CELLULAR ENERGETICS

UNIT 3: CELLULAR ENERGETICS

TABLE OF CONTENTS

  • ENZYMES

  • ENVIRONMENTAL IMPACTS ON ENZYME FUNCTION

  • CELLULAR ENERGY

  • PHOTOSYNTHESIS

  • CELLULAR RESPIRATION

3.1 ENZYMES

TOPIC 3.1 OBJECTIVES/EKS

  • BIG IDEA 2: Energetics - Biological systems use energy and molecular building blocks to grow, reproduce, and maintain dynamic homeostasis.

  • LEARNING OBJECTIVE 3.1.A: Explain how enzymes affect the rate of biological reactions.

ESSENTIAL KNOWLEDGE

  • 3.1.A.1: The structure and function of enzymes contribute to the regulation of biological processes.

    • Definition: Enzymes are proteins that serve as biological catalysts, facilitating chemical reactions by lowering the activation energy.

  • 3.1.A.2: For an enzyme-mediated reaction to occur, the substrate's shape and charge must be compatible with the enzyme's active site.

    • Illustration: This is depicted in the enzyme-substrate complex model.

Key Definitions and Concepts

  • Metabolism: The sum of all chemical reactions occurring in a cell or organism.

    • Metabolic Pathways: Begin with a specific molecule and end with a product, with each step catalyzed by a specific enzyme.

    • Catabolic Pathways: Release energy by breaking down complex molecules into simpler compounds. Example: Cellular respiration, which breaks down glucose in the presence of oxygen.

    • Anabolic Pathways: Consume energy to construct complex molecules from simpler ones. Example: Synthesis of proteins from amino acids.

    • Bioenergetics: The study of how organisms manage their energy resources.

Enzyme Functionality

  • Enzymes accelerate metabolic reactions by lowering energy barriers.

    • Catalyst: A chemical agent that speeds up a reaction without being consumed. An enzyme is a catalytic protein.

    • Example: Hydrolysis of sucrose by the enzyme sucrase.

Definition of Terms

  • Substrate: The reactant that an enzyme acts on.

  • Active Site: The specific region on the enzyme where the substrate binds.

  • Induced Fit Model: The substrate's binding induces changes in the active site, optimizing the catalysis of the reaction.

Activation Energy (EA)

  • Definition: The initial energy required to start a chemical reaction (free energy of activation).

  • Thermal Energy: Commonly provided from surroundings to supply activation energy.

  • Endergonic Reactions: Require a net input of energy.

  • Exergonic Reactions: Result in a net loss of energy.

  • Enzymes lower the activation energy barrier without affecting the change in free energy (∆G).

3.1 PRACTICE FRQ

  • Experiment Example: Reaction rate measurement for human salivary enzyme α-amylase with maltose concentration recorded at specific intervals. Questions include graphing data, explaining changes in reaction rates, predicting outcomes of enzyme concentration changes, and identifying two environmental factors affecting enzyme reactions.

3.2 ENVIRONMENTAL IMPACTS ON ENZYME STRUCTURE

TOPIC 3.2 OBJECTIVES/EKS

  • LEARNING OBJECTIVE 3.2.A: Explain how changes to enzyme structures may affect function.

  • Essential Knowledge 3.2.A.1: Changes to component molecular structures in an enzymatic system can alter function or efficiency.

    • Denaturation: Occurs from changes in temperature, pH, or chemical environment, disrupting structure and eliminating catalytic ability.

    • Optimal Conditions: Every enzyme has an optimal temperature and pH.

Denaturation Effects

  • Reversibility: In some cases, denaturation may be reversible, restoring enzyme activity.

Environmental Factors Impacting Enzyme Activity

  • Temperature: Higher temperatures increase molecular movement, enhancing reaction rates until enzyme denaturation occurs.

  • pH Levels: Changes in pH affect enzyme structure via proton concentration, impacting hydrogen bonds.

