2 Energetics And Enzymes Flashcards
Q: Define enzyme?
A: protein that acts as a catalyst to induce chemical changes in other substances while itself remaining unchanged
Q: Define Gibbs free energy?
A: the amount of energy within a molecule that can perform useful work at a constant temperature
Q: Do reactions spontaneously proceed towards products with lower or higher entropy?
A: higher
Q: What is the unit for Gibbs free energy?
A: kJ/mol
Q: How do you calculate Gibbs free energy of a reaction?
A: free energy of p - that of r
Q: For a reactive to occur simultaneously, what does delta G need to be?
A: negative
Q: What is a coupled reaction and why are they useful?
A: energetically unfavourable reaction coupled with a favourable one which results in overall negative delta G
Allows energetically unfavourable reactions to take place
Q: Define transition state.
A: particular conformation of a substrate where atoms are rearranged electronically and geometrically for reaction to proceed
Q: What do enzymes do to get substrate in transition state? How do they put strain on bonds?
A: oxidation reactions (electron removal) or reduction (gain)
Q: What is lysozyme and where is it found?
A: first line of defence against bacteria and nasal secretions and tears
Q: How does lysozyme catalyse reactions?
A: catalysed hydrolysis of sugar molecules in bacterial cell walls, causes damage and bacteria die
Copolymer of N-acetyl glucosamine NAG and N-acetyl muramic acid NAM with glycosidic bond between
Glu35 protonates oxygen and causes a break and glu35 to lose a H
Water is deprotonated by glu35 so that it gains a H and the hydroxyl group binds to remaining sugar
Asp52 stabilises the positive charge in transition state
Q: What’s the optimum pH of lysozyme?
A: 5 where asp52 is ionised and glu35 is not
Q: What does NAD stand for?
A: Nicotinamide adenine dinucleotide (coE)
Q: What process produces lots of of free NAD+?
A: anaerobic respiration where pyruvate becomes lactate
Q: What does NAD+ readily catalyse and accept?
A: dehydrogenation and a proton and 2 electrons
Q: What is the role of lactate dehydrogenase?
A: conversion of lactate to pyruvate using NAD+ in liver
Q: What does glucose 6 phosphatase do?
A: catalyse removal of phosphate group from glucose 6 phosphate in liver to release glucose from the glycogen stores when blood glucose is low
Q: What is the Km of an enzyme? For practical purposes? How is it affected by competitive inhibition? how? By non competitive inhibition?
A: Km (Michaelis constant) of the enzyme, an inverse measure of affinity.
For practical purposes, Km is the concentration of substrate which permits the enzyme to achieve half Vmax
increase Km by interfering with the binding of the substrate
unchanged
Q: What is Vmax of an enzyme? How does competitive inhibition affect? Non competitive?
A: rate of reaction when the enzyme is saturated with substrate is the maximum rate of reaction=Vmax
unchanged- inhibitors can’t bind to the ES
reduced
