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Q1. Which organelle detoxifies drugs and poisons?
Smooth endoplasmic reticulum (SER) detoxifies drugs and poisons. It contains enzymes that metabolize harmful substances, making them less toxic and easier to excrete. Liver cells are rich in SER because the liver is the primary organ responsible for detoxification in the body.
Q2. Which organelle is involved in cell division?
The centrosome is involved in cell division. It contains centrioles, which help in the formation of spindle fibres during mitosis and meiosis. The spindle fibres help in the separation of chromosomes during cell division. Centrosomes are found in animal cells but are absent in most plant cells.
Q3. Which type of microscope is required to see cell organelles clearly?
An electron microscope is required to see cell organelles clearly. It provides much higher magnification and resolution than light microscopes. Organelles like ribosomes, endoplasmic reticulum, and Golgi apparatus can be seen clearly only with an electron microscope.
Q4. Which organelle is absent in viruses?
Viruses lack all of these—nucleus, cell membrane, and cytoplasm. Viruses are not cells and do not have any cellular organelles. They consist of genetic material (DNA or RNA) surrounded by a protein coat called a capsid. They can only reproduce inside a living host cell.
Q5. Which organelle helps maintain internal balance of the cell?
The plasma membrane helps maintain the internal balance of the cell. It is selectively permeable, controlling what enters and leaves the cell. This maintains the internal environment (homeostasis) by regulating the concentration of ions, nutrients, and waste products.
Q6. Which organelle has its own DNA but is NOT the nucleus?
Mitochondria have their own DNA but are not the nucleus. Mitochondrial DNA is circular and resembles bacterial DNA. This supports the endosymbiotic theory, which suggests that mitochondria were once free-living bacteria. Plastids also have their own DNA.
Q7. Which cells lack a true nucleus?
Prokaryotic cells lack a true nucleus. Their genetic material is not enclosed within a nuclear membrane but is located in a region called the nucleoid. Bacteria and archaea are examples of prokaryotic cells. Eukaryotic cells (animal, plant, fungal) have a true nucleus.
Q8. Which organelle helps in intracellular digestion?
Lysosomes help in intracellular digestion. They contain digestive enzymes that break down foreign particles, bacteria, and worn-out cell organelles. This process is essential for keeping the cell clean and healthy. Lysosomes are often called the “waste disposal system” of the cell.
Q9. Why is cell called the fundamental unit of life?
The cell is called the fundamental unit of life because all living organisms are made of cells and all life activities occur within them. Cells are the basic structural and functional units of life. Every living organism is composed of one or more cells, and all life processes take place inside cells.
Q10. Which organelle contains thylakoids?
Chloroplasts contain thylakoids. Thylakoids are membrane-bound sacs arranged in stacks called grana. They contain chlorophyll, which is essential for photosynthesis. The thylakoid membranes are the site of the light reactions of photosynthesis.
Q11. Which organelle stores cell sap?
Vacuoles store cell sap. Cell sap is a solution of water, minerals, sugars, amino acids, and other dissolved substances. The large central vacuole in plant cells stores cell sap and helps maintain turgidity and rigidity.
Q12. Plant cells swell but do not burst in hypotonic solution because of:
Plant cells swell but do not burst in a hypotonic solution because of the cell wall. The cell wall is rigid and provides structural support. It prevents the cell from bursting by exerting pressure against the expanding cell membrane. Animal cells lack a cell wall and would burst in a hypotonic solution.
Q13. Which cell component is present in all living cells?
The plasma membrane is present in all living cells. It surrounds every cell and controls the movement of substances in and out. Mitochondria, chloroplasts, and a true nucleus are not present in all cells—prokaryotic cells lack mitochondria and chloroplasts, and some cells (like red blood cells) lack a nucleus.
Q14. Cell membrane is mainly made of:
The cell membrane is mainly made of lipids and proteins. It consists of a phospholipid bilayer with proteins embedded in it. This structure is called the fluid mosaic model. The lipids form the bilayer, while proteins help in transport and communication.
Q15. Which cell part controls all metabolic activities?
The nucleus controls all metabolic activities of the cell. It contains the genetic material (DNA), which directs protein synthesis and regulates all cellular processes. The nucleus is often called the “brain” or “control centre” of the cell because it controls cell growth, division, and metabolism.
Q16. Which is the correct order of organisation?
The correct order of organisation is cell → tissue → organ → organism. Cells combine to form tissues, tissues combine to form organs, organs combine to form organ systems, and organ systems combine to form an organism. This is the hierarchical organisation of living things.
Q17. Which organelle controls protein modification?
The Golgi apparatus controls protein modification. It modifies proteins by adding carbohydrates (glycosylation) or lipids, and then packages them into vesicles for transport. The Golgi apparatus is often called the “post office” of the cell.
