Cell theory and What is cell ? Questions in English

(A) $PPLO$ stands for Pleuropneumonia-like organisms,which are the smallest known living cells.
According to the $NCERT$ textbook,the size of $PPLO$ is approximately $0.1 \ \mu m$.
Among the given options,$0.10 \ \mu m$ to $0.15 \ \mu m$ is the most accurate range representing the size of these organisms.

(D) The correct answer is $D$. The egg of an ostrich weighs nearly $1.5 \ kg$ and requires about $50 \ \text{minutes}$ to boil. It is the largest single cell and the largest egg among all living animals.

(A) The nerve cell (neuron) is the longest cell in the human body. These cells can reach lengths of up to $1 \ m$ or more,as they extend from the spinal cord to the extremities of the limbs to transmit electrical impulses throughout the body.

(A) The "Cell theory" was proposed by $M.J. Schleiden$ and $T. Schwann$ in $1838-1839$.
$M.J. Schleiden$ (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.
$Theodore Schwann$ (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.

(C) In the present time,three types of cells are known based on their structural complexity and nuclear organization:
$1$. $Prokaryotic$ cells: These lack a well-defined nucleus and membrane-bound organelles.
$2$. $Mesokaryotic$ cells: These possess a nucleus with permanently condensed chromosomes that lack histones (e.g.,Dinoflagellates).
$3$. $Eukaryotic$ cells: These contain a well-defined nucleus enclosed by a nuclear envelope and membrane-bound organelles.

(D) Matthias Schleiden was a German botanist. In $1838$,he 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.

(B) Rudolf Virchow proposed the theory of 'Omnis cellula-e cellula' in $1855$.
This theory states that new cells arise only from pre-existing cells by the process of cell division.
Therefore, the correct option is $B$.

(C) The book '$Micrographia$' was published in $1665$ by the English scientist $Robert$ $Hooke$.
In this book,he described his observations of thin slices of cork under a primitive microscope.
He coined the term '$cell$' to describe the box-like structures he observed in the cork tissue.

(B) $Robert \ Hooke$ was an English scientist who,in $1665$,examined thin slices of cork under a primitive microscope of his own design.
He observed that the cork appeared to be made of small,box-like compartments,which he termed '$cells$'.
While he did construct a microscope,the most significant scientific contribution associated with his name in biology is the observation and naming of cells from cork tissue.

(D) The study of cell structure and function is known as $Cytology$ or $Cell$ $Biology$.
$Histology$ is the study of tissues.
$Ecology$ is the study of the relationship between organisms and their environment.
$Morphology$ is the study of the external form and structure of organisms.
Therefore,the correct option is $D$.

(A) Robert Hooke,an English scientist,examined thin slices of cork under a primitive microscope in $1665$. He observed that the cork resembled the structure of a honeycomb consisting of many small compartments. He coined the term 'cell' for these compartments. These observations and the corresponding figures were published in his famous book titled 'Micrographia'.

(D) The size of cells is generally very small and cannot be seen with the naked eye.
Most cells range in size from $1 \ \mu m$ to $100 \ \mu m$.
Therefore,the most appropriate and standard unit used to express the size of cells in biology is the micrometer $(\mu m)$,where $1 \ \mu m = 10^{-6} \ m$.

(C) The correct answer is $C$. The term 'Cell' was coined and the structure was discovered by Robert Hooke in $1665$. He observed tiny,box-like compartments in thin sections of cork under a primitive microscope and named them 'cells'.

(D) The cell theory,proposed by $M.J. Schleiden$ and $Theodor Schwann$,states that all living organisms are composed of cells and products of cells.
Later,$Rudolf Virchow$ added that all cells arise from pre-existing cells $(Omnis cellula-e cellula)$.
Therefore,the fundamental concept of cell theory is that cells are the basic structural and functional units of all living organisms.

(D) The correct answer is $(d)$.
Pleuropneumonia-like organisms $(PPLO)$,also known as Mycoplasma,are the smallest known living cells.
Specifically,Mycoplasma gallisepticum has an average size of approximately $0.1$ to $0.3$ $\mu m$.

(B) 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.
Based on these extensive observations,he proposed that the cell is the structural and functional unit of life.
In scientific methodology,when a broad conclusion is drawn from a large number of specific observations,it is termed as a generalization.
Therefore,his idea was a generalization.

(B) Robert Hooke,an English scientist,examined a thin slice of cork under a primitive microscope. He observed that the cork resembled the structure of a honeycomb consisting of many small compartments. He coined the term 'cell' for these compartments in his book 'Micrographia',published in the year $1665$.

