* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download cell - Testlabz.com
Survey
Document related concepts
Cytoplasmic streaming wikipedia , lookup
Signal transduction wikipedia , lookup
Cell membrane wikipedia , lookup
Extracellular matrix wikipedia , lookup
Tissue engineering wikipedia , lookup
Cell growth wikipedia , lookup
Cellular differentiation wikipedia , lookup
Cell culture wikipedia , lookup
Cell nucleus wikipedia , lookup
Cell encapsulation wikipedia , lookup
Cytokinesis wikipedia , lookup
Endomembrane system wikipedia , lookup
Transcript
© CBSEPracticalSkills.com 8 Edulabz International CELL – STRUCTURE AND FUNCTIONS TEXTBOOK QUESTIONS AND THEIR ANSWERS Q.1. A hen’s egg can be seen easily by naked eyes. Is it a cell or a group of cells? Ans. Though the egg of a hen is big enough to be seen by the unaided eye, but it is not a group of cells. It is a single cell. Q.2. How do you define the shape of amoeba in the figure? Ans. Amoeba has no definite shape. It keeps on changing its shape. Q.3. What advantage does amoeba derive by changing its shape? Ans. The change in shape is due to the formation of pseudopodia which facilities movement and help in capturing food. Q.4. What do you observe when you remove the shelf of a boiled egg of hen? CBSEPracticalSkills.com 1 © Edulabz International © CBSEPracticalSkills.com Edulabz International Ans. A white material surrounding the yellow part. Yellow part of the egg is yolk while the white material is albumin. It is a single cell. Q.5. Are the cells in an elephant larger than the cells in a rat? Ans. No, the size of the cells has no relation with the size of the body of the animal. It is related to its function. Q.6. Boojho want to know why plant cells need cell walls? Ans. Cell wall is the outer thick layer in cells of plant. Plant cells need cell wall because it provides the protection against variation in temperature, high wind-speed, atmospheric moisture, etc. Q.7. Draw and label the diagram of human cheek cells. Ans. Q.8. What is absent in animal cells but present in plant cells? CBSEPracticalSkills.com 2 © Edulabz International © CBSEPracticalSkills.com Edulabz International Ans. A cell wall, is absent in animal cells. Q.9. Paheli wants to know if the structure of the nucleus is the same in cells of plants, animals and bacteria? Ans. The nucleus of bacterial cell is not well organiased. There is no nuclear membrane. So, the cells having nuclear material without nuclear membrane are termed as prokaryotic cells. Therefore, bacteria is a prokaryote. Plants and animals both have well organized nucleus and nuclear membrane. So, these are eukaryotes. Q.10. Tabulate the similarities and dissimilarities of plant and animal cells. Ans. Sl. No. Part Plant Cell Animal Cell 1. Cell membrane Present Present 2. Cell wall Present Absent 3. Nucleus Present Present 4. Nuclear membrane Present Present 5. Cytoplasm Present Present 6. Plastids Present Absent 7. Big Vacuoles Present Present CBSEPracticalSkills.com 3 © Edulabz International © CBSEPracticalSkills.com Edulabz International Q.11. Indicate whether the following statements are True (T) or False (F). (a) Unicellular organisms have one-celled body. (b) Muscle cells are branched. (c) The basic living unit of an organism is an organ. (d) Amoeba has irregular shape. Ans. (a) True, (b) True, (c) False, (d) True. Q.12. Make a sketch of the human nerve cell. What function do nerve cells performs? Ans. Functions of human nerve cell : (i) Nerve cells receive message from different parts of body. (ii) They further transfer these message to brain and brain further send commands for functioning of different organs. (iii) They coordinate functioning of different organs of body. Q.13. Write short notes on the following: (a) Cytoplasm CBSEPracticalSkills.com (b) Nucleus of a cell 4 © Edulabz International © CBSEPracticalSkills.com Edulabz International Ans. (a) Cytoplasm : Cytoplasm is a jelly-like substance present between the cell membrane and the nucleus. Various other organelles of cells are present in the cytoplasm. Cytoplasm is made up of chemical substances like carbohydrates, proteins and water. Many chemical reactions such as breakdown of food or synthesis of food take place in it. (b) Nucleus of a cell : Nucleus is the master of the cell. It commands all the functioning of the cell. It is generally located in the centre of the cell and is spherical in structure. A membrane called nuclear membrane separates it from cytoplasm. Nucleus contains a smaller spherical body called nucleolus. In addition, nucleus also contains thread like structures called chromosomes. These carry genes and help in inheritance or transfer of characters from the parents to the offspring. Q.14. Which part of the cell contains organelles? Ans. Cytoplasm. Q.15. Make sketches of animals and plant cells. State three differences between them. Ans. Plant Cell CBSEPracticalSkills.com Animal Cell 5 © Edulabz International © CBSEPracticalSkills.com 1. Cell wall is absent. 1. Plant cell has a rigid cell wall. 2. Plant cell has chloroplasts. 