Ribosomes Questions in English

(C) Prokaryotic cells contain $70\,S$ type ribosomes.
These ribosomes are composed of two subunits: a larger subunit of $50\,S$ and a smaller subunit of $30\,S$.

(D) Ribosomes $\rightarrow$ Protein factory (Site for protein synthesis).
Lysosome $\rightarrow$ Suicidal bags as they contain hydrolytic enzymes.
Nucleolus $\rightarrow$ Site for $rRNA$ synthesis.
Mitochondria $\rightarrow$ Powerhouse of the cell. It is the site for $ATP$ synthesis.

(D) Mitochondria are semi-autonomous organelles that contain their own genetic material and protein-synthesizing machinery.
The ribosomes found within the mitochondria are of the $70\;S$ type,which is similar to the ribosomes found in prokaryotic cells.
In contrast,the ribosomes found in the cytoplasm of eukaryotic cells are of the $80\;S$ type.

(C) Ribosomes are composed of $rRNA$ and various ribosomal proteins,not just $RNA$. Therefore,the statement that they are made up of $RNA$ only is incorrect.

(A) polysome (or polyribosome) consists of several ribosomes attached to a single $mRNA$ molecule.
This structure allows for the simultaneous translation of a single $mRNA$ strand into multiple copies of a polypeptide chain,thereby increasing the efficiency of protein synthesis in bacterial cells.

(C) Ribosomes are classified based on their sedimentation coefficient $(S)$.
Eukaryotic ribosomes are $80S$,which consist of a larger $60S$ subunit and a smaller $40S$ subunit.
The $60S$ larger subunit of eukaryotic ribosomes contains $28S$ $rRNA$,$5.8S$ $rRNA$,and $5S$ $rRNA$.
Since animal cells are eukaryotic,they contain $80S$ ribosomes.
Prokaryotes (bacteria),mitochondria,and chloroplasts contain $70S$ ribosomes.

(B) Magnesium $(Mg^{2+})$ ions play a crucial role in maintaining the structural integrity of ribosomes.
They act as a bridge between the two ribosomal subunits (e.g.,$30S$ and $50S$ in prokaryotes).
At a specific concentration of $Mg^{2+}$,the two subunits remain associated to form a functional ribosome.
If the concentration of $Mg^{2+}$ decreases,the subunits dissociate into their individual components.

(B) The $Ribosome$ is the cell organelle primarily responsible for protein synthesis.
It translates messenger $RNA$ $(mRNA)$ into polypeptide chains,which then fold into functional proteins.
While the $Nucleus$ contains the genetic information $(DNA)$ required for protein synthesis,the actual assembly of amino acids occurs at the $Ribosome$.

(C) In the context of ribosomes,'$S$' stands for the Svedberg unit.
It is a measure of the rate at which a particle sediments in a centrifugal field.
It is also known as the sedimentation coefficient.
This unit reflects the size and density of the ribosome,which determines how fast it settles during ultracentrifugation.

(B) polysome (or polyribosome) is a structure consisting of multiple ribosomes attached to a single $mRNA$ molecule.
Its primary function is to translate the genetic code present on the $mRNA$ into a polypeptide chain (protein).
By having multiple ribosomes reading the same $mRNA$ simultaneously,the cell can produce many copies of the same protein efficiently during active protein synthesis.

(A) Ribosomes are non-membrane-bound organelles found in all living cells,including both prokaryotes and eukaryotes.
In prokaryotes,they are $70S$ type,while in eukaryotes,they are $80S$ type in the cytoplasm and $70S$ type in organelles like mitochondria and chloroplasts.
Centrioles and nucleoli are membrane-less structures but are specific to eukaryotic cells only.

(B) Ribosomes are the sites of protein synthesis in the cell. Because they are responsible for synthesizing proteins,they are commonly referred to as the 'protein factories' of the cell. Among the given options,polyribosomes (or polysomes) are chains of ribosomes attached to a single mRNA molecule,which are actively involved in protein synthesis.

(A) Ribosomes are non-membrane-bound organelles found in both prokaryotic and eukaryotic cells.
They are composed of ribonucleic acids $(RNA)$ and proteins.
According to the $NCERT$ textbook,the size of ribosomes is approximately $15 \text{ nm}$ by $20 \text{ nm}$.
Therefore,the correct option is $A$.

