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STD . 7th, , Sub:Science, 11 Cell structure and micro organism, SUMMATIVE EVALUATION, QUESTIONS AND ANSWERS, , Q. 1. Fill in the blanks with the proper word:, (1) The organelle called the plastids is present in plant cells only, (2) Garbage is converted into fertilizers by micro-organisms.., (3) In the cell, photosynthesis is carried out with the help of chloroplasts, (4) An electron microscope is necessary for the study of microbes/cell organelles, (5) The assembled various lenses to construct a microscope., (6) The nucleus is the most important organelle of the cell., (7) Mitochondria are called the powerhouses of the cell.., (8) The process fermentation of is used for making yoghurt from milk, Q. 2. Match the columns :, Group 'A' - Cell organelle, (1) Mitochondria, (2) Lysosomes, (3) Endoplasmic reticulum, (4) Golgi body, (5) Ribososme, (6) Nucleus, (7) Vacuole, (8) Plastids, Group 'A', (1) Paramoecium, (2) Bacteria of typhoid, (3) Polio virus, (4) Some microbes, Group 'A', (1) Yellow fever, (2) Pneumonia, (3) Cholera, (4) Penicillin, , Group 'B'-Function, Powerhouse of the cell, Destruction of cell, Sprawling net - like transport system, Proper distribution of proteins, Production of pr, Control over Vacuole-Throwing of unwanted material, Throwing of Unwanted Material, Function of photosynthesis., Group 'B', about 100 micrometres, 1 to 3 micrometres, 28 nanometres:, less than 100 micrometres, Group 'B', Bite of female mosquito, Infection contaminated air, Infection due to contaminated water, Antibiotic.

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Q.3. What is difference between us? Plant cell and animal cell., Plant cell, 1. Plant cells have cell wall made up of, cellulose., 2 The cytoplasm of the plant cells is lesser, granular and not dense., 3 . There is a single large vacuole located, in centre which pushes the cytoplasm to, one end., 4. There are no lysosomes., 5. The mitochondria are few in number, 6. Plastids are present only in plant cells., 7. Single or more but large vacuoles, present., 8. The vacuoles are filled up with cell sap., , Animal cell, 1. Animal cells do not have cell wall., 2. The cytoplasm of animal cells is more, granular and dense., 3. The cytoplasm is uniformly distributed, in the cell., 4. Lysosomes are present in the animal cell, 5. The mitochondria are greater in number, as compared to the plant cells., 6. Plastids are absent in the animal cells, 7. Vacuoles are few and temporarily, formed, 8. The vacuoles are filled with food, excretory matter., , (2) Prokaryotic cell and eukaryotic cell., Prokaryotic cell, 1. The nucleus of prokaryotic cell is not, distinct., 2. Prokaryotic cells are about 1 to 10 um, in size., 3. Due to the absence of nuclear, membrane, the nuclear material comes in, contact with the cytoplasm., 4. The cell organelles if present are, without membranes., 5. There is indistinct nucleoid in which, prokaryotic DNA is present. There is a, single chromosome,, 6. Mitochondria are absent in prokaryotic, cells., 7. Chlorophyll is present in the vesicles, and not in plastids., 8. Prokaryotic cells are found in bluegreen algae and bacteria., , Eukaryotic cell, 1. The nucleus of eukaryotic cell is distinct, with nuclear membrane, nucleoli and, nucleoplasm, 2. Eukaryotic cells are about 5 to 100 um size., 3. Due to the presence of nuclear membrane, nucleoplasm and cytoplasmn never come in, physical contact with each other., 4. The cell organelles are always bound with, membranes., 5. The nucleus is distinct with more than one, chromosomes., 6. Mitochondria are present in eukaryotic, cells., 7. Chlorophyll is always inside the, chloroplasts, 8. Eukaryotic cells are found in evolved plants, and animals, , Q. 4. Answer the following questions:, (1) What is a 'cell?, Ans. The structural and functional unit of the body is called a cell.

