Cell: The Unit of Life Quiz
1. Hypothesis that the bodies of animals and plants are composed of cells and products of cells was proposed by : –
Correct Answer: (2) Schwann
Explanation: Theodor Schwann (1839) studied different types of animal cells and reported that cells had a thin outer layer which is today known as the ‘plasma membrane’. He also concluded, based on his studies on plant tissues, that the presence of a cell wall is a unique character of the plant cells. On the basis of this, Schwann proposed the hypothesis that the bodies of animals and plants are composed of cells and products of cells.
Explanation: Theodor Schwann (1839) studied different types of animal cells and reported that cells had a thin outer layer which is today known as the ‘plasma membrane’. He also concluded, based on his studies on plant tissues, that the presence of a cell wall is a unique character of the plant cells. On the basis of this, Schwann proposed the hypothesis that the bodies of animals and plants are composed of cells and products of cells.
2. To keep the cell in the ‘Living state’, various chemical reactions occur in : –
Correct Answer: (3) Cytoplasm
Explanation: The cytoplasm is the main arena of cellular activities in both the plant and animal cells. Various chemical reactions occur in it to keep the cell in the ‘living state’.
Explanation: The cytoplasm is the main arena of cellular activities in both the plant and animal cells. Various chemical reactions occur in it to keep the cell in the ‘living state’.
6. Transport of molecules across the membrane against their concentration gradient is : –
Correct Answer: (4) An energy dependent process
Explanation: Transport of molecules across the membrane against their concentration gradient, i.e., from lower to higher concentration, is an energy-dependent process, in which ATP is utilised. This is called active transport.
Explanation: Transport of molecules across the membrane against their concentration gradient, i.e., from lower to higher concentration, is an energy-dependent process, in which ATP is utilised. This is called active transport.
7. Mark the correct statements related to cell wall .
(a) Non – living rigid structure
(b) Present in fungi and plants
(c) Provides barriers to undesirable macromolecules
(d) Primary cell wall is capable of growth
(e) Primary wall gradually diminishes as the cell matures
Correct Answer: (4) All are correct
Explanation: All the statements (a), (b), (c), (d), and (e) are correct regarding the cell wall. The cell wall is a non-living rigid structure found in fungi and plants, providing structural support and protection. It acts as a barrier to undesirable macromolecules. The primary cell wall is capable of growth and gradually diminishes as the cell matures.
Explanation: All the statements (a), (b), (c), (d), and (e) are correct regarding the cell wall. The cell wall is a non-living rigid structure found in fungi and plants, providing structural support and protection. It acts as a barrier to undesirable macromolecules. The primary cell wall is capable of growth and gradually diminishes as the cell matures.
8. Oligosacchrides present on the outer surface of plasma membrane are important for : –
Correct Answer: (1) cell to cell recognition
Explanation: Oligosaccharides, when attached to proteins (glycoproteins) or lipids (glycolipids) on the outer surface of the plasma membrane, form the glycocalyx. This glycocalyx plays a crucial role in cell-to-cell recognition and adhesion.
Explanation: Oligosaccharides, when attached to proteins (glycoproteins) or lipids (glycolipids) on the outer surface of the plasma membrane, form the glycocalyx. This glycocalyx plays a crucial role in cell-to-cell recognition and adhesion.
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9. The fluid nature of plasma membrane is important from the point of view of how many function in the list given below ?
Cell division, endocytosis, secretion, cell growth, formation of intercellular junctions.
Correct Answer: (4) Five
Explanation: The fluid nature of the plasma membrane is important for all the listed functions: cell growth, formation of intercellular junctions, secretion, endocytosis, and cell division. The ability of lipids and proteins to move within the membrane is crucial for these dynamic cellular processes.
Explanation: The fluid nature of the plasma membrane is important for all the listed functions: cell growth, formation of intercellular junctions, secretion, endocytosis, and cell division. The ability of lipids and proteins to move within the membrane is crucial for these dynamic cellular processes.
10. Presence of which of the following in an eukaryotic cell differentiate it from a prokaryotic cell ?
Correct Answer: (3) Membrane bound cell organelles
Explanation: Eukaryotic cells are characterized by the presence of a well-defined nucleus and membrane-bound organelles (like ER, Golgi, mitochondria, chloroplasts, lysosomes, etc.), which are absent in prokaryotic cells. Both types of cells have a cell membrane, cytoplasm, and ribosomes (though different types).
Explanation: Eukaryotic cells are characterized by the presence of a well-defined nucleus and membrane-bound organelles (like ER, Golgi, mitochondria, chloroplasts, lysosomes, etc.), which are absent in prokaryotic cells. Both types of cells have a cell membrane, cytoplasm, and ribosomes (though different types).
11. Mitochondria and chloroplasts have membranes yet they are not the part of endomembrane system because : –
Correct Answer: (3) Their functions are not coordinated with the ER, golgi body and Lysosomes
Explanation: The endomembrane system includes organelles whose functions are coordinated. These include the endoplasmic reticulum (ER), Golgi complex, lysosomes, and vacuoles. Mitochondria, chloroplasts, and peroxisomes are not considered part of the endomembrane system because their functions are not coordinated with the above components.
Explanation: The endomembrane system includes organelles whose functions are coordinated. These include the endoplasmic reticulum (ER), Golgi complex, lysosomes, and vacuoles. Mitochondria, chloroplasts, and peroxisomes are not considered part of the endomembrane system because their functions are not coordinated with the above components.
12. ER is concerned with the synthesis of : –
Correct Answer: (4) All of the above
Explanation: The Endoplasmic Reticulum (ER) is involved in the synthesis of various molecules. Rough ER (RER) is primarily involved in protein synthesis and secretion, while Smooth ER (SER) is the major site for the synthesis of lipid and steroid hormones. Therefore, ER is concerned with the synthesis of lipids, steroid hormones, and proteins.
Explanation: The Endoplasmic Reticulum (ER) is involved in the synthesis of various molecules. Rough ER (RER) is primarily involved in protein synthesis and secretion, while Smooth ER (SER) is the major site for the synthesis of lipid and steroid hormones. Therefore, ER is concerned with the synthesis of lipids, steroid hormones, and proteins.
13. RER (Rough Endoplasmic Reticulum) : –
(a) Bears 80S ribosomes on their outer surface
(b) Frequently observed in the cells actively involved in protein synthesis and secretion
(c) Are extensive and continuous with outer nuclear membrane
(d) Synthesizes steroid hormones in animal cells
Find out the incorrect statement(s) : –
Correct Answer: (4) d only
Explanation: Statement (d) is incorrect. Rough Endoplasmic Reticulum (RER) is primarily involved in protein synthesis and secretion, bearing 80S ribosomes on its surface. The synthesis of steroid hormones in animal cells is a function of the Smooth Endoplasmic Reticulum (SER), not RER. Statements (a), (b), and (c) are correct regarding RER.
