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Enzymes proportional to the enzyme concentration. By
increasing the enzyme concentration it will also
- Proteins ­ globular tertiary structure. Properties of Enzymes: increase the rate of reaction.
- Boiling enzymes will de-nature them. Enzymes are specific so each enzyme works on
- Speeds up biological reactions. a particular substrate. The turnover number is the number of substrate
- Affected by pH. *For Example- Amylose ­ Starch. Sucrose ­ molecules that enzymes turn into their products in
Sucrose. Catalase ­ Hydrogen peroxide.* one minute.
- They are specific.
High turnover number which means that they
can convert many molecules of substrate in a set Substrate Concentration:
For a reaction to occur, energy is required to time. The enzyme doesn't get used up in the If the amount of enzyme stays the same, the rate
break the bonds between the reactants. reaction. of reaction will increase as the substrate
The amount of energy required is called the Lower the activation energy for a reaction. concentration increases up to a point.
activation energy. When the enzymes are all working as quickly as
Factors Affecting Enzyme Activity: they can, adding more substrate would bring
What Do Enzyme Do:
- Temperature (affects the bonding). about no further increase in the rate of reaction.
- They break large molecules into The enzymes are working flat out.
simpler/smaller molecules.
- pH (affects the bonding).
- Protease breaks down proteins to their - Concentration of substrate. Inhibition:
amino-acids. - Concentration of enzyme. Enzyme inhibition occurs whent the activity of an
- Building up small molecules into more enzyme is slowed down or stopped by another
complex molecules. Temperature: substance.
Increasing the temperature of an enzyme- Competitive. This inhibitor has a similar
- The molecules that enzymes react with controlled reaction brings about an increase in
are called substrates. structure to the active site, and binds onto the
the rate of reaction, but only to a point. For enzyme, preventing the substrate to bind on.
- Substrate binds onto the active site of some enzymes, increasing temperature to 40°C Non-Competitive. This inhibitor binds onto the
the enzyme. brings about a corresponding increase in the rate enzyme, NOT IN THE ACTIVE SITE and
- The active site is specific to a particular of reaction. This is due to the increased kinetic changes its shape.
substrate. energy of the enzyme and substrate molecules.
Enzyme-Substrate Complex: Eventually, the atoms in the enzyme molecule
vibrate so violently that it causes the breaking of
the bonds that hold the enzyme in its tertiary
structure. It has changed and become
Most enzymes have an optimum pH that can
affect the rate of reaction without denaturing the
enzyme. However, at the extremes of pH range
on enzyme becomes unstable and then
If the enzyme and substrate have the same
charges they will repel each other.
Enzyme Concentration:
Provided that the conditions such as temperature
and pH are suitable and there is an excess of
substrate then the rate of reaction will be directly


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