Catalyst effect on equilibrium

Catalyst would change the equilibrium position ONLY IF it could speed up reaction in one direction ONLY.

However, this is not true. Generally speaking, catalysts speed up both forward and backward reaction, but eventually they will be the same again.

No, AT EQUILIBRIUM, amount of sucrose should be the same: zero.
As far as I remember, starch (or amylose, so to speak) are composed of glucose or maltose "monomers" (yes I know maltose is actually a disaccharide); both of them are 6-membered ring.
Sucrose, consists of joined glucose and fructose, which the later has 5-membered ring. I don't think amylase would turn maltose / glucose into sucrose / fructose.

But well, despite that, concentration of products at equilibrium should be the same for with or without catalysts.

Specific shape? Hahaha, what do you think the shape of the enzyme when it releases product (maltose)? WHEN the enzyme molecule releases the product, the product should be fitting in the enzyme, right?


2012-04-30 22:26:26 補充：
In close system, at eqm, there should be both starch, maltose & amylase.
With or without amylase the conc. of products should still be he same.

2012-04-30 22:30:38 補充：
Specific shape.... 想像將一粒molecule 模型放入石膏倒模, 石膏模的形狀正好能fit in the molecule.
If molecule has some functional groups like -OH, then there'd be H-bond forming groups at corresponding site in the active site. There'll be interaction between substrate & active site.

2012-04-30 22:33:50 補充：
AFAIK, Most of the enzymes serve one biological function, speeding up a reaction (forward & backward).
For example, "carbonic anhydrase" in blood helps converting molecular CO2 into carbonic acid, facilitating transport of CO2 in blood. At lungs, partial pressure of CO2 reduces, so H2CO3 decomposes

2012-04-30 22:35:56 補充：
-- to yield CO2.

With one enzyme, both forward & backward rxn would be sped up.
But if one has more than 1 enzyme (like a chain / system / cycle of enzymes), product A could be quickly converted to B then C then D... Reverse of A to reactant could be minimized.

I'm not sure about the reaction
However, in normal case (pressure and temperature no change)
Catalyst only speed up the speed and the system will reach equilibrium in a slower speed (negative catalyst) / faster speed (positive catalyst)
however, the position of equilibrium doesn't change.