n., plural: substrates
In biology, the earthy material where an organism lives
Source: modified by Maria Victoria Gonzaga, from the images provided by Hottuna080, CC BY-SA 3.0. and by Oregon State University, Flickr.
What is a “substrate”? The underlying substances or layers are termed as substrate. The definitions of a substrate in various fields of knowledge vary. In major science fields such as chemistry, it is the major compound that reacts with the reagent under a specified set of reaction parameters. In other words, the substrate definition in chemistry is one in which it means the chemical reactant that takes part in the chemical reaction and on which an enzyme will act upon. In other related science fields such as basic engineering, the substrate is defined as the basic surface with which the paint sticks. In material sciences, the word “substrate” is often used to describe the base of the material on which various processing are carried out under specified reaction parameters to form new layers and films such as coatings. Hence, there are many definitions of the substrate that are available in the literature depending upon its applications and field of study. However, let us focus more on the biological aspect of the substrate.
What are the substrates in biology? In biochemistry, the substances with which the enzymes react to are called substrates. In ecology, the substrate is known as the foundation to which an immobile substance is attached to. In simple words, the substrate is the surface or material from which an organism grows or obtains its nourishment. What is another word for the substrate? Substratum or underlayer is used as the synonym for “substrate”.
Examples of substrates in biology fields, such as biochemistry, plant ecology, reptile ecosystem, and microbial ecology are elaborated below.
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 in between them.
Enzyme Substrate Complex. Source: modified by Maria Victoria Gonzaga, BiologyOnline.com, of the diagram from Khan Academy and OpenStax College, CC BY-SA 4.0.
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. Refer to the schematic diagram of the enzyme and substrate above.
Most of the molecules that are present in the human bodies are substrate 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. (Ref. 1)
Enzyme and substrate concentration
It has been very well elaborated by many researchers that for the effective working of an enzyme, the availability of the optimum amount of substrate is mandatory as the increase in the amount of substrate increase the rate of concentration of enzyme activity. Although the rate of reaction will increase after some time reaching a particular value, the rate of enzyme activity will not alter further even though there is plenty of substrates available. The reason for this is the accumulation of substrates in the active sites of the enzyme. Hence, after reaching that particular stage, the enzyme activity will remain constant.
The substrates find many important roles in the synthesis of many sweetening agents, in the modification of antibiotics, used in the production of various washing agents. Additionally, they also find various applications in clinical, forensic, and environmental sectors.
In plant ecology
The most tangible component in our ecosystem is the substrates on which various plants, microbes, and reptiles grow and thus the impact of the substrate in ecology is enormous. The substrate plays a very vital role in the growth and nourishment of the plant and other organisms as they are the means through which they absorb water and minerals from the soil.
It is worth mentioning here that the substrates differ from the natural soil on the percentage of the organic matter present in it as it’s the amount in natural soil is between 1-3% while in substrates, the concentration of organic matter is at least 70%.
The substrates are globally categorized into two types. They are universal substrates and specific substrates. They are commonly used in the mixture of peat, perlite, and organic fertilizers.
The substrates may also be further differentiated from each other on the basis of the plants where they are meant to be applied. In particular, they are substrates for acidic plants, green plants, flowering plants, cacti, succulents, garden, orchids, carnivorous plants, rose bushes, and seed buds.
In reptile ecosystems
The substrates in the reptiles are mostly used in the reptile enclosure. It has been reported in various literature that the relation between the reptile and the substrate needs to be very critically analyzed as not all substrates are suited to all reptiles. For instance, especially for the lizards, the substrate made up of synthetic biodegradable materials is not suitable as they smell with its tongue and the substrate might stick to it causing serious gut illness. Hence, a good starting point of selecting the substrate for the reptile is to closely monitor the animal and its natural habitat. Silica desert sands, calcium sands, wood fiber substrates, beech chips, bark substrates, coco fiber are some of the types of substrates that are most commonly used for various reptiles. (Ref. 2)
In microbial ecology
The enzymes are produced by the microbes in order to acquire nourishment and energy by breaking down complex organic substrates. Hence, it has been believed that the activity of the extracellular enzymes largely depends on the compositions of the substrates. The researchers have published that there are a couple of very important mechanisms through which the variations in the compositions in the substrates affecting the enzymic activities can be explored.
