Monera (Prokaryotes) Questions in English

(B) The correct answer is $B$. In photosynthetic bacteria,the photosynthetic pigments are not contained within membrane-bound organelles like chloroplasts. Instead,they are located in specialized invaginations of the plasma membrane known as $Chromatophores$. These structures contain the necessary molecular components for light harvesting and energy transduction.

(C) $Leptothrix$ is an iron bacterium.
It obtains energy by oxidizing ferrous iron to ferric iron.
The chemical reaction is:
$Fe^{2+} (\text{Ferrous}) \xrightarrow{} Fe^{3+} (\text{Ferric}) + \text{Chemical Energy}$

(C) Green bacteria contain a green pigment known as bacterioviridin (also called Chlorobium chlorophyll).
This pigment is capable of absorbing red light and shows maximum absorption in the wavelength region of $650-660 \ nm$.
Therefore,both Chlorobium chlorophyll-$650$ and Chlorobium chlorophyll-$660$ are associated with these organisms.

(A) Bacterial photosynthesis occurs in the plasma membrane or specialized invaginations of the plasma membrane known as chromatophores. Since bacteria are prokaryotes,they lack membrane-bound organelles like chloroplasts. Among the given options,the process is associated with the cytoplasmic region or membrane structures,but specifically,it is not localized in a chloroplast. However,in the context of typical multiple-choice questions where specific structures like chromatophores are absent,the process is often associated with the cytoplasmic membrane or the cytoplasm itself. Given the options,the most appropriate answer is the cytoplasm,as it is the site where the photosynthetic machinery is located in prokaryotic cells.

(C) The correct answer is $C$.
Purple non-sulphur bacteria contain the pigment bacteriochlorophyll and perform photosynthesis in the presence of simple organic compounds such as organic acids and alcohols.
An example of such a bacterium is $Rhodospirillum \text{ } rubrum$.
The chemical reaction for the conversion of isopropyl alcohol to acetone is:
$2CH_3CHOHCH_3 + CO_2 \xrightarrow{\text{Sunlight}} (CH_2O) + 2CH_3COCH_3 + H_2O$

(C) The correct answer is $C$. Green sulphur bacteria perform anoxygenic photosynthesis.
In this process,they use $H_2S$ (hydrogen sulphide) or other reduced organic and inorganic substances as electron donors instead of $H_2O$ (water).
Since $H_2O$ is not utilized as an electron donor,molecular oxygen $(O_2)$ is not evolved as a byproduct.

(B) Chemosynthetic autotrophs,such as nitrifying bacteria (e.g.,$Nitrosomonas$),obtain energy by oxidizing inorganic substances like ammonia $(NH_3)$ or nitrites $(NO_2^-)$.
This energy is then used to fix atmospheric carbon dioxide $(CO_2)$ into carbohydrates through a process similar to the Calvin cycle.
Therefore,the raw materials for carbohydrate synthesis in these bacteria are $CO_2$ and $H_2O$ (as a source of hydrogen),while the energy is derived from the oxidation of $NH_3$ or $NO_2^-$. Among the given options,$NH_3$ and $CO_2$ represent the essential substrates involved in their metabolic pathway.

(D) Organisms that obtain energy by the oxidation of reduced inorganic compounds (such as $NH_3$,$H_2S$,$Fe^{2+}$,etc.) are known as chemo-autotrophs.
These organisms use the energy released from these chemical reactions to synthesize organic compounds from $CO_2$.
Phototrophs obtain energy from light,while saprozoic organisms feed on decaying organic matter.

(D) Hormones are chemical messengers produced by endocrine glands in multicellular organisms to regulate physiological processes.
$A$. Monkey,$B$. Cat,and $C$. Cockroach are all multicellular animals that possess endocrine systems and produce hormones.
$D$. Bacteria are unicellular prokaryotic organisms.
They do not possess endocrine glands or a complex endocrine system to produce hormones as defined in higher organisms.
Therefore,hormones are absent in bacteria.

