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

$(A)$ The Golgi apparatus is a cellular organelle involved in the modification, sorting, and packaging of proteins for secretion $(A-IV)$.
Mitochondria are known as the powerhouse of the cell as they are the site of aerobic respiration, where energy is transferred from organic compounds into $ATP$ $(B-V)$.
Vacuoles are membrane-bound organelles that store water, nutrients, and waste products $(C-I)$.
Grana are stacked membranous structures within the chloroplasts that contain chlorophyll and are the site of the light-dependent reactions of photosynthesis $(D-II)$.
Therefore, the correct matching is $A-IV, B-V, C-I, D-II$.

$(A)$ $RER$ (Rough Endoplasmic Reticulum) has ribosomes on its surface and is primarily involved in protein synthesis and secretion.
Cell wall provides structural support, rigidity, and protection to the cell.
Flagella are whip-like appendages that enable cell movement.
Lysosomes are membrane-bound organelles containing hydrolytic enzymes, responsible for intracellular and extracellular digestion.

$(B)$. Mycoplasma cells are bacteria that lack a cell wall.
$B$. Plasmid is a small, circular, extrachromosomal $DNA$ molecule found in bacteria.
$C$. Thylakoids are flattened, sac-like structures found inside chloroplasts that form the grana.
$D$. Lysosomes are membrane-bound vesicles containing hydrolytic enzymes, often referred to as the 'suicidal bags' of the cell.
Therefore, the correct matching is $A-II, B-IV, C-III, D-I$.

(C) Pair $A$ is correct: Microtubules are structural components of cilia and flagella.
Pair $B$ is incorrect: Centrioles are involved in spindle formation during cell division. Lysosomes are the organelles that store hydrolytic enzymes.
Pair $C$ is incorrect: Amyloplasts specifically store starch. Elaioplasts store oils and fats,while Aleuroplasts store proteins.
Therefore,only $A$ is correctly matched.

(B) The correct answer is $B$. Plasmodesmata are cytoplasmic bridges that connect the cytoplasm of adjacent plant cells, allowing for transport and communication. The membrane surrounding the vacuole in plants is known as the tonoplast, not plasmodesmata.

(D) Amyloplasts store carbohydrates (starch),$e.g$.,potato,whereas proteins are stored by aleuroplasts. Therefore,$(I)$ is incorrect.
Mitochondria are known as the 'Power house' of the cell because they produce energy in the form of $ATP$. Therefore,$(II)$ is correct.
Chlorophyll pigments are present in the thylakoids,not in the stroma. The stroma contains enzymes for the dark reaction. Therefore,$(III)$ is incorrect.
Axoneme,the core of cilia and flagella,consists of a $9+2$ arrangement of microtubules. Therefore,$(IV)$ is correct.
Thus,the correctly matched pairs are $(II)$ and $(IV)$.

$(A)$ Centrioles are non-membrane bound organelles that help in cell division. They are composed mainly of a protein called tubulin.
Fimbriae are special structures found in bacteria. These are small bristle-like fibers sprouting out of the cell that help bacteria attach to rocks in streams and also to host tissues.
The endomembrane system includes those organelles (like $ER$, Golgi complex, lysosomes, and vacuoles) whose functions are coordinated.
Mitochondria are double-membrane cell organelles that divide by fission and are the site of aerobic respiration.

(C) Mesosomes are specialized structures formed by the extensions of the plasma membrane into the cell.
They are characteristic features of prokaryotes,not eukaryotes.
Mesosomes assist in cell wall formation,$DNA$ replication,and distribution to daughter cells.
They also facilitate respiration,secretion processes,and increase the surface area of the plasma membrane and enzymatic content.

(B) The statement that 'Mitochondria divide by fragmentation' is false. In reality,mitochondria divide by a process called binary fission,which is similar to the division of bacteria. The other statements are correct: ribosomes in a polysome translate $mRNA$ into proteins,the cell theory states that all cells arise from pre-existing cells,and the lipid bilayer of the cell membrane is primarily composed of phosphoglycerides.

(D) Mycoplasma are the smallest cells ($0.3\; \mu m$ in length).
Bacteria typically range from $3$ to $5\; \mu m$ in size.
The egg of an ostrich is the largest isolated single cell.
Nerve cells are not the smallest; in fact,they are among the longest cells in the human body.
Therefore,the statement that nerve cells are some of the smallest cells is incorrect.