Q18. Which plastid stores starch?
Leucoplasts store starch. They are colourless plastids found in plant cells that store starch, oils, and proteins. Amyloplasts are a type of leucoplast that specifically store starch (e.g., in potato tubers). Elaioplasts store oils, and chromoplasts store pigments.
Q19. Which structure allows selective permeability?
The plasma membrane allows selective permeability. It controls what enters and leaves the cell, allowing only certain substances to pass through. This is essential for maintaining the internal environment of the cell and regulating cellular processes. The nuclear membrane also has selective pores, but the plasma membrane is the primary selective barrier of the cell.
Q20. Which cell organelle is called “protein factory”?
Ribosomes are called the “protein factory” of the cell because they are the sites of protein synthesis. Ribosomes read the genetic information from mRNA and assemble amino acids into proteins. This process is essential for cell growth and function.
Q21. Which cell part contains enzymes for digestion?
Lysosomes contain enzymes for digestion. They are filled with digestive enzymes that break down proteins, carbohydrates, lipids, and nucleic acids. Lysosomes digest foreign particles, bacteria, and worn-out cell organelles. They are called the “waste disposal system” of the cell.
Q22. Movement of substances across the plasma membrane without energy is called:
The movement of substances across the plasma membrane without energy is called diffusion. It is the movement of molecules from a region of higher concentration to a region of lower concentration. Osmosis is a special type of diffusion involving water molecules. Active transport requires energy.
Q23. Which cell organelle is absent in plant cells but present in animal cells?
The centrosome is absent in plant cells but present in animal cells. It contains centrioles that help in cell division. Plant cells do not have centrosomes; they form spindle fibres without centrioles. Chloroplasts and cell walls are present in plant cells but absent in animal cells.
Q24. Which organelle is absent in prokaryotic cells?
The nucleus is absent in prokaryotic cells. Prokaryotes do not have a membrane-bound nucleus; their genetic material is located in a region called the nucleoid. They do have ribosomes, cytoplasm, and a cell membrane. Ribosomes in prokaryotes are smaller than those in eukaryotes.
Q25. Which structure decides the boundary of a living cell?
The plasma membrane decides the boundary of a living cell. It is the outermost layer of the cell in animal cells and lies just inside the cell wall in plant cells. The plasma membrane separates the cell’s internal environment from the external environment and regulates the movement of substances.
Q26. Osmosis occurs through a:
Osmosis occurs through a semi-permeable membrane (selectively permeable membrane). Such a membrane allows water molecules to pass through but prevents the passage of solute molecules. The plasma membrane acts as a semi-permeable membrane, allowing osmosis to occur.
Q27. Which cell organelle helps in photosynthesis?
Chloroplasts help in photosynthesis. They contain chlorophyll, which captures light energy and converts it into chemical energy. During photosynthesis, carbon dioxide and water are converted into glucose and oxygen. This process is essential for the survival of plants and for the oxygen supply on Earth.
Q28. Which organelle is involved in fat synthesis?
Smooth ER (SER) is involved in fat (lipid) synthesis. It synthesises lipids, phospholipids, and steroids. SER also plays a role in detoxification and calcium storage. Rough ER is involved in protein synthesis.
Q29. Which process forms transport vesicles from Golgi?
Packaging is the process that forms transport vesicles from the Golgi apparatus. The Golgi apparatus modifies, sorts, and packages proteins and lipids into vesicles. These vesicles then transport the packaged materials to their final destinations within or outside the cell.
Q30. Large central vacuole is characteristic of:
A large central vacuole is characteristic of plant cells. It can occupy up to 50-90% of the cell volume. The central vacuole stores cell sap, maintains turgidity, and provides rigidity to plant cells. Animal cells have small or temporary vacuoles.
Q31. Which cell organelle is common to both plant and animal cells?
Mitochondria are common to both plant and animal cells. They are the sites of cellular respiration, where energy is produced in the form of ATP. Plastids, cell walls, and chloroplasts are found only in plant cells, not in animal cells.
Q32. Ribosomes are made of:
Ribosomes are made of RNA and protein. They are composed of two subunits—a large subunit and a small subunit—both of which contain ribosomal RNA (rRNA) and proteins. Ribosomes are the sites of protein synthesis in the cell.
Q33. Which structure is present in plant cells but absent in animal cells?
The cell wall is present in plant cells but absent in animal cells. The plant cell wall is made of cellulose and provides structural support, protection, and shape to the cell. Animal cells have only a plasma membrane, not a cell wall.
