Mitochondria Questions in English

(C) Janus green $B$ is a vital stain specifically used to observe mitochondria in living cells. It acts as an indicator of the respiratory activity of the mitochondria,turning from blue to colorless when reduced.

(D) The cell organelle known as the powerhouse of the cell is the $Mitochondrion$.
It is called the powerhouse because it produces cellular energy in the form of $ATP$ $(Adenosine Triphosphate)$ through the process of aerobic respiration.

(B) The inner membrane of the mitochondrion forms a number of infoldings known as cristae.
$1$. Cristae: These are the infoldings of the inner mitochondrial membrane that increase the surface area for biochemical reactions.
$2$. Cisternae: These are long,flattened,parallel,sac-like interconnected structures found in the Golgi apparatus or endoplasmic reticulum.
$3$. Microtubules: These are proteinaceous structures that form part of the cytoskeleton of the cell.
$4$. Mesosomes: These are the invaginations of the plasma membrane in bacterial cells,which help in respiration and $DNA$ replication.

(C) Mitochondria are semi-autonomous organelles that divide by fission. Their matrix contains a single circular $DNA$ molecule and ribosomes. The inner membrane of the mitochondria forms infoldings called cristae,which significantly increase the surface area for the attachment of enzymes involved in the electron transport chain and $ATP$ synthesis. Therefore,the statement that cristae decrease the surface area is incorrect.

(C) Mitochondria and chloroplast are considered semi-autonomous organelles because they contain their own circular $DNA$ and $70S$ ribosomes,allowing them to synthesize some of their own proteins.

(C) Mitochondria and chloroplasts are considered semi-autonomous organelles because they contain their own genetic material in the form of $DNA$, as well as $RNA$ and $ribosomes$ for protein synthesis.
Despite this, they are still dependent on the nuclear genome for many of their proteins and functional requirements.

(B) The endosymbiont hypothesis proposes that mitochondria and chloroplasts originated from free-living prokaryotes that were engulfed by a host cell.
Key similarities supporting this include:
$1$. Both mitochondria and chloroplasts contain circular $DNA$,which is similar to the bacterial genome.
$2$. This $DNA$ is not associated with histone proteins,a characteristic feature of prokaryotic $DNA$.
$3$. They possess $70S$ ribosomes,which are characteristic of prokaryotes,rather than the $80S$ ribosomes found in the eukaryotic cytoplasm.

(B) According to the Endosymbiotic Theory,mitochondria and chloroplasts are considered to have originated from independent prokaryotic organisms that were engulfed by a host cell. Therefore,there are $2$ such organelles.

(A) vital stain is a dye used to stain living cells without killing them. Janus green $B$ is a specific vital stain used to identify mitochondria in living cells.
In its oxidized state,Janus green $B$ is blue-green,and in its reduced state,it is colorless.
Inside the mitochondria,the enzyme cytochrome oxidase (part of the electron transport chain) keeps the dye in its oxidized (blue-green) state,thereby making the mitochondria visible under a microscope.
Since the Reason correctly explains the mechanism behind why Janus green $B$ stains mitochondria,both statements are correct and the Reason is the correct explanation of the Assertion.

(B) Mitochondria and chloroplast are the organelles that synthesize $ATP$ in living systems.
In both systems,the electron transport system $(ETS)$ is present,through which electrons are transferred by carrier molecules via a series of redox reactions.
Therefore,energy carrier molecules are continuously oxidized and reduced within the mitochondria and chloroplasts.

(C) Cellular respiration involves four major phases: glycolysis,link reaction,Krebs' cycle,and oxidative phosphorylation.
Glycolysis occurs in the cytoplasm,while the remaining three phases take place within the mitochondrion.
The enzymes for the Krebs' cycle are located in the mitochondrial matrix,and the enzymes for oxidative phosphorylation are embedded in the inner mitochondrial membrane.
Therefore,the mitochondrion is the primary site for respiratory enzymes.

(D) Mitochondria are known as the powerhouses of the cell because food materials are gradually oxidized within them,and the generated energy is stored in the form of $ATP$.
The enzymes required for the Krebs' cycle (aerobic respiration) and fatty acid oxidation are located in the mitochondrial matrix.