Explanation: Statement (d) is incorrect. Rough Endoplasmic Reticulum (RER) is primarily involved in protein synthesis and secretion, bearing 80S ribosomes on its surface. The synthesis of steroid hormones in animal cells is a function of the Smooth Endoplasmic Reticulum (SER), not RER. Statements (a), (b), and (c) are correct regarding RER.
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14. A Golgi complex has : –
Correct Answer: (2) Varied number of cisternae
Explanation: The Golgi apparatus consists of many flat, disc-shaped sacs or cisternae. The number of cisternae in a Golgi complex is variable, ranging from 4 to 8 or more in different cells.
Explanation: The Golgi apparatus consists of many flat, disc-shaped sacs or cisternae. The number of cisternae in a Golgi complex is variable, ranging from 4 to 8 or more in different cells.
15. The cis and the trans faces of golgi body are : –
Correct Answer: (3) Entirely different but interconnected
Explanation: The Golgi cisternae are concentrically arranged near the nucleus with distinct convex cis or the forming face and concave trans or the maturing face. The cis and the trans faces of the organelle are entirely different, but interconnected.
Explanation: The Golgi cisternae are concentrically arranged near the nucleus with distinct convex cis or the forming face and concave trans or the maturing face. The cis and the trans faces of the organelle are entirely different, but interconnected.
16. Materials to be packaged in the form of vesicles from the…..(i )……..fuse with the…..(ii)…..of the golgi apparatus and move towards the….(iii)… .
Choose the correct terms for blanks : –
Correct Answer: (4) (i) – ER, (ii) – forming face, (iii) – trans face
Explanation: Materials to be packaged in the form of vesicles from the **ER** fuse with the **forming face** (cis face) of the Golgi apparatus and move towards the **trans face** (maturing face). This describes the pathway of protein and lipid modification and transport through the Golgi.
Explanation: Materials to be packaged in the form of vesicles from the **ER** fuse with the **forming face** (cis face) of the Golgi apparatus and move towards the **trans face** (maturing face). This describes the pathway of protein and lipid modification and transport through the Golgi.
17. Digestion of the tail of frog tadpole larva during metamorphosis is : –
Correct Answer: (4) Autolysis
Explanation: Autolysis refers to the self-digestion of cells or tissues by their own enzymes, often occurring after cell death or as part of programmed cell death (apoptosis). The digestion of the tadpole tail during metamorphosis is a classic example of programmed cell death involving lysosomal enzymes, leading to autolysis of the tail cells.
Explanation: Autolysis refers to the self-digestion of cells or tissues by their own enzymes, often occurring after cell death or as part of programmed cell death (apoptosis). The digestion of the tadpole tail during metamorphosis is a classic example of programmed cell death involving lysosomal enzymes, leading to autolysis of the tail cells.
18. Cell sap contains : –
Correct Answer: (4) All of the above
Explanation: The vacuole in plant cells contains cell sap, which is a non-living fluid. Cell sap is a mixture of water, dissolved inorganic and organic substances, including sugars, amino acids, proteins, mineral salts, pigments, and waste products. Therefore, it contains water, reserve food, excretory products, and secretory materials.
Explanation: The vacuole in plant cells contains cell sap, which is a non-living fluid. Cell sap is a mixture of water, dissolved inorganic and organic substances, including sugars, amino acids, proteins, mineral salts, pigments, and waste products. Therefore, it contains water, reserve food, excretory products, and secretory materials.
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19. In plant cells the vacuole can occupies upto……. of the volume of the cell.
Correct Answer: (2) 90 percent
Explanation: In plant cells, the vacuoles are large and prominent. They can occupy up to 90 percent of the volume of the cell, pushing the cytoplasm and nucleus to the periphery.
Explanation: In plant cells, the vacuoles are large and prominent. They can occupy up to 90 percent of the volume of the cell, pushing the cytoplasm and nucleus to the periphery.
20. In which of the following options function is correctly matched with their particular cellular structure ?
Functions Cellular structure
(1) Protein synthesis SFR
(2) Formation of glycoprotein Golgi body
(3) Antolysis RER
(4) Photosynthesis Vacuole
Correct Answer: (2) Formation of glycoprotein – Golgi body
Explanation: The Golgi apparatus is primarily involved in the modification, sorting, and packaging of proteins and lipids. A key function is the glycosylation of proteins and lipids, leading to the formation of glycoproteins and glycolipids.
Incorrect options: (1) Protein synthesis occurs on ribosomes, not SFR (Smooth Endoplasmic Reticulum). (3) Autolysis is associated with lysosomes, not RER (Rough Endoplasmic Reticulum). (4) Photosynthesis occurs in chloroplasts, not vacuoles.
Explanation: The Golgi apparatus is primarily involved in the modification, sorting, and packaging of proteins and lipids. A key function is the glycosylation of proteins and lipids, leading to the formation of glycoproteins and glycolipids.
Incorrect options: (1) Protein synthesis occurs on ribosomes, not SFR (Smooth Endoplasmic Reticulum). (3) Autolysis is associated with lysosomes, not RER (Rough Endoplasmic Reticulum). (4) Photosynthesis occurs in chloroplasts, not vacuoles.
21. The number of mitochondria per cell is variable depending on the : –
Correct Answer: (2) Physiological activity of the cells
Explanation: The number of mitochondria per cell is variable depending on the physiological activity of the cells. Cells that are metabolically very active, such as muscle cells or liver cells, have a higher number of mitochondria to meet their energy demands, while less active cells have fewer.
Explanation: The number of mitochondria per cell is variable depending on the physiological activity of the cells. Cells that are metabolically very active, such as muscle cells or liver cells, have a higher number of mitochondria to meet their energy demands, while less active cells have fewer.
22. Mitochondria : –
(a) are easily visible under the microscope (without specifically stained)
(b)are typically sausage – shaped or cylindrical
(c) are double membrane bound structure
(d) have two aqueous compartments
Option :
Correct Answer: (3) a incorrect and b, c, d correct
Explanation: (a) Incorrect: Mitochondria are not easily visible under the microscope without specific staining. They require staining to be observed. (b) Correct: They are typically sausage-shaped or cylindrical. (c) Correct: They are double membrane-bound structures. (d) Correct: They have two aqueous compartments: the outer compartment (intermembrane space) and the inner compartment (matrix).
