Microbial MetabolismMetabolism: Energy and Enzymes
METABOLISM From the Greek term, metaballein, meaning change. Pertains to all chemical reactions and physical workings of the cell.
Energy Defined as the capacity to do work or to cause particular changes. Cellular metabolism – the totality of all chemical reactions that a cell carries out. Metabolism- obtain energy and materials for growth.
ATP Is the central chemical in the energy transformations of cellular metabolism ATP cannot be stored for long periods of time so it must be continually made.
Role of Enzymes Cellular metabolism is based on chemical reactions catalyzed by enzymes. Enzymes are biological catalysts – accelerate the rates of chemical reactions. Most are proteins but a very few are RNA.
Enzymes Increase rates of a cell’s chemical reactions by more than a million times. Energy is required for a chemical reaction to occur. Enzymes lower activation energy.
Energy of Activation Increasing thermal energy (heating), which increases molecular velocity Increasing the concentration of reactants, or Adding a catalyst
Enzymes Exhibit high degree of substrate specificity. The enzymes a particular cell synthesizes will determine which chemical reactions occur in cellular metabolism of that cell. Substrate + E E-S complex E + Product
Enzyme Structure Enzymes can be classified as simple or conjugated. Simple – consist of protein alone Conjugated – protein + nonprotein
Enzyme Anatomy Active Site Allosteric Site Co enzyme Cofactor Apoenzyme Holoenzyme
Apoenzyme: Specificity and the ActiveSite Range in size Exhibit levels of molecular complexity
Enzyme Specificity The apoenzyme of each enzyme differs from others in its primary structure Nuances in polypeptide folding Surface features of the tertiary structure provide a unique and specific site
Synthesis & Hydrolysis Reactions Bacterial cells are constantly in a frenzy of activity, constantly synthesizing proteins, DNA, and RNA. Anabolic Reactions – Condensation Reactions Require ATP Catabolic Reactions – Hydrolysis Reactions
Transfer Reactions by Enzymes Addition or removal of a functional group are important to the overall economy of the cell. Oxidation – Reduction reactionsImportant in metabolic pathwaysRole in molecular conversions
The Role of Microbial Enzymes inDisease Exoenzymes which help bacteria avoid host defenses or promote their multiplication in tissues. Virulence factors or toxins: Streptococcus pyogenes (streptokinase, protease); Staphylococcus aureus (lipases); Pseudomonas aeruginosa (elastase, collangenase)
The Role of Microbial Enzymes inDisease Clostridium perfringens (lecithinase C, lipase)
The Sensitivity of Enzymes to theirEnvironment Activity of an enzyme is influenced by the cell’s environment. Temperature, pH, osmotic pressure Denaturation – disruption causes distortion of the enzyme
Checklist Act as organic catalysts to speed up the rate of cellular reactions Are composed of protein and may require cofactors Have unique characteristics such as shape, specificity, and function Enable metabolic reactions to proceed at a speed compatible with life
Checklist Provide a reactive site for target molecules called substrates Associate closely with substrates but do not become integrated into the reaction products Are not used up or permanently changed by the reaction
Checklist Lower the activation energy required for a chemical reaction to proceed Can be recycled, thus function in extremely low concentrations Are limited by particular conditions of temperature and pH
Metabolic Pathways and Carbon Flow The enzymatically mediated metabolic reactions of a cell proceed via a series of small discrete steps that establish a metabolic pathway. Catabolic Anabolic
Metabolic Pathways Rarely consist of a single action or step. Each step catalyzed by an enzyme. Pathways are interconnected and merge at different sites. Pacemakers – sets the rate of a pathway’s progression. Respond to various control signals
Direct Controls Competitive Inhibition Feedback Control Negative Feedback
Controls on Enzyme Synthesis Enzyme Repression Enzyme Induction
The Pursuit and Utilization of Energy Biosynthesis, movement, transport, or growth could proceed without ENERGY
Nutritional Patterns Among Bacteria Two criteria: Energy (E) source & Carbon (C ) Source Prototrophs – light as primary E source Chemotrophs – redox reactions for E Autotrophs – use CO2 Heterotrophs – require an organic C source