Factors Affecting Enzyme Activity – Class 12 | Chapter – 9 | Biology Short Notes Series PDF

Factors Affecting Enzyme Activity: Enzymes are proteins capable of speeding up a chemical reaction occurring inside our bodies. It usually requires an optimum temperature & pH for its action. Amylase, trypsin, and lipase are some examples of enzymes.

Factors Affecting Enzyme Activity


  • The kinetic energy of molecules also increases with increasing temperature. This means that there are more random collisions between molecules per unit of time in a fluid.
  • Because enzymes catalyze reactions by randomly colliding with Substrate molecules, increasing the temperature speeds up the reaction, resulting in more product formation.
  • As the temperature rises, more bonds, particularly the weaker Hydrogen and Ionic bonds, will break due to strain. When bonds within the enzyme are broken, the Active Site changes shape.
  • However, increasing the temperature increases the Vibrational Energy of molecules, specifically enzyme molecules, putting strain on the bonds that hold them together.
  • As temperature rises, the shapes of more enzyme molecules’ Active Sites become less complementary to the shape of their Substrate, and more enzymes are denatured. This reduces the rate of reaction.
  • Because the Active Site is no longer complementary to the shape of the Substrate, it is less likely to catalyze the reaction. The enzyme will eventually become denatured and cease to function.
  • In summary, as temperature rises, the rate of reaction rises initially due to increased Kinetic Energy. However, the effect of bond breaking will increase over time, and the rate of reaction will begin to slow.


  • The rate of an enzyme-catalyzed reaction is affected by changing the concentrations of the enzyme and the substrate. Controlling these factors in a cell is one way for an organism to regulate enzyme activity and thus metabolism.
  • Changing the concentration of a substance affects the rate of reaction only if it is the limiting factor: that is, it is the factor that prevents a reaction from proceeding at a faster rate.
  • If it is the limiting factor, increasing concentration will increase the rate of reaction up to a point where it will no longer affect the rate of reaction. This is because it will no longer be the limiting factor and will be replaced by another factor limiting the maximum rate of reaction.
  • As a reaction progresses, the rate of reaction decreases as the Substrate is depleted. In an experimental situation, the highest rate of reaction, known as the Initial Reaction Rate, is the maximum reaction rate for an enzyme.

Enzyme Concentration

  • Transient bonds formed between enzymes and their substrates catalyze reactions by lowering the activation energy and stabilizing the transition state.
  • Given an abundance of substrates and necessary cofactors, enzymatic reactions with higher enzyme concentrations will reach equilibrium before those with lower enzyme concentrations.
  • Simply put, a higher enzyme concentration means that there are more enzyme molecules available to process the substrate. Because of the high levels of the enzyme-substrate complex, the reaction has a faster initial catalytic rate, which gives it a head start in the shift toward reactant-product equilibrium.

Substrate Concentration

  • When a geometrically and electronically complementary substrate can access the enzyme’s catalytic or active site, catalytic activity occurs. The active residues transiently bond with the substrate, catalyzing the substrate’s transformation into a product.
  • As a result, the greater the number of substrate-occupied active sites, the greater the catalytic activity and the faster the shift toward enzyme-product equilibrium.
  • The Michaelis-Menten kinetics, which describes the relationship between enzyme activity and substrate concentration in two stages, is followed by the majority of enzymes. The relationship between the two is initially linear and plateaus as the number of unbound active sites decreases.

pH Value

  • Proteins, like enzymes, contain electrical charges due to the sequence of their amino acid residues because they are made up of a chain of amino acids.
  • The majority of the amino acids in the chain serve as the foundation for intramolecular interactions that give the enzyme its three-dimensional structure. Few others serve as functional residues at the active site of the enzyme.
  • Overall, the amino acids determine substrate specificity and limit enzyme activity to a narrow pH range. Most enzymes work best in slightly acidic or basic environments.
  • However, because some enzymes are native to extremely acidic or basic environments, they are most active in these pH ranges.

Inhibitor or Effector

  • Many enzymes rely on non-substrate and non-enzyme molecules to regulate or initiate catalysis. Certain enzymes, for example, rely on metal ions or cofactors to establish catalytic activity.
  • Many enzymes, such as allosteric enzymes, rely on effectors to activate their catalytic activities and promote or inhibit their subsequent binding to substrates.
  • Similarly, inhibitors may bind to the enzyme or its substrate in order to inhibit ongoing enzymatic activity and prevent subsequent catalytic events.
  • When inhibitors form strong bonds to the enzyme’s functional group, the effect on enzyme activity is irreversible, rendering the enzyme permanently inactive.
  • Reversible inhibitors, as opposed to irreversible inhibitors, only render enzymes inactive when bound to the enzyme.
  • Competitive inhibitors compete with substrates for binding to the enzyme functional group residues at the catalytic sites. Other types of inhibitors bind to the non-substrate binding allosteric site rather than the catalytic site.
  • It is non-competitive if an inhibitor binds to the enzyme concurrently with the enzyme-substrate binding. An inhibitor is uncompetitive if it only binds to a substrate-occupied enzyme.

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By Team Learning Mantras