(C) The genetic material of bacteria consists of a single circular $DNA$ molecule.
Unlike eukaryotic cells,bacterial $DNA$ is not organized into nucleosomes by histone proteins.
Instead,the $DNA$ is organized in large loops held by certain proteins,a structure known as the nucleoid.
Therefore,the bacterial genome contains $DNA$ without histone proteins.

(C) An auxotroph is a mutant organism that has lost the ability to synthesize one or more essential compounds required for its growth, such as amino acids or vitamins.
In $1944$, Beadle and Tatum irradiated $Neurospora \, crassa$ with $X$-rays and obtained a number of these nutritional mutants, which they termed auxotrophs.
These organisms require the addition of the specific missing nutrient to their growth medium to survive.

(A) Bacteria are prokaryotic organisms that typically possess a single,circular chromosome. Since they do not undergo meiosis and do not have homologous pairs of chromosomes like eukaryotes,their genetic material is considered haploid. Therefore,the bacterial genome refers to the total number of genes located upon a haploid set of chromosomes.

(B) Organisms that derive energy from the oxidation of reduced inorganic compounds (such as ammonia,nitrites,or hydrogen sulfide) are known as $Chemoautotrophs$.
These organisms use this chemical energy to fix carbon dioxide into organic compounds,as they do not rely on sunlight for energy production.

(C) The genus $Staphylococcus$ is derived from the Greek word '$staphyle$',meaning 'bunch of grapes',and '$kokkos$',meaning 'berry'. These bacteria are Gram-positive cocci that divide in multiple planes,resulting in the formation of irregular,grape-like clusters.

(C) Cyanobacteria,also known as blue-green algae,are photosynthetic prokaryotes.
They contain chlorophyll $a$ and phycobiliproteins,such as phycocyanin,which give them their characteristic blue-green color.
They are autotrophic organisms capable of performing oxygenic photosynthesis.

(A) $Vibrio$ $cholerae$ is a curved,rod-shaped bacterium that possesses a single polar flagellum.
Bacteria with a single flagellum at one end are classified as $Monotrichous$.
Therefore,$Vibrio$ $cholerae$ belongs to the $Monotrichous$ group.

(C) Mycoplasma are bacteria that lack a cell wall,which makes them naturally resistant to antibiotics that target cell wall synthesis,such as Penicillin.
$Tetracycline$ is a broad-spectrum antibiotic that inhibits protein synthesis by binding to the $30S$ ribosomal subunit.
Since $Mycoplasma$ rely on protein synthesis for growth and survival,$Tetracycline$ is highly effective in inhibiting their growth.
Therefore,$Tetracycline$ is the most effective choice among the given options.

(A) Oxygenic photosynthesis is a process where $H_2O$ is used as an electron donor,resulting in the release of $O_2$ as a byproduct.
Cyanobacteria,such as $Oscillatoria$,are the only prokaryotes that perform oxygenic photosynthesis,similar to green plants.
$Rhodospirillum$,$Chlorobium$,and $Chromatium$ are examples of anoxygenic photosynthetic bacteria that use compounds like $H_2S$ instead of $H_2O$ as electron donors,thus they do not release $O_2$.

(B) Blue-green algae (Cyanobacteria) are prokaryotic organisms that lack membrane-bound organelles like chloroplasts.
In these organisms,the photosynthetic pigments are located in specialized membrane structures called lamellisomes or thylakoid membranes,which are extensions of the plasma membrane.
Therefore,photosynthesis occurs in the lamellisomes.

(B) The kingdom $Monera$ consists of prokaryotic organisms.
Prokaryotes are characterized by the absence of a membrane-bound nucleus and other membrane-bound organelles.
Instead of a true nucleus,they contain a region called the $nucleoid$ where their genetic material (circular $DNA$) is located.
Kingdoms $Protista$,$Fungi$,and $Plantae$ consist of eukaryotic organisms which possess a well-defined nucleus.

