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Q1. Plastids are present in:
Plastids are present in eukaryotic cells, specifically in plant cells and some algae. They are membrane-bound organelles that perform functions like photosynthesis (chloroplasts), storage of starch (leucoplasts), and pigment storage (chromoplasts). Prokaryotic cells, bacteria, and viruses do not have plastids.
Q2. The nucleus controls:
The nucleus controls all the processes of the cell. It contains the genetic material (DNA) that directs the synthesis of proteins, controls cell division, and regulates all metabolic activities. The nucleus is often called the “brain” or “control centre” of the cell.
Q3. The cheek cell material is transferred to the slide with the help of:
Cheek cell material is transferred to the slide with the help of a brush (camel hair paintbrush). After scraping the inside of the cheek with a toothpick or spatula, the material is gently rubbed onto a clean slide using a brush to spread it evenly for observation.
Q4. Eukaryotic cells have:
Eukaryotic cells have membrane-bound organelles like the nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, and plastids. These organelles are enclosed by membranes, allowing compartmentalization of cellular functions. This is a defining feature of eukaryotic cells.
Q5. Organisms having nuclear membrane are called:
Organisms having a well-defined nuclear membrane are called eukaryotes. Their genetic material is enclosed within a membrane-bound nucleus. Examples include plants, animals, fungi, and protists. Prokaryotes (bacteria and archaea) lack a nuclear membrane.
Q6. Another stain used for colouring cells is:
Methylene blue solution is another stain used for colouring cells. It is commonly used to stain animal cells like cheek cells because it stains the nucleus blue and makes cellular structures visible under the microscope. Iodine is typically used for plant cells like onion peel.
Q7. The nucleus is usually:
The nucleus is usually spherical or oval in shape. It is a prominent, centrally located structure in most cells. However, its shape can vary depending on the cell type. For example, in some cells, the nucleus may be elongated or irregular.
Q8. Chromosomes appear as:
Chromosomes appear as rod-shaped structures when the cell is about to divide. During cell division, chromatin material condenses and becomes visible as distinct, rod-shaped chromosomes. At other times, DNA exists as chromatin (thread-like material).
Q9. Cytoplasm takes up:
Cytoplasm takes up very little stain compared to the nucleus. Because it is a watery, translucent substance, it appears light or almost colourless under the microscope. The nucleus, being denser, takes up more stain and appears darker.
Q10. Cytoplasm is the fluid content inside the:
Cytoplasm is the fluid content inside the plasma membrane (cell membrane) but outside the nucleus. It contains various organelles, enzymes, and dissolved substances. It is the site where most cellular activities take place.
Q11. Cells observed after onion peel are taken from:
Cells observed from onion peel are taken from the leaf (scale leaf) of the onion bulb. Onion is a modified stem (bulb) with fleshy scale leaves. The thin, transparent epidermis of these scale leaves is peeled off and used for observation under a microscope.
Q12. The covering of nucleus is called:
The covering of the nucleus is called the nuclear membrane (or nuclear envelope). It is a double-layered membrane that surrounds the nucleus and separates its contents from the cytoplasm. It has pores that allow the exchange of materials between the nucleus and the cytoplasm.
Q13. Size of eukaryotic cells generally ranges from:
The size of eukaryotic cells generally ranges from 5 to 100 micrometres (μm). For example, human red blood cells are about 7 μm in diameter, while some plant cells can be up to 100 μm long. Prokaryotic cells are much smaller, typically 1–10 μm.
Q14. Cell organelles are enclosed by:
Cell organelles are enclosed by membranes. Each organelle has a specific membrane that separates it from the cytoplasm and allows it to perform its specific function. For example, mitochondria have two membranes, the nucleus has a nuclear membrane, and the endoplasmic reticulum is membrane-bound.
Q15. Membrane-bound cell organelles in eukaryotic cells are:
Membrane-bound cell organelles are present in eukaryotic cells. This is a defining feature of eukaryotic cells. These organelles include the nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, and plastids. Their presence allows compartmentalization of cellular functions.
Q16. Which solution can also be used instead of iodine for staining?
Safranin solution can also be used for staining cells instead of iodine. Safranin is a red dye that stains the nucleus and other structures red. It is commonly used in plant cell staining. Iodine is used for onion peel, while methylene blue is used for cheek cells.
Q17. Chromosomes are visible clearly when the cell is:
Chromosomes are visible clearly when the cell is about to divide. During the resting phase (interphase), the genetic material exists as chromatin (thread-like). When the cell prepares to divide, chromatin condenses into distinct, rod-shaped chromosomes that can be seen under the microscope.
