Mix Example-Cell: The Unit of Life Questions in English

(D) The primary distinction between prokaryotic and eukaryotic cells is the presence of a well-defined,membrane-bound nucleus in eukaryotes,which is absent in prokaryotes.
Additionally,eukaryotic cells contain membrane-bound cell organelles (such as mitochondria,endoplasmic reticulum,and Golgi apparatus) which are absent in prokaryotic cells.
Prokaryotes possess a single circular chromosome (nucleoid),whereas eukaryotes have multiple linear chromosomes organized within the nucleus.
Therefore,all the mentioned features contribute to the fundamental differences between these two cell types.

(D) The volume of a $1 \ ml$ pipette is $1 \ cm^3 = 10^{-6} \ m^3$.
Assuming the diameter of a typical bacterium is approximately $1 \ \mu m$ $(10^{-6} \ m)$,the volume of one bacterium is roughly $(10^{-6} \ m)^3 = 10^{-18} \ m^3$.
To find the number of bacteria that can fit in the pipette,we divide the total volume by the volume of one bacterium:
Number of bacteria $= \frac{10^{-6} \ m^3}{10^{-18} \ m^3} = 10^{12}$ bacteria.
Thus,a $1 \ ml$ pipette can contain about $10^{12}$ bacteria.

(C) Desmosomes are specialized intercellular junctions that provide strong adhesion between cells.
These junctions are associated with intermediate filaments of the cytoskeleton,which are known as tonofilaments.
When these tonofilaments aggregate or bundle together,they are referred to as tonofibrils.
Since both terms are used to describe these cytoskeletal structures associated with desmosomes,the correct answer is both $(a)$ and $(b)$.

(C) Phagocytosis is the process by which a cell engulfs solid particles,such as bacteria or dead cells.
This process was first discovered and described by Elie Metchnikoff.
He also coined the term 'phagocytosis' to describe this cellular mechanism of defense.

(D) cell organelle is a specialized subunit within a cell that has a specific function and is usually enclosed within its own lipid bilayer membrane.
$A$,$B$,and $C$ (Mitochondria,Ribosome,and Golgi complex) are recognized as cell organelles. Although ribosomes are non-membrane-bound,they are universally classified as organelles.
$D$ (Microsome) is not a true cell organelle; it is an artifact formed from the fragmentation of the endoplasmic reticulum during cell homogenization and centrifugation.

(A) The relative sizes of biological and chemical entities are as follows:
$1$. $Cell$: Typically ranges from $10-100 \ \mu m$.
$2$. $Nucleus$: Typically ranges from $5-10 \ \mu m$.
$3$. $Chromosome$: Typically ranges from $1-5 \ \mu m$.
$4$. $Water \ molecule$ $(H_2O)$: Approximately $0.3 \ nm$.
$5$. $Oxygen \ atom$ $(O)$: Approximately $0.15 \ nm$.
Therefore,the correct descending order of size is: $Cell > Nucleus > Chromosome > Water \ molecule > Oxygen \ atom$.

(D) The term $Cytosomes$ refers to the specialized structures or bodies found within the cytoplasm of a cell.
In prokaryotic organisms like $Bacteria$,the cytoplasm contains various inclusions and structures often referred to as cytosomes.
In eukaryotic cells,organelles such as $Chloroplasts$ and $Mitochondria$ contain their own internal compartments and structures that are sometimes classified under this broad terminology.
Therefore,$Cytosomes$ can be associated with all the mentioned structures depending on the biological context.

(B) The correct answer is $B$.
Plasmodesmata are microscopic channels which traverse the cell walls of plant cells and some algal cells,enabling transport and communication between them.
The membrane surrounding the vacuole in plants is known as the $tonoplast$,not plasmodesmata.
Therefore,the pair in option $B$ is incorrectly matched.

