Biomolecules Notes

 The chapter "Biomolecules" is about the complex organic molecules found in living organisms, such as carbohydrates, proteins, lipids, and nucleic acids, which are essential for life 

• Carbohydrates: Energy source and structural components.   
• Protein: Enzymes, antibodies, and structural components.   
• Lipids: Energy storage, formation of cell membranes and hormones.   
• nucleic acids: DNA and RNA, which store genetic information

Biomolecules are essential for the functions of living organisms, such as cell division, metabolic reactions, tissue repair, growth, and other biological processes.

Example:

• Carbohydrates: Glucose, starch, cellulose.   
• Proteins: insulin, hemoglobin, enzymes.   
• Lipids: Fats, oils, cholesterol.   
• Nucleic acids: DNA, RNA.

HOW TO ANALYSE CHEMICAL COMPOSITION?

We can continue asking in the same way, what type of organic compounds are found in living organisms? How does one go about finding the answer? To get an answer, one has to perform a chemical analysis. We can take any living tissue (a vegetable or a piece of liver, etc.) and grind it in trichloroacetic acid (Cl3CCOOH) using a mortar and a pestle. We obtain a thick slurry. If we were to strain this through a cheesecloth or cotton we would obtain two fractions. One is called the filtrate or more technically, the acid-soluble pool, and the second, the retentate or the acid-insoluble fraction. Scientists have found thousands of organic compounds in the acid-soluble pool.

PRIMARY AND SECONDARY METABOLITES

The most exciting aspect of chemistry deals with isolating thousands of compounds, small and big, from living organisms, determining their structure and if possible synthesising them. If one were to make a list of biomolecules, such a list would have thousands of organic compounds including amino acids, sugars, etc. For reasons that are given in section 9.10, we can call these biomolecules as ‘metabolites’. In animal tissues, one notices the presence of all such categories of compounds shown in Figure 9.1. These are called primary metabolites. However, when one analyses plant, fungal and microbial cells, one would see thousands of compounds other than these called primary metabolites, e.g. alkaloids, flavonoids, rubber, essential oils, antibiotics,

BIOMACROMOLECULES

The molecules in the insoluble fraction with the exception of lipids are polymeric substances. Then why do lipids, whose molecular weights do not exceed 800 Da, come under acid insoluble fraction, i.e., macromolecular fraction? Lipids are indeed small molecular weight

compounds and are present not only as such but also arranged into structures like cell membrane and other membranes. When we grind a tissue, we are disrupting the cell structure. Cell membrane and other membranes are broken into pieces, and form vesicles which are not water soluble. Therefore, these membrane fragments in the form of vesicles get separated along with the acid insoluble pool and hence in the macromolecular fraction. Lipids are not strictly macromolecules.