Q18. Cytoplasm is enclosed by:
Cytoplasm is enclosed by the cell membrane (plasma membrane). The cell membrane surrounds the entire cell and separates the cytoplasm (and its organelles) from the external environment. In plant cells, the cell wall is present outside the cell membrane.
Q19. When iodine solution is added, cells get coloured differently due to:
When iodine solution is added, cells get coloured differently due to their chemical composition. Different cellular structures have different chemical compositions—the nucleus is rich in proteins and nucleic acids, the cytoplasm contains various substances, and the cell wall is made of cellulose. These differences affect how much stain they absorb.
Q20. Membrane-bound organelles are absent in:
Membrane-bound organelles are absent in prokaryotic cells. Prokaryotes like bacteria have a simple structure with no membrane-bound nucleus or organelles. Their genetic material is not enclosed in a nuclear membrane. Eukaryotic cells have membrane-bound organelles.
Q21. Chromatin material appears as:
Chromatin material appears as an entangled mass of thread-like structures in the nucleus. It is made of DNA and proteins. When the cell is not dividing, the DNA is in the form of chromatin, which is thin, thread-like, and spread throughout the nucleus.
Q22. The nuclear membrane is made of:
The nuclear membrane is made of a double layer (bilayer) of lipids. It has two membranes—an outer membrane and an inner membrane—with a space between them. This double membrane separates the nucleus from the cytoplasm and has pores for material exchange.
Q23. In photosynthetic prokaryotic bacteria, chlorophyll is associated with:
In photosynthetic prokaryotic bacteria, chlorophyll is associated with membranous vesicles (infoldings of the plasma membrane). Prokaryotes lack chloroplasts (plastids). Instead, their photosynthetic pigments are located in membrane-bound structures called chromatophores or thylakoid membranes.
Q24. Viruses lack:
Viruses lack membranes. They are not cells and do not have a cell membrane or any other membrane-bound structures. A virus is composed of genetic material (DNA or RNA) surrounded by a protein coat called a capsid. Some viruses have an outer envelope, but they do not have a true membrane.
Q25. Before cell division, chromatin material gets organised into:
Before cell division, chromatin material gets organised into chromosomes. The chromatin (thread-like DNA) condenses and coils to form distinct, rod-shaped chromosomes. This makes it easier for the cell to divide and distribute the genetic material equally between daughter cells.
Q26. Which regions of the cell appear darker after staining?
After staining, some regions of the cell appear darker. The nucleus, which contains DNA and proteins, takes up more stain and appears darker. The cytoplasm takes up very little stain and appears lighter. This differential staining helps in identifying different parts of the cell.
Q27. Cells lacking nuclear membrane are called:
Cells lacking a nuclear membrane are called prokaryotes. In these cells, the genetic material is not enclosed within a nucleus. Examples include bacteria and archaea. The term “prokaryote” means “before nucleus,” indicating their primitive structure.
Q28. Which stain is used for colouring cheek cells?
Methylene blue is used for colouring cheek cells. It is a basic dye that stains the nucleus blue and makes cellular structures visible under the microscope. Iodine is typically used for plant cells like onion peel. Methylene blue is preferred for animal cells because it stains the genetic material clearly.
Q29. Viruses show life characteristics only when they:
Viruses show life characteristics only when they enter a living body (host cell). Outside a host, viruses are inert and do not show any signs of life. Once inside a host, they use the host’s cellular machinery to multiply and carry out life functions.
Q30. Viruses multiply by using:
Viruses multiply by using the host cell machinery. They do not have their own ribosomes, enzymes, or other organelles to carry out reproduction. Once inside a host, they hijack the host’s cellular machinery to replicate their genetic material and produce new virus particles.
Q31. Prokaryotic cells usually have how many chromosomes?
Prokaryotic cells usually have a single chromosome. The genetic material is a single, circular strand of DNA. This is in contrast to eukaryotic cells, which have multiple linear chromosomes. The single chromosome is located in the nucleoid region, not enclosed by a nuclear membrane.
Q32. Size of prokaryotic cells generally ranges from:
The size of prokaryotic cells generally ranges from 1 to 10 micrometres (μm). Bacteria are typical examples of prokaryotic cells and are much smaller than eukaryotic cells (which range from 5 to 100 μm). This small size allows for efficient exchange of materials across the cell membrane.
Q33. DNA stands for:
DNA stands for Deoxyribo Nucleic Acid. It is the genetic material that contains the instructions for the development, functioning, and reproduction of all living organisms. DNA is composed of nucleotides and is found in the nucleus of eukaryotic cells and in the nucleoid of prokaryotic cells.
Q34. In bacteria, the nuclear region is poorly defined due to absence of:
In bacteria (prokaryotes), the nuclear region is poorly defined due to the absence of a nuclear membrane. The genetic material is not enclosed within a nucleus but is instead located in a region called the nucleoid. Bacteria do have DNA, cytoplasm, and ribosomes.
