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Biochem Chapter 6

QuestionAnswer
What are some characterisitics of enzymes? Specificity/ function under mild conditions such of temperature and pH/ and accelerate chemical reactions
Cofactor Inorganic Ion (ex. Ca2+)
Coenzyme Organic or Metalloorganic molecule
Prosthetic Group Conenzyme or metal ion tightly bound to a enzyme protien
Holoenzyme Catalytically active enzyme together with cofactor/coenzyme
Apoprotein Protien part of the holoenzyme
Active Site Where substrate binds and reaction occurs
Substrate Molecule bound to the active site and worked upon
Simple Enzymatic Reaction Equation E + S -> ES -> EP -> E + P
Ground State The starting point for either the forward or reverse reaction
Standard Conditions 1 atm/ 298K/ 1 M
Standard Energy Change in Biochemical Reactions pH 7.0
Transition State The point at which the decay to Substrate or Product is equally possible
Activation Energy Difference in energy between ground state and transition state
Rate of Reaction and Ea relationship Higher Ea = Slower Reaction/ Lower Ea = Faster Reaction
Catalysts Lower Ea
Role of Enzymes Speed up conversion of S -> P and Eq is not affected. Reaction reaches EQ when the rate of reaction speeds up
Reaction Intermediates Transient Chemical Species
How is rate determined? By the rate limiting step (one with the highest Ea)
Reaction rates are linked to? Ea
Reaction equilibria is linked to? Gibbs Free Energy (G)
Values of G Negative = Favorable/ Positive = Not
How do enzymes speed up reactions? Covalent Bond formation between substrate and enzymes functional groups/ non-covalent interactions that form release small amounts of energy that help stabalize interactions . Weak interactions are optimized in the transition state because enzyme site is
Binding Energy Energy dervied from enzyme substrate interaction. Major source of free energy used to lower the Ea of reactions
What kind of interactions are the main driving force for enzyme catalysis? Weak binding interactions (mostly formed in the transition state make the largest contribution)
Where does specificty in an enzyme come from? The binding energy
What is specificty dervied from? Many weak interactions between the enzyme and the substrate
Things that need to occur for a reaction to take place Reduction in entropy/ removal of solvation shell/ distortion of substrates/ proper alignment of catalytic groups on the enzyme
How does binding energy overcome the factors needed for a reaction to take place? Hold substrate in place/ Enzyme-substrate interactions replace most the bonds with water/ Change in conformation induced by weak interactions
Induced Fit Bring specific functional groups into position on the enzyme and allows for more weak interactions to occur as conformational change occurs
Catalytic Mechanisms General Acid-Base/ Covalent/ Metal Ion
General Acid-Base Catalysis Proton transfer mediatedd by other classes of molecules
Covalent Catalysis Transient covalent bond is formed between enzyme and the substrate. An enzyme with a nucleophilic group is used an helps alter the reaction pathway with a lower energy
Metal Ion Catalysis Help orient the substrate for reaction or stabalize a charged reaction transition states and mediate redox reaction
Chymotrypsin Catalysis Methods Covalent Catalysis (Cleavage of Bond and formation of a bond between Ser residue on enzyme and part of the substrate)/ General Acid-Base Catalysis
Initial Rate (Vo) When S is much greater than E in concentration
Vmax Region where substrate increases will not increase the initial rate (essentially when all the enzyme has been saturated with the substrate (ES form))
Pre-Steady State Period in which ES concentration builds up
Steady State ES remains constant over time
Steady-state Kinetics Analysis of Initial Rates
Steady-State Assumption Rate of formation is equal to rate of breakdown
Find Vo Vo = 1/2Vmax
Michaelis Menton Graph Vo = Y/ S = X
Double Reciprocal Plot 1/Vo = Km/vmax[s] + 1/vmax; Slope = Km/Vmax; Y-intercept = 1/vmax (1/vo = Y; 1/S = X)
Reversible Enzyme Inhibition Competitive inhibitor competes with substrate for the active site of an enzyme. Inhibitor occupies active site of enzyme.
Uncompetitive Inhibitor Binds at a different site than the active site
Mixed Inhibitor Binds to both ES or E
pH and Enzyme Activity Can shift how bonds are formed with the substrate or eliminate bonds that are necessary
Function of Chymotrypsin Cuts bonds adjacent to aromatic amino acids/ Trp/ Phe/ Tyr
Zymogen Inactive Precursor which must be cleaved
Methods of Enzyme Regulation Proteolytic Cleavage/ Phosphorylation/ Proenzymes
Proenzymes Must be cleaved
Created by: nikeshhajari on 2009-07-15



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