Cell: the unit of life Sample paper

Q1. Cell theory was given by

  • 1) Meselson and Stahl
  • 2) Robert Hooke
  • 3) Robert Brown
  • 4) Schleiden and Schwann

Solution

M. J. Schleiden and Theodore Schwann first put forward the cell theory in 1839. The theory was published in their paper ‘Microscopic Investigations on the Similarities of Structure and Growth in Animals and Plants’.

Q2. Name the following: Plastids which store oil Plastids which store proteins Plastids which store starch

Solution

Plastids which store oil – Elaioplasts Plastids which store proteins – Aleuroplasts Plastids which store starch – Amyloplasts

Q3. A cell, when kept in a sugar solution, gets dehydrated. Then the solution is

  • 1) Isotonic
  • 2) Hypotonic
  • 3) Hypertonic
  • 4) None of the above

Solution

If a cell is placed in a hypertonic solution, then it loses water due to exosmosis and gets dehydrated.

Q4. Which of the following organelles does not have a membrane?  

  • 1) Chloroplast  
  • 2) Mitochondria  
  • 3) Nucleus  
  • 4) Ribosome  

Solution

Ribosomes are composed of RNA and proteins and are not surrounded by any membrane.     The nucleus, chloroplasts and mitochondria, all are surrounded by a double-layered membrane.  

Q7. Mitochondria are called power houses of the cell. Justify.

Solution

Mitochondria are the sites of aerobic respiration. They produce cellular energy in the form of ATP. Hence, they are called powerhouses of the cell.

Q6. The site of protein synthesis is

  • 1) SER
  • 2) Ribosome
  • 3) Golgi body
  • 4) Lysosome

Solution

Ribosomes use the mRNA as a template, traverse each codon (3 nucleotides) of the mRNA and pair it with the appropriate amino acid provided by tRNA. The amino acid chain elongates at the ribosome and results in the formation of an appropriate protein. 

Q7. Cell theory is not applicable to  

  • 1) Algae  
  • 2) Virus  
  • 3) Fungus  
  • 4) Bacteria  

Solution

A virus is not considered as a living organism as it cannot grow.     A virus cannot replicate unless it infects a cell.     It then uses the host’s machinery for producing multiple copies of viruses.     Thus, even cell theory does not apply to viruses.  

Q8. State the functions of the cell wall in a prokaryotic cell.

Solution

Functions of the cell wall in a prokaryotic cell are as follows: It determines the shape of the cell. It provides strong structural support to prevent the cell from bursting or collapsing.

Q9. An enzyme which increases the rate of permeability across the plasma membrane is  

  • 1) Amylase  
  • 2) Permease  
  • 3) Catalase  
  • 4) Gelatinase  

Solution

Permeases act as transport proteins. They help in the transport of specific substances down their concentration gradient across the cell membrane.     Permeases thus help to increase the permeability of the membrane by transporting substances which were otherwise impermeable.  

Q10. Mesosome in a bacterial cell is  

  • 1) Plasmid  
  • 2) Connection between two cells  
  • 3) Plasma membrane infolds for respiration  
  • 4) None of the above  

Solution

Prokaryotic cells have a special membranous structure, mesosome, which is formed by the extensions of the plasma membrane into the cell. They help in cell wall formation, DNA replication and distribution to daughter cells. They also help in respiration, secretion processes and to increase the surface area of the plasma membrane and enzymatic content.   

Q11. A cell swells up when kept in

  • 1) Hypotonic solution
  • 2) Hypertonic solution
  • 3) Any of the above
  • 4) Isotonic solution

Solution

A cell in a hypotonic solution will absorb water by endosmosis. The increased volume of water in the cell will result in swelling up of the cell. 

Q12. Which of the following is not a function of the cytoskeleton in a cell?  

  • 1) Cell motility  
  • 2) Support of the organelle  
  • 3) Maintenance of cell shape and structure  
  • 4) Intracellular transport  

Solution

An elaborate network of a filamentous proteinaceous structure present in the cytoplasm is called cytoskeleton.     The cytoskeleton carries out functions such as mechanical support, motility and maintenance of the shape of the cell.   

