We will now discuss biomolecules. This is Chapter 9 in NCERT, within the unit of Cell Unit of Life, which also includes Cell Cycle and Biomolecules. These three chapters collectively form one unit.
There is vast diversity among living organisms in our biosphere. We have been learning about this since we started studying the living world. A question that arises in our minds is: are all living organisms made up of the same chemical elements and compounds?
You have learned in chemistry about how elemental analysis is performed. If we perform such an analysis on plant tissue, animal tissue, or microbial paste, we obtain a list of elements like carbon, hydrogen, oxygen, and several others, along with their respective proportions by mass per unit of tissue. This is a very important piece of information.
If the same analysis is performed on a piece of Earth's crust, an example of non-living matter, we obtain a similar list. What are the differences between these two lists? In absolute terms, no significant difference can be made out. All the elements present in a sample of Earth's crust are also present in a sample of living tissue.
However, a closer examination reveals that the relative abundance of carbon and hydrogen, with respect to other elements, is higher in any living organism than in the Earth's crust. This presents an interesting point.
All elements present in a sample of Earth's crust are also present in a sample of living organism. This statement is incorrect.
Carbon and hydrogen, with respect to other elements, are higher in any living organism. This statement is correct.
Both options are correct. The correct answer is therefore, both A and B. Got it? This is a good question and has a high chance of appearing. Remember this.
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, and grind it in trichloroacetic acid using a mortar and pestle. Do you know what a mortar and pestle is? A grinding stone or a mortar and pestle, like those small ones used for grinding spices.
So, what do we need to find out? The question is interesting. Pay attention. How does one go about finding the answer? To what kind of answer? What type of organic compounds are found in living organisms? To get an answer, one has to perform a chemical analysis. We can take any living tissue, a vegetable or a piece of liver, and grind it in trichloroacetic acid using a mortar and pestle.
We obtain a thick slurry. If we were to strain this through a muslin cloth or cotton, we would obtain two fractions. We would obtain a thick slurry. If we were to strain this through a muslin cloth or cotton, we could obtain two fractions. One would be called the filtrate, or more technically, the acid soluble pool. And the second would be the residue, or the acid insoluble fraction. Scientists found thousands of organic compounds in the acid soluble pool. Let's visualize this process. What was done first? A leaf was taken.
The leaf was ground. With what? Trichloroacetic acid. What was obtained? A thick slurry. Then what was done? It was filtered through a cloth. What was obtained? Two fractions. The acid soluble pool and the acid insoluble fraction.
This lecture segment discusses how to identify and isolate organic compounds from living tissues.
In higher education, students will learn about analyzing living tissue samples. The process involves extracting compounds and then subjecting them to various separation techniques until a single compound is isolated from the rest.
Essentially, it's about isolating and purifying a specific compound. Analytical techniques are then applied to this compound to understand its molecular formula and probable structure.
All carbon compounds obtained from living tissue are termed biomolecules. Living organisms also contain inorganic elements within their compounds.
To determine the presence of these elements, a slightly different, but destructive, experiment is required. The speaker then pauses, indicating a shift to a new topic or a more detailed explanation.
Here's the transcription and translation of the lecture segment:
In my opinion, a good question arises from this. In higher classes, you will learn about the analysis of living tissue samples and the identification of particular organic compounds. It will suffice to say here that one extracts the compound and subjects the extract to various separation techniques. We will advance this further.
This is the entire acid-soluble pool.
Various separation techniques are employed here. This is a very important line; pay close attention. Various separation techniques are used until one has separated a compound from all other compounds. One isolates and purifies a compound. Analytical techniques are applied to the compound to give us an idea of its molecular formula.
Compound A, Compound B, Compound C.
Here is the transcription and translation of the provided lecture chunk into pure, highly readable English:
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Following this, we have various compounds. For these compounds, what do we do? We apply an analytical approach. Applying analytical techniques to compounds gives us an idea of their molecular formula and the probable structure of the compound.
The analytical method is used to identify the structure and molecular formula. So, we can form an assertion. "After separation of organic matter, analytical methods are essential." This is an assertion. An analytical method helps to identify the structure and molecular formula of a compound.
This is the beauty of studying. You can see the entire study in terms of assertion and reason. The assertion is: "After separation of organic matter, analytical methods are essential." The reason is: Analytical methods help to identify the structure and molecular formula of the compound.
Let's move forward. All the carbon compounds that we get from living tissue can be called biomolecules. All carbon compounds from living tissue are biomolecules. However, living organisms also have inorganic elements and compounds within them. How do we know this? A slightly different but destructive experiment has to be done. This is what we will do now.
We take a small amount of living tissue, for example, a leaf or liver. This is called wet weight. Then, we dry it. All the water evaporates. The remaining material gives the dry weight. Now, if the tissue is fully burned, all the carbon compounds are oxidized to gaseous forms, like CO2 and water vapor, and are removed. What remains is called ash. This ash contains inorganic elements like calcium and magnesium. Inorganic compounds like sulfate and phosphate are also seen in the acid-soluble filtrate.
Why are we getting sulfate and phosphate in the fraction where organic matter is present? Because organic matter is made up of inorganic substances. Are we getting phosphate? That means phosphate is present in the organic matter.
This is the wet weight. Then, we dry it to get the dry weight.
Now, if the tissue is fully burned, all the carbon compounds are oxidized to gaseous forms.