(C) The Kingdom $Monera$ includes all prokaryotic organisms.
$Cyanobacteria$ (also known as blue-green algae) are photosynthetic prokaryotes,which classify them under the Kingdom $Monera$.
$Euglena$ belongs to the Kingdom $Protista$.
$Amoeba$ belongs to the Kingdom $Protista$.
$Yeast$ is a unicellular fungus belonging to the Kingdom $Fungi$.

(A) The kingdom $Monera$ is the only kingdom among the five kingdoms that consists of prokaryotic organisms. $Protista$,$Fungi$,$Plantae$,and $Animalia$ are all eukaryotic kingdoms.

(C) Prokaryotic organisms are characterized by the absence of a well-defined nucleus and membrane-bound organelles.
$1$. Yeast is a unicellular fungus (eukaryote).
$2$. Sargassum is a brown alga (eukaryote).
$3$. Blue-green algae (Cyanobacteria) are prokaryotes.
$4$. Spirogyra is a green alga (eukaryote).
Therefore,the correct answer is Blue-green algae.

(B) The cell wall of organisms belonging to the $Bacteria$ domain is composed of peptidoglycan (also known as murein).
In contrast,the cell wall of $Archaea$ is composed of pseudopeptidoglycan or other polysaccharides and proteins,lacking peptidoglycan.
$Eukarya$ domain organisms have cell walls made of cellulose (plants),chitin (fungi),or lack a cell wall (animals).

(C) $Archaea$ are a group of prokaryotes that can survive in extreme environments.
$1$. $Methanogens$ are found in marshy areas and the gut of ruminant animals.
$2$. $Halophiles$ are found in extremely salty areas.
$3$. $Thermoacidophiles$ are found in hot springs where temperatures are very high and the environment is acidic.
$4$. $Spirochetes$ are a phylum of Gram-negative bacteria,not $Archaea$.
Therefore,the correct answer is $Thermoacidophiles$.

(B) Methanogens are a group of specialized archaea that produce methane $(CH_4)$ as a metabolic byproduct in anoxic conditions.
They are commonly found in the gut of several ruminant animals such as cows and buffaloes,where they help in the digestion of cellulose.
They are also present in marshy areas,which is why methane is often called marsh gas.

(B) According to the three-domain system proposed by Carl Woese,all living organisms are classified into three domains: $Archaea$,$Bacteria$,and $Eukarya$.
$Eubacteria$ (true bacteria) belong to the domain $Bacteria$.
$Archaea$ includes ancient bacteria,and $Eukarya$ includes all eukaryotic organisms.

(B) The domain $Bacteria$ (also known as $Eubacteria$) includes a vast majority of known pathogenic organisms that cause diseases in humans,animals,and plants. While some archaea exist in extreme environments,they are generally not known to be pathogenic to humans. Eukarya includes protists,fungi,plants,and animals,which may contain pathogens,but the domain $Bacteria$ is most characteristically associated with the broad category of well-known pathogenic prokaryotes.

(B) The domain $Archaea$ consists of prokaryotic organisms that are distinct from $Bacteria$.
One of the primary biochemical differences is that the cell walls of $Archaea$ lack peptidoglycan,which is a characteristic component of bacterial cell walls.
Instead,$Archaea$ possess cell walls composed of various proteins,polysaccharides,or pseudomurein.
Therefore,the correct characteristic is that their cell wall is not made of peptidoglycan.

(B) Spirochetes are a phylum of Gram-negative bacteria that have long,helically coiled cells. They are characterized by the presence of axial filaments (endoflagella) located between the inner and outer membranes,which allow them to move in a corkscrew-like motion. Therefore,they are classified as Gram-negative bacteria.

(B) Archaebacteria are a special group of bacteria that live in some of the most harsh habitats.
Halophiles are a type of Archaebacteria that specifically thrive in extremely salty areas (halophilic environments).
Methanogens are found in marshy areas and the gut of ruminant animals.
Thermoacidophiles are found in hot springs.
Therefore,the correct option is $B$.

