Energy Transformations Ch.6

Types of Systems? CLOSED, exchanges only energy OPEN, exchanges matter and energy

What is the transformation?

Terminology Metabolism- all chem. rxns Coupled reactions: Catabolic pathways Release energy by breaking down complex molecules (cell respiration) Anabolic: consume energy Build complex molecules (protein synthesis)

Which is catabolic and which is anabolic? Anabolic Catabolic

Describe the energy transformations

Thermodynamics First Law Energy can be transferred and transformed but cannot be created or destroyed Second Law –energy transfers increases the entropy of the universe Entropy – quantitative measure of disorder Closed system – earth Open system - organisms

Combine the first and second Law Quantity of energy is constant Quality (type) of energy is not constant

Free Energy – understand to apply to enzymes Amount of energy available to do work G = Gibbs free energy H = enthalpy or total energy of molecule Term: enthalpy not in text T = temperature in 0 K (C +273) S = entropy  G =  H - T(  S)

Significance of free energy understand to apply to enzymes Maximum amt. of energy to do work Indicates whether a reaction will occur spontaneously Spontaneous reaction will occur without additional energy (move from unstable to stable)  G decreases (-  G ) in spontaneous rxn.

High energy system Enthalpy – total energy of molecule Unstable Tend to change to more stable state A decrease in enthalpy (like ball rolling down slide) and increase in entropy of universe-- reduce free energy Contribute to spontaneous process

Free energy and equilibrium Free energy decreases as approach equilibrium Spontaneous and exergonic Free energy increases as pushed away from equilibrium Non-spontaneous and endergonic At equilibrium –>  G = 0

At equilibrium A system can do no work Metabolic disequilibrium necessary for life of cell

Energy Transformations?

Exergonic Reactions Products have less free energy than reactants Energetically down hill Spontaneous reaction  G is negative Respiration

Endergonic Reaction Products store more free energy than reactants Energetically uphill Non-spontaneous: requires energy input  G is positive photosynthesis

Why is this all important? ENZYMES…speed up metabolic reactions by lowering energy barriers. They cannot change the  G for a reaction. Can hasten reactions that would’ve occurred anyways (hasten spontaneous reactions)

ATP Immediate source of energy that drives cellular work Adenosine triphosphate Nucleotide with unstable phosphate bonds Nucleoside: adenine joined to ribose 3 phosphates attached to ribose Nucleoside + phosphates= nucleotide

nucleoside

Hydrolysis of unstable bonds between phosphates Terminal phosphate bonds unstable Products of hydrolysis more stable Exergonic (spontaneous)—releases free energy (  G is negative) Produces ADP + P  G = -7.3kcal/mole in lab In living cell –13kcal/mol

ATP performs work requires enzymes Energy coupling: Exergonic hydrolysis coupled with endergonic phosphorylation Phosphorylation – transfer of P to another molecule Molecule receiving P becomes more active

Regeneration of ATP Continual rapid process 10 7 molecules used and made/sec/cell ADP + P  ATP Requires energy --- from respiration or light (in plants) Endergonic—energy storing