Table of Contents
- What Is The Substrate Of An Enzyme?
- Enzyme-substrate Complex
- Factors Affecting The Formation Of The Enzyme-Substrate Complex
- Lesson Summary
Enzymes are proteins that catalyze (initiate and accelerate) biochemical reactions. A catalyst is a substance that lowers the activation energy of chemical reactions. Activation energy is the energy required for a reaction to take place. Enzymes lower the activation energy by:
Enzymes are important in a biological system because they enable important reactions to occur at a rate that supports the life of the organism. Without them, life-sustaining reactions would cease to exist at a useful rate, and the organism would die.
Enzymes accelerate cellular activities such as:
An enzyme's active site is the portion of the enzyme where a reaction occurs. What is the substrate of an enzyme? An enzyme substrate, the substance upon which an enzyme acts, lands in the active site and is converted into an enzyme-substrate product, the substance produced as a result of the reaction. Enzymes hold substrates in positions that make molecular bond-breaking and bond-forming easier to accomplish.
Examples of enzymes in the human body include:
What is an enzyme-substrate complex? The enzyme-substrate complex definition is a temporary molecule formed when the substrate binds to the enzyme. When an enzyme binds to its substrate, it undergoes a conformational change or temporary change in shape. However, once the product(s) is released, the enzyme will regain its original shape.
There are two models of the enzyme-substrate complex that scientists have proposed over the years:
The lock and key model was the first, and now the outdated, model used to describe the physical and molecular interaction between enzyme and substrate. It was proposed that the shape of the enzyme never changes and that the substrate has a complementary shape that fits the enzyme perfectly, much like a lock and key.
Scientists eventually discovered that the enzyme changes its shape slightly (through a conformational change) to maintain a tight fit on the substrate. This is called induced fit. Even with the conformational change, enzymes will only catalyze a specific reaction when the proper substrate is bound.
Just as enzymes are particular about the substrate they bind, they are also particular regarding the environmental factors in which they function. The factors that affect optimal enzyme functionality include:
Enzymes prefer to work in their respective ideal pH ranges. The preferred range often depends on where the enzymes are located within the human body. For example, enzymes in the intestine work at an optimal pH of 7.5 while enzymes in the stomach work at an optimal pH of 2. The stomach maintains an acidic environment to destroy pathogens (infectious agents) and aid digestion. Enzymes that exist outside of their ideal pH range run the risk of denaturing, losing their shape and function.
Temperature also plays a large role in enzyme functionality. Most enzymes work at the optimal body temperature of 98.6 degrees Fahrenheit or 37 degrees Celcius. Extremely high temperatures can also denature enzymes and affect the chemical bonds in the active site. While low temperatures may not have as much of a detrimental effect, the enzyme may work less efficiently.
Optimal conditions also include enzyme and substrate concentration. A reaction will not move forward if there are not any enzymes to catalyze the reaction. In the same way, a reaction cannot move forward if there are not any substrates to catalyze. Both enzyme and substrate concentrations must match not only each other but also the body's need for the expected product.
An enzyme is a protein that catalyzes a biochemical reaction. A catalyst is a substance that initiates or accelerates a reaction. Enzymes catalyze biochemical reactions by lowering the activation energy required to start a chemical reaction. Enzymes are essential for biochemical reactions because, without them, chemical reactions would not be carried out quickly enough to sustain life. Enzymes bind the substrates at their active site. A substrate is a substance or molecule upon which an enzyme acts. The active site is the portion of the enzyme where the reaction occurs. When the enzyme binds the substrate, it becomes the enzyme-substrate complex.
The induced fit model is considered the most accurate representation of how a substrate binds to the active site of an enzyme: the substrate enters the active site of the enzyme. The enzyme slightly changes shape as it bonds with the substrate to create the enzyme-substrate complex. After the reaction is complete, the enzyme releases a product (the substance or molecule created from the reaction). Enzymes are highly specific and work optimally under certain conditions. Enzymes only work on one specific substrate. Even if a similar molecule binds in place of the substrate, the reaction will not occur. A change in temperature or pH can change the shape of an enzyme and impede its ability to bond with a substrate.
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Lactase is an example of an enzyme. It binds the substrate lactose, a milk sugar, to create the two monosaccharides glucose and galactose.
The substrate of an enzymatic reaction is the substance or molecule upon which an enzyme acts. It is the object that is transformed into a product, and a product is a substance produced as a result of the reaction.
A substrate is a substance or molecule that binds to an enzyme. When the two are combined, they create an enzyme-substrate complex.
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