Science For Class 9

Science For Class 9 The Fundamental Unit of Life Q 1 Name two major functional regions of a cell. Mark (1) View Answer Q 2 Every multi-cellular organism has come from a single cell. How? Mark (1) View Answer Q 3 Who discovered the nucleus in the cell? Mark (1) View Answer Q 4 Who discovered the cell? Mark (1) View Answer Q 5 What substances form cell membrane and cell wall? Mark (1) View Answer Q 6 Name two-cell organelles, which have DNA apart from nucleus. Mark (1) View Answer Q 7 Name the cell organelles that are found only in plant cell. Mark (1) View Answer Q 8 Name the cell organelle that is found only in animal cell. Mark (1) View Answer Q 9 Name the cell organelle in which cristae are present? Mark (1) View Answer Q 10 On what factors do shape and size of cell depend? Mark (1) View Answer Q 11 Who coined the term protoplasm? Mark (1) View Answer

Q 12 What are chromosomes? Where are they present in the cell? Marks (2) View Answer Q 13 Why is the plasma membrane called a selectively permeable membrane? Marks (2) View Answer Q 14 Why is the cell called the structural and functional unit of life? Marks (2) View Answer Q 15 What are multicellular organisms? Give examples. Marks (2) View Answer Q 16 What are unicellular organisms? Give examples. Marks (2) View Answer Q 17 Who presented the cell theory for the first time? What was it? Marks (2) View Answer Q 18 Who discovered free-living cells and how? Marks (2) View Answer Q 19 Name the non - living parts of a cell. Marks (2) View Answer Q 20 Which cell organelle is known as the kitchen of the cell? Why? Marks (2) View Answer Q 21 How do substances like CO2 and water move in and out of the cell? Marks (3) View Answer Q 22 Explain the terms. a) Endocytosis b) Plasmolysis Marks (3) View Answer

Q 23 Write any four differences between the plasma membrane and cell well. Marks (3) View Answer Q 24 Define- a) Diffusion b) Osmosis Marks (3) View Answer Q 25 When and how the cells were discovered? Marks (3) View Answer Q 26 Name the living parts of a cell. Marks (3) View Answer Q 27 Why are Mitochondria known as power house of the cell? Marks (3) View Answer Q 28 What are the types of plastids? Write their names and fuctions. Marks (3) View Answer Q 29 Differentiate between prokaryotic and eukaryotic cell. Marks (5) View Answer Q 30 What will happen if we put an animal cell or a plant cell into a solution of sugar or salt in water? Marks (5) View Answer Q 31 Differentiate between diffusion and osmosis. Marks (5) View Answer Q 32 How does an Amoeba obtain its food? Marks (5) View Answer Q 33 Draw various cells from Human body Marks (5) View Answer Q 34 How will you relate nucleus with DNA? Marks (5)

View Answer Q 35 Write one fuctions of each of the following cell organelles. a) Plasma membrane b) Mitochondria c) Lysosomes d) Endoplasmic reticulum e) Vacuoles 1(Ans) The two major functional regions of a cell area) Nucleus b) Cytoplasm 2(Ans) Cells divide to produce cells of their own kind. Thus, all cells come from pre - existing cells. 3(Ans) Robert Brown in 1831 discovered the nucleus in the cell. 4(Ans) Robert Hooke discovered the cells. 5(Ans) Cell membrane is made up of proteins and lipids.Cell wall is made up of cellulose. 6(Ans) 1) Plastids (2) Mitochondria 7(Ans) Plastids and cell wall. 8(Ans) Centriole 9(Ans) Mitochondria 10(Ans) The shape and size of cell depend on the functions they perform. 11(Ans) J.E. Purkinje 12(Ans) Chromosomes are visible rod-shaped structures present in the nucleus. They are composed of DNA and protein.Chromosomes contain information for inheritable features from parents to next generation in the form of DNA molecules.

13(Ans) The plasma membrane allows or permits the entry and exit of some materials in and out of the cell. It also prevents movement of some other materials in the cell membrane. Therefore, it is called a selectively permeable membrane. 14(Ans) Cell is called structural and functional unit of life because (i) All the living organisms are made up of cells. (ii) All the functions taking place in the body of organisms are also performed by the cells within themselves( 15Ans) The organisms which are made up of many cells and these cells perform various functions of the body are known as multicellular organisms, e.g.fungi, plants, animals. (Ans) Some organisms are made up of a single cell only. They are known as unicellular organisms. e.g. Amoeba, Chlamydomonas, Paramecium and Bacteria. 16(Ans) Two biologists, Schleiden (1839) and Schwann (1839) presented the cell theory. This stated that all the plants and animals are composed of cells and the cell is the basic unit of life. 17(Ans) Leeuwenhoek with the improved microscope discovered the free-living cells in pond water for the first time. 18(Ans) 1.Cell wall (plants only) 2.Vacuoles

3.Granules (cell inclusions)

