What Are Metabolites and Biomacromolecules? Definitions, Types, and Functions
Hundreds of different organic compounds combine in varying proportions to form the cells of our body. Besides these, the metabolic reactions in our body too form intermediate products called metabolites. Thus, the organic compounds that are produced as a result of metabolism or are required for it are called metabolites.
As is evident, all metabolites can be called biomolecules. Larger and more complex biomolecules are called biomacromolecules. Also, there are two broad categories of metabolites. These are primary metabolites and secondary metabolites.
Let's find out more about primary and secondary metabolites examples.
Primary and Secondary Metabolites
Primary metabolites are manufactured in the cell and are essential for the growth of cells. Amino acids, nucleotides, polyols, vitamins and organic acids are some significant primary metabolites examples.
On the other hand, secondary metabolites are produced by an organism’s body and are not required for primary metabolic processes. Furthermore, these play a very essential role in ecological activities. For example, secondary metabolites such as drugs, flavours, dyes, fragrances, pesticides and pigments have widespread applications in the pharmaceutical industry as well as in agriculture.
Various Functions of Secondary Metabolites include:
Acting as symbiotic agents between plants and microorganisms.
Acting as asexual hormones.
Functioning as transport agents.
Can be used as agents against other fungi, bacteria and amoeba.
Pop Quiz 1
Which of these are secondary metabolites examples?
Pigments.
Dyes.
Flavours.
All of the above.
In plants, secondary metabolites can carry out several functions.
Firstly, these can drastically slow down the germination of plant spores until favourable conditions are met.
Secondly, these can protect dormant spores from foreign agents such as amoeba.
Thirdly, these can wipe off all competitive microbes from the surrounding environment during germination.
Activity: Revise your concepts by writing down a short secondary metabolites definition in your notebook.
Biomacromolecules
Biological molecules or biomolecules are substances that the cells of our body produces. These are only found in living organisms. Furthermore, they are key cellular components and perform a broad range of functions which are essential for our growth and survival. Biomolecules are of two types: biomicromolecules and biomacromolecules.
Most of the critical nutrients that our body needs are biomacromolecules meaning, the proteins, the carbohydrates and fats that we consume are all examples of biological macromolecules.
Moreover, biomacromolecules also play a critical role in the proper functioning of cells and their structure. Almost all biomacromolecules are polymers, which are chains of monomers linked together. Typically, these polymers comprise of nearly identical monomers, which combine in different ratios to form these complex biomacromolecules. To enumerate this, the average size of a biomacromolecule ranges between 800-1000 Daltons, and feature a very complicated molecular structure.
In addition, biomacromolecules can be divided into four broad types. The common biomacromolecules examples are carbohydrates, proteins, lipids and nucleic acids. In other words, all these types of biomacromolecules are built from smaller monomers that are linked to each other utilising covalent bonds. Given these points, it’s important to note that lipids are an exception and not polymers. They are not made of monomers.
Lipids are also a very crucial part of our cell membranes. Despite its high molecular weight, lipids are insoluble in acids.
The Nobel Laureate Hermann Staudinger first coined the term “macromolecule” in the 1920s. Significantly, he was the first to theorise that large biomolecules are usually made of small biomolecules linked together by means of covalent bonds.
Pop Quiz 2
Which of these is not a Biomacromolecule?
Carbohydrates.
Proteins.
Hydrochloric acid.
Lipids.
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FAQs on Metabolites and Biomacromolecules: Key Concepts for Biology
1. What are biomacromolecules and why are they considered the 'building blocks of life'?
Biomacromolecules are large, complex organic molecules that are essential for the structure and function of all living organisms. They are called the 'building blocks of life' because they perform a vast range of critical functions, including providing structural support (like collagen), storing energy (like starch), carrying genetic information (like DNA), and catalysing biochemical reactions (like enzymes).
2. What are the four major types of biomacromolecules found in living cells?
The four principal classes of biomacromolecules found in all living organisms are:
- Carbohydrates: Primarily serve as a source of energy and structural components.
- Proteins: Act as enzymes, structural elements, and transport molecules.
- Nucleic Acids (DNA and RNA): Store and transmit genetic information.
- Lipids: Function in energy storage, form cell membranes, and act as signalling molecules.
3. How are biomacromolecules different from biomicromolecules?
The primary difference lies in their size and complexity. Biomicromolecules (e.g., amino acids, simple sugars, nucleotides) are small, simple molecules with low molecular weight. In contrast, biomacromolecules (e.g., proteins, polysaccharides, nucleic acids) are large polymers formed by the linking of many biomicromolecules (monomers) together, resulting in a high molecular weight.
4. What is a metabolite, and what is the key difference between primary and secondary metabolites?
A metabolite is any substance produced or consumed during metabolism. The key difference between the two types is their role in the organism:
- Primary metabolites (e.g., glucose, amino acids) are directly involved in normal growth, development, and reproduction. Their absence is immediately lethal.
- Secondary metabolites (e.g., alkaloids, tannins, pigments) are not directly involved in these core processes but often have important ecological functions, such as defence or attraction. Their absence is not immediately lethal.
5. What are the basic building blocks (monomers) for proteins, carbohydrates, and nucleic acids?
The monomer units for these key biomacromolecules are:
- Proteins are built from amino acids.
- Carbohydrates (specifically polysaccharides) are built from monosaccharides (simple sugars like glucose).
- Nucleic Acids are built from nucleotides.
6. Why are proteins often called the 'workhorses' of the cell?
Proteins are called the 'workhorses' because of their incredible functional diversity, which surpasses all other biomacromolecules. They perform most of the active roles in a cell. For example, enzymes catalyse reactions, haemoglobin transports oxygen, antibodies fight infections, and actin and myosin enable muscle contraction. Their specific three-dimensional structure dictates their unique function, allowing them to carry out nearly every task of a living cell.
7. How does the structure of a polysaccharide like starch relate to its function as an energy storage molecule?
The structure of starch is perfectly suited for energy storage in plants. It is a polymer of glucose linked in a way that forms a compact, helical shape. This allows a large amount of glucose (energy) to be packed into a small volume within the cell, minimising osmotic effects. The branched structure of amylopectin, a component of starch, provides many endpoints for enzymes to quickly release glucose molecules when energy is needed by the plant.
8. Are lipids strictly considered biomacromolecules? Explain why or why not.
No, lipids are not strictly considered biomacromolecules according to the classic definition. While they are essential biomolecules found in the acid-insoluble fraction during analysis, they differ in two key ways:
- They are not polymers: Unlike proteins or nucleic acids, lipids are not made of repeating monomer units.
- Lower Molecular Weight: Their molecular weight is generally less than 1,000 Daltons, which is below the typical threshold for a macromolecule. They are part of the acid-insoluble pool simply because their hydrophobic nature causes them to form large aggregates or vesicles in aqueous environments.
9. Why is DNA considered a more stable genetic material than RNA?
DNA is chemically more stable than RNA, making it better for the long-term storage of genetic information. This stability comes from two main structural differences:
- Sugar Type: DNA contains deoxyribose sugar, which lacks a hydroxyl (-OH) group at the 2' carbon position. RNA has ribose sugar, which has this reactive -OH group, making it more susceptible to hydrolysis and degradation.
- Structure: The double-helix structure of DNA provides protection for the nucleotide bases on the inside, shielding them from chemical and environmental damage. RNA is typically single-stranded and more exposed.
