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Factors Affecting Enzyme Activity

Factors affecting enzyme activity include temperature, pH, substrate concentration, and the presence of inhibitors or activators. These ultimately affect the rate of chemical reactions in biological systems. Keep reading for more detailed A-level Biology revision!

Factors affecting enzyme activity include temperature, pH, substrate concentration, and the presence of inhibitors or activators.

Read more about Enzyme Inhibitors

  • Biochemical reactions are necessary for growth, repairing damaged tissues, and obtaining energy and they take place in all living organisms’ bodies. These reactions are called ‘metabolism’ and they happen all the time in living organisms. If they stop working, this leads to the death of the organism.
  • All the reactions that occur in living organisms require high activation energy to take place. To reduce the cell’s consumption of energy, there is a catalyst to ensure that the chemical reactions occur rapidly and reduce the activation of energy. This catalyst is the enzymes.
Enzyme activation energy
Enzyme activation energy
  • Enzymes are biological catalysts made up of large protein molecules. They speed up the chemical reactions inside the cell. The enzyme is made up of a combination of amino acids which for a chain of polypeptides between each other.
  • Enzymes are similar to other chemical catalysts. They participate in the reaction without getting affected. In other words, they speed up the chemical reactions inside the cells without getting consumed. Enzymes are affected by the hydrogen ion concentration (pH) and the temperature. Enzymes are highly specific compared to other catalysts, and each enzyme is specialized for one reactant substance. This reactant substance is called substrate, and it is specialized for one type of reaction or a few reactions. Enzymes lower the activation energy required to get the reaction started. Collectively, these are the most important properties of the enzyme.
  • There are several factors that affect the speed of an enzyme’s action, such as the concentration of the enzyme, the concentration of the substrate, temperature, hydrogen ion concentration (pH), and the presence of inhibitors.

Factor 1: Concentration of Enzyme

Enzyme Concentration
Enzyme Concentration
  • As the concentration of the enzyme is increased, the velocity of the reaction proportionately increases. This property is used for determining the activities of serum enzymes during the diagnosis of diseases.

Factor 2: Concentration of Substrate

Substrate Enzyme Concentration
Substrate Enzyme Concentration
  • In the presence of a given amount of enzyme, the rate of enzymatic reaction increases as the substrate concentration increases until a limiting rate is reached, after which further increase in the substrate concentration produces no significant change in the reaction rate. At this point, so much substrate is present that essentially all of the enzyme active sites have substrate bound to them.
  • In other words, the enzyme molecules are saturated with substrate. The excess substrate molecules cannot react until the substrate already bound to the enzymes has reacted and been released (or been released without reacting).

Factor 3: Effect of Temperature

  • The protein nature of the enzymes makes them extremely sensitive to thermal changes. Enzyme activity occurs within a narrow range of temperatures compared to ordinary chemical reactions. As you have seen, each enzyme has a certain temperature at which it is more active. This point is called the optimal temperature, which ranges between 37 to 40C°.
  • The enzyme activity gradually lowers as the temperature rises more than the optimal temperature until it reaches a certain temperature at which the enzyme activity stops completely due to the change of its natural composition.
  • On the other hand, if the temperature lowers below the optimal temperature, the enzyme activity lowers until the enzyme reaches a minimum temperature at which the enzyme activity is the least. The enzyme activity stops completely at 0C°, but if the temperature rises again, then the enzyme gets reactivated once more.
Enzyme activity and temperature
Enzyme activity and temperature

Factor 4: Effect of pH

  • The potential of hydrogen (pH) is the best measurement for determining the concentration of hydrogen ion (H+)in a solution. It also determines whether the liquid is acidic, basic or neutral. Generally, all liquids with a pH below 7 are called acids, whereas liquids with a pH above 7 are called bases or alkalines. Liquids with pH 7 are neutral and equal the acidity of pure water at 25 C°. You can determine pH of any solution using the pH indicators.
pH Indicators
pH Indicators
  • Enzymes are protein substances that contain acidic carboxylic groups (COOH) and basic amino groups (NH2). So, the enzymes are affected by changing the pH value.
  • Each enzyme has a pH value that it works at with maximum efficiency called the optimal pH. If the pH is lower or higher than the optimal pH, the enzyme activity decreases until it stops working. For example, pepsin works at a low pH, i.e, it is highly acidic, while trypsin works at a high pH, i.e, it is basic. Most enzymes work at neutral pH 7.4.
Enzyme PH activity
Enzyme PH activity

Factor 5: Effect of Activators

  • Some of the enzymes require certain inorganic metallic cations, like Mg2+, Mn2+, Zn2+, Ca2+, Co2+, Cu2+, Na+, K+ etc., for their optimum activity. Rarely, anions are also needed for enzyme activity, e.g. a chloride ion (CI) for amylase.

Frequently Asked Questions on Factors Affecting Enzyme Activity

Which factors affect the activity of enzymes?

The factors affecting the activity of enzymes are given below:

 Enzyme concentration

 Substrate concentration



How does enzyme concentration affect the activity of enzymes?

The rate of reaction is directly proportional to the concentration of enzyme in that reaction. By increasing the enzymes concatenated, the rate of reaction can be increased.

How does pH affect the activity of enzymes?

Every enzyme works efficiently on optimum pH. A change in the optimum pH results in the denaturation of the enzyme.

What happens to enzymes on very high temperatures?

The rate of reaction is increased with the increase of temperature but up to a certain limit. If the temperature is increased further, the enzyme is denatured.

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