(A) Peptidoglycan (murein) is a characteristic component of the cell wall in most Bacteria.
$A$,$C$,and $D$ are all members of the domain Bacteria and possess peptidoglycan in their cell walls.
$B$ (Halophiles) belong to the domain Archaea.
Archaea are known for having cell walls composed of pseudopeptidoglycan,proteins,or polysaccharides,but they lack true peptidoglycan.
Therefore,Halophiles do not have a cell wall made of peptidoglycan.

(A) The domain $Archaea$ consists of organisms that are known as extremophiles. These organisms can survive in harsh environmental conditions such as high temperatures,high salinity,and extreme $pH$ levels,where other life forms cannot survive. Therefore,the correct option is $A$.

(B) In the three-domain system of classification proposed by Carl Woese,all living organisms are classified into three domains: $Bacteria$,$Archaea$,and $Eukarya$.
$1$. $Bacteria$ (or $Eubacteria$) is a domain that includes true bacteria.
$2$. $Spirochetes$ are a phylum of Gram-negative bacteria that have long,helically coiled cells.
$3$. $Methanogens$ belong to the domain $Archaea$.
$4$. $Molds$ are fungi,which belong to the domain $Eukarya$.
$5$. $Worms$ are animals,which belong to the domain $Eukarya$.
Therefore,$Spirochetes$ is the correct answer as it represents a group within the domain $Bacteria$.

(A) The first living forms on Earth are believed to be simple,unicellular,prokaryotic organisms. According to the $5$-kingdom classification system,these organisms are placed in the kingdom $Monera$. They are characterized by the absence of a well-defined nucleus and membrane-bound organelles. Therefore,$Monera$ represents the most primitive and earliest group of living organisms.

(C) The cell wall of $Eubacteria$ (true bacteria) is composed of $peptidoglycan$ (also known as $murein$).
$Cyanobacteria$ are a group of photosynthetic $Eubacteria$,and therefore,they also possess a $peptidoglycan$ cell wall.
$Archaebacteria$ have a unique cell wall composition that lacks $peptidoglycan$,often containing pseudomurein or other proteins/polysaccharides.
Since $Cyanobacteria$ are a subset of $Eubacteria$,the most accurate description provided in the options is that $Eubacteria$ and $Cyanobacteria$ possess $peptidoglycan$ cell walls.

(B) The kingdom $Monera$ includes all prokaryotic organisms.
$Archaebacteria$ are ancient bacteria that live in extreme environments.
$Eubacteria$ are 'true bacteria' characterized by a rigid cell wall.
$Cyanobacteria$ (blue-green algae) are photosynthetic prokaryotes.
Since all these groups consist of prokaryotic organisms,they are all classified under the kingdom $Monera$.

(D) The kingdom $Monera$ consists of prokaryotic organisms.
These organisms exhibit diverse modes of nutrition.
Some members of $Monera$ (like cyanobacteria) are autotrophic,meaning they can synthesize their own food.
Other members are heterotrophic,meaning they depend on other organisms for food.
Therefore,the kingdom $Monera$ includes both autotrophic and heterotrophic organisms.

(D) Cyanobacteria are prokaryotic organisms belonging to the kingdom Monera.
In prokaryotes,the genetic material is not enclosed within a nuclear membrane.
This naked,circular,double-stranded $DNA$ molecule,which is not associated with histone proteins,is located in a specific region of the cytoplasm called the nucleoid (or genophore).
Therefore,the genetic material of cyanobacteria is known as the nucleoid.

(D) well-defined nucleus is a characteristic feature of eukaryotic cells.
Prokaryotic cells,such as those belonging to the kingdom $Monera$,lack a membrane-bound nucleus.
$Anabaena$ is a genus of filamentous cyanobacteria (blue-green algae),which are prokaryotic organisms.
Therefore,$Anabaena$ lacks a well-defined nucleus,while lichens,fungi,and green algae are all eukaryotic organisms that possess a well-defined nucleus.