Q34. Cristae are found in:
Cristae are found in mitochondria. They are the folded inner membrane structures of mitochondria that increase the surface area for ATP production. The cristae contain enzymes involved in oxidative phosphorylation, which generates ATP during cellular respiration.
Q35. Which cell organelle modifies and packages proteins?
The Golgi apparatus modifies and packages proteins. It receives proteins from the endoplasmic reticulum, modifies them (e.g., by adding carbohydrates), and packages them into vesicles for transport to their final destinations. It is often called the “post office” of the cell.
Q36. Which process involves engulfing of food by Amoeba?
Endocytosis involves the engulfing of food by Amoeba. The Amoeba extends pseudopodia around the food particle, forming a food vacuole. This process is also called phagocytosis. Endocytosis is a form of active transport that requires energy.
Q37. Osmosis is the movement of:
Osmosis is the movement of water molecules across a selectively permeable membrane from a region of higher water concentration to a region of lower water concentration. It is a special type of diffusion that involves only water. Solutes, proteins, and gases move by other processes.
Q38. Which organelle forms lysosomes?
The Golgi apparatus forms lysosomes. The digestive enzymes produced by the rough ER are sent to the Golgi apparatus, where they are modified and packaged into vesicles called lysosomes. Lysosomes then carry out intracellular digestion.
Q39. Which structure gives rigidity to plant cells?
The cell wall gives rigidity to plant cells. It is a rigid, non-living layer made of cellulose that surrounds the plasma membrane. The cell wall provides structural support, protection, and shape to the plant cell. It prevents the cell from bursting in hypotonic solutions.
Q40. Which plastid is responsible for green colour of leaves?
Chloroplasts are responsible for the green colour of leaves. They contain chlorophyll, which is a green pigment that captures light energy for photosynthesis. Chromoplasts give colours to flowers and fruits (yellow, orange, red), while leucoplasts are colourless and store food.
Q41. Which organelle is responsible for synthesis of ATP?
Mitochondria are responsible for the synthesis of ATP. During cellular respiration, mitochondria break down glucose and produce ATP (Adenosine Triphosphate), the energy currency of the cell. This is why mitochondria are called the “powerhouse of the cell.”
Q42. Which structure connects nucleus and cytoplasm?
Nuclear pores connect the nucleus and the cytoplasm. They are small openings in the nuclear membrane that allow the exchange of materials between the nucleus and the cytoplasm. RNA, proteins, and other molecules pass through these pores.
Q43. Which organelle transports proteins inside the cell?
The endoplasmic reticulum (ER) transports proteins inside the cell. Proteins synthesised by ribosomes on the rough ER enter the ER lumen and are transported to the Golgi apparatus for further processing. The ER also transports lipids.
Q44. Which organelle helps in intracellular transport?
The endoplasmic reticulum (ER) helps in intracellular transport. It forms a network of membrane-bound channels that transport materials (proteins, lipids, and other molecules) from one part of the cell to another. It also transports materials to the Golgi apparatus for packaging.
Q45. The cell wall of plants is mainly composed of:
The cell wall of plants is mainly composed of cellulose. Cellulose is a complex carbohydrate (polysaccharide) that gives the cell wall its strength and rigidity. It is made of glucose units linked together in long chains. Cellulose is the most abundant organic polymer on Earth.
Q46. The smallest living unit capable of independent existence is a:
The smallest living unit capable of independent existence is a cell. Cells are the basic structural and functional units of life. Some organisms are unicellular (made of one cell), and that single cell performs all life functions independently. Organelles, tissues, and organs cannot exist independently.
Q47. Which of the following cells lacks mitochondria?
Red blood cells (RBCs) lack mitochondria. They do not have mitochondria because they need to carry oxygen efficiently, and mitochondria would consume some of the oxygen. RBCs generate energy through anaerobic respiration. Other cells like nerve cells, muscle cells, and liver cells have mitochondria.
Q48. The plasma membrane is also called:
The plasma membrane is also called the cytoplasmic membrane because it surrounds the cytoplasm. It is the outermost layer of the cell in animal cells and lies just inside the cell wall in plant cells. It is also called the cell membrane.
Q49. Which organelle maintains cell shape in plants?
The vacuole helps maintain cell shape in plants. The large central vacuole filled with cell sap exerts turgor pressure against the cell wall, keeping the cells firm and maintaining the shape of the plant. This is why plants wilt when they lose water—the vacuoles shrink and turgor pressure is lost.
Q50. Bacterial cells contain genetic material in the form of:
Bacterial cells contain genetic material in the form of a nucleoid. The nucleoid is a region in the cytoplasm where the bacterial DNA is located. It is not enclosed by a nuclear membrane. Bacterial cells also may contain small circular DNA molecules called plasmids, but the main genetic material is in the nucleoid.