Biological MoleculesEnzymes

Ahmed Swaleh Mohamed

Boukeem Baffoe

Mohamed Ayman Ali

Ahmed Ayman Ali

Daisy Sowah

Structure

Enzymes are globular proteins: they have a tertiary structure with many hydrogen bonds holding them, they are also soluble in water which helps them catalyse many biochemical reactions.

Classification of enzymesEnzymes are classified by the type of reaction they catalyse.The name of an enzyme identifies the reacting substance.(most enzymes end in "ase") For example sucrase catalyzes the hydrolysis of sucrose.The name also describes the function of the enzyme.For example oxidises catalyze oxidation reactions.

-ASE

Speeding up reactionsAs biological catalysts they are able to speed up biochemical reactions without being used up in the process which helps them to catalyze more reactions with a few added since they can be reused.They have a specific active site for a specific substrate to be formed or broken down.

Enzymes catalyse reactions by lowering activation energies, they do this by creating an alternative pathway for chemical reactions to occur.

How?

Enzyme Inhibitors

Inhibitors are substances which have a similar structure to the enzyme substrates hence fitting in its activesite and stopping its activity permanently or temporarily.There are two main types of inhibitors, they are: competitive inhibitors and in competitive inhibitors .

What are competitive inhibitors??

If an inhibitor molecule binds with the activesite of the enzyme then there is competition between the inhibitor and the substrate.If there is more of the substrate then there is more chance of collision with the active sit than the inhibitor.If other wise then the inhibitor binds with the active site and inhibits its functionThey are said to be reversible as they can be reversed by increasing substrate concentration.

What are non-competitive inhibitors?

These are inhibitors which bind permanently to the enzymes active sit and there fore no competition occurring between the substrate and the inhibitor.They are irreversible as they bind to another part of the enzyme thus altering the position of hydrogen bonds and changing the 3D shape of the enzyme. This changes the shape of the active site and makes it impossible for the substrate to fit in, therefore permanently inhibiting enzymes function.

Enzyme cofactors

They are non-protein substances that work by altering the shape of an enzyme so as to make it participate effectively during an enzymatic reaction.

Cofactors ensure that an enzyme controlled reaction takes place at an appropriate rate There are mainly two types of Cofactors: coenzyme and metal ions Coenzymes are organic molecules that bind to the active with the substrate to help reactions occur. They can be recycled and used again.Metal ions are known as the common Cofactors. They speed up the formation of the enzyme substrate complex by altering the charge in the active site or the end shape of the complex A coenzyme which is a permanent part of an enzyme is called a Prosthetic group. An important group of coenzymes are vitamins. Most Coenzymes are obtained from vitamins. For example, vitamin B12 acts as coenzyme. They are also obtained from nucleotides such as adenosine triphosphate In the absence of the right cofactor, the enzyme would not function

Reaction Rate

Blue line, with respect to product and red line with respect to reactants

Factors Affecting reaction rate

Temperature: enzymes work best at an optimum temperature.Below this, an increase in temperature provides more kinetic energy to the molecules involved. The numbers of collisions between enzyme and substrate will increase so the rate will too.Above the optimum temperature, and the enzymes are denatured. Bonds holding the structure together will be broken and the active site loses its shape and will no longer work.pH: as with temperature, enzymes have an optimum pH. If the pH changes much from the optimum, the chemical nature of the amino acids can change.This may result in a change in the bonds and so the tertiary structure may break down. The active site will be disrupted and the enzyme will be denatured.Enzyme concentration: at low enzyme concentration there is great competition for the active sites and the rate of reaction is low. As the enzyme concentration increases, there are more active sites and the reaction can proceed at a faster rate.Eventually, increasing the enzyme concentration beyond a certain point has no effect because the substrate concentration becomes the limiting factor.Substrate concentration: at a low substrate concentration there are many active sites that are not occupied. This means that the reaction rate is low.When more substrate molecules are added, more enzyme-substrate complexes can be formed. As there are more active sites, and the rate of reaction increases.Eventually, increasing the substrate concentration yet further will have no effect. The active sites will be saturated so no more enzyme-substrate complexes can be formed.

UsesENZYME USE

proteaseused to pre-digest proteins during the

manufacture of baby foods

lipase

used - together with protease - in biological

detergents to break down - digest - the substances

in stains into smaller, water soluble substances

carbohydrase

used to convert starch syrup, which is relatively cheap, into sugar syrup, which is more valuable -

for example, as an ingredient in sports drinks

isomerase

used to convert glucose syrup into fructose syrup - fructose is sweeter than

glucose, so it can be used in smaller amounts in

slimming foods

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