Cell theory and What is cell ? Questions in English

(C) The correct matches are as follows:
$A$. Matthias Schleiden was a German botanist $(A-2)$.
$B$. Theodor Schwann was a British Zoologist $(B-4)$.
$C$. Robert Brown discovered the nucleus $(C-1)$.
$D$. Antonie van Leeuwenhoek was the first to describe a living cell $(D-3)$.
Therefore,the correct sequence is $(A-2), (B-4), (C-1), (D-3)$.

(C) The cell theory was formulated by Matthias Schleiden $(1838)$ and Theodor Schwann $(1839)$.
They proposed that all living organisms are composed of cells and products of cells.
They also stated that the cell is the structural and functional unit of living organisms.
However,their theory failed to explain how new cells are formed.
This was later explained by Rudolf Virchow in $1855$ with the concept of 'Omnis cellula-e cellula',which states that all cells arise from pre-existing cells.

(A) To arrange the cells in ascending order of size,we compare their approximate dimensions:
$1$. $Mycoplasma$ are the smallest known cells,measuring about $0.3 \ \mu m$ in length.
$2$. Typical $Bacteria$ range from $3$ to $5 \ \mu m$ in length.
$3$. Human $RBCs$ are about $7.0 \ \mu m$ in diameter.
$4$. The egg of an Ostrich is the largest isolated single cell,which is significantly larger than the others.
Therefore,the correct ascending order is $Mycoplasma (II) < Bacteria (III) < Human \ RBCs (IV) < Ostrich \ egg (I)$.
Thus,the correct sequence is $II-III-IV-I$.

(D) The biological organization of living organisms begins at the sub-microscopic molecular level. Atoms combine to form molecules,which then form macromolecules,organelles,and eventually cells. Therefore,the fundamental basis of life's organization starts at the sub-microscopic molecular level.

(C) The $\mathring{A}$ is a unit of length equal to $10^{-10} \, m$.
One micrometer $(\mu m)$ is equal to $10^{-6} \, m$.
To convert $\mathring{A}$ to micrometers:
$1 \, \mathring{A} = 10^{-10} \, m = 10^{-4} \times 10^{-6} \, m = 10^{-4} \, \mu m$.
$10^{-4} \, \mu m = 0.0001 \, \mu m$.
Therefore, $1 \, \mathring{A} = 0.0001 \, \mu m$.

(B) $Matthias$ $Schleiden$ (a German botanist) in $1838$ and $Theodor$ $Schwann$ (a British zoologist) in $1839$ independently formulated the $Cell$ $Theory$.
$Schleiden$ observed that all plants are composed of cells,and $Schwann$ reported that animal cells have a thin outer layer (plasma membrane) and plant cells have a cell wall.
Together,they proposed that the bodies of plants and animals are composed of cells and products of cells.
Therefore,their names are associated with the $Cell$ $Theory$.

(A) The modern Cell Theory (Cell Principle) states that all living organisms are composed of cells and products of cells. Furthermore,all cells arise from pre-existing cells ($Omnis$ $cellula-e$ $cellula$). The discovery of organelles like mitochondria and chloroplasts,which contain their own $DNA$ and can replicate independently,supports the idea that cells are the fundamental units of life and that they possess the machinery for reproduction and self-maintenance. Thus,the theory has been refined over time to include these observations.

(D) The primary advantage of an electron microscope over a light microscope is its significantly higher resolving power.
Resolving power is the ability to distinguish between two closely placed objects.
$A$ light microscope uses visible light (photons) which has a relatively long wavelength,limiting its resolution to about $200-300 \ nm$.
An electron microscope uses a beam of electrons,which has a much shorter wavelength than visible light,allowing it to achieve a resolution of about $0.1-0.2 \ nm$.
This high resolution allows scientists to observe fine details of cellular organelles that are invisible under a light microscope.

(A) The concept of "Omnis cellula-e cellula" means that all cells arise from pre-existing cells.
This concept was first proposed by Rudolf Virchow in $1855$.
He modified the hypothesis of cell theory proposed by Schleiden and Schwann to give it a final shape.

(A) The cell is the basic structural and functional unit of living organisms.
In $1855$, Rudolf Virchow explained that all cells arise from pre-existing cells through cell division, a concept he summarized as "Omnis-cellula-e-cellula".
Robert Hooke was the first to discover the basic units of life and termed them "cells".
Anton van Leeuwenhoek was the first to observe living unicellular organisms, including bacteria.
Robert Brown described the nucleus as a characteristic spherical body found in plant cells.