Explanation: (a) Incorrect: Mitochondria are not easily visible under the microscope without specific staining. They require staining to be observed. (b) Correct: They are typically sausage-shaped or cylindrical. (c) Correct: They are double membrane-bound structures. (d) Correct: They have two aqueous compartments: the outer compartment (intermembrane space) and the inner compartment (matrix).
23. Site of ATP formation in mitochondria is : –
Correct Answer: (3) F1 particle
Explanation: The inner mitochondrial membrane forms a number of infoldings called cristae. On the inner mitochondrial membrane and cristae, there are numerous stalked particles called F0-F1 particles (or ATP synthase). The F1 headpiece is the site of ATP synthesis (oxidative phosphorylation).
Explanation: The inner mitochondrial membrane forms a number of infoldings called cristae. On the inner mitochondrial membrane and cristae, there are numerous stalked particles called F0-F1 particles (or ATP synthase). The F1 headpiece is the site of ATP synthesis (oxidative phosphorylation).
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24. Mitochondria are believed to be of symbiotic origin from bacteria because they have similarity with bacteria in : –
Correct Answer: (4) All of the above
Explanation: Mitochondria (and chloroplasts) are considered semi-autonomous organelles and are believed to have evolved from symbiotic bacteria. This is supported by several similarities: they both possess their own circular DNA (similar to bacterial plasmids), 70S ribosomes (similar to bacterial ribosomes), and divide by binary fission, much like bacteria.
Explanation: Mitochondria (and chloroplasts) are considered semi-autonomous organelles and are believed to have evolved from symbiotic bacteria. This is supported by several similarities: they both possess their own circular DNA (similar to bacterial plasmids), 70S ribosomes (similar to bacterial ribosomes), and divide by binary fission, much like bacteria.
25. Mitochondria are the sites of : –
Correct Answer: (4) Aerobic respiration
Explanation: Mitochondria are the sites of aerobic respiration. They are responsible for generating most of the cell’s supply of adenosine triphosphate (ATP), used as a source of chemical energy, through the process of oxidative phosphorylation. This is why they are often called the “powerhouses” of the cell.
Explanation: Mitochondria are the sites of aerobic respiration. They are responsible for generating most of the cell’s supply of adenosine triphosphate (ATP), used as a source of chemical energy, through the process of oxidative phosphorylation. This is why they are often called the “powerhouses” of the cell.
26. In the stem of potato, presence of which of the following is significant ?
Correct Answer: (1) Amyloplasts
Explanation: Plastids are classified into chloroplasts, chromoplasts, and leucoplasts. Leucoplasts are colorless plastids of varied shapes and sizes with stored nutrients. Amyloplasts are leucoplasts that store carbohydrates (starch), e.g., potato. Elaioplasts store oils and fats, while aleuroplasts store proteins. The potato stem is known for its starch storage, hence amyloplasts are significant.
Explanation: Plastids are classified into chloroplasts, chromoplasts, and leucoplasts. Leucoplasts are colorless plastids of varied shapes and sizes with stored nutrients. Amyloplasts are leucoplasts that store carbohydrates (starch), e.g., potato. Elaioplasts store oils and fats, while aleuroplasts store proteins. The potato stem is known for its starch storage, hence amyloplasts are significant.
27. The chloroplasts contain : –
Correct Answer: (4) Fat soluble pigments carotenoids and chlorophylls.
Explanation: Chloroplasts contain chlorophyll and carotenoid pigments. Both chlorophylls and carotenoids are fat-soluble pigments. Anthocyanins are water-soluble pigments found in vacuoles, not chloroplasts.
Explanation: Chloroplasts contain chlorophyll and carotenoid pigments. Both chlorophylls and carotenoids are fat-soluble pigments. Anthocyanins are water-soluble pigments found in vacuoles, not chloroplasts.
28. Outer membrane of chloroplast is comparatively more permeable than inner membrane : –
Correct Answer: (3) Due to the presence of porins
Explanation: The outer membrane of chloroplasts (and mitochondria) is highly permeable to small molecules due to the presence of porins, which are channel-forming proteins. The inner membrane is much less permeable and more selective.
Explanation: The outer membrane of chloroplasts (and mitochondria) is highly permeable to small molecules due to the presence of porins, which are channel-forming proteins. The inner membrane is much less permeable and more selective.
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29. The stroma of the chloroplast contains enzymes for the synthesis of : –
Correct Answer: (4) Carbohydrates and proteins
Explanation: The stroma of the chloroplast contains enzymes required for the synthesis of carbohydrates and proteins. The dark reactions of photosynthesis (Calvin cycle), which synthesize carbohydrates, occur in the stroma. Additionally, chloroplasts have their own ribosomes and machinery for synthesizing some of their proteins.
Explanation: The stroma of the chloroplast contains enzymes required for the synthesis of carbohydrates and proteins. The dark reactions of photosynthesis (Calvin cycle), which synthesize carbohydrates, occur in the stroma. Additionally, chloroplasts have their own ribosomes and machinery for synthesizing some of their proteins.
30. Chloroplasts are called semiautonomous organelles of the cell because they have : –
Correct Answer: (4) All of the above
Explanation: Chloroplasts are considered semi-autonomous organelles because they possess their own genetic material (DNA and RNA), ribosomes (70S type), and enzymes necessary for the synthesis of some of their own proteins. This allows them to function somewhat independently of the nuclear genome.
Explanation: Chloroplasts are considered semi-autonomous organelles because they possess their own genetic material (DNA and RNA), ribosomes (70S type), and enzymes necessary for the synthesis of some of their own proteins. This allows them to function somewhat independently of the nuclear genome.
31. Ribosomes are known as : –
Correct Answer: (3) Universal cell organelle
Explanation: Ribosomes are known as universal cell organelles because they are present in all living cells, both prokaryotic and eukaryotic. They are the sites of protein synthesis.
Explanation: Ribosomes are known as universal cell organelles because they are present in all living cells, both prokaryotic and eukaryotic. They are the sites of protein synthesis.
32. Ribosomes are composed of : –
Correct Answer: (3) Ribonucleic acid and proteins.
Explanation: Ribosomes are granular structures composed of ribonucleic acid (rRNA) and proteins. They are not composed of DNA.
Explanation: Ribosomes are granular structures composed of ribonucleic acid (rRNA) and proteins. They are not composed of DNA.
33. If the concentration of magnesium ions in the cell is less than 0.001 M, then it will affect the synthesis of : –
Correct Answer: (2) Proteins
Explanation: Magnesium ions ($Mg^{2+}$) are crucial for the structural integrity and function of ribosomes. Ribosomes are the sites of protein synthesis. A low concentration of magnesium ions (less than 0.001 M) can cause the dissociation of ribosomal subunits, thereby inhibiting protein synthesis.
