Class 11 Biology WBCHSE Cell The Unit Of Life Questions And Answers
Question 1. What is a biomembrane or biological membrane?
Answer:
Biomembrane or biological membrane
The membrane surrounding the cytoplasm of all cells and organelles of eukaryotic organisms which contain similar repeating units of protein-lipid, is called biomembrane or biological membrane.
Question 2. What is a unit membrane?
Answer:
Membrane
The protein-lipid-protein membrane which encloses many cells and cell organelles is known as a unit membrane. It was previously believed to be composed of three layers—an inner lipid layer enclosed by two outer protein layers.
Cell: The Unit of Life questions and answers PDF
Question 3. Why is ER called reticulum?
Answer:
ER consists of a mesh or reticulum in the endoplasm region of cytoplasm and so ER is known as endoplasmic reticulum.
Question 4. What is autophagosome?
Answer:
Autophagosome
These are secondary lysosomes that digest the cell’s own constituents through a process called autophagy.
Read and Learn More WBCHSE Solutions For Class 11 Biology
Question 5. Why cell wall of bacteria or prokaryotic cells is tough?
Answer:
The cell wall of bacteria or prokaryotic cells is tough due to the presence of peptidoglycan (a compound made of oligosaccharides and protein).
Question 6. What is known as a mesosome? What is its function?
Answer:
Mesosome: The folded region of plasma membrane towards the cytoplasm in a prokaryotic cell, mainly in the case of Gram-negative bacteria, is known as mesosome.
Function: It helps in respiration, replication, and cell division.
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Class 11 biology Cell: The Unit of Life Q&A
Question 7. What is the characteristic feature of prokaryotic ribosomes?
Answer:
Characteristic feature of prokaryotic ribosomes
The ribosome of a prokaryotic cell is 70S and it remains scattered within the cytoplasm.
Question 8. What is the characteristic feature of the eukaryotic ribosome?
Answer:
Characteristic feature of the eukaryotic ribosome
The ribosome of the eukaryotic cell is the 80S (in organelles, it is 55S or 70S) and these are attached to either the surface of RER or nuclear membrane or may remain scattered within the cytoplasm.
Question 9. What is the composition of the cytoplasmic skeleton?
Answer:
Composition of the cytoplasmic skeleton
The cytoplasmic skeleton is made up of microfilament, microtubule, and intermediate filament.
Question 10. Where does transcription take place in prokaryotic and eukaryotic cells?
Answer:
Transcription occurs in the cytoplasm of a prokaryotic cell and in the nucleus of a eukaryotic cell.
Question 11. What is microfibril?
Answer:
Microfibril
The main structural component of the cell wall which is made up of glucose units is called microfibril. It is composed of 20 micelle fibers.
Question 12. What is micelle?
Answer:
Micelle
The primary fiber formed by arranging numerous cellulose units (100) parallel is called a micelle.
Short answer questions on Cell: The Unit of Life
Question 13. What is desmotubule?
Answer:
Desmotubule
The thin (20 nm), simple or branched, membrane-bound tubule, present at the center of plasmodesmata is called a desmotubule.
Question 14. What are lonesome?
Answer:
Lonesome
Fungi, some algae, and some higher plant cells contain mesosome-like inner folds of plasma membrane. These are known as lonesomes. Their function is similar to mesosomes.
Question 15. What is chromocentre?
Answer:
Chromocentre
The dark, chromatin-containing parts in the nuclear reticulum is called chromocentres or karyosomes.
Question 16. What is perimitochondrial space?
Answer:
Perimitochondrial space
The space between inner and outer mitochondrial membranes which contains water, enzymes, and mineral salts, is called perimitochondrial space.
Question 17. What are oxysome granules or granules or elementary granules?
Answer:
The tennis racket-like structures arranged like chains in the inner wall of mitochondria (M-face) are the oxysome granules or granules. They contain the enzyme ATPase.
Cell: The Unit of Life chapter-wise questions with solutions
Question 18. What is a diplosome?
Answer:
Diplosome
The pair of centrioles in a centrosome is known as a diplosome.
Question 19. What are Microbodies?
Answer:
Microbodies
The unit membrane-bound, oxidizing organelles that are found scattered within the cytoplasm and carry out oxidation are called microbodies, such as—peroxisome, glyoxysome, and spherosome.
Question 20. What is a chromophobe cell?
Answer:
Chromophobe cell
The cells which do not have any affinity for dyes, are called chromophobe cells. These cells are found in the frontal part of the pituitary gland.
Question 21. How do salivary juice and tears act as bacteriocidal fluid?
Answer:
Salivary juice and tears contain lysozyme, an enzyme that hydrolyses the peptidoglycan layer of the cell wall of the bacterial cells. As a result, lysozyme can destroy invading pathogens.
