6. Bioenergetics and ATP Synthesis (Ch 5)
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Bioenergetics and ATP Synthesis
Chapter 5
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Catchphrase
KEEP CALM AND LOVE PHYSICS
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Energy in Organisms
All organisms require energy to survive.
Organisms act as energy transformers, converting energy into new forms.
Chemical reactions in cells involve energy transformations.
Example: Green plants convert radiant energy (sunlight) into chemical energy (glucose).
Humans are described as 'energy parasites' because they rely on other organisms for their energy.
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Thermodynamics
Definition: Study of energy and its various forms.
Focuses on energy conversion from one form to another.
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Definition of Thermodynamics
The study of energy transformations within matter.
Concerned with energy storage, transformation, and dissipation to drive reactions.
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Objectives of Thermodynamics
Understand the relationship between heat and work in biological systems.
Analyze influences of energy changes in biological processes.
Predict temperature effects on biological phenomena in systems at equilibrium (e.g., bioreactors).
Comprehend biochemical processes.
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Biological Perspective of Thermodynamics
Thermodynamic changes are crucial for:
Growth
Reproduction
Photosynthesis
Respiration
Examples:
Light to chemical: photosynthesis
Chemical to chemical: cellular respiration
Chemical to electrical: Nervous system
Chemical to mechanical: Muscles
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Biological Energy Needs
Cells need energy to maintain:
Body structure
Movements
Concentration gradients
Electrical gradients across membranes
Temperature regulation in some animals
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Bioenergetics
Study of energy transformations in living organisms.
Organisms derive, transform, and utilize energy to counter disorder and decay.
Strategies for energy derivation:
Photoautotrophs: derive energy from the sun.
Chemoheterotrophs: obtain energy from organic substances in the environment.
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Principles of Bioenergetics
Thermodynamic laws govern energy transformations and work in biological contexts.
Incorporates chemical and physical principles influencing living organisms.
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Energy Conversion Process
Energy conversion in systems:
Combustion: Gasoline --> Kinetic energy + waste (Heat + CO2 + Water)
Cellular respiration: Glucose --> ATP + waste (Heat + CO2 + Water)
Living organisms require a constant energy supply to maintain order.
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Introduction to Thermodynamics Laws
Important concepts:
1st law of Thermodynamics
2nd law of Thermodynamics
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Entropy
Definition: State of energy and matter condition.
Example: Aerobic organisms extract free energy from glucose, using oxidation with molecular oxygen.
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Entropy Dynamics
Oxidized products (CO2 + H2O) returned to surroundings increase overall entropy, while the organism remains stable.
Entropy increases due to heat dissipation and molecular disorder.
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Enthalpy
Definition: Total heat content of a system.
Enthalpy = Internal energy + Pressure x Volume (H = U + PV).
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Gibbs Free Energy
Definition: Energy available to perform work and oppose entropy.
H = Enthalpy
G = Free energy
T = Temperature
S = Entropy (energy unavailable for work).
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Enthalpy in Reactions
Enthalpy accounts for heat flow at constant pressure during chemical reactions affecting pressure-volume changes.
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Understanding Bioenergetics
Changes in reaction energy inform on nature:
Exergonic reaction: ∆G < 0 (spontaneous)
Endergonic reaction: ∆G > 0 (requires energy input)
Standard free energy change (∆Gº) evaluated at pH 7 and 1 M concentration of reactants/products.
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Equilibrium and Free Energy
At equilibrium, reactants/products concentrations stabilize (∆G = 0).
More available free energy correlates with greater distance from equilibrium (∆G < 0).
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Reaction Spontaneity
Exergonic: ∆G < 0, spontaneous (e.g., energy released).
Endergonic: ∆G > 0, non-spontaneous (e.g., energy input needed).
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Chemical Reactions Summary
Exothermic Reaction: Negative ∆H, heat produced (e.g., CH4 + 2O2 → CO2 + 2H2O).
Endergonic Reaction: Positive ∆G, non-spontaneous (e.g., NH2 + NH3 → Glutamine, ∆G = +3.4 kcal/mol).
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Catabolism vs Anabolism
Catabolism: Exergonic reactions, breaking down chemicals, e.g., glycolysis, fatty acid breakdown.
Anabolism: Endergonic reactions, building complex molecules using energy from photosynthesis or respiration.
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Energy Coupling in Reactions
Energetically unfavorable reactions can be coupled with exergonic reactions.
Example: ATP hydrolysis coupled with glucose phosphorylation leads to spontaneous reactions.
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ATP as Energy Currency
ATP hydrolysis releases significant free energy (∆G = -56 kJ/mol).
ATP concentrations maintained away from equilibrium illustrate homeostasis in cells.
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Electron Transport and ATP Generation
Overview of electron transport chain processes and metal centers involved.
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Oxidation-Reduction Reactions
Oxidation = removal of electrons.
Reduction = gain of electrons.
Redox reaction = paired oxidation and reduction reactions.
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[Incomplete Page]
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Mitochondrial and Chloroplast ATP Production
Overview of ATP production processes in mitochondria and chloroplasts during photosynthesis.
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Final Pathways in Cellular Metabolism
Overview of pathways such as Krebs cycle and fatty acid metabolism to produce Acetyl CoA.
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ATP Synthase Functionality
Description of ATP synthesis driven by the H+ gradient during electron transport and chemiosmosis.
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Photosynthesis and ATP Creation
Process of harnessing light energy in chloroplasts to produce ATP.
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H+ Gradient and ATP Synthesis
The gradient across the thylakoid membrane drives ATP biosynthesis.
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ATP Formation Summary
Overview of the ATP synthesis process involving ADP and inorganic phosphate.
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Energy Storage in Nutrients
Energy stored in high-energy bonds of nutrients and its release during metabolic processes.
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Chemiosmosis in ATP Synthesis
Presence of ATP synthase in chloroplasts, similarities to mitochondrial pathways, and mechanistic details.