Glossary
Active site
The specific region on an enzyme where the substrate binds and where catalysis occurs.
Example:
In the lock-and-key model, only the correct key (substrate) can fit into the active site (lock) of the enzyme.
Competitive Inhibitors
Molecules that resemble the enzyme's natural substrate and bind directly to the active site, preventing the actual substrate from binding.
Example:
A drug designed to block a bacterial enzyme might act as a competitive inhibitor, fitting into the enzyme's active site instead of the bacterial substrate.
Denatures
The process by which a protein, such as an enzyme, loses its characteristic three-dimensional structure due to extreme conditions like high temperature or non-optimal pH, leading to a loss of function.
Example:
Boiling an egg causes the proteins in the egg white to denature, turning from clear liquid to solid white.
Enzyme Concentration
The amount of enzyme present in a given volume, which directly influences the rate of an enzymatic reaction.
Example:
Increasing the enzyme concentration in a laundry detergent can lead to faster breakdown of stains.
Enzymes
Biological catalysts, typically proteins, that accelerate the rate of biochemical reactions by lowering the activation energy without being consumed in the process.
Example:
Lactase is an enzyme that helps break down lactose in dairy products, allowing individuals with lactose intolerance to digest milk sugars.
Induced fit
A model describing how an enzyme's active site changes shape slightly upon substrate binding to achieve a tighter fit, optimizing catalysis.
Example:
When glucose binds to hexokinase, the enzyme undergoes a conformational change, demonstrating the induced fit model.
Inhibitors
Molecules that bind to an enzyme and decrease its activity, often by altering its shape or blocking its active site.
Example:
Many medications act as inhibitors to specific enzymes in the body, helping to regulate biological processes or fight diseases.
Limiting Reagent
The reactant that is completely consumed first in a chemical reaction, thereby determining the maximum amount of product that can be formed.
Example:
If you're baking cookies and run out of flour before other ingredients, the flour is the limiting reagent for the number of cookies you can make.
Noncompetitive Inhibitors
Molecules that bind to an enzyme at an allosteric site (a site other than the active site), causing a conformational change that alters the active site's shape and reduces its ability to bind substrate.
Example:
Some heavy metals can act as noncompetitive inhibitors, binding to enzymes at remote sites and disrupting their function throughout the body.
Optimal Temperature
The specific temperature at which an enzyme exhibits its maximum activity or rate of reaction.
Example:
Human amylase works best at 37°C, which is its optimal temperature for breaking down starches in the mouth.
Optimal pH
The specific pH value at which an enzyme functions most efficiently and exhibits its highest catalytic activity.
Example:
Pepsin, an enzyme in the stomach, has an optimal pH of about 2, allowing it to function effectively in the highly acidic stomach environment.
Renaturation
The process by which a denatured protein, under certain conditions, can refold into its original, functional three-dimensional structure.
Example:
After being gently heated and then cooled, some proteins can undergo renaturation, regaining their original shape and activity.
Structure dictates function
A fundamental principle in biology stating that the specific three-dimensional shape of a molecule, like an enzyme, determines its biological role and activity.
Example:
If a protein's unique folding is disrupted, its structure dictates function principle explains why it will lose its ability to perform its intended job.
Substrate Concentration
The amount of reactant molecules available for an enzyme to act upon, which affects the reaction rate up to a saturation point.
Example:
If you have a limited amount of enzyme, increasing the substrate concentration will initially speed up the reaction until all enzyme active sites are constantly occupied.
pH
A measure of the acidity or alkalinity of a solution, indicating the concentration of hydrogen ions (H+).
Example:
Lemon juice has a low pH (around 2), making it highly acidic, while baking soda solution has a high pH (around 9), making it basic.