(D) Prokaryotic cells are characterized by the absence of a well-defined nucleus,which means they lack a nucleolus.
They also lack membrane-bound organelles such as mitochondria,endoplasmic reticulum,Golgi apparatus,and lysosomes.
Additionally,prokaryotes do not possess centrioles,which are typically found in eukaryotic cells for spindle formation during cell division.
Therefore,all the listed structures are absent in prokaryotic cells.

(D) mature plant cell is characterized by the presence of a rigid cell wall,a large central vacuole that occupies most of the cell volume,and the protoplasm (which includes the cytoplasm and the nucleus).
Therefore,all three components—protoplasm,cell wall,and vacuole—are present in a mature plant cell.

(A) Both plant and animal cells are eukaryotic cells and share several common organelles.
$1$. The $\text{Cell membrane}$ (plasma membrane) is present in all cells to regulate the movement of substances.
$2$. The $\text{Nucleolus}$ is a dense region within the nucleus where ribosomal $RNA$ synthesis occurs, found in both cell types.
$3$. In contrast, the $\text{Cell wall}$ and $\text{Chloroplast}$ are specific to plant cells and are not found in animal cells.
Therefore, the correct pair is $\text{Cell membrane}$ and $\text{Nucleolus}$.

(A) Pinocytosis, often referred to as $ \text{'cell drinking'} $, is the process by which cells ingest extracellular fluid and dissolved solutes by forming small vesicles.
Phagocytosis, often referred to as $ \text{'cell eating'} $, is the process by which cells engulf large solid particles, such as food material, bacteria, or other foreign bodies, into large vesicles called phagosomes.
Therefore, the fundamental difference lies in the nature of the material ingested: pinocytosis involves fluid substances, while phagocytosis involves solid food material or foreign bodies.

(B) Pinocytosis,often referred to as 'cell drinking',is a process of endocytosis where cells ingest extracellular fluid and dissolved solutes by forming small vesicles at the cell membrane.
Phagocytosis is the process of 'cell eating' where the cell engulfs large solid particles.
Cyclosis refers to the streaming movement of cytoplasm within a cell.
Osmosis is the movement of water molecules across a semi-permeable membrane from a region of higher water potential to a region of lower water potential.

(A) Ephagy (also known as defecation or exocytosis) is the process by which cells remove metabolic waste products or undigested materials from the cytoplasm to the extracellular environment. This process involves the fusion of a vesicle containing waste materials with the plasma membrane,followed by the release of its contents outside the cell. Therefore,the removal of metabolic waste by exocytosis is the correct definition.

(D) Organelles are classified based on the number of membranes surrounding them.
$1$. Double membrane-bound organelles include the nucleus,mitochondria,and chloroplasts.
$2$. Single membrane-bound organelles include lysosomes,vacuoles,Golgi apparatus,endoplasmic reticulum,sphaerosomes,and glyoxysomes.
$3$. Non-membrane-bound organelles include ribosomes and centrosomes.
Since lysosomes,sphaerosomes,and glyoxysomes are all single membrane-bound structures,the correct answer is $D$.

(D) In eukaryotic cells, certain organelles lack a lipid bilayer membrane.
$1$. Centrioles are non-membranous structures involved in cell division.
$2$. Ribosomes are protein-synthesizing machinery composed of RNA and proteins, lacking a membrane.
$3$. Nucleolus is a dense, spherical structure within the nucleus that is also non-membranous.
Therefore, all the listed options are correct.

(D) The fundamental unit of life is the cell,which consists of a living content known as protoplasm.
Protoplasm includes the cytoplasm and the nucleus,which are present in both plant and animal cells.
In contrast,the cell wall and chloroplast are specific to plant cells,and while Golgi bodies are present in both,the most fundamental shared living component is the protoplasm.

(B) The $pH$ of the protoplasm is slightly acidic to neutral,typically ranging between $6.7$ and $7.2$.
Among the given options,$6.8$ is the most accurate value representing the normal $pH$ of the protoplasm.