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(2) Name the different organelles in a cell?, Ans. Nucleus, endoplasmic reticulum, ribosome, Golgi body, lysosomes, mitochondria, plastids, vacuoles are all different cell organelles., (3) When is electron microscope used?, Ans. When the cells or structures such as microbes or cell organelles which are to be, magnified up to two billion times of their actual size, the electron microscope is used., (4) What are micro-organisms?, Ans. The living organisms on the earth which are in every environment but can be seen, only under compound microscope are called micro-organisms., (5) Which are the different types of micro-organisms?, Ans. Bacteria, virus, fungi, algae and protozoan are all the different types of microorganisms., (6) Who discovered the process of fermentation?, Ans. Louis Pasteur discovered the process of fermentation., Q. 5. Answer the following questions:, (1) Who formulated the theory of cellular structure? When? Write in brief., Ans. In 1838, the two scientists M. J. Schleiden and Theodore Schwann formulated a, theory about cellular structure. The theory is follows: "All the living organisms are made, up of cells and the cell is the fundamental component of living organisms., (2) What are cell organelles. Write down the names of different cell organelles found in, plant and animal cells., Ans. (1) Cell organelles are the subunits in the cells which perform a characteristic and, specific function in the cell. They are also called the organs of cells. (2) The structure of cell, organelles can be seen only with the help of electron microscope. (Exception: nucleus and, chloroplast) Every cell organelle is bound by a lipid-protein membrane which carries out, specific function. (4) The membrane of an organelle keeps it separate from rest of the, cytoplasm. (5) Each organelle carries out different metabolic functions. (6) Nucleus,, endoplasmic reticulum, ribosomes, Golgi apparatus, mitochondria, plastids (chromoplasts, and leucoplasts) and vacuoles are the cell organelles in plant cells. (7) Nucleus,, endoplasmic reticulum, ribosomes, Golgi apparatus, mitochondria, lysosomes and, vacuoles are the cell organelles in animal cells., (3) Explain the uses and the harmful effects of micro-organisms., Ans. 1. Uses of micro-organisms ::, (1) Micro-organisms decompose the wastes and sewage water. (2) By the process of, decomposition, they keep the environment clean. Fertilizers are prepared from wastes by

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this process. With the help of biogas plant, the biogas is prepared by the micro-organisms., (3) The microbes residing in the soil and in the root nodules of leguminous plants help in, biological und in nitrogen fixation. This helps in increasing fertility of soil and also in, increasing the protein content of seeds in legumes. (4) Micro-organisms help in the, formation of curd and other milk-based products. (5) The process of fermentation is used, for producing alcohol from grains and fruits, bread from flour as well as in the production, of acetic acid, citric acid, lactic acid, vitamins, antibiotics, etc. (6) Processes like tanning of, skin, production of ropes and strings from agave are also done with help of microbes. (7), Oil slick is cleared with the help of some specific bacteria., II. Harmful effects of micro-organisms:, (1) Micro-organisms spoil the food. In hot and humid air there is fugal attack on food. (2), Microbes produce enterotoxins and cause food toxic resulting into food poisoning. (3), Harmful microbes cause diseases in plants, animals and human. Amoebiasis, typhoid., cholera, hepatitis, gastro are caused by water and food borne microbes. (4) Microbes, cause diseases like malaria, dengue, elephantiasis, yellow fever, chikungunya, Zika fever,, etc. These disses are caused after mosquito transfers the microbes into human body., Common cold, cough, diphtheria, pneumonia, tuberculosis are diseases of respiratory, tract which are caused try microbes, (5) What exactly happens when we have fever?, Ans. (1) When we are in good health, our body temperature is about 37 °C. (2) But upon, the invasion of a harmful microbe, our immunity starts raising the body temperature. This, is a immune response to fight against a disease causing microbes. (3) We call this, increased temperature as fever. (4) Some microbes are destroyed by raised body, temperature. Thus having a fever is a good sign of immunity., (6) What are antibiotics? How are they prepared? What is their use?, Ans. (1) Antibiotics are the types of medicines to destroy the pathogens and retard. their, growth. (2) They are produced with the help of specific microbes, e.g., the antibiotic in the, penicillin is prepared from a fungus. (3) Diseases which were considered incurable are, now under control because of antibiotics. e.g., Tuberculosis, typhoid, cholera, etc. (4), Domestic animals are also treated by mixing antibiotics with their food. They are also, protected against infectious diseases (5) Plant diseases are also controlled with the help of, antibiotics., Q.6 Answer the following Questions with neat and well labelled diagrams., (1) Sketch and describe in your own words , the plant cell and animal cell.

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1. Plant cell: (1) There is cellulose cell wall in plant cells which is the outermost covering of, the cell. (2) Inside the cell wall there is a plasma membrane that encloses cytoplasm. Cell, organelles are embedded in the cytoplasm. (9) Plastid is an important cell organelle, present only in plant cells. Of these chloroplasts perform photosynthesis. (4) Nucleus,, endoplasmic reticulum, Golgi body, mitochondria are the cell organelles present in the, cytoplasm. (6) Vacuole is usually single and large. Since it is present in the centre of the, cell, d stained the cytoplasm is pushed to one end., II. Animal cell: (1) The outermost covering is plasma membrane. (2) Inside this there is, cytoplasm in which the cell organelles are embedded. (3) The cell organelles are as, following: Nucleus, Golgi body, endoplasmic reticulum and many smaller vacuoles., (2) Describe prokaryotic cell with neat, well labelled and suitable diagram., Ans. (1) Micro-organisms have prokaryotic type of cells. (2) They have We call the, prokaryotic structure. (3) They do not have nucleus with nuclear membrane, instead there, is nucleoid.(3) Cell organelles enclosed in cell membranes are lacking. (4) Cell wall, and cell, membrane and nucleoid are the only. me antibi parts in the prokaryotic cells., , Q.7. Use your Brain Power:, (1) Where do the life processes of unicellular organisms take place?, Ans. All the life processes of unicellular organisms take place in a single cell. Their feeding,, digestion, excretion all take place through one cell. During reproduction the same cell, divides into two.