The CO2 is completely gone. And what remains is ash. Ash contains inorganic elements like calcium and magnesium.
The ash contains inorganic elements like calcium and magnesium. Salts like sulfates and phosphates are also seen in the acid-soluble fraction. Therefore, elemental analysis gives the elemental composition of living tissue in the form of hydrogen, oxygen, chlorine, and carbon. While analysis for compounds gives an idea of the kind of organic and inorganic constituents.
In terms of elements, it tells us the quantity of hydrogen, oxygen, chlorine, and carbon present in the living tissue. However, when we analyze compounds, it helps us understand the types of organic and inorganic constituents present. It allows you to determine which elements are present and what they are forming. You can determine the amounts, identify which elements are present, and through analysis, understand what they are forming.
From a chemical perspective, one can identify functional groups like aldehydes, ketones, and aromatic compounds. But from a biological perspective, we classify them into amino acids, molecular bases, and fatty acids.
In the acid-soluble fraction, there are organic compounds, not inorganic elements. So this statement is incorrect. It contains inorganic compounds, not elements.
Elemental analysis gives elemental composition.
Acid soluble pools have organic compounds and inorganic compounds like sulfates and phosphates.
The statement: Acid soluble pools generally have organic compounds, yet they also have inorganic compounds. The reason for this is that organic compounds are made up of...
This lecture segment discusses organic and inorganic compounds, particularly focusing on amino acids from a biological perspective.
The speaker begins by stating that living organisms are composed of both organic and inorganic compounds.
They then clarify that while chemistry might classify compounds based on functional groups like aldehydes or ketones, biology categorizes them differently. From a biological viewpoint, compounds are classified into amino acids, nucleotides, bases, and fatty acids.
Amino acids are defined as organic compounds that contain both an amino group and an acidic group. These groups are attached to the same carbon atom, referred to as the alpha carbon. Because of this arrangement, they are called alpha-amino acids.
These alpha-amino acids can be thought of as substituted methanes. They possess four distinct substituent groups occupying the four positions around a central atom: a hydrogen atom, a carboxyl group, an amino group, and a variable group, denoted as 'R'.
The nature of the 'R' group determines the variety of amino acids. While many amino acids exist, only about 20 types are found in proteins. The 'R' group in these proteinaceous amino acids can be simple, like a hydrogen atom (as in glycine) or a methyl group (as in alanine), or more complex structures like a hydroxymethyl group (as in serine). The lecture mentions that three of these 20 types are presented in a diagram.
The speaker then illustrates a point using a chemical structure, highlighting that the amino group is attached to the alpha carbon. They explain that while this structure possesses an amino group and a variable group, it is not an alpha-amino acid because the amino group is not attached to the alpha carbon. The carbon adjacent to the carboxyl group is the alpha carbon. The amino group in this specific example is attached to a beta carbon. Therefore, it's a beta-amino acid, not an alpha-amino acid.
The speaker emphasizes that all proteinaceous amino acids are alpha-amino acids. This distinction is crucial because only alpha-amino acids can form proteins. If a compound is to be used in protein synthesis, it must adhere to this alpha-amino acid structure.
Here is the transcription and translation of the lecture chunk:
The lecture discusses amino acids, focusing on their structure and properties. It explains that the R-group in an amino acid can be modified, leading to different types. For example, changing the R-group to hydrogen results in glycine, while changing it to a methyl group yields alanine. If the R-group is CH2OH, it forms serine.
Glycine is identified as the simplest amino acid. It is noted that glycine is optically inactive because it has two hydrogen atoms attached to the alpha-carbon. In contrast, most other amino acids are optically active.
The chemical and physical properties of amino acids are largely determined by their functional groups: the amino group (-NH2) and the carboxyl group (-COOH). However, the R-group also plays a significant role. The ability to change the R-group explains why the properties of amino acids vary.
If the R-group is modified, the overall behavior of the amino acid can change. This is because the chemical and physical properties do not solely depend on the amino and carboxyl groups; they are also influenced by the R-group.
The lecture also touches on the classification of amino acids based on their amino and carboxyl groups. They can be acidic, basic, or neutral. For instance, valine is a neutral amino acid, while glutamic acid is acidic, and lysine or arginine are basic.
Furthermore, there are aromatic amino acids like tyrosine, phenylalanine, and tryptophan. The text highlights that the ionizable nature of the amino and carboxyl groups allows amino acids to exist in different forms depending on the pH. In solutions of varying pH, the structure of an amino acid changes, a phenomenon known as the zwitterion.
The lecture segment discusses the behavior of amino acids under different pH conditions.
When an amino acid is placed in an acidic environment (low pH), it receives a hydrogen ion (H+). This leads to the amino acid becoming positively charged, forming a cation.
Conversely, in a basic environment (high pH), the amino acid encounters hydroxide ions (OH-). In this scenario, a hydrogen ion from the amino acid is removed, and it combines with the hydroxide ion to form water (H2O). The amino acid then carries a negative charge, becoming an anion.
There is a specific pH at which an amino acid exists in a neutral, zwitterionic form, meaning it has both a positive and a negative charge, resulting in no net charge. This particular pH is known as the isoelectric point.
At the isoelectric point, the amino acid is in its zwitterion state. If the pH is lowered below this point towards acidic conditions, the amino acid will gain a proton and become a cation. If the pH is raised above the isoelectric point towards basic conditions, the amino acid will lose a proton and become an anion. This concept is frequently tested in exams.