3.2 Environmental Impacts on Enzyme Function

Conditions affecting enzyme activity

Changes in shape(denaturation)

Changes in substrate concentration

Inhibitors

Changes in shape

proteins have a 3D shape held together by different interactions/bonds

if there is a change to the shape of the protein, it will change the function or efficiency of the enzyme

aka denaturation

Denaturation

a loss of both structure and function of an enzyme due to conditions that cause it to unfold from its normal conformation

sometimes can be reversed, but only if the primary structure remains intact and the environment returns to optimal condition before further damage happens

caused by temperature,pH, and chemical environment

temperature-while the rate of the enzyme activity initially increased with temperature increase(due to collision), outside of the optimal range heat can break hydrogen and ionic bonds that hold the protein in the 3D shape

pH- outside of the optimal range, pH can disrupt hydrogen bonds in the enzyme and can alter charges or amino acids, changing the shape of the active site, making it harder or impossible for a substrate to bind

chemical environment-substances around the protein, like salts, detergents, solvents, or alcohol can unfold proteins

Change in substrate concentration

substrate concentration can change the rate of reactions 

at low concentrations, substrate collide infrequently with enzymes which equals a slow reaction rate

as substrate concentration increases, the reaction rate increases (increases collision with enzymes) until the enzymes become saturated(the maximum rate at which it can combine with substrates and produce products)

Regulation of enzyme activity

cells can adjust the activity of enzymes through

competitive and noncompetitive inhibition

allosteric regulation (a form of noncompetitive control)

Competitive inhibitors

reduce enzyme activity by blocking substrates from binding to the active site

reversible

inhibition can be reversed with increased substrate concentrations

Noncompetitive inhibitors

bind to an area other than the active site (the allosteric sites), which changes the shape of the active site, preventing substrates from binding and changing the activity of the enzyme

inhibition can be permanent of reversible

permanent: inhibitor binds with covalent bonds,cell must synthesize new enzymes to overcome effects ex. toxins and poisons

reversible: inhibitor binds with weak interactions, enzyme resumes function when inhibitor releases

Allosteric regulation

regulatory molecules bind to an allosteric site which either increases enzyme activity(activator) or decreases enzyme acitivity(inhibitor)

a form of noncompetitive control

most noncompetitive inhibitors function through allosteric regulation, but allosteric regulation is a broader category that also includes unique enzymes that have multiple active sites that are regulated allosterically. Allosteric regulation also includes activators

Feedback inhibition

when the end product of a metabolic pathway is an allosteric inhibitor to an earlier enzyme in the same pathway