Catalysts and Inhibitors

[budullewraagh]

i know what they are and what they do, but i do not understand how they do what they do. how do catalysts and inhibitors have their effects?

[mikeasdfasdf]

i remember hearing at least some catalysts work because of their shape. A catalyst may wedge itself between atoms in the molecule, weakening bonds?

 

I'm not at all sure of the correctness of this answer but i hope i've been a little help.

[budullewraagh]

right, i remember learning in my molecular bio class that proteins were broken because enzymes came into contact in a certain way...i just need more specifics on the exact mechanics

[Bryn]

An enzymes works by providing an alternative reaction pathway that has a lower activation energy.

 

e.g.

Without catalyst

A + b -> C

 

With catalyst

 

A + Catalyst -> A/catalyst complex + B -> catalyst + c

 

Remeber a catalyst is always on the side of the products as well as the reactants, it is not used up, but it does change during the reation.

 

Not too sure on the mechanics of them working but i think they work in a variety of ways. Reacting to create better leaving groups, pushing groups outa the way so another group has more space round it, so is more likly to react with (be hit by) the other reactant etc etc.

 

As for inhibitors there are two basic types of inhibitors, in terms of biochemical reactions anyway. One which binds with the active site of the enzyme (the bit that fits onto the substrate molecule), and stops the substrate entering. This is called competative inhibition. This is reversable.

 

The other type of inhibitor binds to a seperate region of the enzyme and alters the shape of the active site so it can no longer bind to the substrate. This is, surprisingly, called non-competative inhibition. This second type is not reversable.

 

As for inhibitors in a purely chemical sense dunno the mechanics, just that they inhibit

[Skye]

Catalysts usually work by stabilising the transition state of the reaction. The transition state is literally the state the molecules are in as they transition from reactants to products. The catalyst binds to the transition state in a way that makes it more stable, then is released as the product is formed.

[YT2095]

exactly what Skye said

 

it also can work by lowering the activation energy during a reaction.

[mikeasdfasdf]

how does the catalyst lower the activiation energy?

[dryan]

To simplify things, for a chemical reaction to occur, two molecules have to collide in the correct way. Sometimes the two molecules will hit and bounce apart. A catalyst holds the reactants in the right position, so more of the "reactive" collisions occur.

Heating increases kinetic energy and therefore the number of collisions so it will almost always increase rate, (but may work with or against you in the equilibrium).