(A) $(i)$ Cells exhibit diverse shapes such as disc-like, polygonal, columnar, cuboid, thread-like, or even irregular, depending on the specific function they perform.
$(ii)$ Human red blood cells $(RBCs)$ are approximately $7.0 \; \mu m$ in diameter. (Note: The original question stated $7.0 \; mm$, which is corrected to $7.0 \; \mu m$ for scientific accuracy).
$(iii)$ The cytoplasm is a semi-fluid matrix that occupies the volume of the cell and serves as the primary site for various cellular activities.
$(iv)$ The cytoplasm contains various chemical reactions that are essential to maintain the cell in a living state.
Therefore, all the given statements are correct.

(A) Statement $(i)$ is incorrect because centrioles are present in almost all animal cells and are typically absent in plant cells.
Statement $(ii)$ is correct; ribosomes are indeed the sites of protein synthesis.
Statement $(iii)$ is incorrect because the middle lamella is primarily composed of calcium and magnesium pectates, not calcium carbonate.
Statement $(iv)$ is correct; the smooth endoplasmic reticulum $(SER)$ is the primary site for the synthesis of lipids and steroidal hormones in animal cells.
Therefore, statements $(i)$ and $(iii)$ are incorrect.

(A) Statement $(i)$ is incorrect because the plasma membrane is not considered part of the endomembrane system.
Statement $(ii)$ is correct as the Endoplasmic Reticulum $(ER)$ is involved in the transport of materials,protein synthesis (Rough $ER$),and lipid/glycogen synthesis (Smooth $ER$).
Statement $(iii)$ is correct as ribosomes are the sites of protein synthesis.
Statement $(iv)$ is correct as mitochondria are the sites of aerobic respiration,oxidative phosphorylation,and $ATP$ production.
Therefore,statements $(ii), (iii),$ and $(iv)$ are correct.

(D) Statement $(i)$ is incorrect because the endomembrane system includes the endoplasmic reticulum $(ER)$,Golgi complex,lysosomes,and vacuoles. Mitochondria,chloroplasts,and peroxisomes are not part of the endomembrane system as their functions are not coordinated with these organelles.
Statement $(ii)$ is correct. Smooth endoplasmic reticulum $(SER)$ is the major site for lipid synthesis.
Statement $(iii)$ is correct. Rough endoplasmic reticulum $(RER)$ contains ribosomes on its surface and is actively involved in protein synthesis.
Statement $(iv)$ is incorrect. The mitochondrial matrix contains a single circular $DNA$ molecule,a few $RNA$ molecules,and $70\; S$ ribosomes,not $80\; S$ ribosomes.
Therefore,statements $(ii)$ and $(iii)$ are correct.

(A) Statement $A$ is correct: The $Na^+/K^+$ pump uses $ATP$ to transport ions against their concentration gradient,which is a classic example of active transport.
Statement $B$ is incorrect: In animal cells,lipid-like steroidal hormones are synthesized in the $SER$ (Smooth Endoplasmic Reticulum).
Statement $C$ is incorrect: In plant cells,the vacuoles can occupy up to $90\%$ of the volume of the cell.
Statement $D$ is incorrect: Chlorophyll and carotenoid pigments are responsible for trapping light energy essential for photosynthesis,not leucoplasts (which are primarily for storage).

(C) The correct statements are $(i), (ii)$ and $(iv)$.
$(i)$ Statement $(i)$ is correct because prokaryotic cells lack membrane-bound organelles,including membrane-bound inclusion bodies.
$(ii)$ Statement $(ii)$ is correct as ribosomes are the universal site for protein synthesis in both prokaryotes and eukaryotes.
$(iii)$ Statement $(iii)$ is incorrect because pili are surface appendages that facilitate conjugation (transfer of genetic material) and attachment,but they do not play a role in motility. Flagella are the structures responsible for motility in bacteria.
$(iv)$ Statement $(iv)$ is correct because the cell membrane of prokaryotes is a lipid bilayer with embedded proteins,which is structurally similar to that of eukaryotic cells.

(A) The endomembrane system includes the Endoplasmic Reticulum $(ER)$,Golgi complex,Lysosomes,and Vacuoles because their functions are coordinated.
$Mitochondria$ is not considered a part of the endomembrane system because its functions are not coordinated with these organelles.

(A) Mitochondria,chloroplasts,and the nucleus are all cell organelles that are enclosed by a double membrane structure.
- Mitochondria and chloroplasts are semi-autonomous organelles containing their own $DNA$ and $70S$ ribosomes.
- The nucleus is the control center of the cell,bounded by the nuclear envelope (double membrane).
- They are not part of the endomembrane system,which includes the endoplasmic reticulum,Golgi complex,lysosomes,and vacuoles.

