12.4.1.2 compare competitive and non-competitive inhibition of enzymes

Grade 12 Enzymes

Enzyme Lab Answers

Click Here

What you should already know about Enzymes:

Lock and Key Model

Induced Fit Model

Factors affecting Enzyme Activity

Low temperatures result in insufficient thermal energy for the activation of an enzyme-catalysed reaction to proceed

Increasing the temperature will increase the speed and motion of both enzyme and substrate, resulting in higher enzyme activity

This is because a higher kinetic energy will result in more frequent collisions between the enzymes and substrates

At an optimal temperature (may vary for different enzymes), the rate of enzyme activity will be at its peak

Higher temperatures will cause enzyme stability to decrease, as the thermal energy disrupts the enzyme’s hydrogen bonds

This causes the enzyme (particularly the active site) to lose its shape, resulting in the loss of activity (denaturation)

Changing the pH will alter the charge of the enzyme, which in turn will alter protein solubility and overall shape

Changing the shape or charge of the active site will diminish its ability to bind the substrate, abrogating enzyme function

Enzymes have an optimal pH (may differ between enzymes) and moving outside this range diminishes enzyme activity

Increasing substrate concentration will increase the activity of a corresponding enzyme

More substrates mean there is an increased chance of enzyme and substrate colliding and reacting within a given period

After a certain point, the rate of activity will cease to rise regardless of any further increases in substrate levels

This is because the environment is saturated with substrate and all enzymes are bound and reacting (V_max)

Use of Enzymes in Industry

It is very costly to use enzymes only once, but most enzymes are only commercially available in liquid or dehydrated forms and once they have been used in solution it is very difficult and time consuming to separate them from the product.

• To allow their re-use, enzymes may be immobilised (attached to an inert, insoluble material such as calcium alginate to form a gel capsule around them). This way, the enzymes will be hold in place throughout the reaction, easily separated from the products and may be used again

Immobilised enzymes are utilised in a wide variety of industrial practices:

Biofuels – Enzymes are used to breakdown carbohydrates to produce ethanol-based fuels
Medicine – Enzymes are used to identify a range of conditions, including certain diseases and pregnancy
Biotechnology – Enzymes are involved in a number of processes, including gene splicing
Food production – Enzymes are used in the production and refinement of beers and dairy products
Textiles – Enzymes are utilised in the processing of fibres (e.g. polishing cloth)
Paper – Enzymes assist in the pulping of wood for paper production

Enzyme Inhibition

An enzyme inhibitor is a molecule that disrupts the normal reaction pathway between an enzyme and a substrate

Enzyme inhibitors can be either competitive or non-competitive depending on their mechanism of action

In a normal reaction, a substrate binds to an enzyme (via the active site) to form an enzyme-substrate complex. The shape and properties of the substrate and active site are complementary, resulting in enzyme-substrate specificity. When binding occurs, the active site undergoes a conformational change to optimally interact with the substrate (induced fit) This conformational change destabilises chemical bonds within the substrate, lowering the activation energy. As a consequence of enzyme interaction, the substrate is converted into product at an accelerated rate

Competitive

Have similar shape to the enzyme's normal substrate.
Can fit into the enzyme's active site, preventing the substrate from binding.
Relative concentrations of the inhibitor and the substrate will affect the degree to which a competitive inhibitor slows down a reaction.

If an inhibitor molecule binds only briefly to the site, there is competition between it and the substrate for the site. If there is much more of the substrate present than the inhibitor, substrate molecules can easily bind to the active site in the usual way, and so the enzyme’s function is unaffected. However, if the concentration of the inhibitor rises, or that of the substrate falls, it becomes less and less likely that the substrate will collide with an empty site. The enzyme’s function is then inhibited. This is therefore known as competitive inhibition

Non-Competitive

Have different shape than the substrate.
Do not bind to the active site.
Bind to a different part of the enzyme --> changes the enzyme's shape (including the active site) --> substrate can not bind with enzyme.
Relative concentrations of the inhibitor and the substrate does not affect the degree to which a non-competitive inhibitor slows down a reaction (if you add more substrate, it still won't be able to bind).

A different kind of reversible inhibition takes place if a molecule can bind to another part of the enzyme rather than the active site. While the inhibitor is bound to the enzyme it can seriously disrupt the normal arrangement of hydrogen bonds and hydrophobic interactions holding the enzyme molecule in its three-dimensional shape. The resulting distortion ripples across the molecule to the active site, making the enzyme unsuitable for the substrate. While the inhibitor is attached to the enzyme, the enzyme’s function is blocked no matter how much substrate is present, so this is an example of noncompetitive inhibition

MEMORIZE ME

Link for animation overview of types of Inhibition of Enzymes

Google Sites

Report abuse