Within a molecule you have intramolecular and intermolecular interactions.
Right now I’m going to delve into what are know as Van Der Waals forces. All of these forces are intermolecular forces (between molecules).Here they are: dipole-dipole, dipole induced -dipole, and induced dipole-induced dipole
1. Dipole- Dipole
Essentially, a polar molecule which is bonded covalently (Ex: HCl). It has a dipole moment. The negative chlorine end aligns itself and is attracted to the positive hydrogen end of another HCl molecule. These forces in comparison to intramolecular interactions are incredibly weak, but they are the strongest type of intermolecular forces. Hydrogen bonding is a form of dipole-dipole intermolecular forces (and can have an effect on physical properties such as expected boiling points).
2. Dipole induced -Dipole:
In this scenario, we have one polarity covalent molecule and one very neutral molecule. An Example would be say, HCl and CH4 or Ar or any other molecule which does not have a dipole moment. Essentially what happens is the polar end (doesn’t matter which end) of the polar molecule exhibiting a dipole moment (in our example HCl) induces or causes the neutral molecule or atom to experience a temporary dipole moment.
3. Induced dipole- induced dipole
These are also known as London Dispersion forces. All systems of molecules contain them even if that system contains dipole-dipole forces (no one talks about them then because they are so weak in comparison!). I’m sure you can deduce what this type of interaction entails. Yes, two neutral molecules which temporarily induce a dipole moment between each other. To understand this you need to picture the system as dynamic. Electrons are always moving and even in “happy” neutral, stable molecules electrons sometimes find themselves lumped together for a small fraction of time before equalizing again. This can occur from interaction with light, changes in the thermodynamic properties of a system, intermolecular forces, electron movement, etc.When this happens a small negative charge will be at one end of the molecule and it will induce a neutral molecule next to it.
Most information from:
Lennard Jones Potential:
This is basically some math behind the qualitative explanation of attraction.
The below link is fairly concise. And here’s the equation in case seeing it rings any bells.
U(r) = 4 ε [(σ/r)12 - (σ/r)6]
In the early 1900s, a Canadian woman named Maud Leonora Menten went to Germany to work with Leonor Michaelis at the University of Berlin. By this time in scientific history, Michaelis and Menten knew that enzymes could perform chemical reactions. From the work of Victor Henri, they hypothesized that there would be a quantitative relationship between the amount of enzyme around compared to the concentration—but nobody had ever analyzed this properly before. Henri had the basic idea right, but had forgotten to take some key factors into account. In just that one year, Menten worked with Michaelis to set up experiments to test this and to properly control those other aspects that Henri didn’t, and collected the data to write the paper describing analyses and equations that transformed the way scientists thought about enzyme function and provided the foundation on which modern biochemistry is built.
All of this was done without even knowing how much enzyme they were working with, just diluting some kind of preparation of it in different proportions to substrate (which was sucrose) and without having modern molecular analysis tools available.
(#women in science: Maud Menten!)
So we left off with d[ES]/dt = 0 = k1[E][S]-k-1[ES]-k2[ES]
But we want for the goal is to express the overall rate. The enzyme-substrate complex is an intermediate, and not in the overall rate formula, so [ES] needs to be expressed in terms of [E]. These two are connected by:
[ET] = [E] + [ES], where ET is the total concentration of enzyme in the system and it is equal to the amount of free enzyme plus the amount of the complexed enzyme. By solving for [E], we obtain the relation [E] = [ET] -[ES].
Now we substitute the [E] value in the equation for d[ES]/dt with the one just derived.
d[ES]/dt = 0 = k1([ET]-[ES])[S]-k-1[ES]-k2[ES]
d[ES]/dt = 0 = k1[ET][S]-k1[ES][S]-k-1[ES]-k2[ES]
Solve for [ES]:
[ES] = (k1[ET][S]/k1[S]+ k-1+ k2)
The term (k-1+ k2/ k1) is defined as the Michaelis constant, kM. To get this constant in our equation, divide the numerator and the denominator by k1 (essentially multiplying by one (k1/ k1)):
[ES] = ((k1/k1)[ET][S]/((k1[S]+ k-1+ k2)/k1))
which reduces to:
[ES] = ([ET][S])/ ([S]+ kM)
The rate which the product is consumed is:
d[P]/dt = k2[ES] which= (k2[ET][S])/ ([S]+ kM)
And this is how you derive the Michaelis-Menten equation.
My professor is doing biochemical research which means he’s going to be fond of putting some this stuff on the final. So this is a deeper look at catalysts, enzymatic catalysts in particular.
Enzymes are proteins which selectively bind to small active sites on substrates. Enzymes are specific substrates and reactions which they catalyze. Most common way of naming enzymes is just to add the suffix -ase to the name of the substrate it binds to.
Ex: Telomeres are the noncoding sequences at the end of DNA strands which protect genetic material from damage during DNA replication. Telomerase is the enzyme which allows for the production of telomeres. Active telomerase is present is early cells such as stem cells and cancer cells giving them a sort of “immortal” quality as they can indefinitely replicate. (Example: HeLa cells! We’re still using replications of her cells!)
Classes of Enzymes:
Many enzymes require metal ions or small organic molecules, such as vitamins, which catalyze electron transfer RXNs. Enzymes find alternative pathways with lower activation energy and the kinetics of enzymes are calculated and studied by the steady-state approximation known as Michaelis-Menten kinetics.
Two or more stable compounds which come together to form another stable compound are called coordination compounds.
This is explained by Alfred Werner’s theory (1893): certain metals, especially transition metals, have two types of valence or bonding capacity. The primary valance is based on the number of electrons he atom loses in forming the metal ion. The secondary valence is what caused the bonding of other groups to the central atom. These groups are called ligands.
A complex is any species involving coordination of ligands to a metal center, which can be an atom or an ion. The complex itself can be positive, negative or a neutral molecule.
The coordination number is the number of points around the metal center where bonds to ligands can form (ranging typically from 2-12, with 6 as the most common).