Explanation: Magnesium ions ($Mg^{2+}$) are crucial for the structural integrity and function of ribosomes. Ribosomes are the sites of protein synthesis. A low concentration of magnesium ions (less than 0.001 M) can cause the dissociation of ribosomal subunits, thereby inhibiting protein synthesis.
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34. In the animal cell, 70 S ribsomes are found in: –
Correct Answer: (2) Mitochondria
Explanation: In animal cells, 70S ribosomes are found exclusively in mitochondria. Plastids (chloroplasts) are found in plant cells and also contain 70S ribosomes. Eukaryotic cells (including animal cells) have 80S ribosomes in the cytoplasm and on the ER.
Explanation: In animal cells, 70S ribosomes are found exclusively in mitochondria. Plastids (chloroplasts) are found in plant cells and also contain 70S ribosomes. Eukaryotic cells (including animal cells) have 80S ribosomes in the cytoplasm and on the ER.
35. An elaborate network of filamentous proteinaceous structures present in the cytoplasm is involved in : –
Correct Answer: (2) Maintenance of the shape of the cell
Explanation: The elaborate network of filamentous proteinaceous structures in the cytoplasm is collectively referred to as the cytoskeleton. The cytoskeleton provides mechanical support, maintains the shape of the cell, and is involved in cell motility.
Explanation: The elaborate network of filamentous proteinaceous structures in the cytoplasm is collectively referred to as the cytoskeleton. The cytoskeleton provides mechanical support, maintains the shape of the cell, and is involved in cell motility.
36. Both the cilium and flagellum emerge from ……. like structure called the basal body.
Correct Answer: (2) Centriole
Explanation: Both cilia and flagella are hair-like outgrowths of the cell membrane. They emerge from centriole-like structures called the basal body.
Explanation: Both cilia and flagella are hair-like outgrowths of the cell membrane. They emerge from centriole-like structures called the basal body.
37. Cilium and flagellum are : –
Correct Answer: (4) Covered with plasma membrane
Explanation: Cilia and flagella are hair-like outgrowths of the cell membrane. Their core, called the axoneme, is covered by the plasma membrane.
Explanation: Cilia and flagella are hair-like outgrowths of the cell membrane. Their core, called the axoneme, is covered by the plasma membrane.
38. Arms of ‘A’ tubules in cilium and flagellum, consist of an enzymatic protein : –
Correct Answer: (2) Dynein
Explanation: The axoneme of cilia and flagella has a 9+2 arrangement of microtubules. The peripheral doublets (A and B tubules) have arms extending from the A tubule. These arms are composed of the enzymatic protein dynein, which is responsible for the movement of cilia and flagella by hydrolyzing ATP.
Explanation: The axoneme of cilia and flagella has a 9+2 arrangement of microtubules. The peripheral doublets (A and B tubules) have arms extending from the A tubule. These arms are composed of the enzymatic protein dynein, which is responsible for the movement of cilia and flagella by hydrolyzing ATP.
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39. Which of the following is correct regarding arrangement of microtubules in centrioles ?
Correct Answer: (3) 9 (Triplet) + 0
Explanation: The centrioles are made up of nine evenly spaced peripheral fibrils of tubulin protein. Each of the peripheral fibril is a triplet. The adjacent triplets are also linked. The central part of the proximal region of the centriole is also proteinaceous and called the hub, which is connected with tubules of the peripheral triplets by radial spokes made of protein. Thus, the arrangement of microtubules in centrioles is 9+0 (nine peripheral triplets and no central microtubules). The 9+2 arrangement is characteristic of cilia and flagella axonemes.
Explanation: The centrioles are made up of nine evenly spaced peripheral fibrils of tubulin protein. Each of the peripheral fibril is a triplet. The adjacent triplets are also linked. The central part of the proximal region of the centriole is also proteinaceous and called the hub, which is connected with tubules of the peripheral triplets by radial spokes made of protein. Thus, the arrangement of microtubules in centrioles is 9+0 (nine peripheral triplets and no central microtubules). The 9+2 arrangement is characteristic of cilia and flagella axonemes.
40. Radial spokes in centrioles connect the peripheral microtubules : –
Correct Answer: (3) With central hub
Explanation: In centrioles, the central part of the proximal region is proteinaceous and called the hub. This hub is connected with the tubules of the peripheral triplets by radial spokes, which are also made of protein.
Explanation: In centrioles, the central part of the proximal region is proteinaceous and called the hub. This hub is connected with the tubules of the peripheral triplets by radial spokes, which are also made of protein.
41. Centrioles are : –
Correct Answer: (2) Membrane less
Explanation: Centrioles are non-membranous organelles. They are cylindrical structures made of microtubules and are part of the centrosome in animal cells.
Explanation: Centrioles are non-membranous organelles. They are cylindrical structures made of microtubules and are part of the centrosome in animal cells.
42. Nucleus as a “cell organelle” was first described by ……………….. as early as ……………
Correct Answer: (2) Robert Brown, 1831
Explanation: The nucleus as a cell organelle was first described by Robert Brown in 1831. Robert Hooke discovered cells in 1665.
Explanation: The nucleus as a cell organelle was first described by Robert Brown in 1831. Robert Hooke discovered cells in 1665.
43. Nuclear envelope consists of parallel membranes with a space called perinuclear space which is about : –
Correct Answer: (2) 100 to 500 Å
Explanation: The nuclear envelope is a double membrane structure that separates the nucleus from the cytoplasm. It consists of two parallel membranes with a space between them called the perinuclear space, which is about 10 to 50 nm (or 100 to 500 Å) wide.
Explanation: The nuclear envelope is a double membrane structure that separates the nucleus from the cytoplasm. It consists of two parallel membranes with a space between them called the perinuclear space, which is about 10 to 50 nm (or 100 to 500 Å) wide.
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44. Large and more numerous nucleoli are present in cells actively carrying out –
Correct Answer: (3) Protein synthesis
Explanation: The nucleolus is the site of ribosomal RNA (rRNA) synthesis and ribosomal biogenesis. Cells that are actively synthesizing proteins require a large number of ribosomes, and thus, they have larger and more numerous nucleoli to facilitate the production of these ribosomes.
Explanation: The nucleolus is the site of ribosomal RNA (rRNA) synthesis and ribosomal biogenesis. Cells that are actively synthesizing proteins require a large number of ribosomes, and thus, they have larger and more numerous nucleoli to facilitate the production of these ribosomes.
45. (a) Spherical structure
(b) Present in the nucleoplasm
(c) Membraneless
(d) Site for ribosomal RNA synthesis
Above given informations are true for which cell structure ?