3. Plant cell lacks centrosomes. Edulabz International 2. Chloroplasts are absent. 3. Centrosomes are present. Q.16. State the differences between eukaryotes and prokaryotes. Ans. Eukaryotes Prokaryotes 1. Nucleus is bounded by nuclear CBSEPracticalSkills.com 1. Nucleus is not bounded by nuclear membrane. 6 © Edulabz International © CBSEPracticalSkills.com membrane Edulabz International 2. Membrane bound 2. Possess membrane organelles are absent. bound organelles. 3. All higher plants 3. Bacteria and blue green and animals are algae are prokaryotes. eukaryotes. Q.17. Where are chromosomes found in a cell? State their functions. Ans. Chromosomes are found in the nucleus of a cell. Their function is to carry ‘genes’ and help in inheritance or transfer of characters from the parents to the offspring. Q.18. ‘Cells are the basic structural units of living organism’. Explain. Ans. Cells are similar in basic structure, but attain different shapes in the different organs. A group of similar cells combine to form a tissue and many tissues combined together to form an organ and organ combined to form a organ system/organism. [Cells → Tissue → Organ → Organ system → Organism.] So cell is the basic structural unit of an organism. All basic functions for the survival of an organism take place inside CBSEPracticalSkills.com 7 © Edulabz International © CBSEPracticalSkills.com Edulabz International cells so, cells are the basic structural units of a living organism. Q.19. Explain why chloroplasts are found only in plant cells? Ans. The chloroplasts green coloured pigments called chlorophyll which synthesis food in plants by the process of photosynthesis. Since food is manufactured only by plants, so, chloroplasts are present only in plants. Q.20. Complete the following crossword with the help of clues given below : Across 1. This is necessary for photosynthesis. 3. Term for component present in the cytoplasm. 6. The living substance in the cell. CBSEPracticalSkills.com 8 © Edulabz International © CBSEPracticalSkills.com 8. Edulabz International Unit of inheritance present on the chromosomes. Down wards 1. Green plastids 2. Formed by collection of tissues. 4. It separates the contents of the cell from the surrounding medium. 5. Empty space in the cytoplasm. 7. A group of cells. Ans. Across Down 1. Chlorophyll ; 1. Chloroplasts 3. Organelle 2. Organ 6. Protoplasm 4. Membrane CBSEPracticalSkills.com 9 © Edulabz International © CBSEPracticalSkills.com 8. Genes Edulabz International 5. Vacoule 7. Tissue Q.21. Find out the diseases which are passed on from parents to the offspring. Ans. The disease which are passed on from parents to the offspring, are called genetic diseases. 1. Colour blindness – The person cannot differentiate redgreen colours. Reason – It is due to a recessive allele on x-chromosome. 2. Haemophilia – It is a disorder of the blood, where a vital factor for clotting the blood is absent, hence, clotting is abnormally delayed and such bleeding may become fatal. Reason – It is due to a recessive allele on x-chromosome. 3. Albinism – The albinos cannot synthesize skin pigment melanin, hence they have their iris, hairs and skin without pigment. Reason – Such diseases appear when both the parents of the affected person are heterozygous and carriers of the CBSEPracticalSkills.com 10 © Edulabz International © CBSEPracticalSkills.com Edulabz International disease, so the parents do not show the disease, but the it appears in the siblings. 4. Muscular dystrophy – Progressive deterioration of muscles makes a person invalid at an early age. Reason – It is due to recessive allele on x-chromosome. Q.22. Write a short not on ‘genetically modified crops’. Ans. Genetically modified crops are crops produced from genetically modified organism that have their DNA altered through genetic engineering. Genetically modified crops were first put on the market in the early 1990’s. The most common modified crops are derived from plants. for eg. soyabean, corn and cotton seed. The process involve the DNA from one organism, modified it in a laboratory and then inserted into the target organism’s genome to produce new and useful genotype. Q.23. Find out about Bt cotton from an agriculture expert. Ans. Bt cotton, a transgenic plant, produces an insect controlling protein. The gene which has been derived from the naturally occurring bacterium, Bacillus thuringiensis. The cotton hybrids containing Bt gene produces its own toxin. Thus CBSEPracticalSkills.com 11 © Edulabz International © CBSEPracticalSkills.com Edulabz International reducing the use of chemical insecticide and providing a major benefit to cotton growers and the environment. Advantages : Bt cotton appears to be safe for the farmers and for consumers. The toxicity of each Bt type is limited to one or two insect and is non-toxic to vertebrates and many beneficial arthopods. The reason is that Bt works by binding to the appropriate receptor on the surface of midglit epithelial cells. Any organism that lacks the appropriate receptors in its gut cannot be affected by Bt. CBSEPracticalSkills.com 12 © Edulabz International