19(Ans) Chloroplast is known as kitchen of the cell as photosynthesis takes place resulting in synthesis of food. 20(Ans) Gases like CO2 and O2 move in and out of the cell by diffusion from their higher concentration to lower concentration. Water enters the cell by endosmosis through semi-permeable plasma membrane from its higher concentration to lower concentration. Similarly, water moves out of the cell by exosmosis when a cell is placed in a hypertonic solution. 21(Ans) a) Endocytosis- The flexibility of the cell membrane enables the cell to engulf food and other material from its external environment. Such processes are known as endocytosis. b) Plasmolysis- When a living plant cell loses water through osmosis, there is shrinkage or contraction of the contents of the cell away from the cell wall. This phenomenon is known as plasmolysis. 22(Ans) Plasma Membrane Cell Wall 1.It is made up of lipids and protein. 1.It is made up of cellulose. 2.It is living. 2.It is dead. 3. Present in both plant and animal cell. 3.Found exclusively in plant cell. 4.It regulates entry and exit of molecules in and out 4.Cell wall provides structural strength to the plants. of the cell. 23Ans) a) Diffusion - It is the spontaneous movement of molecules from region of their high concentration to their lower concentration leading finally to uniform concentration. It is faster in the gaseous phase than in liquids and solids. b) Osmosis- It is the movement of solvent (water) molecules from region of its higher concentration to its lower concentration through a semi - permeable membrane. Osmosis is a purely mechanical process by which cells absorb water without spending any amount of energy.

24(Ans) In 1665, Robert Hooke observed a thin slice of cork(part of the bark of a tree)under a self - designed microscope and observed astructure like a honeycomb consisting of many little compartments. Robert Hooke called these boxes as cells. Cell is a Latin word usedfor a little room. 25(Ans) 1. Plasma Membrane 2.Cytoplasm 3. Endoplasmic reticulam (ER) a)Smooth ER (b) Rough ER 4.Mitochondria 5.Golgi apparatus 6.Ribosomes 7.Lysosomes 8.Centrioles (animals only) 9.Plastids (plants only) (26Ans) Mitochondria are called power house of cell because respiration takes place in them and energy is released in the form of adenosine tri-phosphate (ATP). The cell uses this energy to perform various functions such as mechanical work and making of new chemical compound . 27(Ans) Plastids are of three types i) Leucoplasts- Leucoplasts store starch, protein and fat. ii) Chromoplasts- Chromoplasts provide colour to fruits and flowers. iii) Chloroplasts- Green coloured chloroplast is the site of photosynthesis as it contains chlorophyll.

28(Ans)

Feature 1. Nucleus

2. Organelles 3. Cell division 4. Examples

Prokaryotic cell Eurkaryotic Lacks true nucleus. Circular DNA lies True nucleus bound by nuclear naked in the cytoplasm. No chromosomes, membrane contains DNA, nucleolus or nuclear membrane. chromosomes, nucleolus and nuclear Nuclecoplasm undifferentiated from membrane present, Nucleoplasm cytoplasm. differentiated from cytoplasm. Membrane – bound organelles like Membrane – bound organelles present. Golgibodies, plastids, mitochondria and endoplasmic reticular (ER) are absent. Divides by simple fission, spindle is not Divides by mitosis or by meiosis. formed, no mitosis and meiosis. Bacteria and cyanobacterica (blue – green All other organism. algae).

29(Ans) Feature 1. Nucleus

2. Organelles 3. Cell division 4. Examples

Prokaryotic cell Eurkaryotic Lacks true nucleus. Circular DNA lies True nucleus bound by nuclear naked in the cytoplasm. No chromosomes, membrane contains DNA, nucleolus or nuclear membrane. chromosomes, nucleolus and nuclear Nuclecoplasm undifferentiated from membrane present, Nucleoplasm cytoplasm. differentiated from cytoplasm. Membrane – bound organelles like Membrane – bound organelles present. Golgibodies, plastids, mitochondria and endoplasmic reticular (ER) are absent. Divides by simple fission, spindle is not Divides by mitosis or by meiosis. formed, no mitosis and meiosis. Bacteria and cyanobacterica (blue – green All other organism. algae).

30(Ans) Osmosis will takes place and the movement of water molecules will depend on the concentration of the surrounding solution. 1. If the medium surrounding the cell has a higher water concentration than the cell, it means that the outside solution is very dilute, then the cell will gain water by osmosis. Such a solution is known as a hypotonic solution. The cell is likely to swell up. This is called endosmosis. 2. If the medium has exactly the same water concentration as the cell, there will be no net movement of water across the cell membrane. Such a solution is known as an isotonic solution. The cell will stay the same size. 3. If the solution has a lower concentration of water than the cell, meaning that it is a very concentrated solution, the cell will lose water by osmosis. Such a solution is known as a hypertonic solution. The cell will shrink. This process is called exosmosis.

(Ans) Nucleus is located in the center of the cell. It is the main cell organelle and controls all the activities of cell. A membrane having pores surrounds it. Its chief compounds are chromatin material and nucleolus. Chromatin material when condenses form knot like structures called chromosomes. Chromosomes contain hereditary units called genes, which in turn are made up of DNA. These DNA are carriers of characters from one generation to another. (Ans) a) Plasma membrane or cell membrane: It controls the entry and exit of material from the cell to outside and from outside to inside. It also protects the cell. b) Mitochondria: Cellular respiration takes place resulting

in release of energy. Hence, they are

also known as powerhouse of the cell. c) Lysosomes: They contain powerful enzyme that can digest and remove worn out cell organelles. d) Endoplasmic Reticulum (ER): Rough Endoplasmic Reticulum (RER)-It synthesizes proteins. Smooth Endoplasmic Reticulum (SER)- It synthesizes fats and lipids. They are filled with a liquid called cell sap and provide turgidity and rigidity to plant cells.