Correct Answer: (1) Nucleolus
Explanation: All the given statements accurately describe the nucleolus: it is a spherical structure, present in the nucleoplasm, is membraneless, and is the primary site for ribosomal RNA (rRNA) synthesis.
Explanation: All the given statements accurately describe the nucleolus: it is a spherical structure, present in the nucleoplasm, is membraneless, and is the primary site for ribosomal RNA (rRNA) synthesis.
46. Read the following statements (A – D)
(A) Nuclear matrix or nucleoplasm contains nucleolus and chromatin
(B) Outer nuclear membrane usually remains continuous with the ER and also bears ribosomes on it
(C) Nuclear pores are the passages through which movement of protein molecules take place in only one direction from nucleus to the cytoplasm.
(D) Nucleous act as ribosome factory
Which of the above statements are correct?
Correct Answer: (4) A, B, D
Explanation: (A) Correct: The nuclear matrix or nucleoplasm contains the nucleolus and chromatin. (B) Correct: The outer nuclear membrane is indeed continuous with the endoplasmic reticulum and often has ribosomes attached to its surface. (C) Incorrect: Nuclear pores allow movement of molecules (proteins, RNA) in both directions, not just from nucleus to cytoplasm. (D) Correct: The nucleolus is the primary site for ribosomal RNA synthesis and assembly of ribosomal subunits, hence it acts as a “ribosome factory.”
Explanation: (A) Correct: The nuclear matrix or nucleoplasm contains the nucleolus and chromatin. (B) Correct: The outer nuclear membrane is indeed continuous with the endoplasmic reticulum and often has ribosomes attached to its surface. (C) Incorrect: Nuclear pores allow movement of molecules (proteins, RNA) in both directions, not just from nucleus to cytoplasm. (D) Correct: The nucleolus is the primary site for ribosomal RNA synthesis and assembly of ribosomal subunits, hence it acts as a “ribosome factory.”
47. Interphase nucleus has loose and indistinct network of nucleoprotein fibres called chromatin, but during different stages of cell division, cells show ‘structured chromosomes’ in place of the : –
Correct Answer: (1) Nucleus
Explanation: During interphase, the nucleus contains a loose and indistinct network of nucleoprotein fibers called chromatin. However, during different stages of cell division (M phase), the chromatin condenses to form distinct, structured chromosomes, and the nuclear envelope (and thus the nucleus as a distinct entity) disappears.
Explanation: During interphase, the nucleus contains a loose and indistinct network of nucleoprotein fibers called chromatin. However, during different stages of cell division (M phase), the chromatin condenses to form distinct, structured chromosomes, and the nuclear envelope (and thus the nucleus as a distinct entity) disappears.
48. Histone proteins are rich in which of the following amino acids ?
Correct Answer: (2) Arginine and Lysine
Explanation: Histone proteins are positively charged proteins that associate with negatively charged DNA to form nucleosomes, the basic unit of chromatin. They are rich in basic amino acid residues like lysine and arginine, which have positively charged side chains at physiological pH.
Explanation: Histone proteins are positively charged proteins that associate with negatively charged DNA to form nucleosomes, the basic unit of chromatin. They are rich in basic amino acid residues like lysine and arginine, which have positively charged side chains at physiological pH.
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49. Every chromosome essentially has the _______ on the sides of which disc shaped structures called _______ are present.
Choose the correct words for the blanks respectively
Correct Answer: (3) Centromere, Kinetochores
Explanation: Every chromosome essentially has a primary constriction or the centromere. On the sides of the centromere, disc-shaped structures called kinetochores are present. These kinetochores serve as the attachment sites for spindle fibers during cell division.
Explanation: Every chromosome essentially has a primary constriction or the centromere. On the sides of the centromere, disc-shaped structures called kinetochores are present. These kinetochores serve as the attachment sites for spindle fibers during cell division.
50. Chromosome, which has centromere slightly away from the middle of the chromosome resulting into one shorter arm and one longer arm, is called –
Correct Answer: (1) Submetacentric
Explanation: * **Metacentric:** Centromere exactly in the middle, forming two equal arms. * **Submetacentric:** Centromere slightly away from the middle, resulting in one shorter arm and one longer arm. * **Acrocentric:** Centromere close to one end, resulting in one extremely short arm and one very long arm. * **Telocentric:** Centromere at the terminal end, resulting in only one arm.
Explanation: * **Metacentric:** Centromere exactly in the middle, forming two equal arms. * **Submetacentric:** Centromere slightly away from the middle, resulting in one shorter arm and one longer arm. * **Acrocentric:** Centromere close to one end, resulting in one extremely short arm and one very long arm. * **Telocentric:** Centromere at the terminal end, resulting in only one arm.
51. Read the following statements : –
(A) Both the chromatids of chromosome are joined by a structure called centromere
(B) During cell division spindle fibres are attached to satellite
(C) Telomeres are rich in Guanine base.
(D) Every chromosome essentially has a secondary constriction
Find out correct sequence of true (T) and false (F) statements
Correct Answer: (3) T F T F
Explanation: (A) True: Both chromatids of a chromosome are joined at the centromere. (B) False: During cell division, spindle fibers are attached to the kinetochores, which are disc-shaped structures on the sides of the centromere, not to the satellite region. (C) True: Telomeres are repetitive DNA sequences at the ends of chromosomes, often rich in Guanine (e.g., TTAGGG in humans). (D) False: Not every chromosome essentially has a secondary constriction. While some chromosomes have secondary constrictions (e.g., nucleolar organizer regions), it’s not a universal feature of *every* chromosome. The primary constriction (centromere) is essential for every chromosome.
Explanation: (A) True: Both chromatids of a chromosome are joined at the centromere. (B) False: During cell division, spindle fibers are attached to the kinetochores, which are disc-shaped structures on the sides of the centromere, not to the satellite region. (C) True: Telomeres are repetitive DNA sequences at the ends of chromosomes, often rich in Guanine (e.g., TTAGGG in humans). (D) False: Not every chromosome essentially has a secondary constriction. While some chromosomes have secondary constrictions (e.g., nucleolar organizer regions), it’s not a universal feature of *every* chromosome. The primary constriction (centromere) is essential for every chromosome.
52. A single human cell contain approximately ………… long thread of DNA distributed among its …….. chromosomes
Correct Answer: (2) 2 meter, 46
Explanation: A single human cell contains approximately 2 meters long thread of DNA distributed among its 46 (23 pairs) chromosomes. This vast length of DNA is tightly packed into the nucleus.
Explanation: A single human cell contains approximately 2 meters long thread of DNA distributed among its 46 (23 pairs) chromosomes. This vast length of DNA is tightly packed into the nucleus.
