidation-Reduction Reactions • also known as redoxreactions • involves the transfer of one or more electrons from one substance to another • oxidized: the compound that loses electrons • reduced: the compound that gains electrons • most of the energy released during a redox reaction is trapped in the cell by ATP being formed

Generation of ATP • phosphate groups with covalent bonds are unstable and easily broken • the addition of P to a chemical compound is called phosphorylation Adenosine – P~P + energy + P Adenosine – P~P~P ADP ATP ~represents a “high-energy” bond in the following diagram

Phosphorylation

ATP in the Metabolic Pathway During certain metabolic reactions the addition of a phosphate to ADP (adenosine diphosphate) forms ATP (adenosine triphosphate). The above process require an input of energy. When a phosphate is removed from ATP, forming ADP, energy is released. The phosphate groups of ATP are unstable and easily broken, thus releasing the phosphate group and energy.

Precursor Metabolites • metabolic intermediates produced in catabolic pathways (releasing energy), can be siphoned off and used in anabolic pathways • these intermediates serve as building blocks to make the macromolecules needed by the cells • this process takes place in anabolic pathways (requires energy)

Metabolic Schemes:Central Metabolic Pathway • central metabolic pathway is used to oxidize glucose (preferred energy source of cells) completely to carbon dioxide • glycolysis • respiration • fermentation Sugar fermentation test

Electron Transport Chain To produce energy a cell needs an electron donor (organic or inorganic), a system of electron carriers and a final energy acceptor (organic or inorganic)

Glycolysis • most common pathway for the oxidation of glucose • organic glucose is broken down with a net result of 2 ATP molecules and two molecules of pyruvic acid

Cellular Respiration • in the presence of oxygen (aerobic) pyruvic acid (from glycolysis) is further oxidized to H2O and CO2 • the transfer of energy is released from the pyruvic acid to ATP

Fermentation • in the absence of oxygen (anaerobic) pyruvic acid (from glycolysis) is further converted to alcohol and organic acids • a net gain of only 2 molecules of ATP result from fermentation, indicating that most of the energy is still in the alcohol or acid molecules

Summary • to produce energy all cells need • an electron donor (organic or inorganic) • a system of electron carriers • a final electron acceptor (organic or inorganic) One Two Three Click icons in order to view a summary

Microbial Metabolism