How to analyse chemical composition? Questions in English

(B) In the hierarchy of biological organization,atoms are the fundamental building blocks of matter. When two or more atoms combine chemically,they form a molecule. Molecules further combine to form macromolecules,which then organize into cellular structures like organelles. Therefore,the immediate result of the combination of atoms is a molecule.

(B) The correct answer is $B$. Molecules are composed of atoms and are extremely small in size,typically ranging from a few $\mathring{A}$ to a few nanometers.
Because they are far below the resolution limit of a standard light microscope,they are classified as $Sub-microscopic$ entities.

(C) In the hierarchy of biological organization,atoms are the fundamental units of matter. When two or more atoms combine chemically,they form molecules. Therefore,molecules are formed by the combination of atoms.

(B) The hierarchy of biological organization begins at the atomic level. Atoms combine to form molecules. These molecules further organize into macromolecules,which then form organelles,cells,tissues,organs,and organ systems. Therefore,the immediate level of organization formed by the combination of atoms is molecules.

(D) The correct answer is $D$.
Living organisms require $6$ essential elements in relatively large amounts for their structural organization and metabolic processes.
These elements are Carbon $(C)$,Hydrogen $(H)$,Oxygen $(O)$,Nitrogen $(N)$,Phosphorus $(P)$,and Sulphur $(S)$.
Therefore,the six elements that make up about $98$ percent of the mass of every living organism are $C, H, N, O, P,$ and $S$.

(C) When a plant tissue is burnt,the carbon compounds are oxidized and released as $CO_2$ and water vapor. The remaining material is called 'ash'.
Ash contains inorganic elements like calcium,magnesium,potassium,phosphate,and sulphate.
Cellulose is an organic compound (a polysaccharide) that is completely oxidized during the burning process and is therefore not present in the ash.

(B) According to the $NCERT$ textbook, the average composition of a cell is as follows:
- Water: $70-90\%$
- Proteins: $10-15\%$
- Carbohydrates: $3\%$
- Lipids: $2\%$
- Nucleic acids: $5-7\%$
- Ions: $1\%$
Matching these with the given columns:
$A$ (Water) matches with $2$ $(70-90\%)$
$B$ (Proteins) matches with $1$ $(10-15\%)$
$C$ (Carbohydrates) matches with $4$ $(3\%)$
$D$ (Lipids) matches with $5$ $(2\%)$
$E$ (Nucleic acids) matches with $3$ $(5-7\%)$
$F$ (Ions) matches with $6$ $(1\%)$
Therefore, the correct sequence is $2-1-4-5-3-6$.

(B) Water is the most abundant chemical component of living organisms.
According to the $NCERT$ textbook,water constitutes approximately $70-90\%$ of the total cellular mass of a cell.
It acts as a universal solvent and is essential for all metabolic processes occurring within the cell.

(D) Water is the most abundant chemical compound in living organisms.
In a typical human body,water constitutes approximately $65-70\%$ of the total body weight.
This water is essential for various physiological processes,including acting as a solvent for biochemical reactions,thermoregulation,and transport of nutrients and waste products.
Therefore,the correct range for the water content in the human body is $65-70\%$.

(C) Living organisms are primarily composed of carbon,hydrogen,oxygen,and nitrogen.
These four elements constitute approximately $99\%$ of the total mass of the living system.
Carbon $(C)$,Hydrogen $(H)$,Oxygen $(O)$,and Nitrogen $(N)$ are the fundamental building blocks of biological macromolecules like proteins,nucleic acids,carbohydrates,and lipids.
Therefore,the correct option is $CHON$.

(C) Living organisms are primarily composed of elements such as carbon,hydrogen,nitrogen,oxygen,phosphorus,and sulfur. These elements constitute the bulk of biological macromolecules like proteins,nucleic acids,lipids,and carbohydrates. Phosphorus is essential for $DNA$,$RNA$,and $ATP$,while sulfur is a critical component of certain amino acids like cysteine and methionine.