(C) The surface area of a cell increases by the square of its radius $(r^2)$,while the volume increases by the cube of its radius $(r^3)$.
As the cell size increases,the volume grows much faster than the surface area.
Therefore,the surface area to volume ratio $(SA/V)$ decreases as the cell size increases.
This is a critical factor that limits the maximum size a cell can reach,as it must maintain an efficient exchange of materials across its membrane.

(A) The term 'protoplasm' was coined by Jan Evangelista Purkinje in $1839$. He used this term to describe the living content of the cell,which includes the cytoplasm and the nucleus.

(C) Protoplasm is the living content of the cell,which includes the cytoplasm and the nucleus. Water is the most abundant component of protoplasm,accounting for about $70-90$% of its total weight. Considering the entire body composition of an organism,the protoplasmic content (living matter) constitutes approximately $95$% of the total body weight,while the remaining $5$% consists of non-living materials like cell walls,extracellular matrix,and skeletal structures.

(B) The correct answer is $B$. Protoplasm is considered the "physical basis of life".
This term was famously coined by Thomas Henry Huxley in $1868$, who described protoplasm as the physical basis of life because it contains all the essential components and chemical processes necessary for life to exist within a cell.

(A) The protoplasm theory, which states that protoplasm is the physical basis of life, was proposed by Max Schultze for animal cells. However, it was $Strasburger$ who specifically established and extended the protoplasm theory to plant cells in $1884$.

(A) The term "physical basis of life" for protoplasm was coined by Thomas Henry Huxley in $1868$. He emphasized that protoplasm is the fundamental substance that constitutes all living organisms and is responsible for all vital activities.

(D) The hierarchy of biological organization starts from atoms and molecules,which are non-living components.
Life,as a functional unit,begins at the level of the $Cell$.
While molecules like amino acids are the building blocks of life,they do not possess the characteristics of life (such as metabolism,reproduction,or homeostasis) until they are organized into a cellular structure.

(A) The unit $nm$ stands for nanometer, which is equal to $10^{-9} \, m$.
To convert $nm$ to $\mathring{A}$, we know that $1 \, \mathring{A} = 10^{-10} \, m$.
Therefore, $1 \, nm = 10^{-9} \, m = 10 \times 10^{-10} \, m = 10 \, \mathring{A}$.
Thus, option $A$ is correct.

(A) The term $Protoplasm$ was coined by $Johannes$ $Evangelista$ $Purkinje$ in $1839$.
$Protoplasm$ is the living content of the cell that is surrounded by the plasma membrane.
It includes the cytoplasm and the nucleus.
Therefore,the correct option is $A$.

(A) The term 'protoplasm' was coined by Jan Evangelista Purkinje in $1839$. It refers to the living content of a cell,which includes the cytoplasm and the nucleus.

(B) The term 'protoplasm' was coined by $Jan$ $Evangelista$ $Purkinje$ in $1839$.
It refers to the living content of the cell,which includes the cytoplasm and the nucleus.
$Felix$ $Dujardin$ originally described this substance as 'sarcode',but $Purkinje$ gave it the name 'protoplasm'.

(B) The term $Protoplasm$ was coined by $Purkinje$ in $1839$. It is a complex, semi-fluid, jelly-like substance that constitutes the living part of the cell. $Huxley$ described $Protoplasm$ as the physical basis of life because all vital activities of the cell, such as metabolism, growth, and reproduction, occur within it. Therefore, option $B$ is the correct answer.

(D) The term "Protoplasm" was coined by $J.E. Purkinje$ in $1839$.
It refers to the living content of the cell, which includes the cytoplasm and the nucleus.
$Robert Hooke$ discovered the cell, while $Schwann$ proposed the cell theory for animals.

(C) The term $Sarcode$ was coined by the French biologist $Felix$ $Dujardin$ in $1835$ to describe the living substance found inside the cells of lower animals (protozoa). Later,this term was replaced by the term $Protoplasm$ by $Purkinje$ in $1839$ and $Von$ $Mohl$ in $1846$.

(A) The cell theory was originally proposed by $Matthias$ $Schleiden$ $(1838)$ and $Theodor$ $Schwann$ $(1839)$.
They described that all plants and animals are composed of cells and products of cells.
However,their theory did not explain how new cells were formed.
In $1855$,$Rudolf$ $Virchow$ first explained that cells divide 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.

(B) The size of cells varies greatly. Mycoplasma are the smallest cells ($0.3 \ \mu m$ in length). Nerve cells are some of the longest cells. The egg of an ostrich is the largest isolated single cell.

