Prokaryotic cell Questions in English

(D) The sentence is grammatically and biologically incomplete because it fails to specify that mesosomes are extensions of the $plasma \ membrane$.
Mesosomes are specialized membranous structures formed by the extensions of the $plasma \ membrane$ into the cell in the form of vesicles, tubules, and lamellae.
Therefore, the correct description should be: "In prokaryotic cells, the internal extension structure of the $plasma \ membrane$ is called a mesosome."

(A) Inclusion bodies are non-membrane bound structures found in the cytoplasm of prokaryotic cells.
They serve as reserve material for the cell and are stored in the cytoplasm in the form of particles.
These are collectively referred to as storage particles (e.g.,phosphate granules,cyanophycean granules,and glycogen granules).
Therefore,the correct option is $A$.

(C) Prokaryotic cells are defined by the absence of a membrane-bound nucleus and other membrane-bound organelles.
Bacteria,$Mycoplasma$,and $PPLO$ (Pleuro Pneumonia-Like Organisms) are classic examples of prokaryotic organisms.
The egg of an ostrich is a single cell,but it is a eukaryotic cell,as it contains a well-defined nucleus and membrane-bound organelles.
Therefore,the egg of an ostrich is not an example of a prokaryotic cell.

(C) In bacteria, the cell envelope consists of a tightly linked three-layered structure: the outermost $Glycocalyx$, followed by the $Cell \text{ } wall$, and then the $Plasma \text{ } membrane$.
$Glycocalyx$ is the outermost layer, which can be in the form of a loose sheath called the $slime \text{ } layer$ or a thick and tough layer called the $capsule$.
Therefore, the correct answer is $Glycocalyx$.

(D) Prokaryotic cells are characterized by the absence of a well-defined nucleus and membrane-bound organelles.
$A$. Circular $DNA$ is a characteristic feature of prokaryotic cells.
$B$. Mesosomes are specialized membranous structures formed by the extensions of the plasma membrane into the cell,which is a characteristic of prokaryotes.
$C$. Ribosomes are present in prokaryotic cells (specifically $70S$ type).
$D$. The term 'foldings in genetic material of third stage' is scientifically incorrect and does not describe any known feature of prokaryotic cells. Therefore,it is not a characteristic of prokaryotic cells.

(D) Prokaryotic cells are characterized by the absence of a membrane-bound nucleus and membrane-bound organelles.
$1.$ The egg of an ostrich is a single eukaryotic cell.
$2.$ $PPLO$ (Pleuro Pneumonia-Like Organisms) are prokaryotic.
$3.$ Tracheids are specialized eukaryotic cells found in the xylem of plants.
$4.$ Blue-green algae (Cyanobacteria) are prokaryotic organisms.
$5.$ Bacteria are prokaryotic organisms.
$6.$ Animal cells are eukaryotic cells.
Therefore,the group consisting of prokaryotic cells is $2, 4,$ and $5$.

(D) In prokaryotic cells,the plasma membrane undergoes invagination to form specialized structures known as $Mesosomes$.
These extensions can take the form of vesicles,tubules,or lamellae.
$Mesosomes$ play a crucial role in various cellular processes such as $DNA$ replication,cell wall formation,respiration,and secretion.

(B) In prokaryotes,especially bacteria,resistance to antibiotics is primarily conferred by the presence of $Plasmid$.
$Plasmids$ are small,circular,double-stranded $DNA$ molecules that are distinct from the cell's chromosomal $DNA$.
They often carry genes that provide advantages to the bacteria,such as antibiotic resistance genes,which allow the bacteria to survive in the presence of specific antibiotics.
$Mesosomes$ are involved in respiration and cell wall formation,$Glycocalyx$ provides protection and adhesion,and $Flagella$ are responsible for motility.

(D) In prokaryotic cells,the cell envelope consists of a tightly linked three-layered structure.
Starting from the outermost layer to the innermost layer,the sequence is:
$1$. Glycocalyx (outermost layer)
$2$. Cell wall (middle layer)
$3$. Cell membrane (innermost layer)
Therefore,the correct sequence is Glycocalyx $\rightarrow$ Cell wall $\rightarrow$ Cell membrane.

(B) The bacterial cell envelope consists of a tightly linked three-layered structure.
Starting from the outermost layer to the innermost layer,the sequence is:
$1$. Glycocalyx (outermost layer)
$2$. Cell wall (middle layer)
$3$. Cell membrane (innermost layer)
Therefore,the correct sequence is Glycocalyx - Cell wall - Cell membrane.