(A) The Assertion states that organisms are made up of cells,which is a fundamental principle of the Cell Theory.
The Reason states that cells are the structural units of living organisms and maintain a steady chemical composition within their boundaries (homeostasis).
Since the structural organization of an organism is derived from its cellular composition,the Reason correctly explains why organisms are made up of cells.

(A) The statement $(a)$ is incorrect because Robert Brown did not discover the cell; he discovered the nucleus in $1831$.
Robert Hooke discovered the cell in $1665$ while examining a thin slice of cork.
Schleiden and Schwann proposed the cell theory,which states that all living organisms are composed of cells and products of cells.
Rudolf Virchow later expanded the cell theory by explaining that all cells arise from pre-existing cells (Omnis cellula-e cellula).
Unicellular organisms are indeed capable of independent existence and perform all essential life functions within a single cell.

(B) According to the cell theory,specifically the concept of $Omnis$ $cellula-e$ $cellula$ proposed by Rudolf Virchow,new cells arise only from pre-existing cells through the process of cell division.
This principle states that cells do not originate from abiotic materials or spontaneous generation,but rather from the division of already existing living cells.

(N/A) Multicellular organisms are composed of millions to trillions of cells.
Each cell or group of cells is specialized to perform a specific function.
Cells that are specialized to perform similar functions are grouped together to form tissues.
Consequently,a particular physiological function is carried out by a specific group of cells at a definite location within the body.
Since different groups of cells perform different tasks,this organization is referred to as the division of labour in multicellular organisms.

(N/A) Cells are the fundamental structural and functional units of all living organisms.
They are capable of performing all essential biochemical processes required for survival,such as respiration,digestion,and excretion.
Since all metabolic activities occur within the cell to maintain life,the cell is considered the functional unit of life.
Furthermore,because all organisms are composed of one or more cells,it is also defined as the structural unit of life.

(C) $\Rightarrow$ $A$ cell is the fundamental structural and functional unit of all living organisms.
$\Rightarrow$ All physiological and biochemical processes within an organism depend on the structure, type, and number of cells present. Thus, the cell is the basic unit of life.
$\Rightarrow$ The life of every multicellular organism begins from a single-celled structure called the $Zygote$. New cells are generated through the repeated division of this $Zygote$.
$\Rightarrow$ These cells subsequently differentiate to form tissues, organs, organ systems, and eventually the entire body of the organism.
$\Rightarrow$ $Totipotency$: It is the ability of a single cell to divide and produce all the differentiated cells required to form a complete organism.
$\Rightarrow$ Historical Context:
$\Rightarrow$ $Anton$ $van$ $Leeuwenhoek$ was the first to observe and describe a living cell.
$\Rightarrow$ $Robert$ $Hooke$ $(1665)$ observed a thin slice of cork under a microscope. He described the honeycomb-like structures as 'cells'.
$\Rightarrow$ $Robert$ $Brown$ $(1831)$ discovered the nucleus. The subsequent invention and improvement of the microscope, leading to the electron microscope, revealed the complex structural details of the cell.

(N/A) $\Rightarrow$ In $1838$,Matthias Schleiden and Theodore Schwann presented the cell theory.
$\Rightarrow$ Matthias Schleiden was a German botanist. He observed that all plants are composed of different kinds of cells which form the tissues of the plant.
$\Rightarrow$ $A$ British zoologist,Theodore Schwann,studied different types of animals and reported that cells had a thin outer layer,which is now known as the plasma membrane. He also concluded that the presence of a cell wall is a unique character of plant cells.
$\Rightarrow$ Both scientists together formulated the cell theory,which stated:
$(a)$ All living organisms are composed of cells and their products.
$(b)$ The cell is the structural and functional unit of all living organisms.
$\Rightarrow$ However,this theory did not explain how new cells were formed.
$\Rightarrow$ Rudolf Virchow (in $1855$) first explained that cells divide and new cells are formed from pre-existing cells (Omnis cellula-e cellula).
$\Rightarrow$ He modified the hypothesis of Schleiden and Schwann to give the cell theory its final shape:
$(i)$ All living organisms are composed of cells and products of cells.
$(ii)$ All cells arise from pre-existing cells.