The mechanisms are referred to as the resource limitation model and substrate simulation model. The scientists believe that the diversity and quantity of the substrates available to the microbes play a vital role in influencing their microbial activity and both of the said mechanisms are followed there.
For example, by unceasing the diversity of the substrate, the enzyme activity gets enhanced as the substrate is available to many of the enzymes and this has been very well elaborated by the substrate simulation model. The substrate stimulation model can occur because of the greater diversity of the substrate and that increases the number of niches available to the microbes, thus paving the path of the formation of a more diversified community of microbes.
Similarly, the type and magnitude of the enzyme activity and its dependence on the compositions of the substrates added have been very well predicted by the resource limitation model.
For example, synergistic effects can arise by the addition of the complementary resources such as the addition of compounds of carbon and nitrogen together can have way constructive effects on the enzymic acidity as compared to feeding both carbon and nitrogen alone and these facts have been supported by resource limitation model. Hence, it can be perceived that the composition and concentration of the substrates always have key effects on the catalytic activity of the enzymes. Moreover, the combination of a suitable enzyme and a substrate is also very important to maintain the equilibrium between their activities. (Ref. 3)
Biological Importance of Substrate
The earthly material or surface where the various microorganisms such as plant, fungus, and algae lives, grows, ar attach is termed as substrate. For instance, the algae living on the rock may well serve as the substrate for another living thing that lives on top of the algal underlayer while the rock can be said as a substrate for the said algae.
In an aqueous environment, the substrate is the material at the bottom of the marine waters or the one that forms the bed of a stream. It, therefore, includes rocks, sand, gravel, and dirt. As such, they are essential as a source of minerals and nutrients, especially for organisms that live and thrive in it. It also renders bottom dwellers some sort of protection from predators as they can camouflage and be hard to see at the bottom.
Although the examples of substrates are many in various fields still there are many common substrates that can be seen in our daily life. Carbohydrates, such as glucose, starch, and sucrose, act as the substrates for the enzymes, like maltase and salivary amylase. As for enzymes trypsin and chymotrypsin, the substrates they act upon are proteins and peptides, which are present in various foods such as grains and meat we consume on daily basis. Lipids are the substrates for lipase enzyme. (Ref. 4)
It can be concluded from the above discussion that the underlying substances or layers are basically termed as substrate and this definition varies from one field to another. Substratum is another word that has been very often used as the synonym of the substrate. The molecule acted upon by an enzyme is referred to as a substrate. Furthermore, each enzyme needs a well-specified substrate to perform its catalytic activities while there are many active sites that 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.
Most of the molecules that are present in the human bodies are substrate at the initial stage. 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. It has been very well elaborated by many researchers that for the effective working of an enzyme, the availability of the optimum amount of substrate is mandatory as the increase in the amount of substrate increase the rate of concentration of enzyme activity.
Substrates have diversified applications that vary from one field to another. In biochemistry, the substances that act on the active sites of the enzymes are called substrates. Thus, new bonds are formed between the active sites and the substrates. Such reactions are also known as enzyme-catalyzed reactions.
In ecology, the surface where the various microorganisms such as plant, fungus, and algae lives are termed as substrates. Hence, the algae living on the rock will act as the substrate for any other living that lives at the top of algae while the rock can be said as a substrate for the said algae.
The enzymes are produced by the microbes to acquire nourishment and energy through the breakdown of very complex organic substrates. The activity of the extracellular enzymes largely depends on the compositions of the substrates.
- Gulaboski, R., Kokoskarova, P., & Risafova, S. (2020). Analysis of enzyme-substrate interactions from square-wave protein-film voltammetry of complex electrochemical-catalytic mechanism associated with reversible regenerative reaction. Journal of Electroanalytical Chemistry, 868, 114189. https://doi.org/10.1016/j.jelechem.2020.114189
- Substrates for Reptiles. (2014). Anapsid.Org. http://www.anapsid.org/substrates2.html
- Hernández, D. L., & Hobbie, S. E. (2010). The effects of substrate composition, quantity, and diversity on microbial activity. Plant and Soil, 335(1–2), 397–411. https://doi.org/10.1007/s11104-010-0428-9
- Iouna. (2019, November 14). Know The Types Of Substrates For Plants (Part 1). Bonnes Pratiques. https://bonnespratiques-ead.net/know-the-types-of-substrates-for-plants-part-1/
©BiologyOnline. Content provided and moderated by BiologyOnline Editors.