(C) The bacterial genome,also known as the genophore or nucleoid,consists of a single,circular,double-stranded $DNA$ molecule. Unlike eukaryotic cells,prokaryotic $DNA$ is not enclosed within a nuclear membrane and lacks histone proteins,which are characteristic of eukaryotic chromatin. Therefore,the correct description is a single double-stranded $DNA$.

(D) Plasmids are small,circular,double-stranded $DNA$ molecules that are distinct from a cell's chromosomal $DNA$.
They are naturally found in bacterial cells and some eukaryotes like yeast.
Plasmids are considered extra-chromosomal genetic material because they replicate independently of the chromosomal $DNA$.
They often carry genes that provide advantages to the host,such as antibiotic resistance.

(B) Bacteria are prokaryotic organisms. The genetic material in bacteria is typically a single,large,circular $DNA$ molecule,which is often referred to as the bacterial chromosome or nucleoid.
Unlike eukaryotes,it is not enclosed within a nuclear membrane and does not contain histones.

(B) In prokaryotic cells like bacteria,membrane-bound organelles such as mitochondria are absent.
Mesosomes are specialized membranous structures formed by the extensions of the plasma membrane into the cell in the form of vesicles,tubules,and lamellae.
These structures play a crucial role in cellular respiration,$DNA$ replication,and the secretion process.
Therefore,the mesosome acts as the site of respiration in bacteria.

(D) Photosynthetic bacteria are prokaryotic organisms that lack membrane-bound organelles like chloroplasts.
Instead,they possess specialized membranous structures called $Chromatophores$ that extend into the cytoplasm.
These $Chromatophores$ contain the pigments necessary for photosynthesis,allowing the bacteria to capture light energy.

(D) Bacterial cells typically contain a single,circular,double-stranded $DNA$ molecule,which is often referred to as the bacterial chromosome or nucleoid. While most bacteria possess a single circular chromosome,some species have been found to contain linear chromosomes or multiple chromosomes. However,within a single bacterial cell,the chromosomal structure is consistent,meaning they are either circular or linear,but not both simultaneously.

(B) In bacteria, $Fimbriae$ are small, bristle-like fibers sprouting out of the cell. They are known to help bacteria attach to rocks in streams and also to the host tissues. $Root hairs$ are found in plants, $Mesosomes$ are infoldings of the plasma membrane in bacteria involved in respiration and secretion, and $Holdfast$ is a structure found in algae for attachment.

(C) The bacterial genome,often referred to as the genophore or nucleoid,consists of a single,circular,double-stranded $DNA$ molecule. Unlike eukaryotic cells,prokaryotic cells lack a defined nucleus and do not contain histone proteins to package their $DNA$. Therefore,the correct description is a single double-stranded $DNA$ molecule.

(C) Golgi bodies are membrane-bound organelles found in eukaryotic cells.
Prokaryotic cells,such as $Bacteria$ and $Blue-green$ $algae$ $(Cyanobacteria)$,lack membrane-bound organelles,including the Golgi apparatus.
Therefore,Golgi bodies are absent in bacteria and blue-green algae.

(D) The prokaryotic flagellum is a thin,hair-like appendage that extends from the cell surface.
It is composed of a protein called flagellin.
Unlike eukaryotic flagella,which have a $9 + 2$ microtubule arrangement,the prokaryotic flagellum is a helical structure made of protein subunits arranged in a spiral or helical fashion.
Therefore,the correct description is that the protein molecules are arranged in a helical manner.

(B) Prokaryotic cells are characterized by the absence of a membrane-bound nucleus and other membrane-bound organelles.
In prokaryotes,the genetic material is present as a naked circular $DNA$ molecule in the nucleoid region,not enclosed by a nuclear membrane.
Plasma membrane,ribosomes,and mesosomes are all characteristic structures found in prokaryotic cells.
Therefore,the nuclear membrane is the structure that is $NOT$ found in a prokaryotic cell.

(D) In bacteria,the glycocalyx is an outer layer composed of polysaccharides and/or polypeptides.
It provides a sticky or slimy character to the bacterial cell,which helps in adhesion to surfaces and protects the cell from phagocytosis by the host immune system.
Therefore,the correct option is $D$.

(D) $E. coli$ (Escherichia coli) is a prokaryotic organism.
In all prokaryotes,the genetic material consists of a single,circular,double-stranded $DNA$ molecule.
Therefore,the genetic material in $E. coli$ is double-stranded $DNA$.

(C) Bacterial chromosomes are typically circular $DNA$ molecules. While the vast majority of bacteria possess a single circular chromosome,some species may contain $1-3$ chromosomes. These chromosomes are consistently circular in structure and are not linear. Therefore,the correct description is that they are always circular.