(C) The cell theory was formulated by Matthias Schleiden and Theodor Schwann.
$1$. It states that all living organisms are composed of cells and products of cells.
$2$. Later,Rudolf Virchow added the concept of 'Omnis cellula-e cellula',which means all cells arise from pre-existing cells.
Therefore,both statements $A$ and $B$ are correct components of the cell theory.

(B) In $1665$,the English scientist Robert Hooke examined a thin slice of cork under a primitive microscope.
He observed that the cork was composed of small,box-like compartments which he termed 'cells' (Latin for 'little rooms').
This was the first time that the term 'cell' was used in a biological context,marking the discovery of the cell.

(B) In $1838$,Matthias Schleiden,a German botanist,examined a large number of plants and observed that all plants are composed of different kinds of cells which form the tissues of the plant.
At about the same time $(1839)$,Theodore Schwann,a British zoologist,studied different types of animal cells and reported that cells had a thin outer layer which is today known as the 'plasma membrane'.
Together,Schleiden and Schwann formulated the 'Cell Theory',which states that all living organisms are composed of cells and products of cells.

(B) Rudolf Virchow $(1855)$ first explained that cells divide and new cells are formed from pre-existing cells.
This concept is famously known as 'Omnis cellula-e cellula'.
He modified the hypothesis of the cell theory proposed by Schleiden and Schwann to give it a final shape.

(N/A) $\Rightarrow$ In $1838$,Matthias Schleiden and Theodore Schwann presented the cell theory.
$\Rightarrow$ Matthias Schleiden was a German botanist. He observed that all plants are composed of different kinds of cells which form the tissues of the plant.
$\Rightarrow$ $A$ British zoologist,Theodore Schwann,studied different types of animals and reported that cells had a thin outer layer,which is now known as the plasma membrane. He also concluded that the presence of a cell wall is a unique character of plant cells.
$\Rightarrow$ Together,these scientists formulated the cell theory,which states:
$(a)$ All living organisms are composed of cells and products of cells.
$(b)$ The cell is the structural and functional unit of all living organisms.
$\Rightarrow$ However,this theory did not explain how new cells were formed.
$\Rightarrow$ Rudolf Virchow (in $1855$) first explained that cells divide and new cells are formed from pre-existing cells (Omnis cellula-e cellula).
$\Rightarrow$ He modified the hypothesis of Schleiden and Schwann to give the cell theory its final shape:
$(i)$ All living organisms are composed of cells and products of cells.
$(ii)$ All cells arise from pre-existing cells.

(N/A) cell is defined as the fundamental structural and functional unit of all living organisms. To be considered a living cell,it must possess the following attributes:
$1$. Cell Membrane: $A$ semi-permeable boundary made of a phospholipid bilayer that regulates the entry and exit of substances.
$2$. Cytoplasm: $A$ semi-fluid matrix that serves as the site for various metabolic reactions essential for life.
$3$. Genetic Material: Presence of $DNA$ (or $RNA$ in some cases) that stores and transmits hereditary information,enabling growth,development,and reproduction.
$4$. Metabolic Machinery: Presence of organelles like ribosomes for protein synthesis,mitochondria for energy production $(ATP)$,and enzymes for biochemical pathways.
$5$. Division of Labour: Different cell organelles perform specific functions (e.g.,Golgi bodies for packaging,Endoplasmic Reticulum for synthesis,Lysosomes for digestion) to maintain cellular homeostasis.
$6$. Ability to Reproduce: The capacity to divide and produce new cells,which is the basis for the continuity of life.

(N/A) Rudolf Virchow $(1855)$: He modified the hypothesis of cell theory by explaining that cells divide and new cells are formed from pre-existing cells,famously stated as 'Omnis cellula-e cellula'.
$(b)$ Schleiden and Schwann: Matthias Schleiden $(1838)$ observed that all plants are composed of different kinds of cells which form the tissues of the plant. Theodor Schwann $(1839)$ reported that animal cells had a thin outer layer which is today known as the 'plasma membrane'. Together,they formulated the cell theory,which states that all living organisms are composed of cells and products of cells.

(B) $\Rightarrow$ Rudolf Virchow (in $1855$) first explained that cells divide and new cells are formed from pre-existing cells.
$\Rightarrow$ He modified the hypothesis of Schleiden and Schwann to give the cell theory its final shape.
$\Rightarrow$ The two main postulates of the cell theory are:
$(i)$ All living organisms are composed of cells and products of cells.
$(ii)$ All cells arise from pre-existing cells (Omnis cellula-e cellula).

