Microbial Metabolism Overview

Microbial Metabolism

• Metabolism is the buildup and breakdown of nutrients within a cell
• Metabolism provides energy and creates substances that sustain life
• Catabolic pathways break down macromolecules into simpler component parts, releasing energy
• Anabolic pathways build up macromolecules by combining simpler molecules, using energy
• Catabolic and anabolic pathways are linked by energy, with catabolic reactions providing the energy for anabolic reactions

Dental Plaque

• Dental plaque consists of bacteria

Big Picture: Metabolism

• Microbial metabolism can cause disease and food spoilage
• Many metabolic pathways are beneficial rather than pathogenic

Key Concepts: Metabolism

• Enzymes facilitate metabolic reactions
• ATP is used by cells to manage energy needs
• Catabolic reactions couple with ATP synthesis
• Anabolic reactions couple with ATP breakdown

Catabolic and Anabolic Reactions

• Catabolism breaks down complex molecules, providing energy and building blocks for anabolism; exergonic
• Anabolism uses energy and building blocks to build complex molecules; endergonic

Figure 5.1 The role of ATP in Coupling Anabolic and Catabolic Reactions

• Catabolism releases energy by oxidation of molecules; generating CO2 and H2O
• Energy is released by ATP hydrolysis
• Anabolism uses energy to synthesize macromolecules
• Energy is stored in molecules of ATP

Catabolic and Anabolic Reactions

• Metabolic pathways are sequences of enzymatically catalyzed chemical reactions in a cell
• Metabolic pathways are determined by enzymes
• Enzymes are encoded by genes

Collision Theory

• Chemical reactions occur when atoms, ions, and molecules collide
• Activation energy is the collision energy required for a chemical reaction to occur
• Reaction rate is the frequency of collisions containing enough energy to bring about a reaction
• Reaction rate can be increased by enzymes or by increasing temperature, pressure, or concentration

Enzymes and Chemical Reactions

• Catalysts speed up chemical reactions without being altered
• Enzymes are biological catalysts
• Enzymes act on a specific substrate and lower the activation energy
• Substrate contacts the enzyme's active site to form an enzyme-substrate complex
• Substrate is transformed and rearranged into products, which are released from the enzyme
• Enzyme is unchanged and can react with other substrates

Figure 5.3a & 5.3b The Mechanism of Enzymatic Action

• Shows the steps involved in enzymatic action, including substrate binding, complex formation, product release and enzyme recycling

Enzyme Specificity and Efficiency

• Enzymes have specificity for particular substrates
• Turnover number is the number of substrate molecules an enzyme converts to a product per second; generally 1 to 10,000

Naming Enzymes

• Names of enzymes usually end in -ase and are grouped based on the reaction they catalyze
• Oxidoreductase: oxidation-reduction reactions
• Transferase: transfer functional groups
• Hydrolase: hydrolysis
• Lyase: removal of atoms without hydrolysis
• Isomerase: rearrangement of atoms
• Ligase: joining of molecules; uses ATP

Figure 5.4 Components of a Holoenzyme

• Holoenzyme is composed of an apoenzyme (inactive protein portion), and a cofactor (nonprotein activator)
• Together they form a functioning complex.

Factors Influencing Enzyme Activity

• Factors that influence enzyme activity: temperature, pH, substrate concentration, inhibitors
• High temperature and extreme pH denature proteins
• If the substrate concentration is high, the enzyme catalyzes at its maximum rate

Figure 5.6 Denaturation of a Protein

• Shows how high temperature and extreme pH can denature proteins and make them inactive

Figure 5.5a,b,c Factors that Influence Enzymatic Activity

• Plots of enzymatic activity versus Temperature, pH and Substrate concentration. They show the effect on reaction activity for variations in each factor.

Inhibitors

• Competitive inhibitors fill the active site of an enzyme and compete with the substrate
• Noncompetitive inhibitors interact with another part of the enzyme (allosteric site) rather than the active site, in this process called allosteric inhibition

Figure 5.7a-c Enzyme Inhibitors

• Illustrates normal substrate binding, compared with competitive and noncompetitive inhibition

Unnumbered Figure pg. 115

• Illustrates the structurally similar nature of Sulfanilamide and PABA

Feedback Inhibition

• End-product of a reaction allosterically inhibits enzymes from earlier in the pathway

Figure 5.8 Feedback Inhibition

• Shows the pathway, intermediates involved and the key point of allosteric inhibition or feedback inhibition.

Ribozymes

• RNA that function as catalysts by cutting and splicing RNA

Explore the fundamental concepts of microbial metabolism, including the distinction between catabolic and anabolic pathways. Understand how these processes contribute to energy management within cells and their implications for health and disease. Delve into the role of enzymes and ATP in metabolic reactions.