(A) During the process of oxidative phosphorylation,which occurs in the inner mitochondrial membrane,an electron transport system is active.
This process releases a significant amount of free energy.
This energy is utilized by the $F_{1}$ sub-units (also known as the headpiece of the $F_{0}-F_{1}$ complex) located on the inner mitochondrial membrane.
The $F_{1}$ particle contains the $ATP$ synthase enzyme,which catalyzes the synthesis of $ATP$ molecules from $ADP$ and inorganic phosphate.

(A) Mitochondria are known as the powerhouse of the cell because they generate most of the cell's supply of adenosine triphosphate $(ATP)$,which is used as a source of chemical energy.

(B) The mitochondrion is a double-membrane-bound organelle.
The outer membrane forms the continuous limiting boundary of the organelle.
The inner membrane is folded into a number of infoldings called $cristae$ towards the matrix.
These $cristae$ significantly increase the surface area of the inner membrane to accommodate more enzymes for the electron transport chain and $ATP$ synthesis.
Therefore,the inner membrane has a much greater surface area than the outer membrane.

(C) Mitochondria are typically sausage-shaped or cylindrical structures.
According to the $NCERT$ textbook,the dimensions of mitochondria are as follows:
Diameter: $0.2$ to $1.0 \ \mu m$ (average $0.5 \ \mu m$).
Length: $1.0$ to $4.1 \ \mu m$.
Therefore,option $C$ is the correct choice.

(A) Mitochondria are double-membrane bound organelles. The inner membrane of the mitochondria forms a number of infoldings called cristae towards the matrix. These cristae increase the surface area for various biochemical reactions,such as the electron transport chain,which is essential for $ATP$ production.

(A) $F_1$ particles,also known as oxysomes or $F_0-F_1$ complexes,are located on the inner mitochondrial membrane.
These particles project into the mitochondrial matrix.
They are responsible for $ATP$ synthesis during oxidative phosphorylation.

(B) Mitochondria are semi-autonomous organelles that divide by binary fission,not multiple fission. Therefore,the statement that they divide by multiple fission is incorrect. Mitochondria are indeed the sites of aerobic respiration where $ATP$ is produced,and their number per cell varies based on the metabolic demand of the cell.

(A) Aerobic respiration involves the complete oxidation of organic substances in the presence of oxygen,releasing $CO_2$,water,and a large amount of energy in the form of $ATP$.
This process occurs in the mitochondria of eukaryotic cells.
The Krebs cycle and the Electron Transport System $(ETS)$ take place within the mitochondria,making it the site of aerobic respiration.

(C) Phosphorylation is the process of adding a phosphate group to a molecule,typically $ADP$,to form $ATP$.
In eukaryotic cells,this occurs primarily through two mechanisms: photophosphorylation and oxidative phosphorylation.
$1$. Photophosphorylation occurs in the chloroplasts during photosynthesis,where light energy is used to synthesize $ATP$.
$2$. Oxidative phosphorylation occurs in the mitochondria during cellular respiration,where energy released from the electron transport chain is used to synthesize $ATP$.
Therefore,both chloroplasts and mitochondria are the key organelles involved in the synthesis of $ATP$ via phosphorylation.

(C) All living cells possess a plasma membrane,cytoplasm,and genetic material ($DNA$ or $RNA$).
However,mitochondria are membrane-bound organelles found only in eukaryotic cells.
Prokaryotic cells,such as bacteria,lack membrane-bound organelles like mitochondria.
Therefore,mitochondria are not necessarily found in all living cells.

(B) is the correct answer because mitochondria do not divide in synchrony with the cell cycle.
Mitochondria are semi-autonomous organelles that replicate independently of the cell cycle through a process similar to binary fission in prokaryotes.
They contain their own circular $DNA$ ($A$ is true).
They are the sites of aerobic respiration where they store and release chemical energy in the form of $ATP$ ($C$ is true).
They contain inner membrane folds called cristae which increase the surface area for biochemical reactions ($D$ is true).