Q13. Who proposed the fluid mosaic model of the plasma membrane? Describe the detailed structure of the plasma membrane in eukaryotic cells.

Solution

Singer and Nicolson proposed the fluid mosaic model of plasma membrane.   The plasma membrane is composed of a lipid bilayer. The lipid molecules are arranged in such a way that their polar head are towards the outer side and the hydrophobic tails are on the inner side. This arrangement of lipid molecules ensures that the non-polar tail of hydrocarbons does not come in contact with the aquatic environment present.

The proteins are of two types. Integral proteins which are either partially or totally embedded in the lipid bilayer and peripheral proteins which are present on the surface of the membrane. The quasi fluid nature of lipid enables the lateral movements of proteins within the lipid bilayer. The fluid nature of the membrane enables functions such as cell growth, secretion, endocytosis, cell division and formation of the intercellular junction.

Q14. The plasma membrane consists mainly of

  • 1) Phospholipids embedded in a protein bilayer.
  • 2) Proteins embedded in a polymer of glucose molecules.
  • 3) Proteins embedded in a phospholipid bilayer.
  • 4) Proteins embedded in a carbohydrate bilayer.

Solution

The widely accepted fluid mosaic model of plasma membrane suggests that the plasma membrane is composed of phospholipids arranged in a bilayer. The plasma membrane also contains proteins on the surface and partially or totally buried in a bilayer.

Q15. Cell wall consists of  

  • 1) Lignin, hemicellulose, pectin and lipid  
  • 2) Lignin, hemicellulose, pectin and cellulose  
  • 3) Hemicelluloses, cellulose, tubulin and lignin  
  • 4) Lignin, hemicellulose, protein and lipid  

Solution

In the primary plant cell wall, the major carbohydrates are cellulose, hemicellulose and pectin. Lignin is present in trace amounts.     Secondary cell walls contain about 10-25% of lignin which penetrates the spaces in the cell wall between cellulose, hemicellulose and pectin components, driving out water and strengthening the walls.  

Q16. What are mesosomes?

Solution

Mesosomes are essential infoldings of the cell membrane, a unique characteristic of prokaryotic cells.

Q17. Which of the following is a prokaryote?

  • 1) Bacteria
  • 2) Amoeba
  • 3) Chlamydomonas
  • 4) Spirogyra

Solution

Amoeba is a protozoan, Spirogyra and Chlamydomonas are algae; all three are eukaryotes. Bacteria do not have a well-defined nucleus and membrane-bound organelles are absent; thus, bacteria are prokaryotes.

Q18. What is true about ribosomes?  

  • 1) These are self-splicing introns of some RNAs.  
  • 2) These are composed of ribonucleic acid and proteins.  
  • 3) These are found only in eukaryotic cells.  
  • 4) The prokaryotic ribosomes are 80S, where ‘S’ stands for sedimentation coefficient.  

Solution

Ribosomes are found in both prokaryotic and eukaryotic cells. Prokaryotes have 70S ribosomes and eukaryotes have 80S ribosomes.     Ribosomes are composed of 32-67% RNA and the rest are proteins.  

Q19. A chromosome having a centromere at its middle is  

  • 1) Telocentric  
  • 2) Metacentric  
  • 3) Dicentric  
  • 4) Acrocentric  

Solution

Depending on the position of the centromere, chromosomes are of the following types:           Metacentric chromosome: The centromere is present right in the middle of the chromosome.           Sub-metacentric chromosome: The centromere is present a little away from the middle of the chromosome.           Acrocentric chromosome: The centromere is present close to one of the ends of the chromosome.     Telocentric chromosome: A terminal centromere.  

Q20. Name the following: Chromosome with the centromere located terminally Non-staining secondary constrictions in some chromosomes Component of the nucleus which is stained by basic dyes

Solution

Chromosome with the centromere located terminally: Telocentric chromosome Non-staining secondary constrictions in some chromosomes: Satellite Component of the nucleus which is stained by basic dyes: Chromatin

Q21. Explain the structure of a centrosome.

Solution

The centrosome consists of two centrioles which lie perpendicular to each other. Each centriole has a cart-wheel-like organisation. Each centriole is made of nine peripheral tubulin fibrils which are evenly spaced. Each of the peripheral fibrils is a triplet. The adjacent triplets are linked. The central part of the proximal region of each centriole is called a hub. The hub is connected to peripheral triplets by proteinaceous spokes.

