BIOL 1411 1st Edition Lecture 10 Outline of Last Lecture I. Cytoplasmic ReceptorsII. Transduction and Amplification of SignalIII. Direct cell to cell interaction and communicationOutline of Current Lecture I. Energy Requirements of CellII. ATPIII. EnzymesCurrent LectureI. Ability to acquire and transform energy from one form to another is a characteristic of life- Anabolic reactions: simple molecules complex molecules- Catabolic reactions: complex simpler ones- Thermodynamicso 1st Law of Thermodynamics: energy is neither created nor destroyedo 2nd Law: when energy is converted form one form to another, some of that energy becomes unavailable to do work (no reaction is 100% efficient)- Entropy: disorder in a system, is increasing in the universe- Total Energy= usable energy + unusable energy (entropy)o Enthalpy (H) = free energy (G) + entropy (S)o H=G+TS (Tabsolute temp)o G=H-TSo ΔG= ΔH-T ΔS If delta G is negative free energy is released, exergonic If delta G is positive free energy is consumed, Endergonic- If free energy is not available, the reaction does not occur- Energy-releasing reactions occur spontaneously and always increase disorder in the system- Exergonic:o Releases energy (-G)o Catabolic reactions: complex  simplero Spontaneous- Endergonic:o Consume free energyThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o Anabolic reactions: simple molecules  complexo Is a localized decrease in entropyo Not spontaneous- Chemical Equilibrium: forward and reverse reactions occur at the same time, ΔG- Cells are an example of an open system- Living organisms are highly ordered- Do organisms violate the 2nd law of thermodynamics: no living organisms must have a constant supply of outside energy to maintain order (open system)- Endergonic reactions are coupled to exergonic reactions in ordered metabolic pathways II. ATP- Releases a large amount of energy when hydrolyzed to ADP and Pi- ΔG = -7.3 kcal/mol (exergonic)- Bioluminescenceo Luciferin + O2 + ATP  Oxyluciferin + AMP + PPi + Lighto Enzyme: Luciferarse- ATP couples exergonic and endergonic reactions in the cell- Even thermodynamically favored chemical reactions require some energy to get them started=activation energy- Enzymes are proteins that act as catalysts for biological reactionso The enzyme is not altered by the reactionso Act as a framework in which reactions can take placeo Bring reactants together and increase their free energyIII. Enzymes- Are highly specific for their substrateso Substrate molecules bind to the active site of the enzyme- 3-D shape of the enzyme determines the specificity- Enzyme-Substrate complex (ES)o Is held together by hydrogen bonds, electrical attraction, or covalent bonds- Enzyme (E) may change when bound to the substrate (induced fit) but returns to its original formo E + S  ES  E + P- Enzymes only lower the energy barrier for reactionso Final equilibrium doesn’t changeo ΔG doesn’t change- How Enzymes Worko An enzyme may use one or more mechanisms to catalyze a reaction Orienting the substrates to react Inducing strain in the bonds of the substrates Temporarily adding chemical groups- Acid-Base catalysis: enzyme side chains transfer H+ to or from the substrates, causing a covalent bond to break- Covalent Catalysis: a function group can covalently bond with substrate- Metal ion catalysis: metals on side chains lose or gain electronso Reaction Rate There is a max rate for any given enzyme that depends on the substrate concentration Enzyme concentration is usually much lower than concentration of a substrate If all enzyme is bound to substrate max reaction rateo Enzymatic Pathways are interconnected o Inhibitors- naturally occurring molecules that bind to the enzyme and slow reaction rates Competitive inhibitors: compete with the natural substrate for binding sites Noncompetitive inhibitors: bind to the enzyme at a different site and alter activesite, often function as metabolic regulators Reversible inhibitor: bonds non-covalently to the enzyme Irreversible inhibitor: covalently bonds to side chains of the