(A) Cyclosis,also known as cytoplasmic streaming,is the directed flow of cytosol (the liquid component of the cytoplasm) and organelles around the large central vacuole of a plant cell or other cells.
This movement is driven by the interaction between actin filaments and myosin motor proteins.
It facilitates the distribution of nutrients,proteins,and organelles within the cell.
Therefore,the circular movement of cytoplasm inside the cell is defined as cyclosis.

(B) The streaming movement of protoplasm,also known as cyclosis,is most clearly observed in the staminal hairs of $Tradescantia$.
These cells are large,transparent,and contain a thin layer of cytoplasm that allows for the easy visualization of organelle movement under a light microscope.
Other options like onion peel or pith cells are often used for studying cell walls or general structure,but they are not as effective for observing active cytoplasmic streaming as the staminal hairs of $Tradescantia$.

(A) The cytoplasm of an amoeboid cell is differentiated into two regions: the outer, more viscous, gel-like layer known as the $Ectoplasm$ (or plasma gel) and the inner, more fluid, sol-like region known as the $Endoplasm$ (or plasma sol). Therefore, "plasma gel" refers to the $Ectoplasm$.

(D) Protoplasm is a complex,living substance that forms the physical basis of life.
It is not a simple solution,suspension,or emulsion.
Instead,it is a $polyphasic$ $colloidal$ $system$ consisting of various organic and inorganic substances dispersed in an aqueous medium.
This colloidal nature allows for the dynamic biochemical reactions necessary for cellular functions.

(B) Protein synthesis in animal cells occurs primarily in the cytoplasm,where ribosomes translate mRNA into polypeptide chains.
Additionally,mitochondria contain their own $70S$ ribosomes,which are capable of synthesizing specific mitochondrial proteins encoded by the mitochondrial genome.
Therefore,protein synthesis occurs in both the cytoplasm and the mitochondria.

(B) Plant cells are distinct from animal cells primarily due to the presence of a rigid cell wall,which provides structural support,and the presence of chlorophyll,which is contained within chloroplasts and is essential for photosynthesis. Animal cells lack both a cell wall and chlorophyll. Therefore,option $B$ is the correct answer.

(D) Plastids are specialized organelles that are characteristic features of photosynthetic eukaryotes (such as plants and algae).
Blue-green algae (Cyanobacteria) and bacteria are prokaryotic organisms and do not possess membrane-bound organelles like plastids.
Fungi are heterotrophic (saprophytic) eukaryotes and also lack plastids because they do not perform photosynthesis.
Therefore,plastids are absent in all of the groups mentioned above.

(D) The statement 'All living plant cells contain chlorophyll' is incorrect.
Chlorophyll is a green pigment primarily found in chloroplasts,which are specialized organelles present in photosynthetic cells.
Many plant cells,such as those in roots,tubers,and certain storage tissues,are living but do not contain chlorophyll or chloroplasts as they do not perform photosynthesis.

(C) The $GERL$ system stands for $G$olgi apparatus, $E$ndoplasmic $R$eticulum, and $L$ysosomes. This concept describes the functional and structural continuity between the $E$ndoplasmic $R$eticulum, the $G$olgi complex, and the formation of $L$ysosomes. It was proposed by $Alex Novikoff$ in $1964$.

(C) The correct pair is $C$.
During the telophase stage of cell division,the fragments of the endoplasmic reticulum $(ER)$ associate with the chromosomes to form the new nuclear envelope.
Microsomes are vesicles derived from the $ER$ and are not involved in photosynthesis.
Lysosomes contain hydrolytic enzymes for digestion,not for amino acid synthesis.
Centrosomes are involved in spindle fiber formation,not in providing digestive enzymes.

