What is a Substrate?
The substrate is an umbrella term, which has a variable significance in different disciplines. From the chemical point of view, the core concept of substrates may be understood as the raw materials which, under an enzyme-catalysed reaction, yield a desirable product. The product thus produced can be prepared even without enzymes but the rate than would be slowed down by a million times.
With reference to ecology though, it may refer to the substratum on which an organism lives, but for microbiologists it is the chemical on which microbial organisms can feed and thrive. In the biochemical branch of science, the substrate is a substance on which an enzyme acts to produce the desired product by forming an intermediate.
Biochemical Substrate
The biochemical significance of a substrate is in enzyme catalysis. A biochemical substrate can be considered a raw material used to obtain a certain product. The chemical reaction, thus, occurring, is driven by an enzyme. An enzyme is a proteinaceous molecule of high molecular weight. It may have multiple sites, out of which one is for the attachment of substrate. The lock-key mechanism may explain the enzyme-substrate association, wherein the substrate is the key and the enzyme is the lock. Just like a key fits into a lock, the substrate fits into the active site of an enzyme to give a product.
Enzyme catalysis depicting association of substrate with active site of enzyme
Enzyme Catalysis
Enzymes are usually proteinaceous molecules with the exception of ribozymes which are RNA molecules. They are biological catalysts of high molecular weight, ranging from $2000$ to more than $1$ million Dalton. These catalysts are sensitive to changes in temperature and pH. For most enzymes, the optimum temperature range lies between $298-310$ K and the optimum pH lies in the range of 5-7. Enzyme catalysis can be understood through adsorption and intermediate formation.
The substrate first diffuses and then adsorbs to bind to the enzyme's active site. It then reacts with the active groups, like $-NH_{2}$ , $-COOH$ , $-SH$ , $-OH$ , etc., present around the active site to form an activated complex. This complex finally dissociates to form a product. The product then desorbs and diffuses away from the enzyme. This reaction can be represented in the form of chemical equations as follows:
$E \ + \ S \ \rightarrow \ ES^{*}\\\\ES^{*} \rightarrow \ E \ + \ P$
Every enzyme has a specific condition under which it can work if that condition changes its working efficiency reduces even sometimes enzymes also get denatured as other proteins.
Substrate Specificity
Due to their chemical structure, enzymes are highly specific. One enzyme may react with only certain substrates to yield a specific product. The nature of an enzyme to react with only certain substrates is known as substrate specificity. The size, structure, charges, polarity, and hydrophobicity of the substrate as well as the active site determine the substrate specificity.
Substrate in Other Domains
Substrates have diversified applications that vary from one field to another.
In ecology, substrates describe the surfaces on which different microorganisms, including plants, fungi, and algae, can exist. As a result, the rock can be considered a substrate for the algae living on it, while the algae itself can be said to be a substrate for any organism living on it.
In microbiology, the importance of substrates can be expressed as the source of nutrition and energy for the microorganism. A few examples of unusual substrates bacteria use for growth include carbon monoxide and other toxic environmental pollutants, spent wash, molasses and sewage.
Iron may be referred to as a substrate on which zinc is coated during galvanisation.
Summary
The word substrate holds different meanings and significance in ecological, biological and biochemical fields. The chemical definition of the substrate is related to enzyme catalysis. Enzymes are catalysts which react with substrates to form products. These catalysts are mostly proteinaceous, specific and highly sensitive to temperature and pH changes. In other regards, substrates are also the basic material for our biological processes, these may also be sources of nutrients required for growing a population, or a substrate may also refer to a substrate used for attachment.
List of Related Articles
- Enzymes
- Application of Enzymes
FAQs on Substrate- Meaning, Examples, Types and More
1: What are the functions of substrates?
Substrates are reactants in most chemical reactions. They are the raw materials which convert into products of biological importance. Such reactions are catalysed by biological catalysts called enzymes.
Substrates may also be defined as substratum, which helps in the attachment of various species, providing habitat to some or as a source of nutrition and energy for the growth of some organisms.
2: What is the chromogenic substrate?
A substrate is a raw material which may convert to a useful product through a chemical reaction catalysed by a specific catalyst. Sometimes the substrate may be chromogenic. A chromogenic substrate is one which, on reaction, gives a colour-generating product. One example of such a reaction is the formation of blue colonies in E-coli due to activation of the $\beta$ galactosidase gene.
3: What is the difference between a coenzyme and a substrate?
An organic molecule associated with an enzyme and increases its efficiency is known as a coenzyme. Vitamins are the most common example of coenzymes. The substrate is the raw material converted to the desired product with the help of enzymes.