(A) The size of $PPLO$ (Pleuropneumonia-like organism),also known as Mycoplasma,is approximately $0.1 \; \mu m$.
It is recognized as the smallest known living cell capable of independent existence.

(A) The cell theory provided a unified framework for understanding the biological structure of all living organisms by establishing that the cell is the fundamental unit of life.
By defining the cell as the basic unit,it directed scientific research toward investigating the internal mechanisms and functional processes occurring within cells.
While microscopes were already in use before $1839$,the cell theory gave a specific purpose to microscopic studies,leading to advancements in cell biology.

$(A)$ The correct matches are as follows:
$A$. Leeuwenhoek: He was the first to observe and describe a living cell $(I)$.
$B$. Robert Brown: He discovered the nucleus in the cell $(III)$.
$C$. Schleiden: He concluded that all plants are composed of different kinds of cells $(IV)$.
$D$. Schwann: He reported that the presence of a cell wall is a unique character of plant cells $(II)$.
Therefore, the correct sequence is $A-I, B-III, C-IV, D-II$.

(D) Theodor Schwann,a British Zoologist,studied animal cells and reported that cells had a thin outer layer which is today known as the 'plasma membrane'.
He also concluded,based on his studies on plant tissues,that the presence of a cell wall is a unique character of the plant cells.
Schwann proposed the hypothesis that the bodies of animals and plants are composed of cells and products of cells.
Therefore,all the given statements $(i)$,$(ii)$,and $(iii)$ are related to Schwann.

(A) The concept of "Omnis cellula-e cellula" was proposed by Rudolf Virchow in $1855$. This statement is a fundamental part of the Cell Theory, which explains that new cells are formed by the division of pre-existing cells (Cell Lineage theory).

(D) The size of a typical bacterium ranges from $3 \; \mu m$ to $5 \; \mu m$.
Mycoplasmas are the smallest known cells,with a length of approximately $0.3 \; \mu m$.
Ostrich egg is the largest isolated single cell.
Therefore,the correct answer is $D$.

(C) cell is defined as the fundamental,structural,and functional unit of all living organisms because anything less than a complete structure of a cell does not ensure independent living. This means that for an organism to exist independently,it must possess at least one complete cell.

(C) Biological systems exhibit emergent properties. The properties of organelles are not present in the molecular constituents of the organelle but arise as a result of interactions among the molecular components comprising the organelle. Similarly,the properties of cellular organelles are present in the molecular constituents of the organelle but arise as a result of interactions among the molecular components comprising the organelle. This principle of emergent properties applies to all levels of biological organization.

(A) The term 'cell' was first coined by the English scientist $Robert \ Hooke$ in $1665$. He observed thin slices of cork under a primitive microscope and noticed small,box-like compartments that resembled the cells of a monastery,which he named 'cells'.

(B) Unicellular organisms are capable of independent existence because they perform all essential functions of life within a single cell.
Option $A$ is correct as they exist independently.
Option $C$ is correct as the cell is the fundamental unit of life.
Option $D$ is correct as the cell theory states that nothing less than a complete cell can ensure independent living.
Option $B$ is incorrect because unicellular organisms are fully capable of performing all essential life functions like respiration,excretion,and reproduction within their single cell.

(C) Antonie van Leeuwenhoek was the first scientist to observe and describe living cells,such as bacteria,protozoa,and spermatozoa,using a self-designed microscope. Robert Hooke is credited with discovering the cell in $1665$,but he observed dead cork cells. Robert Brown discovered the nucleus,and Fleming is known for the discovery of penicillin.

(C) The $Cell$ $Theory$ states that all living organisms are composed of cells and that all cells arise from pre-existing cells.
Viruses are considered to be at the boundary between living and non-living things.
They lack a cellular structure,as they do not possess a cell membrane,cytoplasm,or organelles like ribosomes.
They consist only of genetic material ($DNA$ or $RNA$) enclosed within a protein coat (capsid).
Because they are acellular,the $Cell$ $Theory$ is not applicable to viruses.