(A) The correct answer is $A$. Lysosomes are single-membraned organelles,not double-membraned. They are small vesicles formed by the budding off from the trans-face of the Golgi apparatus and contain various hydrolytic enzymes (acid hydrolases) that are active at acidic $pH$. The other statements are correct: Endoplasmic reticulum is a network of tubules involved in transport and synthesis; Leucoplasts are plastids that lack pigments and contain $DNA$ and ribosomes; Sphaerosomes are single-membrane-bound organelles involved in lipid metabolism.

(B) The correct matching is as follows:
$a$. Lysosome: These are membrane-bound organelles containing hydrolytic enzymes,which correspond to $4$.
$b$. Mycoplasma: These are the smallest known living cells that lack a cell wall,which correspond to $1$.
$c$. Thylakoid: These are flattened sac-like structures found inside the chloroplast,which correspond to $3$.
$d$. Bacteriophage: These are viruses that infect bacteria,which correspond to $2$.
Therefore,the correct sequence is $a-4, b-1, c-3, d-2$.

(D) The cell organelles that lack a surrounding membrane are known as non-membranous organelles.
Ribosomes are composed of $RNA$ and proteins and are not enclosed by a membrane.
Centrioles are cylindrical structures composed of microtubules and also lack a membrane.
Therefore,both ribosomes and centrioles are non-membranous cell organelles.

(A) Sphaerosomes are small,spherical,membrane-bound organelles found in plant cells.
They are primarily involved in the storage and synthesis of lipids.
They contain a high concentration of triglycerides (lipids) and the hydrolytic enzyme lipase,which is responsible for the breakdown of these stored fats.

(D) Peroxisomes are small,membrane-bound organelles found in the cytoplasm of eukaryotic cells.
They are primarily involved in metabolic processes,specifically the breakdown of very-long-chain fatty acids and the detoxification of harmful substances.
Peroxisomes are rich in oxidative enzymes,such as catalase and urate oxidase,which produce hydrogen peroxide $(H_2O_2)$ as a byproduct of their metabolic reactions.
They also contain glycolic acid oxidase,which oxidizes glycolic acid (a product of photorespiration) to glyoxylic acid.
Therefore,the correct option is $D$.

(D) Peroxisomes are membrane-bound organelles that contain various oxidative enzymes.
Common enzymes found in peroxisomes include $D$-amino acid oxidase,$L$-hydroxy acid oxidase,and urate oxidase,which are involved in the breakdown of specific substrates and the detoxification of hydrogen peroxide.
Amylase is a digestive enzyme primarily found in saliva and the pancreas,responsible for the hydrolysis of starch into sugars.
Therefore,amylase is not present in peroxisomes.

(C) $1$. Microtubules are the structural components of cilia and flagella,forming the $9+2$ arrangement. This statement is correct.
$2$. Centrioles are involved in spindle fiber formation during cell division,not in storing hydrolytic enzymes. Lysosomes store hydrolytic enzymes. This statement is false.
$3$. Peroxisomes are involved in photorespiration and the breakdown of hydrogen peroxide,not in storing oil,protein,or starch. Leucoplasts (Amyloplasts,Elaioplasts,Aleuroplasts) are responsible for storing these substances. This statement is false.
Therefore,only statement $1$ is correct.

(D) $DNA$ (Deoxyribonucleic acid) is the genetic material found in eukaryotic cells.
It is primarily located in the nucleus of the cell.
However,$DNA$ is also present in semi-autonomous organelles such as mitochondria and chloroplasts,which contain their own circular $DNA$ molecules.
Therefore,$DNA$ is present in all the mentioned locations.

(D) $DNA$ is the genetic material in mitochondria,chloroplasts,and bacteriophages. However,the Tobacco mosaic virus $(TMV)$ contains $RNA$ as its genetic material,not $DNA$.

(D) The cell organelles that contain their own $DNA$ include the nucleus,mitochondria,and chloroplasts.
$1$. The nucleus contains the majority of the cell's genetic material.
$2$. Mitochondria and chloroplasts are semi-autonomous organelles that possess their own circular $DNA$.
$3$. Lysosomes and dictyosomes (Golgi apparatus) are membrane-bound organelles that do not contain $DNA$.
Therefore,the correct option is $D$.