Q22. House-keeping proteins occur in

  • 1) ER
  • 2) Golgi complex
  • 3) Cytoskeleton
  • 4) All of the above

Solution

House-keeping proteins are defined as proteins which are required for the basic functioning of a cell. Important enzymatic and structural proteins are found in the endoplasmic reticulum, Golgi complex and cytoskeleton of cells.

Q23. From the following statements, select the statement that is true:  

  • 1) Golgi apparatus is found only in animal cells.  
  • 2) Animal cells contain microtubules but plant cells do not.  
  • 3) All cells have a cell wall.  
  • 4) Chloroplasts are found in plant cells but not in prokaryotic or animal cells.  

Solution

Animal cells lack a cell wall.     All eukaryotic cells except amoeba and slime moulds contain microtubules.     The Golgi apparatus is present in all eukaryotic cells.     Chloroplasts are found in plant cells. Some prokaryotes (e.g. cyanobacteria) contain chlorophyll, but chloroplast is absent. Animal cells also lack chloroplasts.  

Q24. The core metal of chlorophyll is

  • 1) Cu
  • 2) Ni
  • 3) Mg
  • 4) Fe

Solution

Mg (magnesium) is the core metal of chlorophyll. Chlorophyll contains a complex ring structure called a porphyrin ring. Magnesium is present in the centre of this complex ring.

Q25. Which one of the following has its own DNA?

  • 1) Peroxisome
  • 2) Mitochondria
  • 3) Dictyosome
  • 4) Lysosome

Solution

Mitochondria are semi-autonomous. They have their own DNA, RNA and proteins. Mitochondria can multiply when the energy needs of a cell increase.

Q26. Mitochondria will be more in  

  • 1) Germinating seeds  
  • 2) Dry seeds  
  • 3) None of the above  
  • 4) Dormant seeds  

Solution

The number of mitochondria per cell varies depending on the physiological activities of the cell. Germinating cells require more energy for growth; thus, they require more ATP and more number of mitochondria.  

Q27. Chlorophyll in chloroplasts is located in

  • 1) Pyrenoid
  • 2) Both grana and stroma
  • 3) Stroma
  • 4) Grana

Solution

Stroma is the space enclosed within the membranes in the chloroplast. Stroma contains several flat membranous sacs called thylakoids. Chlorophyll is present in the thylakoids. Thylakoids are arranged in stacks like the piles of coins called grana.

Q28. The largest subunit of prokaryotic ribosomes is  

  • 1) 60S  
  • 2) 30S  
  • 3) 40S  
  • 4) 50S  

Solution

In prokaryotes, ribosomes are associated with the plasma membrane of the cell. They are made of two subunits – 50S and 30S units which when present together form 70S prokaryotic ribosomes.  

Q29. Respiratory enzymes are present in which of the following organelles?  

  • 1) Chloroplast  
  • 2) Lysosome  
  • 3) Mitochondria  
  • 4) Peroxisome  

Solution

Mitochondrion is the site for aerobic respiration in cells. It contains respiratory enzymes necessary for ATP synthesis.  

Q30. What are the three layers bound by the cell envelope in prokaryotic cells?

Solution

The three layers bound by the cell envelope in prokaryotic cells are the outer glycocalyx, the middle cell wall and the inner plasma membrane.

Q31. Three of the following statements regarding cell organelles are correct while one is wrong. Which one is wrong?  

  • 1) Leucoplasts are bound by two membranes, lack pigment but contain their own DNA and protein-synthesising machinery.  
  • 2) Lysosomes are double-membraned vesicles budded off from the Golgi apparatus and contain digestive enzymes.  
  • 3) Sphaerosomes are single-membrane bound and are associated with the synthesis and storage of lipids.  
  • 4) Endoplasmic reticulum consists of a network of membranous tubules and helps in transport, synthesis and secretion.  

Solution

Lysosomes are single-membraned vesicles.     They bud off from the Golgi apparatus during the packaging process.     Lysosomes contain digestive enzymes capable of hydrolysing biological polymers.  