(C) Ribosomes are the granular structures first observed under the electron microscope as dense particles by George Palade in $1953$.
They are composed of ribonucleic acids $(RNA)$ and proteins and are not surrounded by any membrane.
Prokaryotic ribosomes are of the $70S$ type,which are composed of two subunits: a larger subunit $(50S)$ and a smaller subunit $(30S)$.
Eukaryotic ribosomes are of the $80S$ type,which are composed of a larger subunit $(60S)$ and a smaller subunit $(40S)$.
Therefore,$70S$ ribosomes consist of $50S$ and $30S$ subunits.

(B) The term $Palade$ $particle$ refers to $Ribosomes$.
These particles were first observed and described by the Romanian-American cell biologist $George$ $Emil$ $Palade$ in the $1950s$ using an electron microscope.
$Ribosomes$ are dense,granular structures composed of $RNA$ and proteins,and they are the sites of protein synthesis in the cell.

(A) Ribosomes are non-membrane-bound organelles found in all living cells. They are composed of ribonucleic acid $(RNA)$ and proteins. They do not contain deoxyribonucleic acid $(DNA)$ or carbohydrates as their primary structural components. Therefore,the correct composition is $RNA$ and protein.

(D) Ribosomes are the granular structures first observed under the electron microscope as dense particles by George Palade in $1953$.
They are composed of ribonucleic acids $(RNA)$ and proteins and are not surrounded by any membrane.
Eukaryotic ribosomes are of the $80S$ type,while prokaryotic ribosomes are of the $70S$ type.
Each ribosome consists of two subunits.
The $80S$ ribosome is composed of a larger subunit $(60S)$ and a smaller subunit $(40S)$.

(B) Magnesium $(Mg^{2+})$ ions play a crucial role in maintaining the structural integrity of ribosomes. Ribosomes consist of two subunits,a larger and a smaller one. $Mg^{2+}$ ions are required to bind these two subunits together to form a functional ribosome during protein synthesis. If the concentration of $Mg^{2+}$ decreases,the subunits dissociate.

(B) The ribosome is a complex cellular structure composed of ribosomal $RNA$ $(rRNA)$ and various proteins. In eukaryotic cells,the ribosome consists of structural RNAs and approximately $80$ different proteins that work together to facilitate the process of protein synthesis (translation).

(A) Ribosomes are non-membrane-bound organelles found in both prokaryotic and eukaryotic cells.
Statement $A$ is true: Eukaryotic ribosomes are $80S$ (cytoplasmic) and prokaryotic ribosomes are $70S$.
Statement $B$ is true: Every ribosome consists of two sub-units (a larger and a smaller one).
Statement $C$ is true: The $80S$ ribosome is composed of $60S$ and $40S$ sub-units,while the $70S$ ribosome is composed of $50S$ and $30S$ sub-units.
Statements $D$ and $E$ are incorrect because they provide wrong combinations of sub-units.
Therefore,statements $A, B,$ and $C$ are correct.

(C) Ribosomes are non-membrane-bound organelles found in both prokaryotic and eukaryotic cells.
They are the sites of protein synthesis.
Chemically,ribosomes are composed of Ribonucleic acid $\text{(RNA)}$ and proteins.
They do not contain $\text{DNA}$ or lipids as their primary structural components.
Therefore,the correct option is $C$.

(C) Eukaryotic cells contain various membrane-bound organelles such as the Endoplasmic Reticulum $(ER)$,Golgi body,and Lysosomes.
Ribosomes are non-membrane-bound organelles found in both prokaryotic and eukaryotic cells.
Therefore,the Ribosome is the odd one out because it lacks a membrane.

(A) $Mg^{2+}$ ions play a crucial role in maintaining the structural integrity of ribosomes.
During protein synthesis,$Mg^{2+}$ ions act as a binding agent that helps in the association of the two ribosomal subunits ($60S$ and $40S$ in eukaryotes,or $50S$ and $30S$ in prokaryotes) to form a functional $80S$ or $70S$ ribosome,respectively.

(D) Ribosomes are non-membrane bound cell organelles found in both prokaryotic and eukaryotic cells.
In prokaryotes,they are $70S$ ribosomes,whereas in eukaryotes,they can be $80S$ (cytosol) or $70S$ (organelles like mitochondria and chloroplasts).
Lysosomes,centrosomes,and mitochondria are membrane-bound organelles.