(A) The electron microscope was invented by $Max Knoll$ and $Ernst Ruska$ in $1931$. This invention revolutionized cell biology by allowing scientists to view cellular structures at a much higher resolution than light microscopes.

(D) The longest plant cells are the fibers of the plant $Boehmeria \text{ } nivea$, commonly known as $Ramie$ fiber. These fibers can reach lengths of up to $55 \text{ } cm$. While cotton fibers are also plant fibers, they are significantly shorter than $Ramie$ fibers. Vessels and tracheids are components of xylem tissue and are not considered the longest plant cells.

(C) The cell theory was initially proposed by $Schleiden$ and $Schwann$. However,they did not explain how new cells were formed. In $1855$,$Rudolph\, Virchow$ first explained that cells divide and new cells are formed from pre-existing cells $(Omnis\, cellula-e\, cellula)$. This addition completed the cell theory,which is now known as the Modern Cell Theory.

(A) According to the modern cell theory,the cell is the fundamental structural and functional unit of all living organisms. It performs all the essential metabolic and physiological activities required for the survival of the organism. Therefore,a cell exhibits all the functions of a living organism.

(D) The size of cells varies greatly among different organisms.
While most cells are microscopic,some are large enough to be seen with the naked eye.
The largest isolated single cell is the egg of an ostrich.
Therefore,the correct option is $D$.

(B) The concept that "Omnis cellula-e cellula" (new cells arise from pre-existing cells) was proposed by $Rudolf \, Virchow$ in $1855$.
This statement modified the original cell theory, which was initially proposed by $Schleiden$ and $Schwann$, to explain how new cells are formed.

(C) The first person to observe and describe a live cell was $Antony\ van\ Leeuwenhoek$.
He used a simple microscope of his own design to observe bacteria,protozoa,and spermatozoa.
$Robert\ Hooke$ observed dead cork cells and coined the term 'cell',while $M.J.\ Schleiden$ and $Schwann$ are known for proposing the Cell Theory.

(A) The statement "Protoplasm is the physical basis of life" was proposed by $Thomas \text{ } Huxley$ in $1868$.
$Purkinje$ coined the term "protoplasm" for the living content of the cell.
$Lamarck$ is known for his theories on evolution.
$Robert \text{ } Hooke$ discovered the cell in $1665$.

(A) The Cell Theory was formulated by $Matthias$ $Schleiden$ (a German botanist) in $1838$ and $Theodor$ $Schwann$ (a British zoologist) in $1839$.
They collectively proposed that all plants and animals are composed of cells and products of cells.

(C) In $1835$, the French biologist $Felix \text{ } Dujardin$ observed the living substance inside the cell of $Foraminifera$ (a type of protozoa). He named this jelly-like living substance as '$Sarcode$'. Later, $Purkinje$ coined the term '$Protoplasm$' for this same living substance in $1839$.

(D) The study of the structure,function,and behavior of cells is known as $Cell \ Biology$ (also referred to as $Cytology$).
$Oncology$ is the study of cancer.
$Cytogenetics$ is the study of the structure and function of the cell,especially the chromosomes.
$Molecular \ Biology$ is the study of biological activity at the molecular level.

(A) The term "cell" was coined by $Robert\, Hook$ in $1665$. He observed thin slices of cork under a primitive microscope and noticed that they appeared as a honeycomb-like structure consisting of many small compartments, which he named "cells" (Latin for 'little room').

(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.

(C) The cell was first discovered by $Robert\, Hooke$ in $1665$. He observed thin slices of cork under a primitive microscope and noticed small,box-like structures which he termed as 'cells' (Latin for 'little room').

(C) The $Phase$ $contrast$ microscope is specifically designed to visualize transparent specimens,such as living cells,without the need for staining.
It works by converting phase shifts in light passing through a transparent specimen into brightness changes in the image.
$SEM$ ($Scanning$ $Electron$ $Microscope$) and $TEM$ ($Transmission$ $Electron$ $Microscope$) require the specimen to be fixed,dehydrated,and often coated with heavy metals,which kills the cell.
Fluorescent microscopy typically requires the use of fluorescent dyes or proteins to label specific structures,which may not be suitable for observing a cell in its completely natural,unstained state.

(B) In $1665$,$Robert\, Hooke$ examined a thin slice of cork under a primitive microscope and observed box-like structures which he termed as 'cells'.
Therefore,he was the first person to observe and describe cells.

(C) The term $Protoplasm$ was coined by $Purkinje$ in $1839$. It is a complex,semi-fluid,jelly-like substance that constitutes the living part of the cell. $Huxley$ described $Protoplasm$ as the physical basis of life because all vital activities of the cell,such as metabolism,growth,and reproduction,occur within it.