Characteristics of Enzymes

Enzymes are macromolecules that act as biological catalysts, produced in living cells
Most enzymes are globular proteins
Enzymes lower the activation energy of a reaction, increasing the rate of reaction
Enzymes are heat liable/sensitive
Enzymes do not alter the nature or properties of the end products of a reaction
Enzymes are highly specific to the substrate (substrate specific)
Most enzyme-catalyzed reactions are reversible
The rate of enzyme activity is affected by pH, temperature, and substrate concentrations
Enzymes are not used up during a reaction
Enzymes possess active sites where the reaction takes place
Some enzymes need non-proteinous components (cofactors) to catalyze a reaction

The reactant that binds to an enzyme is called the substrate
The enzyme binds to its substrate, forming an enzyme-substrate complex
The catalytic action of the enzyme converts the substrate to the product
The specificity of an enzyme results from its shape, which allows it to bind to a specific substrate
The active site of an enzyme is formed by only a few amino acids
The shape of the active site is complementary to the shape of the specific substrate
Induced fit mechanism: the interactions between the substrate and active site may slightly change the shape of the active site, so that the substrate and active site become complementary to each other

Cofactors are non-proteinous components essential for the catalytic activities of certain enzymes
Cofactors bind to enzymes in two ways: tightly bound and loosely bound
Examples of cofactors include derivatives of vitamins (co-enzymes) and inorganic ions (e.g. Zn2+, Fe2+, Cu2+)

Temperature: increases molecular motion, enhancing the speed of enzyme and substrate molecules, but can lead to denaturation of enzyme molecules beyond the optimum temperature
pH: enzymes function most efficiently within a certain pH range, with alteration of pH leading to decline in enzyme activity
Substrate concentration: increasing substrate concentration increases the probability of collision between the enzyme and substrate molecules, but enzyme molecules can become saturated
Enzyme concentration: increasing enzyme concentration can increase the rate of reaction
Inhibitors: substances that selectively bind to the enzyme, preventing the formation of an enzyme-substrate complex

Competitive inhibitors: resemble the shape and nature of the substrate, competing with the substrate for the active site of the enzyme
Non-competitive inhibitors: bind to a part of the enzyme other than the active site, causing a change in shape and making the active site less effective

Allosteric regulation of enzymes: regulatory molecules bind to specific regulatory sites, affecting the shape and function of the enzyme
Allosteric activation and inhibition: regulatory molecules bind to allosteric sites, stabilizing the active or inactive form of the enzyme
Cooperativity: binding of one substrate molecule can stimulate binding or activity at other active sites, increasing catalytic activity
Feedback inhibition: the end product of a metabolic pathway binds to an enzyme, inhibiting the production of more end products and regulating the metabolic process

Enzymes are macromolecules that act as biological catalysts, produced in living cells
Most enzymes are globular proteins
Enzymes lower the activation energy of a reaction, increasing the rate of reaction
Enzymes are heat liable/sensitive
Enzymes do not alter the nature or properties of the end products of a reaction
Enzymes are highly specific to the substrate (substrate specific)
Most enzyme-catalyzed reactions are reversible
The rate of enzyme activity is affected by pH, temperature, and substrate concentrations
Enzymes are not used up during a reaction
Enzymes possess active sites where the reaction takes place
Some enzymes need non-proteinous components (cofactors) to catalyze a reaction

The reactant that binds to an enzyme is called the substrate
The enzyme binds to its substrate, forming an enzyme-substrate complex
The catalytic action of the enzyme converts the substrate to the product
The specificity of an enzyme results from its shape, which allows it to bind to a specific substrate
The active site of an enzyme is formed by only a few amino acids
The shape of the active site is complementary to the shape of the specific substrate
Induced fit mechanism: the interactions between the substrate and active site may slightly change the shape of the active site, so that the substrate and active site become complementary to each other

Cofactors are non-proteinous components essential for the catalytic activities of certain enzymes
Cofactors bind to enzymes in two ways: tightly bound and loosely bound
Examples of cofactors include derivatives of vitamins (co-enzymes) and inorganic ions (e.g. Zn2+, Fe2+, Cu2+)

Temperature: increases molecular motion, enhancing the speed of enzyme and substrate molecules, but can lead to denaturation of enzyme molecules beyond the optimum temperature
pH: enzymes function most efficiently within a certain pH range, with alteration of pH leading to decline in enzyme activity
Substrate concentration: increasing substrate concentration increases the probability of collision between the enzyme and substrate molecules, but enzyme molecules can become saturated
Enzyme concentration: increasing enzyme concentration can increase the rate of reaction
Inhibitors: substances that selectively bind to the enzyme, preventing the formation of an enzyme-substrate complex

Competitive inhibitors: resemble the shape and nature of the substrate, competing with the substrate for the active site of the enzyme
Non-competitive inhibitors: bind to a part of the enzyme other than the active site, causing a change in shape and making the active site less effective

Allosteric regulation of enzymes: regulatory molecules bind to specific regulatory sites, affecting the shape and function of the enzyme
Allosteric activation and inhibition: regulatory molecules bind to allosteric sites, stabilizing the active or inactive form of the enzyme
Cooperativity: binding of one substrate molecule can stimulate binding or activity at other active sites, increasing catalytic activity
Feedback inhibition: the end product of a metabolic pathway binds to an enzyme, inhibiting the production of more end products and regulating the metabolic process