Q32. Centrosomes are present

  • 1) In animal cells only
  • 2) None of the above
  • 3) In plant cells only
  • 4) In both plant and animal cells

Solution

Centrosomes are found in animal cells only. They help in the formation of spindle fibres during the cell cycle. In plant cells, centrosomes are absent.

Q33. Long, flattened and usually unbranched units arranged in parallel stacks in the endoplasmic reticulum are called

  • 1) Tubules
  • 2) Cisternae
  • 3) Cristae
  • 4) Vesicles

Solution

The endoplasmic reticulum forms tubes known as cisternae. These tubes are an interconnected network of flattened, membrane-enclosed sacs or tubes. 

Q34. What is the length of mycoplasma which is the smallest cell?

Solution

0.3 micron in length.

Q35. Ajay has understood that the important function of the plasma membrane is transport of molecules across the membrane. But he is confused with the processes such as diffusion, active transport, osmosis etc. Answer the following questions to help Ajay understand the various processes involved in the transport of molecules.     What is active transport?   What is osmosis?   Why movement of ions against the concentration gradient requires energy?   What values do you learn here?

Solution

Active transport – It is the movement of ions against their concentration gradient, i.e. from lower to higher concentration across the membrane. This process requires ATP and carrier proteins.   Osmosis – It is movement of water molecules from the region of their higher concentration to the region of their lower concentration through the plasma membrane.   Because the movement of ions occurs from the region of lower concentration to the region of higher concentration, it is against the normal flow of ions. The process needs energy.   The values we learn here are that every task should be completed by understanding its needs. To achieve success in difficult tasks, efforts and hardwork are important.

Q36. During endocytosis,  

  • 1) The cell enables the extracellular digestion of large molecules.  
  • 2) The cell digests itself.  
  • 3) The cell engulfs and internalises materials using its membrane.  
  • 4) The cell divides its cytoplasm during mitosis.  

Solution

During endocytosis, the cell elongates its membrane and then engulfs and internalises the material.     This process is commonly used by Amoeba to obtain food from the surrounding.  

Q37. Write the significance of tonoplasts.

Solution

The tonoplast facilitates the transport of several ions and other materials against the concentration gradient into the vacuole.

Q38. Which of the following is the site of translation of mRNA?

  • 1) Golgi body
  • 2) Ribosomes
  • 3) Nucleus
  • 4) Nucleolus

Solution

Translation of mRNA results in protein synthesis. Ribosomes are called the protein factories of cells. They contain the enzymes for protein synthesis. They also provide the sites for attachment of RNAs which participate in protein synthesis.

Q39. Name the part of the cell wall which helps neighbouring cells to bind together.

Solution

The middle lamella helps neighbouring cells to bind together.

Q40. Na+/K+ pump in a cell is an example of  

  • 1) Diffusion  
  • 2) Passive transport  
  • 3) Active transport  
  • 4) Osmosis  

Solution

The transport of ions or molecules against their concentration gradient requires energy in the form of ATP and is an active process. The Na+/K+ pump facilitates the transport of ions across the plasma membrane against their concentration gradient.  

Q41. Name the organelles which are collectively known as the endomembrane system.

Solution

The endoplasmic reticulum, Golgi complex, lysosomes and vacuoles are collectively known as the endomembrane system.

Q42. Nuclear membrane is absent in  

  • 1) Penicillium  
  • 2) Nostoc  
  • 3) Volvox  
  • 4) Agaricus  

Solution

Prokaryotes do not have a nuclear membrane. Nostoc is a prokaryote. Penicillium and Agaricus are fungi and Volvox is an alga; all three are eukaryotes.  

Q43. Middle lamella is mainly composed of  

  • 1) Muramic acid  
  • 2) Phosphoglycerides  
  • 3) Calcium pectate  
  • 4) Hemicellulose  

Solution

Middle lamella is mainly composed of calcium pectate which holds or glues the different neighbouring cells together.  

Q44. Which method of transport in the plasma membrane does not require a carrier molecule?  

  • 1) Na+-K+ pump  
  • 2) Simple diffusion  
  • 3) Facilitated diffusion  
  • 4) Active transport  

Solution

Neutral solutes can move across the plasma membrane along the concentration gradient by the process of simple diffusion. As the solutes move along the concentration gradient, a carrier is not required.  

