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# Biochem-Enzymes 3

### Med’11 Biochemistry Enzymes

Question | Answer |
---|---|

What is enzyme kinetics? | Study of the rates of enzyme-catalyzed reactions |

What is the velocity of a reaction? | The rate of catalysis, defined as the number of moles of product formed per second |

What is the initial velocity of a reaction? | Measured at the very beginning of a reaction when very little P has been made. It depends on the amount of substrate present |

What is the turnover number (Kcat)? | The number of substrate molecules converted to product per enzyme molecule per unit of time, when E is saturated with substrate (μmol/ min/ mol of enzyme). It is a measure of catalytic activity. |

What happens to enzyme concentration and initial velocity when substrate concentration is very high? | Enzyme concentration: approaches 0 Initial velocity: approaches maximum velocity |

What factors affect enzyme reactivity? | Substrate concentration pH Temperature |

On what assumptions is the Michaels-Mentin equation built? | ES is formed ES in rapid equilibrium with free E Rate of E+P formation is less than rate of ES formation and E+S formation. |

What is the Michaels-Mentin equation? | Vmax [S] V = ________ Km + [S] |

Describe Vmax. | Constant Theoretical, never achieved in reality To be achieved, ALL enzymes must be bound to substrates. V approaches Vmax as substrate concentration increases |

Describe the kinetic activator constant (Km) | Constant Derived from rate constants Under Michaels-Mentin conditions, is the ES dissociation constant Small Km: tight bonding Large Km: weak bonding |

What is the equation for Km? | Km = (K2 + K3) / K1 |

What is the shape of the graph of the Michaels-Mentin equation? | Rectangular hyperbola |

What is the relationship between the Michaels-Mentin equation and the Lineweaver-Burk equation? | The LBE is a double reciprocal equation of the MME so as to give a linear graph to correctly identify the Km and Vmax |

Created by:
Salma O