$\Rightarrow$ Various forms of living organisms are seen in our biosphere.
$\Rightarrow$ All living organisms are formed by similar types of elements or chemicals.
$\Rightarrow$ If we perform elemental analysis on a plant tissue, animal tissue, or a microbial paste, we obtain a list of elements like carbon, hydrogen, oxygen, and several others, along with their respective content per unit mass of a living tissue.
$\Rightarrow$ If the same analysis is performed on a piece of Earth's crust as an example of non-living matter, we obtain a similar list.
$\Rightarrow$ All the elements present in a sample of Earth's crust are also present in a sample of living tissue. However, the relative abundance of carbon and hydrogen with respect to other elements is higher in any living organism than in the Earth's crust.
$\Rightarrow$ Table: Comparison of Elements Present in Non-living and Living Matter:

Element	% Weight of Earth's Crust	% Weight of Human Body
Hydrogen $(H)$	$0.14$	$0.5$
Carbon $(C)$	$0.03$	$18.5$
Oxygen $(O)$	$46.6$	$65.0$
Nitrogen $(N)$	Very little	$3.3$
Sulphur $(S)$	$0.03$	$0.3$
Sodium $(Na)$	$2.8$	$0.2$
Calcium $(Ca)$	$3.6$	$1.5$
Magnesium $(Mg)$	$2.1$	$0.1$
Silicon $(Si)$	$27.7$	Negligible

(N/A) $\Rightarrow$ To understand the types of organic compounds found in living organisms, one has to perform a chemical analysis.
$\Rightarrow$ Take any living tissue (a vegetable or a piece of liver) and grind it in trichloroacetic acid $(Cl_{3}CCOOH)$ using a mortar and pestle.
$\Rightarrow$ We obtain a thick slurry. It is strained through a cheesecloth or cotton, and we obtain two fractions.
$\Rightarrow$ One is called the filtrate or acid-soluble pool, and the second is the retentate or the acid-insoluble fraction. Thousands of organic compounds are found in the acid-soluble pool.
$\Rightarrow$ For the analysis of chemical composition, the extraction of compounds is performed.
$\Rightarrow$ Then, the extraction is subjected to various separation techniques until one has separated a compound from all other compounds.
$\Rightarrow$ In other words, the isolation and purification of the compound are done.
$\therefore$ Analytical techniques, when applied to the compound, give us an idea of the molecular formula and the probable structure of the compound.
$\Rightarrow$ All the carbon compounds that we get from living tissues can be called biomolecules.
$\Rightarrow$ However, living organisms also contain inorganic elements and compounds. How do we know this?
$\Rightarrow$ A slightly different but destructive experiment has to be done. One weighs a small amount of a living tissue (say a leaf or liver, called wet weight) and dries it. All the water evaporates.
$\Rightarrow$ The remaining material gives the dry weight. Now, if the tissue is fully burnt, all the carbon compounds are oxidized to a gaseous form ($CO_{2}$, water vapour) and are removed.
$\Rightarrow$ What remains is called 'ash'. This ash contains inorganic elements (like calcium, magnesium, etc.). Inorganic compounds like sulphate, phosphate, etc., are also seen in the acid-soluble fraction.
$\Rightarrow$ Therefore, elemental analysis gives the elemental composition of living tissue in the form of hydrogen, oxygen, chlorine, carbon, etc., while analysis for compounds gives an idea of the kind of organic and inorganic constituents present in living tissues.
$\Rightarrow$ From a chemistry point of view, one can identify functional groups like aldehydes, ketones, aromatic compounds, etc. But from a biological point of view, we shall classify them into amino acids, nucleotide bases, fatty acids, etc.
$\Rightarrow$ Table: A List of Representative Inorganic Constituents of Living Tissues:

Component	Formula
Sodium	$Na^{+}$
Potassium	$K^{+}$
Calcium	$Ca^{++}$
Magnesium	$Mg^{++}$
Water	$H_{2}O$
Compounds	$NaCl, CaCO_{3}, PO_{4}^{-3}, SO_{4}^{-2}$

(A) $\Rightarrow$ Elemental analysis provides the elemental composition of living tissue in the form of elements like $H$,$O$,$Cl$,$C$,etc.
$\Rightarrow$ In contrast,chemical analysis for compounds provides information about the types of organic and inorganic constituents present in living tissues.
$\Rightarrow$ From a chemical perspective,one can identify functional groups like aldehydes,ketones,and aromatic compounds. However,from a biological perspective,these are classified into amino acids,nucleotide bases,fatty acids,etc.

