Editor’s note: It is a good exercise to determine the configuration (R or S) of each chiral centre presented in this course. Some molecules have the same composition in terms of atoms but differ by their placement. Those molecules are called conformers (of configuration). Amongst them we distinguish enantiomers and diastereoisomers. The distinction was already […]
Author: Dr GERARD Thomas
Chapter 8: chemical kinetics – enzymatic catalysis
It can be done several ways catalysis by proximity (entropic contribution) electrophile and nucleophile catalyses general basic catalysis Catalysis by proximity We compare here an intramolecular process with an intermolecular process. Intermolecular Imidazole is incorporated into many important biological molecules. One of them is the histidine that is present in many proteins and enzymes. The presented reaction is […]
Chapter 8: chemical kinetics – catalysis
Homogeneous catalysis In some conditions, a same reaction A → B can lead to two different kinetics depending on the composition of the solution in which it is. One species C, apparently not intervening in the reaction as it is not consumed by it, increases the speed of reaction. Both reactions occur simultaneously, giving a […]
Chapter 8: chemical kinetics – relaxation to the equilibrium
Reaction of order 1 Considering an equilibrium between two species A and B We can study the return to the equilibrium (or relaxation) after a sudden modification of the conditions such as a jump of temperature or of pressure, or the modification of an electric field. The kinetics of the relaxation towards the equilibrium adapts […]
Chapter 8: chemical kinetics – reactions in solution
The big difference between a solution and a gas is the presence of a solvent. A viscous solvent means that there are more collisions between the molecules of reactant and the molecules of solvent, slowing down the molecules. The first obligation to obtain a reaction is that the reactants have to be close to each […]
Chapter 8: chemical kinetics – kinetic theories
The following theories only apply to elementary reactions, i.e. in reactions in one step. The empirical relation of Arrhenius can be used (this relation is not limited to the elementary reactions): with kexp the kinetic constant found experimentally, Aexp the pre-exponential factor (same dimensions as kexp) and Ea the energy of activation. The goal is […]
Chapter 8: chemical kinetics – orders of reaction
Kinetics is a field of the chemistry that studies the evolution of a chemical process over time. It gives practical information on the reaction and can help to determine its mechanisms. There is already two chapters discussing the basics of kinetics (1, 2) and we will now explore a bit deeper this field of chemistry. […]
Chapter 7b : Glucose catabolism – respiratory chain
In 1935, Engelhardt analysed the rate of ATP in red blood cells (globules rouges) as a function of the rate of oxygen. The experiments showed that the ATP increases with the quantity of O2. Contrarily to the yeast, the blood cells had to be in one piece to observe the phenomenon. Even more, some enzymes […]
Chapter 8 : Glucose catabolism – aerobic oxidation
This process is coupled to the cellular respiration, involves O2 and is way more effective than the anaerobic oxidation. Instead of 2 ATP, the aerobic oxidation generates 38 ATP by glucose. It can also oxidise fatty acids and the carbonate parts of amino acids. The cycle of Krebs: cycle of the citric acid Szent Fuorgue […]
Chapter 7 : Glucose catabolism
Its goal is to supply energy to the cell wherever it is needed. The glycolysis forms pyruvate from the glucose that can next be deteriorated anaerobically to form lactate or ethanol through fermentation. In 1870, Louis Pasteur discovered the functioning of yeasts. He isolated one yeast and added it to a wine that was not […]