(C) In bacteria (prokaryotes),$DNA$ replication is a continuous process that occurs in the cytoplasm. Unlike eukaryotes,bacteria do not have a distinct $S$-phase in their cell cycle. $DNA$ replication must be completed before the cell undergoes binary fission to ensure that each daughter cell receives a complete copy of the genome. Therefore,$DNA$ replication occurs before cell division.

(D) In prokaryotes,chromatophores are internal membrane systems that may become extensive and complex in photosynthetic bacteria. They contain pigments and are structurally and functionally similar to the thylakoids found in eukaryotic chloroplasts,facilitating photosynthesis.

(C) Plasmids are small,circular,double-stranded extra-chromosomal $DNA$ molecules found in prokaryotic cells,such as bacteria.
$1$. The Assertion is incorrect because plasmids are double-stranded,not single-stranded.
$2$. The Reason is incorrect because plasmids are typically found in prokaryotic cells,not eukaryotic cells.
Therefore,both the Assertion and the Reason are incorrect.

(B) Organisms that possess only $70S$ ribosomes are prokaryotes (e.g.,bacteria).
Prokaryotic cells lack a well-defined nucleus and membrane-bound organelles.
The genetic material in prokaryotes consists of a single,double-stranded,circular $DNA$ molecule that is not associated with histone proteins (naked $DNA$).
Therefore,option $B$ is the correct description of the genetic material found in such organisms.

(N/A) mesosome is a convoluted membranous structure formed in a prokaryotic cell by the invagination of the plasma membrane.
Its functions are as follows:
$1$. It aids in the synthesis of the cell wall and the replication of $DNA$.
$2$. It assists in the equal distribution of chromosomes into daughter cells.
$3$. It increases the surface area of the plasma membrane to facilitate various enzymatic activities.
$4$. It plays a role in secretion processes and bacterial respiration.

(A) Prokaryotic cells are unicellular organisms that lack membrane-bound organelles.
The characteristics of prokaryotic cells are as follows:
$1$. Most of them are unicellular.
$2$. They are generally small in size,typically ranging from $0.5-5 \mu m$.
$3$. The nuclear region is poorly defined due to the absence of a nuclear membrane; hence,they lack a true nucleus.
$4$. The genetic material is naked,consisting of a single,circular chromosome. In addition to genomic $DNA$,they often contain small,circular plasmid $DNA$.
$5$. They possess specialized membranous structures called mesosomes,formed by the invagination of the cell membrane. These assist in cell wall synthesis,$DNA$ replication,and the distribution of chromosomes to daughter cells.
$6$. Membrane-bound organelles such as mitochondria,plastids,and the endoplasmic reticulum are absent.
$7$. Most prokaryotic cells have a three-layered cell envelope: the outermost glycocalyx,the middle cell wall,and the innermost plasma membrane,which acts as a protective unit.
$8$. Examples include bacteria and blue-green algae.

(N/A) $\Rightarrow$ Prokaryotic cells are represented by bacteria,blue-green algae,mycoplasma,and $PPLO.$
$\Rightarrow$ They are generally smaller and multiply more rapidly than eukaryotic cells.
$\Rightarrow$ They vary greatly in shape and size. The four basic shapes of bacteria are bacillus,coccus,vibrio,and spirillum.
$\Rightarrow$ The organization of the prokaryotic cell is fundamentally similar even though prokaryotes exhibit a wide variety of shapes and functions.
$\Rightarrow$ All prokaryotes have a cell wall surrounding the cell membrane.
$\Rightarrow$ The fluid matrix filling the cell is the cytoplasm.
$\Rightarrow$ There is no well-defined nucleus. The genetic material is naked,not enveloped by a nuclear membrane.
$\Rightarrow$ Many bacteria have small circular $DNA$ outside the genomic $DNA$. These are called plasmids.
$\Rightarrow$ The plasmid $DNA$ confers certain unique phenotypic characters to such bacteria,such as resistance to antibiotics.
$\Rightarrow$ Plasmid $DNA$ is also used to monitor bacterial transformation with foreign $DNA.$
$\Rightarrow$ $A$ nuclear membrane is not found in prokaryotic cells.
$\Rightarrow$ Cell organelles like endoplasmic reticulum,Golgi bodies,and mitochondria are not present,except for ribosomes.
$\Rightarrow$ $A$ specialized differentiated form of the cell membrane called a mesosome is a characteristic of prokaryotes. They are essentially infoldings of the cell membrane.