Enzyme Inhibition

  • Competitive Inhibitors: Bind to the active site of enzymes, competing with substrates.

  • Noncompetitive Inhibitors: Bind to allosteric sites, altering enzyme shape and effectiveness.

  • Allosteric Regulation: Involves binding of regulatory molecules that can either inhibit or stimulate enzyme activity, affecting overall function.

3.3 CELLULAR ENERGY

TOPIC 3.3 OBJECTIVES/EKS

  • LEARNING OBJECTIVE 3.3.A: Describe the role of energy in living organisms.

  • Essential Knowledge 3.3.A.1: All living systems require an input of energy.

    • Energy input must exceed energy loss to maintain biological order and power cellular processes.

    • Energy release processes can be coupled with energy-requiring processes.

Thermodynamics

  • First Law: Energy is constant; cannot be created or destroyed but can be transformed.

  • Second Law: Every energy transformation increases entropy in the universe.

Cellular Thermodynamics

  • Cells are not in equilibrium and experience constant material flow.

  • Cellular Work Types: Includes transport, mechanical, and chemical work.

  • Energy Coupling: Using an exergonic process to drive an endergonic one, primarily through ATP.

ATP (Adenosine Triphosphate)

  • Structure: Composed of ribose, adenine, and three phosphate groups.

  • Function: ATP acts as the cell’s energy shuttle; energy is released upon hydrolysis of the terminal phosphate bond.

  • ATP Cycle: A renewable process where ATP is reformed from ADP and inorganic phosphate via energy farming from catabolic reactions.

Conservation of Metabolic Pathways

  • Certain metabolic pathways are found across all life forms, indicating a common ancestry. Examples include glycolysis and oxidative phosphorylation.

3.4 PHOTOSYNTHESIS

TOPIC 3.4 OBJECTIVES/EKS

  • LEARNING OBJECTIVE 3.4.A: Describe structural features of chloroplasts and photosynthetic processes.

    • Photosynthesis: A series of reactions using CO2, H2O, and light energy to produce carbohydrates and O2.

    • Photosynthesis Firsts: Evolved in prokaryotic organisms; evidence shows cyanobacterial photosynthesis contributed to early atmospheric oxygen.

Photosynthesis Mechanism Overview

  • Stages:

    1. Light Reactions (occur in thylakoids)

    2. Calvin Cycle (occurs in stroma)

Light Reactions Functionality

  • Electron Transport Chain in thylakoids culminates in ATP and NADPH production.

  • Chemiosmosis: Proton gradient generated enables ATP synthesis via ATP synthase, known as photophosphorylation.

Calvin Cycle Overview

  • Incorporates CO2, ultimately producing sugars (G3P).

  • Carbon fixation catalyzed by Rubisco.

3.5 CELLULAR RESPIRATION

TOPIC 3.5 OBJECTIVES/EKS

  • LEARNING OBJECTIVE 3.5.A: Describe mitochondrial processes and features.

    • Cellular Respiration Pathways: Glycolysis, pyruvate oxidation, citric acid cycle, and oxidative phosphorylation are key components to ATP synthesis.

Cellular Respiration Mechanism Overview

  • Aerobic vs Anaerobic: Differences in electron acceptors (oxygen vs. other compounds).

  • Glycolysis: Unique pathway occurring in the cytosol, leading into pyruvate oxidation.

Key Steps in Respiration

  • Electron Transport Chain (ETC): Involves electron transfer while generating proton gradients across membranes for ATP synthesis through chemiosmosis.

Fermentation Overview

  • Occurs when oxygen isn’t available; facilitates ATP production via substrate-level phosphorylation without the ETC, yielding lactate or ethanol.

Energy Efficiency Calculations

  • Calculative assessments on ATP yields and excess energy management post-glucose metabolism; efficiency specimens detailed in plant and animal models and evolutionary implications of metabolic pathways.