$(a)$. Glyoxysomes are specialized peroxisomes found in plants that contain enzymes for the glyoxylate cycle, which converts stored fats into carbohydrates.
$(b)$. Sphaerosomes are small, spherical organelles in plant cells that are often considered equivalent to lysosomes as they contain hydrolytic enzymes.
$(c)$. Mitochondria are the sites of aerobic respiration and contain the enzyme succinate dehydrogenase in the inner mitochondrial membrane.
$(d)$. Peroxisomes are involved in photorespiration in plants, where they work in conjunction with chloroplasts and mitochondria.
Therefore, the correct matching is $a(ii), b(i), c(iv), d(iii)$.

(C) The correct answer is $C$.
$1$. Peroxisomes contain enzymes like catalase,which break down hydrogen peroxide into water and oxygen. This is a correct match.
$2$. Ribosomes were first observed by George Palade,hence they are often called Palade particles. This is a correct match.
$3$. Glyoxylate enzymes are found in glyoxysomes,which are specialized peroxisomes present in plants (specifically in germinating seeds) but are $NOT$ found in animals. Therefore,this is the mismatched pair.
$4$. Massules (or microtubule organizing centers) are associated with $MTG$ (Microtubule Organizing Centers or MTOCs). This is a correct match.

(C) Based on the provided cell diagram:
$A$ points to the Smooth Endoplasmic Reticulum $(SER)$,which is involved in lipid and steroid hormone synthesis.
$B$ points to the Cell Wall (in a plant cell),which is a non-living rigid structure providing shape and protection.
$C$ points to the Centrioles,which lie perpendicular to each other and have a cartwheel-like organization.
$D$ points to the Mitochondria,which are involved in cellular respiration,not light trapping (that is the function of chloroplasts).
$E$ points to the Rough Endoplasmic Reticulum $(RER)$,which is involved in protein synthesis.
$F$ points to Lysosomes,which are spherical structures rich in hydrolytic enzymes.
Therefore,the statements $A, C,$ and $E$ are correct descriptions of the labeled organelles in the context of the cell structure provided.

(C) In a cell, certain structures are not bound by any membrane.
$1$. $Ribosome$: These are protein-synthesizing machineries found in both prokaryotes and eukaryotes, lacking a membrane.
$2$. $Nucleolus$: A dense spherical body present inside the nucleus, which is not membrane-bound.
$3$. $Centriole$ ($Centrosome$): These are cylindrical structures involved in cell division, which are also non-membranous.
Therefore, the correct set is $Ribosome$, $Nucleolus$, and $Centriole$.

(C) Statement $a$ is correct: Cells actively involved in protein synthesis require more ribosomes,thus they possess larger and more numerous nucleoli.
Statement $b$ is correct: Nuclear pores act as channels for the bidirectional movement of $RNA$ and protein molecules between the nucleus and the cytoplasm.
Statement $c$ is incorrect: The cytoskeleton is a proteinaceous structure (composed of microtubules,microfilaments,and intermediate filaments),not a glycolipid structure.
Statement $d$ is incorrect: Steroidal hormones are synthesized by the Smooth Endoplasmic Reticulum $(SER)$,not the Golgi complex.
Therefore,statements $c$ and $d$ are incorrect.

(A) All the given statements are correct for eukaryotic cells.
$a$. Eukaryotic cells contain $80S$ ribosomes in the cytoplasm and $70S$ ribosomes within organelles like mitochondria and chloroplasts.
$b$. Eukaryotic flagella and cilia exhibit a characteristic $9+2$ microtubule arrangement.
$c$. Cytoplasmic streaming (cyclosis) is a common feature observed in eukaryotic cells.
$d$. In eukaryotic cells,$DNA$ is wrapped around histone proteins to form chromatin,which further condenses into chromosomes.

(B) chemical substance that absorbs radiation when irradiated with $UV$ rays and subsequently emits visible light is known as a fluorochrome. This property is widely used in fluorescence microscopy to label specific biological molecules.

(B) Cytoplasmic streaming movement is also known as cyclosis.
Cyclosis is the directed flow of cytosol and organelles around the large central vacuole of a plant cell or along the paths of the cytoskeleton in other eukaryotic cells.
It facilitates the distribution of nutrients,proteins,and organelles within the cell.
This process is a characteristic feature of eukaryotic cells and is absent in prokaryotes and viruses.

