Substrate in Chemistry


Chemistry terms can be confusing, in part because some terms have multiple related (but different) meanings depending on the branch of chemistry you’re dealing with. Take for example the word ​substrate​ in chemistry: It can refer to either a chemical substrate or an enzyme substrate depending on the context that it’s used in. Because the usages are related, however, learning how the term is used in different types of chemical reactions may give you a better understanding of the concept of substrates as a whole.

Chemical Substrate Definition.

In chemistry, you can define substrate broadly as the medium in which your chemical reaction takes place. It’s a bit more than this, however; the substrate is also typically the reactant of your chemical reaction, meaning that it is the chemical component that is actually acted upon and changed into something else by the reaction. At the end of the reaction, the original substrate reactant will no longer have the same chemical makeup.

It’s worth noting that the substrate is often chemically stable before the reaction, however. In many cases, an outside chemical or application of energy is required to begin the chemical reaction; this outside influence is known as a catalyst. The catalyst begins the reaction, but is not actually a part of it; the end result will still be a change in the substrate but won’t be a combination of the substrate and the catalyst.

For example, in the case of the protein found in milk (casein), which is the substrate for rennin and lansin. Also hydrogen peroxide with catalase enzymeThe first and third steps are reversible, but the second step is not reversible.

With increasing concentration concentration, the reaction rate will increase according to the number of enzymes available.

It is important to know that a concentration that reacts outside the cell (in vitro) does not have to work inside the cell. For example, fatty acid amide hydrolase can break (2-AG) outside the cell but cannot do so inside the cell.

Enzyme Substrates.

In biochemistry, the definition of substrate changes a little. In this context, substrates are typically referred to as “enzyme substrates” and represent the organic materials that an enzyme acts upon to cause a reaction. This is similar to the reactant definition used in general chemistry, but it’s important to note that this definition is a bit more narrow; it only refers to a material present in enzyme reactions, and only a certain type of material.

You might notice a similarity between enzyme reactions with the substrate and the way that catalysts begin a chemical reaction in general chemistry. In the case of biochemistry, enzymes play the role of catalyst to begin a reaction within the substrate without actually being part of the end result of the reaction.

The Core Concept of Substrates.

Despite the slight differences in the general chemistry and biochemistry definitions of substrate, the core concept should be pretty clear. As far as chemistry is concerned, a substrate is generally seen as a chemical material that some other material can act upon to cause a change. The change occurs to the substrate itself and not the outside catalyst or enzyme, and in most cases it could likely happen on its own if enough time were allowed.

As with the more specific definition seen in biochemistry, other niches of chemistry may also have specific definitions of the word “substrate” that differ a bit from the general definition. The core concept will remain the same, however, regardless of the specifics imposed by the niche. While the context and details may differ, substrates in chemistry will always be some form of chemical or molecule that another chemical or object can act upon in some way.

Substrate Examples In biochemistry.

In biochemistry, the definition of the substrate is any substance that reacts to the active site of an enzyme. A chemical bond is formed between the active site and the substrate. Such reactions are also known as enzyme-catalyzed reactions, the bonds through which the substrate gets itself banded to the active sites are exemplified by hydrogen bonds, hydrophobic interactions, or weak Van der Waals forces. After the formation of the enzyme-substrate complex, the enzyme exerts a force on the substances and as a result, they get converted into products. In such a complex, an enzyme needs a well-specified substrate to perform its catalytic activities while many active sites are available in the bodies of the enzymes that attract the substrates towards it. The phenomenon via which the enzymes activate the specified substrates is called substrate specificity. Hence, the substrates are loaded in those active sites so that relatively weaker bonds can be formed between them.

What is the enzyme-substrate complex?

Enzyme (E)+ Substrate (S) → Enzyme-Substrate or ES Complex

The reaction in between the active sites and the substrate occurs at specified parameters and that gives rise to an enzyme-substrate complex that causes the substrate to become part of the product of the particular reaction.

Although the substrate becomes that part of the product, several conformational changes, changes in the size and shape, and the physicochemical properties occur within the enzyme too. Most of the molecules that are present in the human body are substrates at the initial stages. There are many reactions that are occurring in daily life and the majority of them either need extensive energy content or prolonged reaction times to fulfill the completion conditions. Hence, the enzymes assist the reaction by lowering the activation energy and boost up their reaction rates so that the biological and chemical reactions can be completed efficiently.

Once the reaction is completed, the physiochemical properties of the substrate become different depending upon the reaction parameters and the nature of the product formed. It is worth elaborating here that there are many reactions that complete in various steps termed as intermediate reactions.

In such reactions, the product of one reaction becomes the reactant of another until the final step. Hence, it can be concluded that the substrates together with enzymes play a very vital role in many reactions occurring around us.

Reference :

ركيزة (كيمياء حيوية)/

What Is a Substrate in Chemistry?/


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