Lecture_10_Cell Energy I

Cellular Energy Overview

• Cellular Energy I (Ch. 3): Focus on energy utilization, activated carriers, and biosynthesis.

• Course Reference: BIOL 3510: Lecture 10.

Objectives

• Bioenergetics:

  • Definition: Study of energy transformation in living organisms.

  • Key Concepts:

    • First and second laws of thermodynamics.

    • Spontaneity of reactions (ΔG).

    • Connections among catabolism, anabolism, redox reactions, activated carriers, and ATP synthesis.

    • Identification of electron carriers and their reduced/oxidized states.

    • ATP coupling for energy utilization.

Key Concepts in Bioenergetics

• Energy Acquisition: Organisms obtain energy from multiple sources.

• Energy Conversion: Converts energy into ATP, the usable energy form.

• Energy Utilization: ATP fuels cellular processes.

• Energy Storage: Excess energy stored as glycogen or fats.

Thermodynamics

• Two Laws of Thermodynamics:

  1. Energy is conserved (total energy remains constant).

  2. Entropy (disorder) in a closed system increases.

• Spontaneous Reactions:

  • Characterized by a negative change in free energy (ΔG < 0).

  • Reactions with ΔG > 0 are non-spontaneous (require energy).

Biological Order Maintenance

• Living Organisms: Maintain order through:

  • Energy extraction from the environment.

  • Utilization of metabolic processes and regulation.

Thermodynamics and Living Systems

• Living Cells: Open systems that exchange energy with surroundings.

  • Energy conversion generates heat, increasing external disorder.

Photosynthesis

• Photosynthetic Organisms:

  • Include plants, algae, and some bacteria.

• Photosynthesis Reaction:

  • Equation: CO2 + H2O → Sugars + O2

Complementary Processes

• Cellular Respiration:

  • Breakdown of nutrients to gain energy.

  • Involves oxidation, generating energy and carbon skeletons.

• True or False Question: Photosynthesis occurs in specific organisms, while cellular respiration occurs in all life forms.

Redox Reactions

• Oxidation: Removal of electrons from an atom.

• Reduction: Addition of electrons to an atom.

• Connection: Oxidation and reduction occur simultaneously in reactions.

iClicker Question

• Identify the false statement regarding oxidation and reduction processes.

Activated Energy Carriers

• Definition: Store and transfer energy for cellular use.

• Energy Storage:

  • Formed by coupling their production to energetically favorable reactions.

  • Store energy in chemical bonds/electrons.

  • Link breakdown of food energy to biosynthetic processes.

High-Energy Bond Carriers: ATP

• ATP: Most widely used activated carrier.

• Hydrolysis of phosphoanhydride bonds releases considerable energy.

• ATP Cycle: Involves the continual conversion of ATP to ADP and back.

ATP Utilization

• Mechanism:

  • ATP transfers its terminal phosphate to other molecules.

  • Applications include glycolysis, phospholipid synthesis, muscle contraction, active transport.

ATP Hydrolysis in Reactions

• Driving Unfavorable Reactions:

  • Steps:

    1. Activation: ATP donates phosphate to reactants.

    2. Condensation: High-energy intermediate interacts to form products, releasing inorganic phosphate.

Key Electron Carriers

• Types: Include NAD(H), NADP(H), FAD(FADH2), FMN(FMNH2), quinones, transition metal carriers (Cu, Fe).

NADH and NADP(H)

• Roles:

  • NADH: Energy carrier from glycolysis and Krebs cycle, donates electrons in mitochondria.

  • NADPH: Produced via pentose phosphate pathway, used in biosynthetic reactions.

• True or False Question: NADH is for breakdown reactions; NADPH is for biosynthesis.

Electron Carriers: FAD and FMN

• FAD and FMN: Key components in the electron transport chain.

Quinones

• Structure: Cyclic compounds, transfer electrons in mitochondria (ubiquinone) and chloroplasts (plastoquinone).

Metal Electron Carriers

• Involvement of Metals:

  • Key roles in protein complexes, particularly respiratory chain components.

Acetyl Coenzyme A (Acetyl-CoA)

• Metabolic Role: Connects glycolysis to Krebs cycle; acts as a precursor for lipid synthesis.

Synthesis of Activated Carriers

• Energy Coupling: Formation of activated carriers typically involves ATP hydrolysis.

• Examples: Include phosphoenolpyruvate, creatine phosphate, UDP-Glucose, Acyl-CoA.

Activated Carriers Summary Table

• Activated Carrier: ATP (phosphate), NADH, NADPH (electrons/hydrogens), Acetyl CoA (acetyl group), Carboxylated biotin (carboxyl group).

Macromolecule Synthesis

• Reactions: Synthesis (condensation) vs. breakdown (hydrolysis).

  • Condensation: Involves energy input; includes protein, nucleotide, glycogen synthesis.

  • Hydrolysis: Releases energy; includes protein digestion, nucleotide degradation, glycogen breakdown.

Biological Polymer Energy Requirements

• Polymer Synthesis Requirements:

  • Activation of nucleoside monophosphates with ATP for nucleotide chain extension.

  • Hydrolysis of pyrophosphate drives polynucleotide synthesis forward.

Metabolism Overview

• Catabolism:

  • Breaks down molecules, releasing energy.

• Anabolism:

  • Builds molecules, requiring energy.

• Energy Capture: Metabolism of food molecules converts energy into ATP for powering cellular reactions.