(B) The correct matches are as follows:
$(a)$ Cristae: These are the infoldings of the inner mitochondrial membrane that increase the surface area for biochemical reactions. Hence,$(a)-(iii)$.
$(b)$ Thylakoids: These are flattened,disc-like membranous sacs found within the stroma of chloroplasts,which are the sites of light-dependent reactions. Hence,$(b)-(iv)$.
$(c)$ Centromere: This is the primary constriction region on a chromosome where spindle fibers attach during cell division. Hence,$(c)-(i)$.
$(d)$ Cisternae: These are the flattened,disc-shaped sacs that make up the Golgi apparatus. Hence,$(d)-(ii)$.
Therefore,the correct sequence is $(a)-(iii), (b)-(iv), (c)-(i), (d)-(ii)$.

(B) The correct answer is $B$.
Mature sieve tube elements in angiosperms are specialized cells that lose their nucleus,ribosomes,vacuoles,and other organelles at maturity to facilitate the efficient transport of food (phloem sap).
Therefore,the statement that they possess a conspicuous nucleus and usual cytoplasmic organelles is incorrect.
Microbodies (like peroxisomes) are found in both plant and animal cells.
The perinuclear space (the space between the two nuclear membranes) acts as a barrier between the nucleoplasm and the cytoplasm.
Nuclear pores are complex structures that regulate the movement of $RNA$ and proteins between the nucleus and the cytoplasm in both directions.

(D) In eukaryotic cells,most organelles are membrane-bound. However,some organelles lack a membrane.
$1$. $Ribosomes$: These are protein-synthesizing machineries made of $RNA$ and proteins,and they are not enclosed by any membrane.
$2$. $Nucleolus$: This is a dense,spherical structure present inside the nucleus where ribosomal $RNA$ is synthesized; it is also membrane-less.
$3$. $Centrosome$: This is an organelle involved in cell division,consisting of two centrioles surrounded by amorphous pericentriolar material,and it lacks a membrane.
Therefore,$Ribosomes$,$Nucleolus$,and $Centrosome$ are membrane-less organelles.

(B) An $Animal \text{ cell}$ is bounded only by the plasma membrane (cell membrane) as its outermost boundary.
In contrast, $Plant \text{ cells}$, $Bacteria$, and $Fungi$ possess a rigid cell wall outside the plasma membrane, which acts as an additional outer layer.
Therefore, the $Animal \text{ cell}$ is the only one among the given options that lacks a cell wall and has only a single outer membrane.

(C) In the provided diagram of a plant cell:
$1$. $P$ represents the Mitochondrion,which is characterized by its double-membrane structure with inner folds called cristae.
$2$. $Q$ represents the Chloroplast,which is a large,oval-shaped organelle typical of plant cells.
$3$. $R$ represents a Peroxisome,which is a small,spherical,single-membrane-bound organelle involved in metabolic processes.
Therefore,the correct identification is $P =$ Mitochondrion,$Q =$ Chloroplast,and $R =$ Peroxisome.

(C) To determine the number of membrane-bound structures,we classify each organelle:
$1$. Endoplasmic reticulum: Membrane-bound (Single membrane).
$2$. Golgi apparatus: Membrane-bound (Single membrane).
$3$. Ribosomes: Non-membrane-bound.
$4$. Lysosomes: Membrane-bound (Single membrane).
$5$. Mitochondria: Membrane-bound (Double membrane).
$6$. Microbodies: Membrane-bound (Single membrane).
$7$. Centrioles: Non-membrane-bound.
$8$. Nucleolus: Non-membrane-bound.
$9$. Vacuoles: Membrane-bound (Single membrane,Tonoplast).
Counting the membrane-bound structures: Endoplasmic reticulum,Golgi apparatus,Lysosomes,Mitochondria,Microbodies,and Vacuoles.
Total count = $6$.

(D) Based on the biological structures provided in the image:
$P$ (Red blood cells) correspond to image $III$ (round and biconcave).
$Q$ (White blood cells) correspond to image $IV$ (irregular shape).
$R$ (Mesophyll cells) correspond to image $I$ (round and oval cells).
$S$ (Tracheid) corresponds to image $II$ (elongated structure).
Therefore,the correct matching is $(P-III), (Q-IV), (R-I), (S-II)$.