Q35. Prokaryotic cells lack most:
Prokaryotic cells lack most cytoplasmic organelles. They do not have membrane-bound organelles like mitochondria, endoplasmic reticulum, Golgi apparatus, or plastids. They do have ribosomes, but these are not membrane-bound. This is a key difference between prokaryotic and eukaryotic cells.
Q36. Similar nuclear structures are also seen in:
Similar nuclear structures (well-defined nucleus with nuclear membrane) are seen in onion peel cells and other eukaryotic cells. Onion peel cells are plant cells with a prominent nucleus. Bacteria cells (prokaryotes) lack a well-defined nucleus.
Q37. Prokaryotes means:
Prokaryotes means “before nucleus” or “primitive nucleus.” The term comes from Greek—”pro” means before and “karyon” means nucleus. Prokaryotic cells have a primitive or poorly defined nuclear region without a nuclear membrane. Eukaryotes means “true nucleus.”
Q38. Cytoplasm contains:
Cytoplasm contains specialised cell organelles (like mitochondria, ribosomes, endoplasmic reticulum, etc.) along with dissolved substances, enzymes, and water. It is the site of many metabolic reactions and supports the organelles by providing a medium for their activities.
Q39. For cheek cell observation, the inside surface of cheek is scraped using:
For cheek cell observation, the inside surface of the cheek is gently scraped using a clean toothpick, spatula, or ice-cream spoon. The material is then transferred to a slide and stained with methylene blue for observation. A blade or scalpel would be too sharp and could cause injury.
Q40. In prokaryotes, functions of organelles are performed by:
In prokaryotes, the functions of organelles are performed by the poorly organised cytoplasm. Since prokaryotes lack membrane-bound organelles, most metabolic reactions occur in the cytoplasm. Ribosomes are present for protein synthesis, but they are not membrane-bound.
Q41. The undefined nuclear region in prokaryotes is called:
The undefined nuclear region in prokaryotes is called the nucleoid. It is a region where the genetic material (DNA) is located, but it is not enclosed by a nuclear membrane. The nucleoid contains the single circular chromosome of the prokaryotic cell.
Q42. Nuclear membrane has pores to allow transfer of material to:
The nuclear membrane has pores to allow the transfer of material between the nucleus and the cytoplasm. These pores allow RNA, proteins, and other molecules to move in and out of the nucleus. This communication is essential for cellular processes like protein synthesis.
Q43. Chromosomes contain information for inheritance in the form of:
Chromosomes contain information for inheritance in the form of DNA (Deoxyribo Nucleic Acid). DNA carries the genetic instructions that are passed from parents to offspring. It determines the characteristics of an organism and is responsible for heredity.
Q44. What structure appears as a dark coloured dot in cheek cells?
The nucleus appears as a dark coloured dot in cheek cells when stained with methylene blue. The nucleus takes up more stain and appears dark blue or purple. The cytoplasm appears lighter, and the cell membrane is visible as a thin outline. Cheek cells do not have large vacuoles.
Q45. The nucleus plays a central role in:
The nucleus plays a central role in cellular reproduction. It contains the genetic material (DNA) that directs cell division. During cell division, the DNA is replicated and distributed to daughter cells. This ensures that each new cell receives the correct genetic information.
Q46. Chromosomes are composed of:
Chromosomes are composed of DNA and protein. The DNA is tightly coiled around proteins called histones. This packaging helps fit the long DNA molecules into the nucleus. The combination of DNA and protein is called chromatin in the non-dividing state and chromosomes during cell division.
Q47. Functional segments of DNA are called:
Functional segments of DNA are called genes. Each gene contains the instructions for making a specific protein. Genes are the units of heredity and determine the traits of an organism. They are located on chromosomes and are passed from parents to offspring.
Q48. In a non-dividing cell, DNA exists as:
In a non-dividing cell, DNA exists as chromatin material. Chromatin is a thread-like, entangled mass of DNA and proteins. It is not condensed into distinct chromosomes during this stage. When the cell is about to divide, the chromatin condenses to form chromosomes.
Q49. Why is iodine solution put on the onion peel?
Iodine solution is put on the onion peel to stain the cells. Iodine acts as a stain that colours the nucleus and other cellular structures, making them visible under the microscope. Iodine also reacts with starch (if present) to give a blue-black colour, which helps in observing cell structures.
Q50. Each cell organelle performs:
Each cell organelle performs a specific function. For example, mitochondria produce energy (ATP), ribosomes synthesise proteins, lysosomes digest waste, and the nucleus controls cell activities. This division of labour allows the cell to carry out all life processes efficiently.