(B) The chemical formula $CO$ stands for Carbon Monoxide.
It is a colorless,odorless,and tasteless gas that is slightly less dense than air.
It is produced by the incomplete combustion of carbon-containing fuels.

(A) Centrifugation is a technique used for the separation of particles from a solution according to their size,shape,density,and the viscosity of the medium.
In this process,a centrifugal force is applied to the mixture by spinning it at high speeds.
This causes the denser particles to move away from the center of rotation (sedimentation) while lighter particles remain closer to the center.
Therefore,the correct method is Centrifugation.

(B) The dry weight of an organism is the weight of the organism excluding its water content.
Living organisms are primarily composed of organic compounds,which are based on carbon chains.
Carbon,along with hydrogen and oxygen,forms the backbone of biological molecules like carbohydrates,proteins,lipids,and nucleic acids.
Therefore,carbon constitutes the largest proportion of the dry weight of any living organism.

(C) In living organisms,water is the most abundant chemical component. It typically accounts for $70-90\%$ of the total cellular mass. Among the organic biomolecules,proteins are the most abundant,but when considering all chemical components including inorganic substances,water is the most abundant.

(C) The correct sequence for analyzing the chemical composition of living tissues is as follows:
$1$. $IV -$ Taking living tissue (e.g.,a vegetable or piece of liver).
$2$. $II -$ Grinding the tissue in a mortar and pestle with trichloroacetic acid $(Cl_3CCOOH)$ to form a thick slurry.
$3$. $III -$ The process of grinding ensures the breakdown of cellular components.
$4$. $I -$ Filtration of the slurry through cheesecloth or cotton to separate the two fractions.
$5$. $V -$ Obtaining the acid-soluble pool (filtrate) and the acid-insoluble fraction (retentate).
Therefore,the correct order is $IV \rightarrow II \rightarrow III \rightarrow I \rightarrow V$.

(D) $1$. When living tissues are ground in $8.0 \% \text{trichloroacetic acid}$ $(Cl_3CCOOH)$, the chemical components are separated into two fractions.
$2$. The components that dissolve in the acid pass through the cheesecloth or cotton and are called the $\text{Acid-soluble fraction}$ or $\text{Filtrate}$.
$3$. The components that do not dissolve in the acid remain on the cheesecloth or cotton and are called the $\text{Acid-insoluble fraction}$ or $\text{Retentate}$.
$4$. Therefore, the $\text{Acid-insoluble fraction}$ does not pass through the filter.

(C) Biomolecules are chemical compounds found in living organisms. They consist of both organic compounds (such as proteins,carbohydrates,lipids,and nucleic acids) and inorganic compounds (such as water,minerals,and salts). Therefore,the correct answer is $C$.

(A) When a living tissue is dried,the water content evaporates. When this dried tissue is burnt,the carbon compounds (organic components) are oxidized and released as gaseous forms like $CO_2$ and water vapor. The remaining residue is called 'ash'. This ash contains inorganic elements like calcium,magnesium,potassium,sodium,etc. Therefore,the ash obtained after burning living tissue contains only inorganic elements.

(B) Elemental analysis of living tissues gives the elemental composition (e.g.,Hydrogen,Oxygen,Chlorine,Carbon,etc.) of the tissue in the form of $P$.
Chemical analysis (chemical testing) of living tissues gives an idea of the organic and inorganic compounds (e.g.,amino acids,sugars,nucleotides,etc.) present in the tissue in the form of $Q$.
Therefore,$P$ refers to elements like Hydrogen,Oxygen,Chlorine,Carbon,and $Q$ refers to organic and inorganic compounds.