(B) The endomembrane system includes organelles that work together to modify,package,and transport lipids and proteins.
These include the endoplasmic reticulum,Golgi apparatus,lysosomes,and vacuoles.
Chloroplasts and mitochondria are not part of the endomembrane system because their functions are not coordinated with the endomembrane system in the same way.

(B) The endomembrane system includes organelles whose functions are coordinated. These include the Endoplasmic Reticulum $(ER)$,Golgi complex,Lysosomes,and Vacuoles.
$1$. Vacuoles: Part of the endomembrane system.
$2$. Peroxisomes: Not part of the endomembrane system.
$3$. Mitochondria: Not part of the endomembrane system (semi-autonomous).
$4$. Chloroplasts: Not part of the endomembrane system (semi-autonomous).
$5$. Golgi complex: Part of the endomembrane system.
Therefore,only $2$ organelles (Vacuoles and Golgi complex) are part of the endomembrane system.

(B) The correct matches are as follows:
$1$. Sieve tube elements $(P)$ are mature cells that lack a nucleus, hence they are enucleated $(III)$.
$2$. Paramecium $(Q)$ is a ciliate protozoan that contains two types of nuclei (macronucleus and micronucleus), making it binucleate $(I)$.
$3$. A typical cell $(R)$ generally contains a single nucleus, making it uninucleate $(II)$.
$4$. Skeletal muscle cells $(S)$ are formed by the fusion of multiple cells, resulting in a syncytium, which is multinucleate $(IV)$.
Thus, the correct sequence is $P-III, Q-I, R-II, S-IV$.

(D) Porins are large protein channels present in the outer membranes of plastids,mitochondria,and some bacteria.
These proteins allow molecules of the size of small proteins to pass through the membrane.
Therefore,all the given options contain porins in their outer membranes.

(A) The endomembrane system includes the endoplasmic reticulum $(ER)$, Golgi complex, lysosomes, and vacuoles.
Since the functions of the mitochondria, chloroplasts, and peroxisomes are not coordinated with the above-mentioned components, they are not considered part of the endomembrane system.
Therefore, the organelles that are $NOT$ part of the endomembrane system are mitochondria $(A)$, chloroplasts $(C)$, and peroxisomes $(E)$.

(A) The correct matching is as follows:
- Nucleolus $(A)$: It is the site for active ribosomal $RNA$ $(rRNA)$ synthesis $(III)$.
- Centriole $(B)$: Centrioles are organelles that possess an organization like the cartwheel $(II)$.
- Golgi apparatus $(C)$: It is the primary site for the formation of glycoproteins and glycolipids $(I)$.
- Leucoplast $(D)$: These are colourless plastids that are primarily responsible for storing nutrients such as starch,oil,or proteins $(IV)$.
Therefore,the correct sequence is $A-III, B-II, C-I, D-IV$.

(C) - Axoneme is the core structure found in cilia and flagella $(A-II)$.
- Centriole exhibits a characteristic cartwheel pattern in its cross-section $(B-I)$.
- Crista refers to the infoldings of the inner mitochondrial membrane $(C-IV)$.
- Satellite is a small fragment of chromosome separated from the main body by a secondary constriction $(D-III)$.
- Therefore,the correct matching is $A-II, B-I, C-IV, D-III$.

(D) Statement $I$ is correct: Both mitochondria and chloroplasts are semi-autonomous cell organelles bounded by a double-membrane system.
Statement $II$ is correct: The inner membrane of mitochondria contains specific transport proteins that allow the movement of various ions and metabolites,making it relatively more permeable. In contrast,the inner membrane of chloroplasts is highly selective and relatively impermeable to most ions and metabolites,requiring specific transporters for their movement.
Therefore,both statements are correct.

(D) The correct matches are as follows:
$A$. Centromere is the site of attachment for spindle fibers during $Cell \text{ } division$ $(II)$.
$B$. Cilium is a hair-like outgrowth of the cell membrane involved in $Cell \text{ } movement$ $(III)$.
$C$. Cristae are the infoldings of the inner membrane of the $Mitochondrion$ $(I)$.
$D$. Cell membrane is primarily composed of a $Phospholipid \text{ } Bilayer$ $(IV)$.
Therefore,the correct sequence is $A-II, B-III, C-I, D-IV$.