53. Which one of the following nuclear parts is correctly described ?
Correct Answer: (3) Perinuclear space = Contain nucleolus and chromatin
Explanation: (1) Incorrect: Nucleolus is the site for ribosomal RNA synthesis and ribosome biogenesis, not protein synthesis (which occurs on ribosomes). (2) Correct: Heterochromatin is the densely packed, dark-stained region of chromatin, which is transcriptionally inactive. (3) Incorrect: Perinuclear space is the space between the inner and outer nuclear membranes. The nucleolus and chromatin are contained within the nucleoplasm (nuclear matrix), inside the inner nuclear membrane. (4) Incorrect: Centrioles play an important role in cell division in animal cells, forming the spindle poles. Most plant cells lack centrioles.
Explanation: (1) Incorrect: Nucleolus is the site for ribosomal RNA synthesis and ribosome biogenesis, not protein synthesis (which occurs on ribosomes). (2) Correct: Heterochromatin is the densely packed, dark-stained region of chromatin, which is transcriptionally inactive. (3) Incorrect: Perinuclear space is the space between the inner and outer nuclear membranes. The nucleolus and chromatin are contained within the nucleoplasm (nuclear matrix), inside the inner nuclear membrane. (4) Incorrect: Centrioles play an important role in cell division in animal cells, forming the spindle poles. Most plant cells lack centrioles.
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54. If volume of the cell is filled with semi – fluid matrix called cytoplasm, what kind of cell is it?
Correct Answer: (3) Both (1) and (2)
Explanation: The cytoplasm is the semi-fluid matrix that fills the volume of the cell. It is a fundamental component present in both eukaryotic and prokaryotic cells, where many metabolic reactions occur.
Explanation: The cytoplasm is the semi-fluid matrix that fills the volume of the cell. It is a fundamental component present in both eukaryotic and prokaryotic cells, where many metabolic reactions occur.
55. Which of the following is incorrect matching?
Correct Answer: (4) Long and narrow – Nerve cells
Explanation: (1) Correct: Red Blood Cells (RBCs) are typically round and biconcave. (2) Correct: White Blood Cells (WBCs) exhibit amoeboid movement. (3) Correct: Tracheids are elongated cells in plant xylem. (4) Incorrect: Nerve cells (neurons) are typically long and branched, not just “long and narrow.” While they are long, their characteristic feature is their extensive branching for transmitting signals. The description “long and narrow” is not the most accurate or complete for nerve cells compared to the others.
Explanation: (1) Correct: Red Blood Cells (RBCs) are typically round and biconcave. (2) Correct: White Blood Cells (WBCs) exhibit amoeboid movement. (3) Correct: Tracheids are elongated cells in plant xylem. (4) Incorrect: Nerve cells (neurons) are typically long and branched, not just “long and narrow.” While they are long, their characteristic feature is their extensive branching for transmitting signals. The description “long and narrow” is not the most accurate or complete for nerve cells compared to the others.
56. Which of the following statements is not true?
Correct Answer: (3) The glycocalyx layer is similar in all the bacteria.
Explanation: The glycocalyx differs in composition and thickness among different bacteria. It can be a loose sheath called a slime layer or a thick and tough capsule. Therefore, statement (3) is not true.
Explanation: The glycocalyx differs in composition and thickness among different bacteria. It can be a loose sheath called a slime layer or a thick and tough capsule. Therefore, statement (3) is not true.
57. Select the incorrect statement:
Correct Answer: (4) Cells of all living organisms have nucleus.
Explanation: Statement (4) is incorrect. Prokaryotic cells (like bacteria and archaea) do not have a true nucleus. Only eukaryotic cells possess a well-defined nucleus.
Explanation: Statement (4) is incorrect. Prokaryotic cells (like bacteria and archaea) do not have a true nucleus. Only eukaryotic cells possess a well-defined nucleus.
58. Select the incorrect statement:
Correct Answer: (2) Chromoplast contains water soluble carotenoid pigments like carotene and xanthophylls.
Explanation: Statement (2) is incorrect. Carotenoid pigments (like carotene and xanthophylls) are fat-soluble, not water-soluble. They are responsible for the yellow, orange, or red colors in chromoplasts.
Explanation: Statement (2) is incorrect. Carotenoid pigments (like carotene and xanthophylls) are fat-soluble, not water-soluble. They are responsible for the yellow, orange, or red colors in chromoplasts.
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59. Find out the incorrect statement:
Correct Answer: (4) Peripheral fibril of centriole is doublet.
Explanation: Statement (4) is incorrect. The peripheral fibrils of a centriole are triplets, not doublets. The arrangement of microtubules in a centriole is 9+0, meaning nine peripheral triplets and no central microtubules. Doublets are found in the axoneme of cilia and flagella.
Explanation: Statement (4) is incorrect. The peripheral fibrils of a centriole are triplets, not doublets. The arrangement of microtubules in a centriole is 9+0, meaning nine peripheral triplets and no central microtubules. Doublets are found in the axoneme of cilia and flagella.
60. Which of the following is true about the internal structure of axoneme?
Correct Answer: (1) Central sheath is connected to one of the tubules of each peripheral doublet by a radial spoke.
Explanation: The axoneme (core of cilium/flagellum) typically has a 9+2 arrangement. The central pair of microtubules is enclosed by a central sheath, which is connected to one of the tubules (A tubule) of each of the nine peripheral doublets by radial spokes.
Incorrect options: (2) Axoneme is covered by the plasma membrane. (3) Axoneme also contains a central pair of microtubules and nexin links connecting peripheral doublets. (4) Peripheral doublets are connected to each other by nexin links.
Explanation: The axoneme (core of cilium/flagellum) typically has a 9+2 arrangement. The central pair of microtubules is enclosed by a central sheath, which is connected to one of the tubules (A tubule) of each of the nine peripheral doublets by radial spokes.
Incorrect options: (2) Axoneme is covered by the plasma membrane. (3) Axoneme also contains a central pair of microtubules and nexin links connecting peripheral doublets. (4) Peripheral doublets are connected to each other by nexin links.
61. Assertion: Genetic material in prokaryotic is said to be naked.
Reason: Genetic material in prokaryotic is not associated with histone proteins and absence of nuclear envelope around it.
Correct Answer: (1) If both the assertion and the reason are true and the reason is a correct explanation of the assertion.
Explanation: Both the assertion and the reason are true, and the reason correctly explains the assertion. In prokaryotic cells, the genetic material (nucleoid) is considered “naked” because it is not enclosed by a nuclear envelope and is not associated with histone proteins, unlike in eukaryotes.
Explanation: Both the assertion and the reason are true, and the reason correctly explains the assertion. In prokaryotic cells, the genetic material (nucleoid) is considered “naked” because it is not enclosed by a nuclear envelope and is not associated with histone proteins, unlike in eukaryotes.