Q45. Explain the Golgi apparatus and describe its structure.  

Solution

 The Golgi apparatus consists of sac-like structures called cisternae which are flat, disc-shaped. The cisternae are of 0.5-1.0 m.     Cisternae are concentrically arranged near the nucleus.     The convex face of cisternae is called cis which is also known as the forming face.     The concave face of cisternae is called trans which is also known as the maturing face.     The two faces of the Golgi apparatus are different from each other, but they are interconnected.  

Q46. State the function of the primary cell wall found in young plants.

Solution

The function of the primary cell wall found in young plants is growth.

Q47. Which of the following is present in both prokaryotic and eukaryotic cells?

  • 1) Ribosomes
  • 2) Endoplasmic reticulum
  • 3) Nucleus
  • 4) Mitochondria

Solution

Prokaryotes have a 70S ribosome and eukaryotes have an 80S ribosome.

Q48. Name the membranous extension other than the mesosome which is found in cyanobacteria.

Solution

Chromatophores

Q49. Name the plastids which store proteins.

Solution

Aleuroplasts

Q50. Which of the following cell organelles lacks a membrane?

  • 1) Ribosome
  • 2) Liposome
  • 3) Mesosome
  • 4) Mitochondria

Solution

Ribosomes are present in both prokaryotes and eukaryotes. They lack cell membrane. In prokaryotes, ribosomes are present free in the cytoplasm. In eukaryotes, ribosomes may be free in the cytoplasm or attached to the outer surface of the endoplasmic reticulum and nucleus.

Q51. Name the largest cell.

Solution

Egg of an ostrich.

Q52. There is no DNA in  

  • 1) Mature RBCs  
  • 2) An enucleated ovum  
  • 3) Mature spermatozoan  
  • 4) Hair root  

Solution

RBCs when born contain a nucleus. In due course, as the RBCs mature, their nuclei degenerate and so do the DNA.      Mature RBCs lose the nucleus to make more space for accommodating haemoglobin.  

Q53. The endoplasmic reticulum is in continuation with

  • 1) Nuclear membrane
  • 2) Cell wall
  • 3) Mitochondria
  • 4) Golgi body

Solution

The membranes of the ER are continuous with the outer membrane of the nuclear membrane.  

Q54. State the arrangement of microtubules found in cilia and flagella.

Solution

9 + 2

Q55. Mitochondria are semi-autonomous as they possess

  • 1) DNA + RNA + ribosomes
  • 2) DNA
  • 3) Protein
  • 4) DNA + RNA

Solution

Mitochondria are semi-autonomous organelles. For replication and growth, they depend only partially on the cell. They have their own DNA, RNA and ribosomes and can make their own proteins.  

Q56. Lysosomes contain

  • 1) Hormone
  • 2) Hydrolytic enzymes
  • 3) Useful material
  • 4) Lytic enzymes

Solution

Lysosomes contain enzymes which can digest all types of biological polymers – proteins, nucleic acids, carbohydrates and lipids. The enzymes hydrolyse these polymers and break them down. Thus, lysosomes contain hydrolytic enzymes. 

Q57. Which one of these is not a eukaryote?

  • 1) Spirogyra
  • 2) Agaricus
  • 3) Euglena
  • 4) Anabaena

Solution

Euglena and Spirogyra are algae, Agaricus is a fungus; all three are eukaryotes. Anabaena is a cyanobacterium, a prokaryote. It can carry out photosynthesis and nitrogen fixation.

Q58. What is the main arena of the cell and state its function.  

Solution

The cytoplasm is the main arena of the cell, and it is the site for many metabolic activities which occur within the cell.  

Q59. State the function of the smooth endoplasmic reticulum.

Solution

The smooth endoplasmic reticulum is the major site for the synthesis of lipids.

Q60. What does ‘S’ from 70S stand for?

Solution

The ‘S’ (Svedberg unit) from 70S stands for sedimentation coefficient.

