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Redox Reactions
Electron transfer reactions powering life processes.
Energy Transduction
Conversion of energy types in biological systems.
Electrochemical Gradient
Difference in ion concentration across membranes.
Chemiosmotic Coupling
Energy coupling via proton gradients.
Oxidative Phosphorylation
ATP production using electron transport chain.
Photophosphorylation
ATP synthesis from light energy in photosynthesis.
Electron Transport Chain
Series of proteins transferring electrons in membranes.
F1F0-ATPase
Enzyme synthesizing ATP using proton gradients.
ΔG (Gibbs Free Energy)
Energy available to do useful work in reactions.
Spontaneous Reaction
Reaction occurring without external energy input.
Non-spontaneous Reaction
Reaction requiring energy input to proceed.
Chemical Potential Energy
Energy stored in chemical bonds not at equilibrium.
Standard Free Energy (ΔG0)
Free energy change at standard conditions (1 M).
Entropy
Measure of disorder in a system.
Enthalpy (ΔH)
Total energy change during a reaction.
Thermodynamics
Study of energy transformations in systems.
Equilibrium Constant (K)
Ratio of product concentrations to reactants at equilibrium.
Erythrocyte
Most common cell type in the human body.
Oxygen's Role
Essential electron acceptor in cellular respiration.
Photosynthesis
Process converting light energy into chemical energy.
Electron Donor
Substance providing electrons in redox reactions.
Electron Acceptor
Substance receiving electrons in redox reactions.
Proton Gradient
Difference in proton concentration across a membrane.
Thermodynamic Laws
Principles governing energy conservation and dissipation.
Energy Capture
Process of storing energy from environmental sources.
Biochemical Pathways
Series of reactions converting substrates to products.
Hydrolysis Reaction
Reaction breaking down ATP into ADP and phosphate.
Chemical Reaction Displacement
Energy available from systems far from equilibrium.
Vital Spark
Fundamental energy source driving biological processes.
Standard Free Energy Change (ΔG°)
Energy change under standard conditions (1 M).
Mass Action Ratio (Q)
Actual concentration ratio of products to reactants.
Gas Constant (R)
Value of 8.3 J/mol·K used in thermodynamics.
Temperature (T)
Measured in Kelvin; 25 °C equals 298 K.
Free Energy Change (ΔG)
Energy available for work in a system.
Equilibrium Position
State where ΔG equals zero; no net change.
Reaction Quotient (Q)
Current ratio of products to reactants.
ΔG Calculation
ΔG = ΔG° + 2.3RT log [B]/[A].
Energy Coupling
Linking exergonic and endergonic reactions.
ATP Hydrolysis
Conversion of ATP to ADP and Pi releasing energy.
Phosphoryl Transfer Potential
Ability of ATP to donate phosphate groups.
Equilibrium Constant for ATP Hydrolysis
K = 6.32 x 10^5 for ATP to ADP.
ATP/ADP Ratio
Maintained far from equilibrium in cells.
Hexokinase Reaction
Catalyzes phosphorylation of glucose using ATP.
ΔG° for Glycolysis
ΔG° = -2.3RT log Keq; Keq = 7 x 10^-3.
Kinetic Limitation of ATP Hydrolysis
Hydrolysis is slow despite being spontaneous.
Cyanide Toxicity
Inhibits ATP regeneration from ADP.
Energy Conservation in Cells
Free energy stored in ATP/ADP ratio.
Respiration ΔG
ΔG = -2872 kJ/mol for glucose oxidation.
Standard Conditions
Reactants and products at 1 M concentration.
Displacement from Equilibrium
Extent to which a system is away from equilibrium.
Hydrolysis of ATP
Releases energy due to structural strain.
ATP Turnover
Daily turnover of ATP is ~80 kg.
Equilibrium Shift
Reaction favors products or reactants under conditions.
Energy Available for Work
Depends on displacement from equilibrium.
ATP Participation
Drives reactions far from equilibrium.
Oxidation
Loss of electrons during a redox reaction.
Reduction
Gain of electrons during a redox reaction.
Redox Potential
Measure of a molecule's electron transfer capacity.
Spontaneous Electron Transfer
Occurs when ΔG is negative.
Redox System
Involves electron donors and acceptors.
Redox Reaction
Transfer of electrons between molecules.
ΔE0
Difference in redox potential between donor and acceptor.
Standard Redox Potential (E0')
Measured under specific conditions (1 M, 25°C, pH 7).
Faraday Constant (F)
96.5 kJ/V·mol, relates energy to electron transfer.
NADH/NAD Redox Potential
E´0 = -0.32 V, indicates reducing power.
FADH2/FAD Redox Potential
E´0 = -0.21 V, indicates reducing power.
O2/H2O Redox Potential
E´0 = +0.82 V, strong oxidizing agent.
ΔG Equation
ΔG = -nFΔE0' relates energy to electron flow.
Chemical Gradient
Concentration difference across a membrane.
Electron Flow Direction
From lower to higher redox potential.
Iron Rusting
Example of oxidation involving electron transfer.
Biological Reductants
Molecules that donate electrons in reactions.
Biological Oxidants
Molecules that accept electrons in reactions.
Energy from Redox Reactions
Drives ATP synthesis through electron transfer.
High ATP/ADP Ratio
Maintains energy availability in cells.
Redox Gradient
Electrons flow down this gradient to release energy.
Midpoint Potential
E0' in bioenergetics, indicates electron transfer capacity.
Energy Release
Occurs during spontaneous electron transfer.
Oxidation of Glucose
Provides energy for ATP synthesis.
Electrochemical Potential
Energy stored in chemical and electrical gradients.
ΔG
Gibbs free energy change in a reaction.
Concentration Gradient
Difference in solute concentration across a membrane.
[A]i
Intracellular concentration of substance A.
[A]o
Extracellular concentration of substance A.
Membrane Potential (ΔΨ)
Voltage difference across a biological membrane.
Proton Electrochemical Gradient
Energy stored due to H+ concentration and charge differences.
Proton Motive Force (PMF)
Energy available from proton electrochemical gradient.
ΔpH
Difference in pH across a membrane.
Active Transport
Energy-dependent movement of substances against gradients.
Symport
Transport mechanism moving two substances in the same direction.
Substrate-Level Phosphorylation
Direct ATP production through enzyme-catalyzed reactions.
Glycolysis
Metabolic pathway converting glucose to pyruvate.
Glyceraldehyde-3-Phosphate Dehydrogenase
Enzyme catalyzing a key step in glycolysis.
Phosphoglycerate Kinase
Enzyme transferring phosphate to ADP in glycolysis.
High Energy Intermediate
Molecule with high phosphorylation potential in reactions.
ATP Turnover Rate
Rate of ATP recycling in the body, ~1000 times/day.
Metabolism
Chemical processes converting food into energy.
Chemical Equilibrium
State where reactants and products are balanced.
Electronegativity
Tendency of an atom to attract electrons.
pH
Measure of hydrogen ion concentration in a solution.