62. Assertion: In lipid bilayer in membrane, lipid is arranged with polar head towards outer side and the hydrophobic tail towards the inner part
Reason: This ensures that the nonpolar tail of saturated hydrocarbon is protected from aqueous environment.
Correct Answer: (1) If both the assertion and the reason are true and the reason is a correct explanation of the assertion.
Explanation: Both the assertion and the reason are true, and the reason correctly explains the assertion. The fluid mosaic model describes the lipid bilayer as having polar heads facing the aqueous environment (outer and inner surfaces of the membrane) and hydrophobic tails facing inwards, away from water. This arrangement is crucial for the stability of the membrane in an aqueous environment, as it protects the nonpolar tails.
Explanation: Both the assertion and the reason are true, and the reason correctly explains the assertion. The fluid mosaic model describes the lipid bilayer as having polar heads facing the aqueous environment (outer and inner surfaces of the membrane) and hydrophobic tails facing inwards, away from water. This arrangement is crucial for the stability of the membrane in an aqueous environment, as it protects the nonpolar tails.
63. Which of the following is not function of endoplasmic reticulum?
Correct Answer: (1) Formation of acrosome
Explanation: The formation of the acrosome in sperm is a function of the Golgi apparatus, not the endoplasmic reticulum. The ER is involved in detoxification (SER), mechanical support (cytoskeleton-like role), and formation of the nuclear membrane (re-formation after mitosis).
Explanation: The formation of the acrosome in sperm is a function of the Golgi apparatus, not the endoplasmic reticulum. The ER is involved in detoxification (SER), mechanical support (cytoskeleton-like role), and formation of the nuclear membrane (re-formation after mitosis).
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64. Peri – plastidial space is found in:
Correct Answer: (1) Between two membranes of a chloroplast
Explanation: The peri-plastidial space refers to the intermembrane space found between the inner and outer membranes of a chloroplast. This space is analogous to the perinuclear space of the nucleus or the intermembrane space of mitochondria.
Explanation: The peri-plastidial space refers to the intermembrane space found between the inner and outer membranes of a chloroplast. This space is analogous to the perinuclear space of the nucleus or the intermembrane space of mitochondria.
65. Read following statements:
(A) Larger and more numerous nucleoli are present in cells actively carrying out protein synthesis.
(B) The content of nucleolus is continuous with the rest of the nucleoplasm as it is a membrane bound structure.
(C) Nucleolus is main site for synthesis of ribosomal protein.
(D) Nuclear envelope consists of two parallel membranes with a space between called peri – mitochondrial space.
(E) The centrioles form the basal body of cilia or flagella.
How many above statements are not correct?
Correct Answer: (2) 3
Explanation: Let’s evaluate each statement: (A) Correct: Cells actively synthesizing proteins need more ribosomes, hence larger and more numerous nucleoli. (B) Incorrect: The nucleolus is a membraneless structure, so its content is continuous with the nucleoplasm. It is not membrane-bound. (C) Incorrect: Nucleolus is the main site for synthesis of ribosomal RNA (rRNA), not ribosomal protein. Ribosomal proteins are synthesized in the cytoplasm and imported into the nucleolus. (D) Incorrect: The space between the two parallel membranes of the nuclear envelope is called the perinuclear space, not peri-mitochondrial space. Peri-mitochondrial space is the intermembrane space of mitochondria. (E) Correct: Centrioles form the basal bodies of cilia or flagella. Therefore, statements B, C, and D are incorrect. So, 3 statements are not correct.
Explanation: Let’s evaluate each statement: (A) Correct: Cells actively synthesizing proteins need more ribosomes, hence larger and more numerous nucleoli. (B) Incorrect: The nucleolus is a membraneless structure, so its content is continuous with the nucleoplasm. It is not membrane-bound. (C) Incorrect: Nucleolus is the main site for synthesis of ribosomal RNA (rRNA), not ribosomal protein. Ribosomal proteins are synthesized in the cytoplasm and imported into the nucleolus. (D) Incorrect: The space between the two parallel membranes of the nuclear envelope is called the perinuclear space, not peri-mitochondrial space. Peri-mitochondrial space is the intermembrane space of mitochondria. (E) Correct: Centrioles form the basal bodies of cilia or flagella. Therefore, statements B, C, and D are incorrect. So, 3 statements are not correct.
66. Which one of the following is correct?
(a) Nuclear matrix or nucleoplasm contains nucleolus and chromatin.
(b) Outer nuclear membrane usually remains continuous with the ER and also bears ribosomes on it.
(c) Small and lesser number of nucleoli are present in cells actively carrying out protein synthesis.
(d) Perinuclear space forms a barrier between the materials present inside the nucleus and that of the cytoplasm.
Correct Answer: (1) a and b
Explanation: (a) Correct: The nuclear matrix (nucleoplasm) contains the nucleolus and chromatin. (b) Correct: The outer nuclear membrane is continuous with the ER and has ribosomes. (c) Incorrect: Cells actively carrying out protein synthesis have *larger and more numerous* nucleoli, not small and lesser numbers. (d) Incorrect: The perinuclear space is a space between the two nuclear membranes, but the nuclear envelope as a whole (including nuclear pores) regulates transport, not just the perinuclear space acting as a barrier. The nuclear envelope with its pores forms the barrier and regulates passage. Therefore, only statements (a) and (b) are correct.
Explanation: (a) Correct: The nuclear matrix (nucleoplasm) contains the nucleolus and chromatin. (b) Correct: The outer nuclear membrane is continuous with the ER and has ribosomes. (c) Incorrect: Cells actively carrying out protein synthesis have *larger and more numerous* nucleoli, not small and lesser numbers. (d) Incorrect: The perinuclear space is a space between the two nuclear membranes, but the nuclear envelope as a whole (including nuclear pores) regulates transport, not just the perinuclear space acting as a barrier. The nuclear envelope with its pores forms the barrier and regulates passage. Therefore, only statements (a) and (b) are correct.
67. On the basis of ease of extraction membrane proteins are of two type – extrinsic and intrinsic. How can intrinsic protein be separated from membrane?
Correct Answer: (1) By treating with mild detergent
Explanation: Intrinsic (integral) membrane proteins are tightly embedded in the lipid bilayer and often span the entire membrane. They can only be separated from the membrane by disrupting the lipid bilayer, typically using detergents that solubilize the membrane. Extrinsic (peripheral) proteins are loosely associated and can be removed by milder treatments like changes in pH or ionic strength.
