Enzymes- specificity, activity,


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Define an enzyme and active site

  • Enzymes are globular proteins and act as natural catalysts of chemical reactions. The region where the substrates bind to is the active site, and it’s where the reaction is catalyzed.
  • Each active site is specific to the substrate
  • Affected by many things such as temp or pH

Explain substrate specificity

Each active site is specific to its substrate and has a precise shape. This means that only a specific substrate will fit into its active site like a lock and key. The active sites chemically attract the substrate.

Explain the effects of temperature, pH and substrate concentration on activity

Temperature: The reaction only occurs if a successful collision with the active site by the substrate occurs. If temperature is low, the kinetic energy of the substrate is less and there will be a decreased chance of collision. If the temperature is continually increased, it will reach an optimum point before the enzyme denatures.

Because the active site is specific to the substrate, as the vibration from the temperature increases, hydrogen bonds may break.

pH: pH stands for ‘potential hydrogen’. The hydrogen can affect the shape of the bonds as they compete for the interaction with the bonds that holds the enzyme together. If the hydrogen levels deviate too much from what the enzymes were designed for, the enzyme can permanently denature.

Substrate concentration: As reaction depends of the ‘amount’ of successful collisions, the higher the substrate concentration, and the greater the probability of collisions. However as the enzymes available to catalyzes the reactions are finite, increasing substrate concentration will increase reaction rate up to a point before it plateaus due to another limiting factor or simply due to insufficient enzymes.


Optimum Temperature


An enzyme denatures when its structural shape is compromised. This results in the loss of its properties as it requires a specific shape in order to catalyze reactions, and has it has to be replenished by the body.

Causes of denaturation are pH and temperature and are further explained in 3.6.3

Explain the use of lactase in the production of lactose free milk

Some people are born (or acquire) genetic defects that makes them unable to produce certain enzymes. A common example is the enzyme lactase and this is the condition of lactose intolerant people. As the body is unable to break down lactose conventionally, it results in abdominal bloating, cramps and other unpleasant symptoms.

Lactose      –>           Glucose + Galactose


Because of this the milk consumed by them has to be lactose free. To do this, the milk is catalyzed by artificially produced lactase, which produces glucose and galactose. This has the added benefit of not having to add sweeteners.

There are various ways to introduce lactose to the milk. One crude method would be to stir lactose into the milk, though this is inefficient as it requires the continuous production of lactose. A common method is to immobilize the Lactase in agar beads, and the milk is filtered through the beads. No enzyme is lost and the lactose should in theory be fully removed.

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2578 Administrator 03 Jun 2013 18:46:59
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