Biology Chapter on Enzymes

Enzymes and Their Applications

• Enzymes are biological catalysts, crucial for life processes.
• They accelerate reactions without being consumed.
• Enzymes are typically proteins with specific 3D structures.
• The active site on an enzyme is where the substrate binds.
• Enzymes lower the activation energy needed for reactions to proceed.
• Enzyme activity is affected by factors like temperature and pH.
• Many enzymes are highly specific to their substrates, meaning they only bind to certain molecules.

Learning Outcomes

• Thermodynamics principles describe energy changes in chemical reactions.
• Enzymes lower activation energy to enable reactions to occur.
• Enzymes are categorized as proteins involved in biological processes.
• Two key theories explaining enzyme function exist.
• Local environmental conditions impact enzyme activity.
• Competitive and non-competitive inhibitors regulate enzyme activity.
• Enzymes have applications in various industrial and clinical settings.

Principles of Thermodynamics

• Chemical reactions often occur spontaneously, releasing energy.
• Reaction speed depends on substrate concentration, temperature, and the number of collisions between molecules.
• Many reactions are reversible and ultimately reach equilibrium.
• Reaction rates in both directions are equal.

Biology and Equilibrium

• Living cells maintain dynamic metabolism rather than equilibrium.
• Interconnected reactions are essential for energy production and maintaining cellular processes.

What are Enzymes?

• Enzymes are biological macromolecules.
• Essentially, they are catalytic proteins used in biological reactions.
• Essential components of metabolism and speed up processes.
• Without enzymes, most reactions would be too slow to support life.

How Enzymes Work

• Enzymes bind to substrates, forming an enzyme-substrate complex.
• The enzyme's active site precisely matches the specific substrate structure.
• The lock-and-key model and the induced-fit model detail how substrate binding occurs.
• Substrates are converted into products with the enzyme's active site.

Specificity & Catalysis

• Enzyme activity depends partially on substrate concentration.
• A higher substrate concentration results in more active sites being occupied.
• Enzyme saturation occurs when all active sites are occupied, and reaction rate plateaus.

Factors Affecting Enzyme Activity

• Temperature changes the rate of enzymatic reactions.
• Enzymes denature at higher temperatures.
• Enzymes have optimal pH ranges for optimal performance.
• Cofactors (non-protein components) are necessary for active enzyme function.
• Coenzymes (organic molecules) are also essential components that work with enzymes.

Enzymes and Their Roles in Organisms

• Ectothermic organisms' metabolic rates depend on temperature.
• Higher body temperatures lead to faster metabolic rates in ectothermic animals.

Enzyme Kinetics

• Enzyme kinetics describes factors influencing enzyme activity.
• Substrate concentration affects the rate of substrate interactions with enzymes.
• Enzyme saturation is a significant factor in kinetics, where further increases in substrate concentration do not increase reaction rate.

Enzyme Inhibitors

• Enzyme inhibitors can stop or slow the action of enzymes involved in various processes.
• An inhibitor binds to the enzymes' active site with an induced-fit mechanism, temporarily hindering reactions.
• The amount of enzyme can have an effect, as it can increase reaction speed and lessen the inhibitory effects.

Competitive Inhibition

• Inhibitors competing with substrates for the enzyme's active site.
• Increasing substrate concentration can overcome this type of inhibition.

Overcoming Reversible Competitive Inhibition

• Increasing substrate concentration can counteract the effect of inhibitors.
• High substrate concentration results in more enzymes than competing inhibitors.

Non-Competitive Inhibition

• Inhibitors bind to an enzyme at a location other than the active site, creating a change in the enzyme's active site's shape.
• This change hinders the enzyme's ability to catalyze reactions.
• Substrate concentration does not counteract this type of inhibition.

Bio-weapon vs Therapeutic Drug

• Nerve agents irreversibly inhibit enzymes, causing rapid and sometimes fatal effects.
• Some drugs can reversibly inhibit enzymes, creating therapeutic benefits with carefully controlled actions.

Allosteric Activation

• Cellular metabolic processes can be regulated through allosteric activation.
• Activation and deactivation allow the precise regulation required for cellular processes.
• This control is complex, requiring specific regulatory molecules.

Allosteric Activators and Inhibitors

• Allosteric regulation alters an enzyme's activity through binding at a specific site other than the active site.
• Molecules that either activate or hinder an enzyme's function are referred to as activators and inhibitors, respectively.
• Most allosteric enzymes consist of multiple subunits with each containing an active site.
• Binding of a regulator molecule changes enzyme shape, altering function.

Co-operativity

• Substrate binding to one subunit in a multi-subunit enzyme impacts the other subunits.
• Co-operativity amplifies enzyme responses to substrate presence.
• A good example of co-operativity is oxygen binding to hemoglobin.

Feedback Inhibition

• Feedback inhibition is used when reaction product can feedback and inhibit an enzyme earlier in the pathway when needed.
• End product's shape differs from substrate's preventing competitive inhibition.
• The concentration of product regulates enzyme activation, preventing overproduction.

Specific Localisation

• Cellular compartments compartmentalise metabolic reactions, allowing for regulation.
• Ordered metabolic activity is facilitated by the spatial arrangement of enzymes within the cell.

Medicine Application

• Enzymes are used in medical diagnoses and treatment.
• Enzyme tests can detect the presence or absence of specific enzymes in bodily fluids, helping with clinical analysis.
• Enzymes have therapeutic roles in several situations.

Summary of Enzyme Function

• Factors such as substrate concentration, temperature, pH, and inhibitors affect enzyme activity.
• Regulation mechanisms (allosteric activation, feedback inhibition, co-operativity) control metabolic pathways.
• Specific localisation and compartmentalisation of cellular processes supports complex, coordinated function.