Q61. Flagella of prokaryotic and eukaryotic cells differ in

  • 1) microtubular organization and function
  • 2) location in cell and mode of functioning
  • 3) type of movement and placement in cell
  • 4) microtubular organization and type of movement

Solution

Flagella of prokaryotic and eukaryotic species differ in microtubular organization and type of movement. In eukaryotes, the arrangement is 9+2 and specialized whereas in prokaryotes arrangement is 9+0 and is simple.

Q62. Explain the chloroplast and explain its structure.  

Solution

Chloroplasts are oval, spherical, disc-shaped or ribbon-shaped. They are 5-10 mm in length and 2-4 mm in width.     It is a double-membraned organelle.     The space enclosed by the inner membrane is filled with a semi-solid substance called stroma.

Flattened, membranous sacks called thylakoids are present in the stroma.     The stroma contains several enzymes required for protein and carbohydrate synthesis, DNA, ribosomes and RNA.     The thylakoids are arranged like stacks of coins. These stacks are called grana.     Flat membranous tubules called stroma lamellae connect the thylakoids.     The thylakoids contain space within them called a lumen.  

Q63. Write the two important characteristics of unicellular organisms.

Solution

Two important characteristics of unicellular organisms are as follows: They show independent existence. They are capable of performing all essential functions of life.

Q64. Name the smallest cell found.

Solution

Mycoplasma

Q65. Cellular totipotency is demonstrated by

  • 1) All eukaryotic cells
  • 2) Only gymnosperm cell
  • 3) All plant cells
  • 4) Only bacterial cell

Solution

Totipotency is the ability of a cell to regenerate into an entire organism. This ability is demonstrated by all plant cells.

Q66. Describe the two types of membrane proteins.

Solution

Two types of membrane proteins are as follows: Integral membrane proteins: They are partially or totally buried in the membrane. Peripheral membrane proteins: They are present on the surface of the membrane.

Q67. ER works for the synthesis of

  • 1) Mitochondria
  • 2) Protein
  • 3) ATP
  • 4) Golgi body

Solution

The endoplasmic reticulum functions to fold protein molecules and transport them to the Golgi apparatus.

Q68. State the four basic shapes of bacteria.

Solution

The four basic shapes of bacteria are bacillus, coccus, vibrio and spirillum.

Q69. State the main component found in the middle lamella of the cell wall.

Solution

Calcium pectate is the main component found in the middle lamella of the cell wall.

Q70. Explain the process of packaging of materials in the Golgi complex.  

Solution

Materials which need to be packaged are in the form of vesicles.     These vesicles from the endoplasmic reticulum fuse with the cis face of the Golgi apparatus.     From the cis face, the material moves towards the maturing face, i.e. the trans face.  

Q71. Cellular totipotency was first demonstrated by

  • 1) F. C. Steward
  • 2) T. Schwann
  • 3) A. V. Leeuwenhoek
  • 4) Robert Hooke

Solution

F. C. Steward and his co-workers conducted experiments on carrot root tissues and were the first to demonstrate totipotency.

Q72. Name the structure which is responsible for excretion in Amoeba.

Solution

The contractile vacuole is responsible for excretion in Amoeba.

Q73. Name the process by which water moves across the cell membrane.

Solution

Water moves across the membrane by osmosis.

Q74. Describe the general structure of a prokaryotic cell.

Solution

A prokaryotic cell consists of the cell wall which surrounds the cell membrane. The interior of the cell is filled with a matrix called cytoplasm. A well-defined nucleus is absent. The genetic material is naked and not enclosed in a nuclear membrane. Prokaryotic cells show the presence of extra-chromosomal DNA called plasmid. The cell membrane shows some extension in the cytoplasm called mesosomes. These cells show the presence of ribosomes.

Q75. Give the significance of the following:     Quasi fluid nature of lipid   The fluid nature of the membrane  

Solution

Quasi fluid nature of lipid: It enables the lateral movement of proteins within the lipid bilayer.   The fluid nature of the membrane: It enables functions such as cell growth, secretion, endocytosis, cell division and formation of intercellular junction.  

Q76. Tonoplast is the membrane surrounding the

  • 1) Mitochondria
  • 2) Cytoplasm
  • 3) Vacuole
  • 4) Nucleus

Solution

The tonoplast is a single-layered membrane which surrounds a vacuole. It facilitates the transport of ions and other materials from the cytoplasm to the vacuole.