(D) Eduard Strasburger was a prominent botanist who made significant contributions to cell biology.
$1$. He described the process of cell division in plants and observed the formation of the cell plate.
$2$. He coined the term 'nucleoplasm' to describe the protoplasm of the nucleus.
$3$. He also proposed the term 'cytoplasm' to refer to the protoplasm outside the nucleus.
Therefore,all the given statements are correct.

(D) The correct answer is $D$.
Exocytosis is the process by which cells transport secretory products or waste materials out of the cell.
Since phagocytosis involves the intake of large particles into the cell,the process of moving large molecules out of the cell is often referred to as reverse phagocytosis or exocytosis.

(B) The movement of the cytoplasm within a cell is known as cyclosis or cytoplasmic streaming.
This process involves the circulation of the cytosol and organelles around the central vacuole in plant cells.
It facilitates the distribution of nutrients,proteins,and organelles throughout the cell.

(A) The streaming movement of protoplasm,also known as cyclosis,is the directed flow of cytosol and organelles around the large central vacuole of a plant cell.
This phenomenon is most clearly observed in the staminal hairs of $Tradescantia$ because the cells are large,transparent,and contain distinct cytoplasmic strands that allow for easy visualization of the movement under a light microscope.

(B) In a typical green plant cell,there are three distinct types of genomes present:
$1$. Nuclear genome: Located within the nucleus.
$2$. Chloroplast genome: Located within the chloroplasts.
$3$. Mitochondrial genome: Located within the mitochondria.
Therefore,the correct answer is $B$ (Three).

(A) In eukaryotic cells,the vast majority of $DNA$ is located within the nucleus,which contains the genome responsible for most genetic information.
Cytoplasmic $DNA$ is found in organelles such as mitochondria and,in plants,chloroplasts.
This extranuclear $DNA$ represents a very small fraction of the total cellular $DNA$,typically estimated to be between $1\%$ and $5\%$ of the total $DNA$ content.

(D) The genetic code is universal,meaning it is essentially the same in all living organisms,ranging from bacteria (prokaryotes) to complex multicellular organisms (eukaryotes).
While prokaryotes lack membrane-bound organelles like mitochondria and do not undergo mitosis,and generally lack true histones,the genetic code remains a fundamental shared feature.

(D) Vital stains are dyes used to stain living cells without killing them.
$A$. Janus green-$B$ is specifically used to stain mitochondria in living cells.
$B$. Neutral red is a vital stain used to stain the nucleus and vacuoles in living cells.
$C$. Methylene blue is commonly used as a vital stain for bacteria and various cellular components.
Therefore,all the listed options are examples of vital stains.

(D) Porins are large channel proteins that allow the passage of molecules up to the size of small proteins through the outer membranes of mitochondria,plastids,and some bacteria.
These proteins facilitate the diffusion of various substances across these membranes.
Therefore,all the given options are correct.

(D) $DNA$ (Deoxyribonucleic acid) is the genetic material found in eukaryotic cells.
It is primarily located in the nucleus of the cell.
However,$DNA$ is also present in semi-autonomous organelles such as mitochondria and chloroplasts,which contain their own circular $DNA$ molecules.
Therefore,$DNA$ is present in the nucleus,mitochondria,and chloroplasts.

(C) In eukaryotic cells,$DNA$ is primarily found in the nucleus as part of the chromosomes. However,$DNA$ is also present in certain semi-autonomous organelles,specifically mitochondria and chloroplasts. These organelles contain their own circular $DNA$ molecules,which are used for the synthesis of some of their proteins. Therefore,the correct answer is mitochondria and chloroplasts.

(C) Protoplasm is the living content of the cell. It is known to have a characteristic odor that resembles that of garlic. This is due to the presence of certain sulfur-containing compounds within the cellular components.