(D) Let us analyze each statement:
$(A)$ Correct: The lipid component of the plasma membrane is primarily composed of phosphoglycerides.
$(B)$ Incorrect: Polar molecules cannot pass through the non-polar lipid bilayer easily; they require carrier proteins or channel proteins for transport.
$(C)$ Incorrect: The secondary wall is formed on the inner side of the primary wall and it is generally not capable of growth (it is rigid).
$(D)$ Correct: The quasi-fluid nature of the lipid bilayer allows for the lateral movement of proteins within the membrane (Fluid Mosaic Model).
$(E)$ Correct: The middle lamella is a layer primarily made of calcium pectate that acts as a glue to hold neighbouring cells together.
Thus,statements $(B)$ and $(C)$ are incorrect. The total number of incorrect statements is $2$.

(D) The correct answer is $D$.
$A$. Centrioles are composed of nine evenly spaced peripheral fibrils of tubulin protein,which gives a cart-wheel appearance. This is correct.
$B$. Mitochondria are known as the powerhouse of the cell because they produce energy in the form of $ATP$. This is correct.
$C$. Ribosomes are found in the cytoplasm,as well as in other organelles like mitochondria and chloroplasts. This is correct.
$D$. $RER$ (Rough Endoplasmic Reticulum) is involved in protein synthesis. $SER$ (Smooth Endoplasmic Reticulum) is the major site for the synthesis of lipid-like steroidal hormones. Therefore,the matching for $RER$ is incorrect.

(C) The endomembrane system includes the endoplasmic reticulum $(ER)$,Golgi complex,lysosomes,and vacuoles.
These organelles are considered part of the endomembrane system because their functions are coordinated.
Therefore,the Assertion is true,but the Reason is false because the functions of these organelles are indeed coordinated.

(B) Let us analyze each statement:
$(A)$ Incorrect. Centrioles are non-membrane-bound organelles.
$(B)$ Incorrect. In the plasma membrane,the polar heads are towards the outer sides and the hydrophobic tails are towards the inner side.
$(C)$ Correct. Plasmodesmata are channels that traverse the cell walls of plant cells and some algal cells,enabling transport and communication between them.
$(D)$ Correct. The quasi-fluid nature of the lipid bilayer allows for the lateral movement of proteins within the membrane,as described by the fluid mosaic model.
Thus,only statements $(C)$ and $(D)$ are correct. The total number of correct statements is $2$.

(C) Statement $A$ is correct: According to the Cell Theory,a cell is the fundamental unit of life,and anything less than a complete cell cannot exhibit all life processes independently.
Statement $B$ is correct: Eukaryotic cells contain membrane-bound organelles like the nucleus,mitochondria,and endoplasmic reticulum,which create distinct compartments within the cytoplasm.
Statement $C$ is correct: Mitochondria are semi-autonomous organelles that replicate independently of the cell cycle through a process similar to binary fission.
Statement $D$ is correct: The vacuole is a membrane-bound space found in the cytoplasm,containing water,sap,excretory products,and other materials not useful for the cell.
Since all statements $A, B, C,$ and $D$ are scientifically accurate,option $C$ is the correct answer.

(B) The correct answer is $B$ (Mitochondria).
The endomembrane system includes organelles whose functions are coordinated,such as the endoplasmic reticulum $(ER)$,Golgi complex,lysosomes,and vacuoles.
Organelles like mitochondria,chloroplasts,and peroxisomes are not considered part of the endomembrane system because their functions are not coordinated with the endomembrane components,and they do not participate in the same vesicular transport pathway.

(C) Option $C$ is correct. In some prokaryotes like cyanobacteria,there are other membranous extensions into the cytoplasm called chromatophores which contain pigments.
Explanation of other options:
- Option $A$: The core of a cilium or flagellum is called the axoneme,not the basal body.
- Option $B$: Elaioplasts store oils and fats,while amyloplasts store starch. Aleuroplasts store proteins.
- Option $D$: Acrocentric chromosomes have two arms,one very short and one very long,with the centromere situated close to one end.

(D) Statement $A$ is incorrect because the endomembrane system consists of the endoplasmic reticulum,Golgi complex,lysosomes,and vacuoles; mitochondria are not part of it.
Statement $B$ is correct because rough endoplasmic reticulum $(RER)$ has ribosomes attached to its surface.
Statement $C$ is correct because both mitochondria and plastids are semi-autonomous organelles containing circular $DNA$.
Statement $D$ is correct because the cytoskeleton is an elaborate network of proteinaceous filaments consisting of microtubules,microfilaments,and intermediate filaments.
Statement $E$ is incorrect because mitochondria are double-membrane bound structures.
Thus,statements $B, C,$ and $D$ are correct.