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What are some characterisitics of enzymes?
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Biochem Chapter 6
| Question | Answer |
|---|---|
| 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
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