(C) In $1839$,Theodor Schwann,a British Zoologist,studied different types of animal cells and reported that cells had a thin outer layer which is today known as the 'plasma membrane'.
He also concluded,based on his studies on plant tissues,that the presence of a cell wall is a unique character of the plant cells.
On the basis of this,Schwann proposed the hypothesis that the bodies of animals and plants are composed of cells and products of cells.

(B) In $1838$,Matthias Schleiden,a German botanist,examined a large number of plants and observed that all plants are composed of different kinds of cells which form the tissues of the plant. Thus,he proposed the cell theory for plants.

(D) The statement '$Omnis cellula-e cellula$' was proposed by Rudolf Virchow in $1855$.
This Latin phrase means that all cells arise from pre-existing cells.
This concept refined the cell theory,which was originally proposed by Matthias Schleiden and Theodor Schwann,by explaining how new cells are formed.

(C) The phrase '$Omnis$ $cellula-e-cellula$' was proposed by $Rudolf$ $Virchow$ in $1855$.
It translates to '$All$ $cells$ $arise$ $from$ $pre-existing$ $cells$'.
This concept is a fundamental part of the modern Cell Theory,which explains that new cells are formed by the division of previously existing cells.

(C) $1$. Matthias Schleiden $(1838)$ examined a large number of plants and observed that all plants are composed of different kinds of cells which form the tissues of the plant. Thus,$P-I$.
$2$. Theodor Schwann $(1839)$ reported that animal cells had a thin outer layer which is today known as the 'plasma membrane'. He also concluded,based on his studies on plant tissues,that the presence of cell wall is a unique character of the plant cells. Thus,$Q-III$.
$3$. Rudolf Virchow $(1855)$ first explained that cells divided and new cells are formed from pre-existing cells ($Omnis$ $cellula-e$ $cellula$). He modified the hypothesis of Schleiden and Schwann to give the cell theory a final shape. Thus,$R-II$.
Therefore,the correct matching is $(P-I), (Q-III), (R-II)$.

(A) The sizes of various cells are as follows:
$1$. Mycoplasma is the smallest known cell,with a length of about $0.3 \ \mu m$ $(P-III)$.
$2$. Bacteria typically range from $3-5 \ \mu m$ in length $(Q-II)$.
$3$. Human Red Blood Cells (RBCs) are approximately $7 \ \mu m$ in diameter $(R-I)$.
Therefore,the correct matching is $(P-III), (Q-II), (R-I)$.

(C) The smallest cells are $Mycoplasma$ (also known as $PPLO$ - Pleuro Pneumonia Like Organisms), which are about $0.3 \, \mu m$ in length.
The largest isolated single cell is the egg of an ostrich.
The longest cells in the human body are the neurons (nerve cells).
Therefore, $P = Mycoplasma$, $Q = \text{Ostrich egg}$, and $R = \text{Neuron}$.

(C) $A.$ Mycoplasma are indeed the smallest known cells, and their length is approximately $0.3 \mu m$. This statement is correct.
$B.$ Typical bacteria range in size from $3$ to $5 \mu m$. This statement is correct.
$C.$ Human red blood cells (RBCs) have a diameter of about $7.0 \mu m$, not a radius. Therefore, the statement claiming they are $7.0 \mu m$ in radius is incorrect.
Since $A$ and $B$ are correct and $C$ is incorrect, the statement "Only $C$ is incorrect" is the correct choice.

(D) The cell theory was proposed by Matthias Schleiden and Theodor Schwann.
In $1838$,Matthias Schleiden,a German botanist,examined a large number of plants and observed that all plants are composed of different kinds of cells which form the tissues of the plant.
In $1839$,Theodor Schwann,a British zoologist,reported that cells had a thin outer layer which is today known as the 'plasma membrane'.
Together,they formulated the cell theory,which states that all living organisms are composed of cells and products of cells.

(B) The correct option is $B$.
In $1838$, $Matthias \ Schleiden$, a German botanist, examined a large number of plants and observed that all plants are composed of different kinds of cells which form the tissues of the plant.
At about the same time $(1839)$, $Theodor \ Schwann$, a British zoologist, reported that cells had a thin outer layer which is today known as the '$plasma \ membrane$'.
He also concluded, based on his studies on plant tissues, that the presence of cell wall is a unique character of the plant cells.
On the basis of this, $Schwann$ proposed the hypothesis that the bodies of animals and plants are composed of cells and products of cells.
Together, $Schleiden$ and $Schwann$ formulated the cell theory.