Biology: Enzymes

Almost all chemical reactions that take place inside living things are controlled by

enzymes.

what are enzymes

Enzymes are large molecules/chemicals found in living things that act as biological catalysts. 

what are catalysts

Catalysts are chemicals that speed up reactions without getting used up. 

Almost all enzymes are

proteins

function of enzymes

 Enzymes speed up reactions without getting used up. 

Almost all processes in a biological cell need enzymes in order to

occur at significant rates.

Substrates (reactant) 

 in enzymatic reactions, the molecules at the beginning of the process. 

what do enzymes do to the substrate

 Enzyme converts them into different molecules, the products.

what would happen without enzymes

Without enzymes, the reaction would require more energy and more time to produce a product.

Types of Enzyme Reactions

 

synthesis and degraduation

what is synthesis

enzymes putting substrate together

what is degradation

enzymes separating susbtrate

What are Enzymes made of?

Enzymes are protein molecules and so are made up of amino acids. 

 

how many amnio aicds in enzymes

Most enzymes contain between 100 and 1,000 amino acids.

how do the amnio acids put together

These amino acids are joined together in a long chain, which is folded to produce a unique 3D structure.

Why is enzyme shape important ?

The shape of enzymes is the key to their reactions.

the enzyme shape has a

direct effect on how it catalyzes a reaction.

Enzymes have different shapes which is determined by

the sequence of amino acids in its structure, and the bonds which form between the atoms of those molecules.

Different types of enzymes have different

shapes and functions

different types of enzymes have different shapes and functions because 

the order and type of amino acids in their structure is different.

 

enzymes are specific about

which reactions they catalyze

Only molecules with  

exactly the right shape will bind to the enzyme and react.

enzymes react with

reactant, or substrate, molecules.

what is the active site

 The part of the enzyme to which the reactant binds 

The Active site

is a very specific shape and the most important part of the enzyme.

what happens at the active site

in the same way that a key fits into a lock, so a substrate is thought to fit into an enzyme’s active site.

lock

the enzyme

key

the reactant

what is denaturation

=When properties of enzymes are changed due to breaking up of certain bonds, the conformation (shape) of the protein will be changed. 

 Enzymes are proteins made from Amino Acids that are connected together by a 

bond

bonds can

broken

when the bonds of the enzyme are broken

the polypeptide chain changes

when the polypeptide chain changes

changes the shape of the molecule

 

The rate of enzyme–catalyzed reactions depends on

several factors

Factors that affect the rate of a reaction include:

1.    Temperature

2.    pH

3.    Substrate Concentration

 

what is pH

The pH scale measures how acidic or basic something is on a scale of 0 to 14. Things with a lower pH, like grapefruit juice and vinegar, are acidic, while things with a higher pH, like bleach and drain cleaner, are basic (alkaline). In the middle, water has a neutral pH of 7.

optimum

 All enzymes work best at only one particular temperature and pH

 

Different enzymes have different

optimum temperatures and pH values.

The shape of the enzyme irreversibly changes when

the temperature and pH changes sufficiently beyond an enzyme’s optimum, 

When the pH and temperature goes beyond the optimum it affects

the shape of the active site and means that the enzyme will no longer work.

when the enzyme shape is changed and can’t work

 the enzyme is denatured.

Most biological enzyme reactions occur best at temperature of about

30-40^oC.

the reason for the 30-40 degree temperature is becasue

the temperature that they will have been “designed” to work at in most living things.

Some of the bonds that hold enzymes in shape are broken above about

45^oC destroying the “lock and key” fit.,

the lock and key fit destroyed means

the enzyme is denatured

As temperature increases,

the enzyme activity increases.

Optimum Temperature

The temperature that the enzymes works best 

What happens to the active site if the temperature is too high =

the enzymes active site changes shape.

When the enzyme’s active site has changed shape the enzyme

is said to be denatured, and it will no longer work.

Enzymes also work best at

specific particular pH value.

Some enzymes work well in

acid

some enzymes that work well in acid are

stomach enzymes

some enzymes dont need acidicty they need

 a neutral or basic pH.

if  the pH is wrong for the enzyme then the bonds

are broken changing the shape of the enzyme and destroying the lock and key fit and the enzyme is denatured

Enzymes work best within a

range of pH depending on the type of enzyme.

Optimum pH =

The pH that the enzymes works best

If the pH is too high =

the enzymes active site changes shape (denatured).

 

The concentration of a substrate describes

how much substrate molecules are in a cell.

as substrate concentration increases from 0,

more substrate molecules will react with the enzyme

when more substrate molecules will react with the enzyme

the rate of reaction increases.

Higher concentration causes

more collision between molecules.

 

Increasing substrate concentration

increases the frequency with which the enzyme and substrate collide. 

 

Enzyme substrate complex

when enzymes and substrate bind together

More enzyme-substrate complexes form, and the rate of reaction increases.

but with more substrate complexes forming there is a

limit

Saturated =

Eventually all the enzyme active sites will be occupied with substrate. 

Any further increase in substrate concentration has

no further effect on the reaction rate.

Graph: pH

the line only raises at one pH level - optimum

Graph: temperature

the line increases until it decreases after optimum

graph: substrate cocentration

the line increases until it levels off