Energy is life

Thermodynamics Thermal Energy – 2 parts 1) chemical energy stored in bonds of molecules 2) kinetic energy of Brownian motion Temperature = average kinetic energy of molecules Heat = flow of KE from one object/place to another

Metabolism = all biological chm rxn Metabolic pathways = a series of chm rxn resulting in a set product…. each step catalyzed by different enzyme Catabolism = energy releasing pathways ( degradative ) Anabolism = pathways that consume energy to build complex molecules (biosynthetic)

Laws of Thermodynamics 1st law – conservation of energy…. energy not created or destroyed only converted one form to another 2nd law – All systems tend to entropy (chaos) (disorder) unless energy is being put in transforming energy results in loss of organized, usable energy as heat

1865 Philosophical Society of Zurich presentation Clausius concludes: ‘The entropy of the universe tends to a maximum.’ This statement is the best-known phrasing of the second law. Because of the looseness of its language, and lack of specific conditions, e.g. open, closed, or isolated, many people take this simple statement to mean that the second law of thermodynamics applies virtually to every subject imaginable. This, of course, is not true; this statement is only a simplified version of a more extended and precise description.

2nd law - 1854, the Clausius statement: Heat can never pass from a colder to a warmer body without some other change, connected therewith, occurring at the same time Biological version – enzyme mediated chemical reactions cause the change that decreases the entropy of a substance spontaneous processes occur on their own to increase disorder Heat flows from high concentration of heat to low Molecules flow from high concentration to low Diffusion spreads molecules out increasing entropy

1st & 2nd law bio-style 1) The universe tends toward chaos (entropy) 2) Without the input of E. disorder increases …dead things decompose 3) Solar E. is added to ecosystems via photosynthesis 4) Conversion of E from one form to another results in loss of usable energy in form of heat Thus limiting length of food chain…only 10% of energy taken in is passed up chain

Gibbs free energy …G Free energy (G) can perform work ΔG indicates if a reaction will be spontaneous

Negative ΔG increases entropy = spontaneous (new molecules are lower E… degradative) exergonic pathway

Positive ΔG decreases entropy = require an input of energy to occur (synthesizes molecules that are higher E) endergonic pathway

ΔG = ΔH - T ΔS ΔH = change in enthalpy ΔS = change in entropy T = absolute Temperature in Kelvin ΔG = change in Gibbs free energy

Metabolism Exergonic Cellular respiration Endergonic Photosynthesis Catabolism Anabolism Degredative Breaks down large mol. Hydrolysis rxns Increases entropy by Releasing E. (- ΔG) Exergonic Cellular respiration Biosynthetic Builds large molecules Condensation rxns Decreases entropy by Storing E in mol. (+ ΔG) Endergonic Photosynthesis

Energy Coupling Exergonic rxns power endergoninc rxns Energy is transferred via ATP

Adenosine triphosphate Nucleoside used in RNA (ribose + adenine) Plus 3 phosphates Hydrolysis of ATP releases… inorganic phosphate (Pi)+ 13 kcal/mol Proteins can harness that E to … 1) transport molecules (protein pumps) 2) move things ( motor proteins) 3) drive endergonic rxns

ATP drives endergonic rxns by.. Substrate level phosphorylation : enzyme transfers one Phosphate from ATP to a molecule creating an Unstable intermediate(phosphorylated intermediate) Unstable intermediate is a higher energy mol. more likely to react spontaneously…releasing the Pi

Glu + NH3= endergonic (+G) So in body Glu forms an unstable phosphorylated intermediate first Then the Pi is replaced by the lower energy NH3 Combined the reactions are exergonic (-G) & therefore spontaneous

ATP moves proteins by 1) ATP is hydrolyzed and protein is phosphorylated…then Pi is released result: protein changes its structure

2) ATP binds to protein ...hydrolyzing ATP releases energy that causes protein to change shape

Enzymes 1) Proteins (except… ribozymes RNA enzymes) 2)Biological catalysts 3) Speed reactions but are NOT a reactant (not used up) 4) lower activation energy 5) do NOT alter overall ΔG

Enzyme Vocab…. Substrate = reactant enzyme binds Active site = pocket where substrate fits into enzyme Induced fit = alteration of substrate or active site to make a better fit between them

Allosteric site = pocket other than active site where activators & inhibitors can bind

Activators = increase the activity of enzyme … stabilize enzyme in active form Inhibitors = block activity of enzyme …stabilize enzyme in inactive form

Activation Energy lowered by… 1) aligning molecules favorably 2) putting stress on bonds in molecule 3)creating favorable microenvironment

Allosteric Regulation Allosteric regulator molecules all bind to allosteric site activator molecules stabilize enzyme in active form inhibitor molecules stabilize enzyme in inactive form

Specificity of Active Sites 1) Based on shape, size, pH, polarity, charge 2) Substrate held in place by weak interactions (H-bonds, ionic bonds) 3) Enzymes only catalyze one reaction 4) May be reversible (depends on concentrations) 5) Competitive inhibitors mimic substrate, bind active site covalently & inactivate enzyme…. can be overcome by vast in substrate conc.

Feed-Back Inhibition (allosteric) The end-product of a pathway shuts down the first enzyme of the pathway that creates it Prevents overproduction of products

Cofactors Non-protein molecules/atoms needed for enzymes to work Inorganic cofactors include Zn Fe & Cu ions Organic cofactors are called coenzymes include many vitamins & vitamin derivatives and nucleotides like NAD+ & FAD

Things that influence reaction rates.. Concentration of enzymes/coenzymes/cofactors pH Temperature Concentration of substrate Concentration of allosteric molecules Localization of reactions (compartmentalization) Denatured enzymes or altered enzyme structure

Ph effect on enzymes Optimum pH Acidic (lowpH) Basic (highpH)

Temperature Increasing temperature Increases KE Increases reaction rate Excessive Temperature denatures enzyme by Breaking H bonds that Hold enzyme in its secondary structure

Do Scientific Skills Exercise p128 Please read the information and do #1 and #4