Question 22. Water turns red when the beetroot is boiled in it, but this does not happen when the carrot is boiled. Why?
Answer:
Water turns red when the beetroot is boiled in it, but this does not happen when the carrot is boiled.
Vacuole in cells of beetroot contains the pigment yS-cyanin. On boiling the cell membrane dies and becomes permeable, and vacuoles break down and release the pigment into water.
Beta-cyanin being soluble in water, dissolves in it and turns the water red. However, the carotene pigment of carrot is present in the thylakoids of the plastid. On boiling, the pigment is not released into the water.
The pigment is also insoluble in water. So, carrots do not impart any color to water when boiled. It also proves that the cell membrane is semipermeable.
Question 23. Why are mitochondria less in chloroplast-containing green plant cells than in animal cells?
Answer:
Green plant cells which contain chlorophyll can synthesize ATP in chloroplasts as well as mitochondria. But animal cells lack chloroplast and hence, most of the ATP is synthesized by mitochondria only. So, mitochondria are less in green plant cells but more in animal cells.
Question 24. Why are cristae formed in the wall of the inner membrane of mitochondria?
Answer:
Cristae increase the surface area of the inner membrane of mitochondria, thus increasing the availability of enzymes, that are necessary for respiration.
Question 25. Which are the second largest organelle in plant and animal cells?
Answer:
Next to the nucleus, the second largest organelle is plastid in plant cells and mitochondria in animal cells.
Class 11 Biology WBCHSE Cell The Unit Of Life Very Short Question And Answers
Question 1. What is a cell?
Answer:
Cell
The cell is the structural and functional unit of life.
Question 2. Who was the propounder of the unit membrane concept?
Answer: J. D. Robertson was the propounder of the unit membrane concept.
Question 3. Who invented the electron microscope?
Answer: M. Knoll and E. Ruska (1931).
Question 4. What is the resolving power of human eyes?
Answer: 0.1 nm
Question 5. Name the smallest and largest cells of organisms on earth.
Answer: The smallest cell is PPLO and the largest cell is the egg of an ostrich.
Question 6. Name the scientist who introduced the term ‘cell’.
Answer: Robert Hooke
Question 7. What is a cell wall?
Answer:
Cell wall
The thick, rigid, dead, permeable, and cellulosic outermost covering of some protists, fungi, and eukaryotic plant cells is called the cell wall.
Question 8. Give two examples of prokaryotic cells.
Answer: Oscillatoria sp., Anabaena sp.
Question 9. What is a centrosome?
Answer:
Centrosome
The membrane-less organelle that forms spindle fibers during cell division is called a centrosome.
Question 10. What is lysosome?
Answer:
Lysosome
Lysosomes are sac-like structures that are bound by a single membrane and are involved in intracellular digestion.
Question 11. What is the main function of the plasma membrane?
Answer: The plasma membrane allows selective transport of substances in and out of the cell.
Question 12. Mention the major role of the Golgi apparatus.
Answer: Golgi bodies have secretory functions and they secrete enzymes, hormones, mucus, etc.
Question 13. What is pinocytosis?
Answer:
Pinocytosis
The process by which a cell engulfs fluids is called pinocytosis.
Question 14. What is osmosis?
Answer:
Osmosis
The movement of solvent molecules from a region of lower solute concentration through a semipermeable membrane into a region of higher solute concentration is called osmosis.
Question 15. Define cell membrane.
Answer:
Cell membrane
The living, semi-permeable outer covering of cytoplasm is made up of called cell membrane.
Question 16. Who discovered ribosome?
Answer: G. Palade
Question 17. What are plasmodesmata?
Answer:
Plasmodesmata
The membrane-bound tubules of the endoplasmic reticulum that pass through the intervening cell wall and make connections between adjacent plant cells are called plasmodesmata.
Question 18. What do you mean by polysome?
Answer:
Polysome
The complex formed between an mRNA and more than one ribosome is called a polyribosome.
Question 19. What are autophagosomes?
Answer:
Autophagosomes
The double membrane-bound vesicle that encloses worn-out cell organelles and fuses with lysosomes which digest these cell organelles during autophagy, is called autophagosome.
Question 20. What is phagocytosis?
Answer:
Phagocytosis
The process by which a cell engulfs solid substances is called phagocytosis.
Question 21. State the main function of the centriole.
Answer: The centrioles play an important role in cell division by forming a spindle and providing a mechanism for the arrangement and movement of chromatids.
Question 22. What are plastids?
Answer:
Plastids
The double membrane-bound, spherical or oval-shaped, pigmented and unpigmented organelles of plant cells that synthesize organic compounds are called plastids.