(N/A) $\Rightarrow$ Prokaryotic cells are found in bacteria,blue-green algae,mycoplasma,and $PPLO$ (Pleuro Pneumonia-Like Organisms).
$\Rightarrow$ They are generally smaller and multiply more rapidly than eukaryotic cells.
$\Rightarrow$ They vary greatly in shape and size. The four basic shapes of bacteria are:
$(i)$ Bacillus (rod-like)
$(ii)$ Coccus (spherical)
$(iii)$ Vibrio (comma-shaped)
$(iv)$ Spirillum (spiral)
$\Rightarrow$ Despite their diversity in shape and function,the fundamental organization of the prokaryotic cell remains consistent.
$\Rightarrow$ All prokaryotes have a cell wall surrounding the cell membrane (except in mycoplasma).
$\Rightarrow$ The fluid matrix filling the cell is the cytoplasm.
$\Rightarrow$ There is no well-defined nucleus. The genetic material is naked and not enveloped by a nuclear membrane.
$\Rightarrow$ Many bacteria have small circular $DNA$ outside the genomic $DNA$,called plasmids. These confer unique phenotypic characters like antibiotic resistance.

(N/A) $\Rightarrow$ Prokaryotic cells possess a chemically complex cell envelope.
$\Rightarrow$ The cell envelope consists of a tightly bound three-layered structure: $(i)$ the outermost glycocalyx,$(ii)$ the cell wall,and $(iii)$ the plasma membrane.
$\Rightarrow$ Although each layer of the envelope performs a distinct function,they act together as a single protective unit.
$\Rightarrow$ Bacteria are classified into two groups based on differences in their cell envelopes and their response to the Gram staining procedure:
$(i)$ Gram-positive bacteria: Those that take up the Gram stain.
$(ii)$ Gram-negative bacteria: Those that do not take up the Gram stain.
$(i)$ Glycocalyx: The outermost layer. It varies in composition and thickness among different bacteria. It can be a loose sheath called the slime layer or a thick,tough layer called the capsule.
$(ii)$ Cell wall: It determines the shape of the cell and provides strong structural support to prevent the bacterium from bursting or collapsing.
$(iii)$ Plasma membrane: It is semi-permeable and interacts with the external environment. Structurally,it is similar to that of eukaryotes.
$\Rightarrow$ Mesosomes: Special membranous structures formed by the extensions of the plasma membrane into the cell in the form of vesicles,tubules,and lamellae. They assist in cell wall formation,$DNA$ replication,distribution to daughter cells,respiration,secretion,and increasing the surface area of the plasma membrane and enzymatic content.
$\Rightarrow$ Chromatophores: In some prokaryotes like cyanobacteria,there are other membranous extensions into the cytoplasm containing pigments.

(N/A) $\Rightarrow$ Reserve materials in prokaryotic cells are stored in the cytoplasm in the form of inclusion bodies.
$\Rightarrow$ These are not bounded by any membrane system and lie free in the cytoplasm.
$\Rightarrow$ Examples include phosphate granules,cyanophycean granules,and glycogen granules.
$\Rightarrow$ Gas vacuoles are found in blue-green,purple,and green photosynthetic bacteria.

(N/A) $(i)$ Totipotency: It is the ability of a single cell to divide and produce all the differentiated cells in an organism,thereby having the potential to form a complete new organism.
$(ii)$ Prokaryotic cell: $A$ cell that lacks a membrane-bound nucleus and other membrane-bound organelles is called a prokaryotic cell.

(N/A) $(i)$ $A$ eukaryotic cell is a cell that possesses a clearly defined,membrane-bound nucleus and other membrane-bound organelles,such as mitochondria and the endoplasmic reticulum.
$(ii)$ $A$ plasmid is a small,circular,double-stranded $DNA$ molecule that is distinct from a cell's chromosomal $DNA$. Plasmids are naturally found in bacterial cells and can replicate independently.

(N/A) $(i)$ Active transport occurs against the concentration gradient. This process requires the expenditure of metabolic energy,typically in the form of $ATP$.
$(ii)$ When multiple ribosomes are attached to a single $mRNA$ strand,they form a chain-like structure known as a polysome or polyribosome. This structure facilitates the simultaneous translation of a single $mRNA$ into multiple polypeptide chains.
$(iii)$ Inclusion bodies are non-membrane-bound structures found in the cytoplasm of prokaryotic cells. They serve as storage sites for reserve materials such as glycogen granules,phosphate granules,and cyanophycean granules. Note: The original prompt's description regarding enzymes and presence in eukaryotic cells is incorrect; in standard biology,inclusion bodies are characteristic of prokaryotes.