(A) Methanogens and halophiles are both members of the domain $Archaea$ (archaebacteria).
Archaebacteria are distinct from other bacteria because they have a different cell wall structure,which allows them to survive in extreme environmental conditions.
Methanogens are found in marshy areas and the gut of ruminant animals,while halophiles are found in extremely salty areas.
Therefore,the common feature between them is that they both belong to the group of archaebacteria.

(D) Gram-negative bacteria are characterized by a thin peptidoglycan layer and an outer membrane.
$Spirochaetes$ are a phylum of Gram-negative bacteria that have long,helically coiled cells.
$Firmicutes$ are generally Gram-positive (with some exceptions).
$Halophiles$ are Archaea,not bacteria.
$Eubacteria$ is a broad category that includes both Gram-positive and Gram-negative types,but $Spirochaetes$ specifically represents a group of Gram-negative bacteria.

(C) Peptidoglycan (also known as murein) is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of most bacteria,forming the cell wall.
Both Gram-positive and Gram-negative bacteria possess a cell wall containing peptidoglycan.
In Gram-positive bacteria,the peptidoglycan layer is thick,whereas in Gram-negative bacteria,it is relatively thin.
Therefore,peptidoglycan is present in both types of bacteria.

(C) Cyanobacteria,also referred to as blue-green algae,are a phylum of bacteria that obtain their energy through photosynthesis. They are Gram-negative bacteria that contain chlorophyll-$a$ and are capable of oxygenic photosynthesis. Therefore,they are essentially photosynthetic bacteria.

(D) The cell wall of $Eubacteria$ (true bacteria) is composed of $peptidoglycan$ (also known as $murein$).
In contrast,$Archaebacteria$ have cell walls that lack $peptidoglycan$; instead,they are composed of proteins,polysaccharides,or pseudomurein.
Therefore,the presence of $peptidoglycan$ in the cell wall is a characteristic feature of $Eubacteria$.

(D) Bacteria are the sole members of the Kingdom $Monera$.
They are the most abundant micro-organisms.
Based on their mode of nutrition,bacteria can be autotrophic (photosynthetic or chemosynthetic) or heterotrophic (saprophytic or parasitic).
However,the vast majority of bacteria are heterotrophic,meaning they depend on other organisms or dead organic matter for food.
Therefore,the statement 'Most bacteria are heterotrophic and some are autotrophic' is correct.

(B) Gram-positive bacteria are characterized by a thick peptidoglycan cell wall that retains the crystal violet stain during Gram staining.
$Firmicutes$ is a phylum of bacteria,most of which have a Gram-positive cell wall structure.
$Halophiles$ are archaea that thrive in high salt concentrations.
$Spirochaetes$ are a phylum of Gram-negative bacteria with a unique helical shape.
$Methanogens$ are archaea that produce methane as a metabolic byproduct in anoxic conditions.
Therefore,the correct option is $B$.

(B) Thermoacidophiles belong to the group Archaebacteria.
They are specifically adapted to survive in extreme environments,characterized by high temperatures and acidic pH levels.
Option $A$ is incorrect because they are not photosynthetic.
Option $C$ is incorrect because organisms that live in extremely saline habitats are known as halophiles.
Therefore,the correct characteristic is that they live at high temperatures.

(C) The cell wall of bacteria is primarily composed of $Peptidoglycan$ (also known as $Murein$).
$Peptidoglycan$ is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of most bacteria,providing structural support and protection.
$Cellulose$ is found in plant cell walls,$Chitin$ is found in fungal cell walls,and $Lipids$ are the primary components of the cell membrane.

(A) $S$ is true because thermoacidophiles are a group of Archaea specifically adapted to thrive in environments with low $pH$ (acidic) and high temperatures.
$R$ is true because Archaebacteria (Archaea) possess unique cell wall structures (lacking peptidoglycan) and membrane lipids that allow them to survive in extreme habitats such as hot springs,salt marshes,and acidic environments.
Since the ability of thermoacidophiles to survive in these conditions is a direct consequence of their classification as Archaea,$R$ is the correct explanation for $S$.