Unformatted text preview: Energy and Enzymes Exam 1 Results: receive in lab next week Q 19 and Q21 removed due to technical difficulties receive these 2 pts free 50 points total (parts 1 & 2) (must multiply x2 to get % score) Exam adjustment announced next Monday 1 Topics Energy and Enzymes Energy Changes in Reactions Exergonic and Endergonic Reactions Activation Energy Characteristics of Enzymes Enzyme Structure, Active Sites and Turnover Capturing Energy with Cofactors (ATP & NADH) The Important (Exam) Stuff Explain the differences between exergonic and endergonic reactions (see summary slide) Explain how enzymes act as reaction catalysts Describe the structural similarities between ATP and NADH + Describe how ADP and NAD capture energy from biochemical reactions. 2 Simple Thermodynamics (the best kind) Endergonic Reactions Free energy (G) change is positive Reaction is not favorable Reactants Products Exergonic Reactions Free energy (G) change is negative Reaction is favorable Reactants Products Exergonic versus Endergonic 3 Exothermic or Endothermic Exergonic or Endergonic? Releases Energy Requires Energy Changing Chemical Reaction Rates 4 Uncatalyzed and Catalyzed Reactions Enzyme Facts Almost exclusively proteins (some RNAs are catalytic) Act as catalysts (not consumed during reaction) Lower activation energy Influence rate, not equilibrium Usually highly specific (specificity is defined by structure) Form reversible complexes with substrate Often inhibited/regulated by substrate analogs Frequently organized in pathways All end in "ase" (name defines function) 6 types oxidoreductase, transferase, hydrolase, lyase, isomerase, ligase 5 Enzyme Structure & Active Sites o 1 o 2 o 3 o 4 subunits Tiny changes sometimes lead to big "effects" The Catalytic Cycle Enzyme + Substrate(s) = Enzyme + Product(s) 6 Enzyme Turnover Turnover Number = maximum number of substrate molecules converted to product per second 9 DNA Polymerase = 15/s Carbonic Anhydrase = 10 /s HCO to water and CO 3 2 Cofactors and Coenzymes Cofactors = non protein component of enzymes Tightlybound metal ions Examples: Zn, Mo, Cu Covalentlybound organic prosthetic groups Example: heme + Transientlybound organic coenzymes Example: NAD 7 EnzymeCatalyzed Reactions & Biochemical Pathways Biological Sugar Oxidation Free Energy (G) Sugar + O 2 Enzyme catalyzed reactions Chemical Sugar Oxidation Sugar + O 2 Heat, Light "Energized" carriers CO + H O 2 2 CO + H O 2 2 Course of Reaction Course of Reaction ATP chemical energy "Currency" ATP in exergonic reactions Reactants Product ADP + Pi ATP Reactants Products ATP in endergonic reactions Reactants Products ATP ADP + Pi Reactants Products Phosphoanhydride bond energy 8 Redox Reactions and Energy Nicotinamide Adenine Di Nucleotide NAD+ + NADH +H 9 Redox Role of NADH 2 e Alcohol Dehydrogenase NAD+ Zn+ Glucose + 2ADP +2Pi > 2 ethanol + 2CO2 + 2ATP +2H2O Ethanol + NAD+ acetaldehyde + NADH + H+ 10 Text References Pages 109117 (11th Edition) 11 ...
View Full Document
- Spring '08
- Enzyme, endergonic reactions, Reactants Products, Pi ATP Reactants Products, Reactions Free energy, Reactants Products ATP