Objective questions on Cell: The Unit of Life with answers
Question 23. Name the single membrane-bound cell organelle, which is rich in hydrolytic enzymes.
Answer: Lysosome
Question 24. What is the main role of dictyosome?
Answer:
Main role of dictyosome
Dictyosome helps in the secretion and formation of cell walls.
Question 25. What is thylakoid?
Answer:
Thylakoid
Sac-like structures in the chloroplasts that are arranged into stacks are called thylakoids.
Question 26. Who proposed the cell theory?
Answer: Schleiden and Schwann
Question 27. Who discovered the Golgi body?
Answer: Camillo Golgi
Question 28. What is the function of peroxisome?
Answer:
Function of peroxisome
Peroxisome carries out oxidative reactions in the cell and protects the cell from harmful oxidative radicals.
Question 29. Who discovered the nucleolus?
Answer: F. Fontana (1774)
Question 30. What is selective permeability?
Answer:
Selective permeability
A membrane that allows both solvent and solute to pass but in a selective manner, is called a selectively permeable membrane.
Question 31. What is leucoplast?
Answer:
Leucoplast
Colourless plastid that stores fat are called leucoplast.
Question 32. Why is mitochondria called the ‘ powerhouse’ of the cell?
Answer: Mitochondria synthesizes energy in the form of ATP and so is called the ‘power house of the cell’.
Question 33. Where is rRNA synthesized?
Answer:
rRNA is synthesized in the nucleolus.
Question 34. What is active transport?
Answer:
Active transport
The process of transport of biochemical substances across a membrane that requires energy is called active transport.
Question 35. What is cystolith?
Answer:
Cystolith
Cystoliths are calcium carbonate crystals that occur in the form of a bunch of grapes in special enlarged cells in the leaf of plants of certain families.
Question 36. What is raphide?
Answer:
Raphide
Raphides are crystals of calcium oxalate that are stored within specialized plant cells called idioblasts.
Question 37. What are grana?
Answer:
Grana
Thylakoids of chloroplast are arranged in the form of stacks which are called grana.
Question 38. What is the function of lysosomes?
Answer:
The function of lysosomes
Lysosome is the intracellular digestive organelle that hydrolyses damaged and worn-out parts of the cell.
Question 39. State the function of leucoplast.
Answer:
Function of leucoplast
Leucoplast stores fat, proteins, and starch. They are capable of transforming into other plastids.
Question 40. What do you mean by cytoskeleton?
Answer:
Cytoskeleton
The complex network of protein filaments that forms a mesh and structural support of the eukaryotic cell is called the cytoskeleton.
Question 41. What is chloroplast?
Answer:
Chloroplast
The plastid that contains the pigment chlorophyll and is responsible for photosynthesis is called chloroplast. GERL system refers to the associative function of Golgi bodies, endoplasmic reticulum, ribosome, and lysosome.
Question 42. What do you mean by the GERL system?
Answer:
GERL system
The GERL System refers to the associative Function Of Golgi Bodies, Endoplasmic Reticulum, Ribosomes, And Lysosomes.
Question 43. State the function of the centriole.
Answer: Centrioles form spindle fibers during cell division.
Question 44. In the 80S ribosome, what does the letter S stand for?
Answer: ‘S’ stands for Svedberg which is the unit of sedimentation coefficient.
Class 11 Biology WBCHSE
Question 45. Who first showed the presence of mitochondria in living cells?
Answer: Altman
Question 46. Name the internal membrane present in prokaryotic cells.
Answer: Plasma membrane
Question 47. Who discovered the centrosome?
Answer: Edouard Van Beneden in 1883.
Question 48. What is the function of the nuclear membrane?
Answer:
Function of the nuclear membrane
Substances are translocated through the nuclear pore. It also separates the nucleus from the cytoplasm.
Important Cell: The Unit of Life questions and answers
Question 49. What is aleuroplast?
Answer:
Aleuroplast
Aleuroplast is a type of leucoplast that stores protein.
Question 50. Name a secretory material of the cell.
Answer: Zymogen granules.
Question 51. What is the feature of a metacentric chromosome?
Answer: The centromere is present in the middle of the chromosome and the chromosome appears like ‘V’ at the anaphase stage of cell division.
Question 52. What is referred to as the satellite chromosome?
Answer:
The chromosomes that have a small region at the terminal of secondary constriction are called satellite chromosomes.
Question 53. Which pigment is mainly responsible for the color of the carrot?
Answer: Carotene
Question 54. What is the significance of vacuole in a plant cell?
Answer:
Significance of vacuole in a plant cell
Vacuole maintains osmotic pressure for turgidity in a plant cell.