(A) When tissues are ground in trichloroacetic acid $(TCA)$,two fractions are obtained: the filtrate (acid-soluble pool) and the retentate (acid-insoluble fraction or residue).
Inorganic compounds like sulfates,phosphates,etc.,are found in the acid-soluble pool (filtrate) along with other small organic molecules like amino acids and monosaccharides.
However,in the context of standard $NCERT$ biology,inorganic compounds are typically identified in the acid-soluble fraction.

(C) When living tissue is ground in trichloroacetic acid $(TCA)$,the components of the cytoplasm are separated into two fractions:
$1$. The filtrate,which contains small molecular weight compounds,is known as the acid-soluble pool.
$2$. The retentate,which contains macromolecules like proteins,nucleic acids,polysaccharides,and lipids,is known as the acid-insoluble pool.
Since the question asks about the components present in the cytoplasm generally,both fractions represent the chemical composition of the cytoplasm.

(B) In a living organism,water is the most abundant chemical compound.
It constitutes approximately $70-90\%$ of the total cellular mass.
While proteins,carbohydrates,and lipids are essential biomolecules,water serves as the universal solvent and the medium for all metabolic reactions,making it the most concentrated substance in living systems.

(D) According to the average composition of cells as provided in the $NCERT$ textbook (Biomolecules chapter), the percentage of total cellular mass is as follows:
$1$. Proteins: $10-15\%$
$2$. Carbohydrates: $3\%$
$3$. Lipids: $2\%$
$4$. Nucleic acids: $5-7\%$
$5$. Ions: $1\%$
Matching these values with the given columns:
$P$ (Proteins) matches $V$ $(10-15\%)$
$Q$ (Carbohydrates) matches $IV$ $(3\%)$
$R$ (Lipids) matches $I$ $(2\%)$
$S$ (Nucleic acids) matches $II$ $(5-7\%)$
$T$ (Ions) matches $III$ $(1\%)$
Therefore, the correct sequence is $(P-V), (Q-IV), (R-I), (S-II), (T-III)$.

(C) Herbaceous plants are soft-stemmed plants that contain a high percentage of water in their tissues.
Typically, water makes up about $85-90 \%$ of the fresh weight of these plants.
Therefore, the dry matter content, which is the remaining mass after removing all water, is approximately $10-15 \%$ of the total fresh weight.

(D) In living organisms,the elemental composition by weight is dominated by Oxygen $(O)$,followed by Carbon $(C)$,Hydrogen $(H)$,and Nitrogen $(N)$.
According to the data provided in $NCERT$ Biology,the approximate percentage of these elements in the human body is: Oxygen $(O)$ $\approx 65\%$,Carbon $(C)$ $\approx 18.5\%$,Hydrogen $(H)$ $\approx 3.3\%$,and Nitrogen $(N)$ $\approx 3.3\%$.
Therefore,the correct order of abundance is $O > C > H > N$.

(B) The elemental composition of the human body is primarily composed of four major elements: Oxygen,Carbon,Hydrogen,and Nitrogen.
Among these,Oxygen is the most abundant element,accounting for approximately $65\%$ of the total body mass.
Carbon follows at approximately $18.5\%$,Hydrogen at $9.5\%$,and Nitrogen at $3.3\%$.
Therefore,Oxygen is the most abundant element in the human body.

(C) The human body is primarily composed of elements like Oxygen $(O)$,Carbon $(C)$,Hydrogen $(H)$,and Nitrogen $(N)$.
Silicon $(Si)$ is present in the human body in negligible or trace amounts compared to the major elements that constitute biological molecules like proteins,carbohydrates,lipids,and nucleic acids.

(D) The correct answer is $D$ (oxygen).
Oxygen is the most abundant element by weight in the Earth's crust,accounting for approximately $46.6\%$ of its total mass.
Similarly,in the human body,oxygen is the most abundant element,making up about $65\%$ of the total body mass.