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(2) How do the cells acquire definite shapes?, Ans. The cells acquire definite shape due to their cell wall and plasma membrane, (3) How are cells protected?, Ans. The plasma membrane does not allow unwanted substances to enter in the cell. The, cell wall of plant cell also protects the cells. Some protective proteins net against the, harmful microbes. In this way the cells are protected, (4) What are the needs of cells?, Ans. Cells need oxygen, nutrients and water, (5) Why should dry and wet waste be collected separately?, Ans. The wet waste can be decomposed using bacteria. This type of waste is called, biodegradable. The dry waste is not biodegradable. It remains unchanged for a long, period The strewn wastes like this causes ill health and also make a place look dirty. The, waste likes plastic causes harmful effects in the surroundings. We can separate dry and, wet waste. Decomposition of wet waste can make good fertilisers whereas dry waste can, be sold to scrap dealers. Therefore, in order to have a better management of wastes, we, should collect dry and wet waste separately., (6) Why is yoghurt mixed in the batter or dough for making rava-idli, bhature , naan., Ans. Yoghurt contains useful bacteria. They cause fermentation in the batter or dough, if added in proper proportion. In this process, the heat, carbon dioxide and other gases, produced. This helps the flour to rise. The vitamin content also increases and the, preparation become tasty and light. Therefore, is yoghurt mixed in the batter or dough for, making rava idli, bhature, naan., (7) How do preparations like yoghurt, idli, dosa become easy to digest?, Ans. Preparations like idli-dosa are made from the batter that is fermented. Yoghurt also, set with help of useful bacteria which carry out fermentation. The process of fermentation, increases the volume of the substance and make them light, tasty and more nourishing, due to increased vitamin content. Therefore, they are easy to digest., (8) What is the correlation between the normal body temperature of humans which is 37, °C and the optimum temperature for the growth of micro-organism. 15 °C to 35 °C?, Ans. Bacteria grow maximally in the temperature range between 15 °C to 35 °C. E human, body their growth does not take place with the same, the same intensity. If any microbe, enters our body, the temperature automatically rises resulting into fever which kills these, disease causing microbes. Thus naturally man is protected against bacterial attacks, Q.8. Give scientific reasons:, (1) Diseases spread on a large scale during periods of heavy rainfall and floods,

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Ans. The spread of disease is most likely during heavy rainfall and floods. The water and, food gets contaminated. The water logging causes growth of micro-organisms and house, flies. They spread the pathogens rapidly. The humid atmosphere induces food spoilage., Even if flood water recedes, the poodle formed helps in the breeding of mosquitoes. All, such reasons are responsible for epidemic spread of diseases., (2) There is a possibility of food poisoning if we eat stale food., Ans. The stale food is likely to have microbes in it. Some of the microbes produce, enterotoxins. The enterotoxins cause food poisoning. Therefore there is a possibility of, food poisoning if we eat stale food., (3) Soil is turned over during tilling., Ans. There are some useful bacteria in the soil. They help to decompose organic, substances into inorganic nutrients. Thereby they produce fertilizers. Some microbes also, help in nitrogen fixation. They help the plants to get nitrogen. Thus to have better yield of, crop, the soil is turned over during tilling to mix the bacteria., (4) Fungus grows quickly in moist or humid conditions., Ans. The fungus needs suitable conditions for the growth. The moist and humid conditions, are favourable to it. It does not grow in dry conditions., (5) A refrigerator is used in almost every home., Ans. The harmful microbes do not grow in cold temperatures, they grow only in the, temperature range of 15° C to 35° C. Refrigerator has very low temperatures. Food can be, stored there without spoiling. Therefore, to store perishable food items refrigerators have, become essential in every home., (6) Bread 'rises' during baking., Ans. When the bread is prepared yeast is added to it. Yeast is a type of fungus. It, undergoes process of fermentation in the batter of bread and releases carbon dioxide., Therefore, the bread rises during baking., (7) Fodder is soaked in water before offering to cattle., Ans. By adding the fodder into water, it is fermented. By fermentation, the vitamin, Content rises in the fodder, it also becomes easier for digestion. The cattle is thus well, nourished. Therefore, Fodder is soaked in water before offering to cattle.