Cellular Energetics and Enzyme Function

Preparation

• Prepare your pencil, notebook, and highlighter.

Cellular Energetics

• Topic: Cellular Energetics, Catalysis, and Environmental Impacts
• Learning Points: Enzyme Structure, Catalysis, and Environmental Impacts

What are Enzymes?

• Enzymes are proteins that catalyze or speed up chemical reactions.
• They reduce the activation energy required for reactions.

Analysis Question 1: Why are Enzymes Vital for Living Organisms?

• Enzymes are vital because they accelerate biochemical reactions, enabling essential life processes to occur efficiently.

Carbohydrases

• Carbohydrases are enzymes that break down carbohydrates into simple sugars.
• Carbohydrates provide energy.
• Starch is a form of carbohydrate.
• Amylase breaks starch down.

Carbohydrase Example: Salivary Amylase

• Salivary amylase is produced in salivary glands.
• It breaks down starch into maltose, a type of sugar.

Proteases

• Proteases are enzymes that break down proteins into amino acids.

Protease Example: Pepsin

• Pepsin is a protease enzyme produced in the gastric glands of the stomach.
• It starts the process of breaking down proteins into amino acids.

Lipases

• Lipases are enzymes that break down lipids into fatty acids and glycerol.

Lipase Example

• Lipase enzymes are produced in the pancreas.
• They work in the small intestine (duodenum) to turn lipids into fatty acids and glycerol.

Enzyme Structure

• Enzymes are composed of amino acid chains folded into specific 3D structures.
• Active site: The region where the substrate binds to the enzyme.
• Lock-and-key model: The enzyme and substrate fit precisely.

Analysis Question 2: How does Enzyme Structure Relate to Its Function?

• The specific 3D structure of an enzyme, especially the active site, determines which substrates bind to it and are catalyzed.

Analysis Question 3: How Does Lactase Enzyme Specifically Break Down Lactose in Milk?

• A specific enzyme breaks down lactose.

Induced Fit Model

• Active site shape slightly changes when substrate binds.
• Efficiency increases, increasing substrate turnover.

Analysis Question 4: What Advantage Does the Induced Fit Model Provide over the Lock-and-Key Model?

• The induced fit model explains how enzymes are flexible and efficient by adapting to the substrate.

Drug Design and Enzyme Inhibition

• Drug design considers the induced fit model for better enzyme inhibition.

Enzyme Catalysis

• Enzymes decrease activation energy for chemical reactions.
• They do not change the reaction's equilibrium.
• They remain unchanged after catalysis.
• They catalyze both forward and reverse reactions.

Analysis Question 5: How do Enzymes Affect the Rate of Chemical Reactions?

• Enzymes lower the activation energy required for reactions.
• This significantly increases the rate at which products are formed.
• Catalase is an example that rapidly decomposes hydrogen peroxide in cells.

Cofactors and Coenzymes

• Cofactors are non-protein components necessary for enzyme function.
• Coenzymes are organic cofactors, often derived from vitamins.
• NAD+ and coenzyme A are examples.

Analysis Question 6: How do Cofactors Contribute to Enzyme Function?

• Cofactors assist enzymes in catalyzing reactions by providing necessary chemical components or facilitating electron transfer.
• Example: Iron in hemoglobin.

Enzyme Inhibition

• Enzyme inhibitors are molecules that interact with enzymes (temporary or permanent).
• They reduce enzyme-catalyzed reaction rate or prevent normal enzyme function.
• Types include competitive, non-competitive, and uncompetitive.

Analysis Question 7: How Does Competitive Inhibition Differ from Non-competitive Inhibition?

• Competitive inhibitors bind to the active site, whilst non-competitive inhibitors bind elsewhere, affecting the enzyme's shape.

Analysis Question 8: How does Non-competitive Inhibitors Affect the Enzyme's Shape and Function?

• Non-competitive inhibitors bind to a site separate from the active site.
• This causes a conformational change in the enzyme's structure, altering the shape of the active site and preventing substrate binding.

Real-Life Examples of Enzyme Inhibition

• Designing pharmaceutical drugs to inhibit enzymes, through either competitive or non-competitive mechanisms is a central concept in drug discovery.

Environmental Impacts on Enzyme Function

• Temperature increases enzyme activity, and optimal temperature is peak.
• High temperatures denature enzymes.
• Cold temperatures slow down enzyme activity.

pH Effects on Enzymes

• Each enzyme has an optimal pH range
• pH affects enzyme shape (and charge distribution).
• Extreme pHs denature enzymes.
• Some enzymes are adapted to function in extreme environments (ex. some enzymes in detergents).

Salt Concentration Effects on Enzymes

• Salt concentration affects enzyme activity and interactions.
• Some enzymes require specific ion concentrations.
• Example: Carbonic anhydrase.

Salt and Enzyme Activity: Other Examples

• DNA Polymerase depends on magnesium ions during DNA replication.
• Alkaline Phosphatase depends on calcium ions for activity.
• ATPase depends on magnesium ions to hydrolyze ATP.

Analysis Question 9: Why Are Some Enzymes Adapted to High Salt Concentrations?

• Enzymes in organisms living in high salt environments are adapted to maintain their structure and function under those conditions.

Examples of Enzymes Adapted to Specific Environments

• Specific enzymes found in bacteria living in harsh environments like extreme salt concentrations.
• Examples include amylase, protease, lipase, nucleoside diphosphate kinase, and malate dehydrogenase. Specific examples of bacteria (e.g., Halobacterium, Haloarcula, Halomonas, Salinibacter) were listed.
• Some species (e.g., Halomonas) have been found on the Titanic shipwreck and identified in relation to iron.

This quiz covers key concepts in cellular energetics, including the structure and function of enzymes, their role in catalysis, and their environmental impacts. It specifically looks at different types of enzymes such as carbohydrases and proteases and their significance for living organisms.