Q77. What are inclusion bodies? Write the names of the inclusion bodies found in prokaryotic cells.

Solution

Inclusion bodies are the reserve materials stored in the cytoplasm of prokaryotic cells. The following inclusion bodies are found in prokaryotic cells: Phosphate granules, cyanophycean granules and glycogen granules.

Q78. What are the structures called which give an appearance as beads on a string in the chromosomes when viewed under an electron microscope?

  • 1) Base pairs
  • 2) Genes
  • 3) Nucleosomes
  • 4) Nucleotides

Solution

Nucleosomes are particles present on the chromatin fibre which give a beaded appearance to the chromatin. A nucleosome consists of a DNA which wraps a histone octamer.

Q79. Define tonoplast.

Solution

The tonoplast is the thin membrane which covers the vacuole.

Q80. Name the two cells which lack a nucleus.

Solution

The cells which lack a nucleus are as follows: Mammalian erythrocytes Sieve tube cells of vascular plants

Q81. Name any two carotenoid pigments.

Solution

The carotenoid pigments are xanthophyll and carotene.

Q82. Write the functions of the cytoskeleton.  

Solution

Functions of cytoskeleton:     It provides mechanical support and motility to the cell.   It maintains the shape of the cell.  

Q83. Distinguish between rough endoplasmic reticulum and smooth endoplasmic reticulum.

Solution

Rough Endoplasmic Reticulum Smooth Endoplasmic Reticulum It is the site of protein synthesis and secretion. It is the site of lipid synthesis. Ribosomes are present on their surface. Ribosomes are absent.  

Q84. Who discovered the cell nucleus?

Solution

Robert Brown discovered the cell nucleus.

Q85. When is the glycocalyx called a slime layer?  

Solution

The glycocalyx is called a slime layer when it is in the form of a loose sheath.  

Q86. State the postulates of the cell theory.

Solution

Cell Theory: All living organisms are composed of cells and are products of cells. All cells arise from pre-existing cells.

Q87. Which one of the following structures between two adjacent cells is an effective transport pathway?

  • 1) Endoplasmic reticulum
  • 2) Plastoquinones
  • 3) Plasmodesmata
  • 4) Plasmalemma

Solution

The cell wall and middle lamellae may be traversed by plasmodesmata which connects the cytoplasm of neighbouring cells and helps in transport.

Q88. Distinguish between metacentric and submetacentric chromosomes.  

Solution

Metacentric Chromosome Sub-metacentric Chromosome Centromere is located centrally.   Centromere is slightly away from the centre of the chromosome.   Both the arms are equal.   One arm is shorter and one arm is longer.      

Q89. The powerhouse of the cell is

  • 1) Endoplasmic reticulum
  • 2) Ribosomes
  • 3) Mitochondria
  • 4) Golgi bodies

Solution

Mitochondria convert the chemical energy found in glucose and other nutrients in the presence of oxygen, resulting in formation of ATP molecules. Thus, mitochondria are called powerhouses of a cell.

Q90. Distinguish between active transport and osmosis.

Solution

Active Transport Osmosis Movement of ion occurs against the concentration gradient, i.e. from lower to higher concentration. Movement of water molecules occurs across the concentration gradient, i.e. from higher to lower concentration. Carrier proteins are required to facilitate the movement of ions. Carrier proteins are not required. ATP is utilised for the transport of ions across the membrane. Energy is not required.  

Q91. Distinguish between plant cell and animal cell.

Solution

Plant Cell Animal Cell Possess cell wall. Cell wall is absent. Plastids are present. Plastids are absent. Large, permanent vacuoles are present Vacuoles are small and temporary. Centrioles are absent. Centrioles are present.  

Q92. Write the names of any four prokaryotic cells.

Solution

Blue-green algae Mycoplasma PPLO (Pleuro-Pneumonia-Like Organisms) Bacteria

Q93. Name the scientist who described the nucleus for the first time.

Solution

Robert Brown described the nucleus for the first time.

Q94. Who proposed the fluid mosaic model of the cell membrane?

Solution

Singer and Nicolson proposed the fluid mosaic model of the cell membrane.

Q95. State the function of the rough endoplasmic reticulum.