Explanation: Intrinsic (integral) membrane proteins are tightly embedded in the lipid bilayer and often span the entire membrane. They can only be separated from the membrane by disrupting the lipid bilayer, typically using detergents that solubilize the membrane. Extrinsic (peripheral) proteins are loosely associated and can be removed by milder treatments like changes in pH or ionic strength.
68. Enzymes of Calvin cycle are located in:
Correct Answer: (2) Stroma of chloroplast
Explanation: The Calvin cycle (light-independent reactions of photosynthesis), which involves the fixation of carbon dioxide and synthesis of carbohydrates, takes place in the stroma of the chloroplast. The stroma contains all the necessary enzymes for these reactions.
Explanation: The Calvin cycle (light-independent reactions of photosynthesis), which involves the fixation of carbon dioxide and synthesis of carbohydrates, takes place in the stroma of the chloroplast. The stroma contains all the necessary enzymes for these reactions.
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69. Match column I with column II & select the correct option: –
Column I Column II
(a) Contractile vacuole (i) Osmo regulation
(b) Mitochondria (ii) ATP synthesis
(c) Lysosomes (iii) Glycosylation
(d) Golgi body (iv) Hydrolytic enzymes
Correct Answer: (3) (a) – (i), (b) – (ii), (c) – (iv), (d) – (iii)
Explanation: (a) Contractile vacuole: Primarily involved in osmoregulation and excretion in some protists. (b) Mitochondria: Known as the powerhouse of the cell, responsible for ATP synthesis through aerobic respiration. (c) Lysosomes: Contain hydrolytic enzymes (acid hydrolases) for intracellular digestion. (d) Golgi body: Involved in packaging, modification, and transport of proteins and lipids, including glycosylation (addition of carbohydrate groups).
Explanation: (a) Contractile vacuole: Primarily involved in osmoregulation and excretion in some protists. (b) Mitochondria: Known as the powerhouse of the cell, responsible for ATP synthesis through aerobic respiration. (c) Lysosomes: Contain hydrolytic enzymes (acid hydrolases) for intracellular digestion. (d) Golgi body: Involved in packaging, modification, and transport of proteins and lipids, including glycosylation (addition of carbohydrate groups).
70. How many cell organelles in the list given below are surrounded by single membrane?
Mitochondria, Lysosome, Chloroplast, Golgi apparatus, Nucleus, Nucleolus, Endoplasmic reticulum, Ribosome, Peroxisome, Centriole
Correct Answer: (1) Four
Explanation: * **Single membrane-bound:** Lysosome, Golgi apparatus, Endoplasmic reticulum, Peroxisome. (4 organelles) * **Double membrane-bound:** Mitochondria, Chloroplast, Nucleus. * **Membraneless:** Nucleolus, Ribosome, Centriole. Therefore, there are four single membrane-bound organelles in the list.
Explanation: * **Single membrane-bound:** Lysosome, Golgi apparatus, Endoplasmic reticulum, Peroxisome. (4 organelles) * **Double membrane-bound:** Mitochondria, Chloroplast, Nucleus. * **Membraneless:** Nucleolus, Ribosome, Centriole. Therefore, there are four single membrane-bound organelles in the list.
71. Regarding differences between animal & plant cells, which of the following statement is correct?
Correct Answer: (2) Animal cells contain centrioles & plant cells contain plastids, cell wall and large central vacuole.
Explanation: * Animal cells typically have centrioles (involved in cell division and flagella/cilia formation). They lack a cell wall. * Plant cells typically have plastids (like chloroplasts), a rigid cell wall, and a large central vacuole. They generally lack centrioles (except in some lower plants). Therefore, statement (2) correctly highlights these key differences.
Explanation: * Animal cells typically have centrioles (involved in cell division and flagella/cilia formation). They lack a cell wall. * Plant cells typically have plastids (like chloroplasts), a rigid cell wall, and a large central vacuole. They generally lack centrioles (except in some lower plants). Therefore, statement (2) correctly highlights these key differences.
72. Read the following statements with respect to mitochondria: –
(i) It divides and increases its number by binary fission.
(ii) During the early course of evolution these were prokaryotes.
(iii) Its matrix performs electron transport chain, and the inner membrane performs Kreb’s cycle.
(iv) These are fully autonomous organelles.
(v) Its matrix possess 70S ribosomes, RNA and linear dsDNA.
How many of the above statements are correct?
Correct Answer: (2) Two
Explanation: Let’s evaluate each statement: (i) Correct: Mitochondria divide by binary fission, similar to bacteria. (ii) Correct: According to the endosymbiotic theory, mitochondria are believed to have originated from prokaryotic cells that were engulfed by early eukaryotic cells. (iii) Incorrect: The electron transport chain (ETC) occurs on the inner mitochondrial membrane, while the Krebs cycle (TCA cycle) occurs in the mitochondrial matrix. (iv) Incorrect: Mitochondria are semi-autonomous, not fully autonomous. They depend on the nuclear genome for the synthesis of many of their proteins. (v) Incorrect: The mitochondrial matrix possesses 70S ribosomes, RNA, and circular dsDNA, not linear dsDNA. Therefore, only statements (i) and (ii) are correct.
Explanation: Let’s evaluate each statement: (i) Correct: Mitochondria divide by binary fission, similar to bacteria. (ii) Correct: According to the endosymbiotic theory, mitochondria are believed to have originated from prokaryotic cells that were engulfed by early eukaryotic cells. (iii) Incorrect: The electron transport chain (ETC) occurs on the inner mitochondrial membrane, while the Krebs cycle (TCA cycle) occurs in the mitochondrial matrix. (iv) Incorrect: Mitochondria are semi-autonomous, not fully autonomous. They depend on the nuclear genome for the synthesis of many of their proteins. (v) Incorrect: The mitochondrial matrix possesses 70S ribosomes, RNA, and circular dsDNA, not linear dsDNA. Therefore, only statements (i) and (ii) are correct.
73. What is the correct arrangement of Lipid molecules in the cell membrane
Correct Answer: (4) Polar head – Outside, Non – polar tails – Inner side
Explanation: According to the fluid mosaic model, the lipid bilayer of the cell membrane is composed of amphipathic lipid molecules (phospholipids). These molecules are arranged with their polar (hydrophilic) heads facing outwards towards the aqueous environment (both extracellular and intracellular sides) and their non-polar (hydrophobic) tails facing inwards, forming the core of the membrane, away from the aqueous environment.
Explanation: According to the fluid mosaic model, the lipid bilayer of the cell membrane is composed of amphipathic lipid molecules (phospholipids). These molecules are arranged with their polar (hydrophilic) heads facing outwards towards the aqueous environment (both extracellular and intracellular sides) and their non-polar (hydrophobic) tails facing inwards, forming the core of the membrane, away from the aqueous environment.
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