Enzymes

Biological catalysts made from proteins

They speed up chemical reactions by decreasing activation energy

Substrate fits enzyme active site perfectly

the proximity of the substrate leads to a change in the enzyme that forms the functional active site. This distorts the bonds in the substrate and lowers the activation energy

the substrate and enzyme fit together

have a molecular shape similar to the substrate allowing them to occupy the active site of an enzyme

attaches themselves to the enzyme at a binding site which changes the shape of the active site preventing enzyme substrate complex forming

Where the inhibitor changes the shape of the enzyme in a non-competitive inhibitor

They can be reused repeatedly and are therefore effective in small amounts

the minimum amount of energy required to activate the reaction

They lower the activation energy which allows them the reaction to take place at a lower temperature

They have a specific 3-D structure (tertiary) that is the result of their sequence of amino acids.

enzyme-substrate complex

• Come into physical contact with its substrate -have an active site which fits the substrate

measuring its time course - the formation of the products of the reaction -the disappearance of the substrate

A rise in temperature increase the kinetic energy of molecules which causes more collisions. More effective collisions means more enzyme substrate complexes. rate of reaction increases.

causes the bonds in the enzyme to break resulting in the enzyme to change shape and the substrate fits less easily, slowing the rate of reaction. The enzyme becomes so disrupted that it stops working altogether (denatured)

permanent change to the active site causing the enzyme to stop functioning

each enzyme has a optimum pH if the pH is changed from the optimum it will reduce the rate of reaction.if the change in pH is beyond a certain pH the enzyme becomes denatured.

-A change in the pH alters the charge on the amino acids that make up the active site of the enzyme. Results in the substrate no longer being becoming attached to the active site- enzyme substrate complex can’t be formed -depending on how significant the change in pH is, it may cause the bonds maintaining the enzymes tertiary structure to break and therefore the active site changes shape

enzymes being catalysts in a reaction they are not used up and therefore work effectively at very low concentrations.As long as there is an excess of substrate an increase in the amount of enzyme leads to proportionate increase in the rate of reaction.

if the concentration of enzyme is fixed and substrate concentration is slowly increased, the rate of reaction increases in proportion to the concentration of substrate

substances that directly or indirectly interfere with the functioning of the active site of an enzyme and so reduce its activity

increased substrate concentration