Solution

The rough endoplasmic reticulum is involved in protein synthesis and secretion.

Q96. Name any one cell organelle which is not bound by the membrane.

Solution

Ribosome

Q97. Define cytoskeleton.

Solution

The cytoskeleton is the network of filamentous proteinaceous structures present in the cytoplasm.

Q98. Write the expanded form of PPLO.

Solution

PPLO – Pleuro-Pneumonia-Like Organisms

Q99. State the name of the scientists who observed ribosomes under an electron microscope for the first time.

Solution

George Palade observed ribosomes under an electron microscope for the first time.

Q100. Who coined the term chromatin?  

Solution

Flemming coined the term chromatin.  

Q101. What was the drawback of the cell theory proposed by Schleiden and Schwann?

Solution

The cell theory which was explained by Schleiden and Schwann could not explain how new cells were formed.

Q102. Explain the mitochondrion and describe its structure.

Solution

Structure of Mitochondrion:     Mitochondria are usually cylindrical. The diameter is 0.2 to 1.0 mm, and the length is 1.0 to 4.1 mm. It is a double membrane structure. The outer and inner membranes divide the lumen of the mitochondrion into two compartments – the outer compartment and the inner compartment. The inner compartment is in the form of several folding called cristae which increase the surface area to trap more light energy. The inner compartment is filled with matrix. The matrix consists of mitochondrial DNA, ribosomes and RNA.

Q103. Who explained the concept Omonis cellula e cellula?  

Solution

Rudolf Virchow explained the concept Omonis cellula e cellula.  

Q104. Define endoplasmic reticulum.

Solution

The endoplasmic reticulum is a network of tiny tubular structures scattered in the cytoplasm.

Q105. Name the subunits of which a prokaryotic ribosome is made.

Solution

A prokaryotic ribosome is made of 50S and 30S subunits.

Q106. Name the lipid component of the plasma membrane.  

Solution

Phosphoglycerides form the lipid component of the plasma membrane.  

Q107. Name the two substances which are majorly produced in Golgi bodies.

Solution

Glycoproteins and glycolipids.

Q108. Who discovered Golgi bodies?

Solution

Camillo Golgi discovered Golgi bodies.

Q109. Define polysome.

Solution

The polysome is a structure formed when several ribosomes attach to a single-stranded mRNA to form a chain.

Q110. State the functions of mesosomes.  

Solution

Functions of mesosomes:     Mesosomes help in cell wall formation.   They also help in DNA replication and distribution to daughter cells.   They help in respiration, secretion and to increase the surface area of the plasma membrane and the enzyme content.

Q111. State the compartments of the intracellular space formed due the endoplasmic reticulum.

Solution

The two compartments of the intracellular space formed due the endoplasmic reticulum are Luminal compartment Extraluminal compartment

Q112. Define cell. 

Solution

The cell is the fundamental structural and functional unit of all living organisms.

Q113. Explain the arrangement of microtubules in cilia and flagella.

Solution

A cilium or flagellum is covered with the plasma membrane. Its core is known as axoneme. The axoneme consists of nine pairs of doublets of radially arranged peripheral microtubules. A pair of microtubules is located centrally. Such an arrangement of microtubules in the axoneme is referred to as the 9 + 2 array. The central microtubules are connected to each other by a bridge, and they are enclosed by a central sheath. The central sheath is connected to one of the peripheral tubules from each doublet by nine spokes.

Q114. Write the name of the structure which connects the cytoplasm of two cells. OR Name the structure which traverses the cytoplasm and the middle lamella to connect two neighbouring cells through their cytoplasm.

Solution

Plasmodesmata connect the cytoplasm of two cells.

Q115. Which is the longest cell?

Solution

Nerve cell is the longest cell.

Q116. State the ratio of proteins and lipids of the plasma membrane of human erythrocytes.

Solution

The plasma membrane of human erythrocytes contains 52% of proteins and 40% of lipids.

Q117. Name the scientist who first described a live cell.

Solution

Anton Von Leeuwenhoek first described a live cell.

Q118. Name the pigments which impart the following colour to plants, flowers or fruits. Orange Yellow Green White/Colourless

Solution

Orange – Carotene Yellow – Xanthophyll