(N/A) $(i)$ Peptidoglycan:
Location: It is a component of the bacterial cell wall,providing structural support.
Function: It provides protection against osmotic lysis and mechanical stress.
$(ii)$ Mesosome:
Location: These are specialized membranous structures formed by the extensions of the plasma membrane into the cell in prokaryotes.
Function: They play a crucial role in cell wall formation,$DNA$ replication,distribution of $DNA$ to daughter cells,respiration,secretion processes,and increasing the surface area of the plasma membrane and enzymatic content.

(A) $(i)$ The smallest cell is $Mycoplasma$ (about $0.3 \ \mu m$ in length),while the largest isolated single cell is the egg of an ostrich.
$(ii)$ In bacteria,the glycocalyx can be a loose sheath called the $Slime$ layer,or it can be thick and tough,which is called the $Capsule$.

(A) $(i)$ Living cytoplasmic structures that perform specific functions are known as cell organelles. Cell inclusions are non-living storage products like glycogen or fat droplets.
$(ii)$ $A$ nucleoid is a region containing genetic material in prokaryotic cells,which lacks a nuclear membrane. Eukaryotic cells possess a well-defined nucleus with a nuclear envelope.

(A) $(i)$ In prokaryotic cells like bacteria,the plasma membrane extends into the cytoplasm to form structures called $Mesosomes$. These are involved in cell wall formation,$DNA$ replication,and respiration.
$(ii)$ $Pili$ are elongated,tubular structures made of a special protein called $pilin$. They are found in many bacteria and are specifically involved in the process of conjugation,which is the transfer of genetic material between bacteria.

(C) Inclusion bodies are non-membrane-bound structures found in prokaryotic cells that serve as storage sites for reserve materials like glycogen granules,phosphate granules,and cyanophycean granules. They lie free in the cytoplasm. They are not involved in the ingestion of food particles; therefore,statement $C$ is incorrect.

(B) Inclusion bodies are non-membrane-bound structures found in the cytoplasm of prokaryotic cells.
They serve as storage sites for reserve materials such as phosphate granules,cyanophycean granules,and glycogen granules.
They lie free in the cytoplasm and are not involved in the ingestion of food particles; ingestion is typically a process associated with eukaryotic cells (e.g.,phagocytosis).
Therefore,the statement that they are involved in the ingestion of food particles is incorrect.

(D) In prokaryotic cells,the genetic material is not enclosed within a membrane-bound nucleus. Instead,the $DNA$ is organized in a region known as the nucleoid. This region contains the circular $DNA$ molecule and associated proteins,but it lacks a nuclear envelope.

(C) In prokaryotic cells,there is no well-defined nucleus or membrane-bound organelles.
Transcription (the synthesis of $mRNA$ from $DNA$) and translation (the synthesis of proteins from $mRNA$) both take place in the cytoplasm.
Because there is no nuclear envelope to separate the genetic material from the ribosomes,these two processes can even occur simultaneously.

(D) $PPLO$ stands for Pleuro-Pneumonia-Like Organisms,which are also known as $Mycoplasma$.
$Mycoplasma$ are prokaryotic organisms.
Prokaryotic cells lack a well-defined nucleus and membrane-bound organelles.
Since $PPLO$ do not possess a nucleus,none of the processes like replication,transcription,or translation occur within a nucleus.
Therefore,the correct answer is $D$.

(D) The bacterial nucleoid is the region within a prokaryotic cell that contains the genetic material.
In bacteria,the genetic material consists of a single,double-stranded,circular $DNA$ molecule.
This $DNA$ is not enclosed within a nuclear membrane,which is why it is referred to as a nucleoid.
Therefore,the correct description is a double-stranded circular $DNA$.

(C) In prokaryotic cells,inclusion bodies serve as reserve material storage. In blue-green,purple,and green photosynthetic bacteria,these inclusion bodies are specifically known as gas vacuoles (or gas vesicles),which provide buoyancy to the cells.

(C) The correct answer is $C$.
- $70S$ ribosomes are characteristic of prokaryotic cells.
- Chromatophores are specialized membrane-bound vesicles containing pigments found in some photosynthetic prokaryotes (e.g.,Cyanobacteria).
- Circular $DNA$ is a hallmark of prokaryotic organisms.
- Since chromatophores are not present in all prokaryotes (only in photosynthetic ones),these features collectively are found in some prokaryotes.

(C) Bacteria and blue-green algae are $PROKARYOTIC$ unicellular organisms which are devoid of a membrane-bound nucleus and membrane-bound organelles.
Golgi apparatus is present in plant cells as single units known as $DICTYOSOMES$.