"AKC SCIENCE CLASSES"
CLASS 09 TH (CBSE AND MP BOARD)
CHAPTER 05
FUNDAMENTAL UNITS OF LIFE
BASIC CONCEPT
1) Cell is the structural and function unit of life.
2) Cell biology is the study of all aspects of cell structure and function.
3) The term 'cell' was given by Robert Hooke.
4) M.J. Schleiden and T. Schwann proposed the cell theory. Rudolf Virchow modified the cell theory and stated that every cell arises from pre-existing cell.
5) Viruses are an exception of cell theory.
6) Smallest organism (cell) is PPLO, whereas the largest cell is ostrich egg.
7) In prokaryotes, a wall organised nucleus is absent and membrane-bound organelles are lacking e.g., bacteria and blue green algae.
8) In eukaryotes, a well organised nucleus is present and membrane-bound organelles are present. e.g., all plants, animals, fungi and protists.
9) Cell membrane provides shape and protection to the cell. It is selectively permeable.
10) The membrane through which substances do not move out is called impermeable ; through which both solute and solvent can pass is called permeable ; through which only solvent can pass is called semipermeable and through which only solvent can pass is called semipermeable and through which solvent and some solutes can pass is called selectively permeable membrane.
11) When the movement of molecules takes place from higher concentration to the lower concentration without the expenditure of energy, it is known as passive transport.
12) The process of movement of a substance (solid, liquid or gas) from the region of its higher concentration to lower concentration so as to spread it uniformly is called diffusion.
13) The diffusion of water (solvent) through a semipermeable membrane from a region of higher concentration to the region of lower concentration is called osmosis.
14) When cell is kept in highly concentrated solution, it shrinks ; when kept in dilute solution it swells.
15) The outflow of water from the cell towards the external solution is called exosmosis, whereas the inflow of water into the cell is called endosmosis.
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16) Cell wall provides shape, rigidity and protection to cell.
17) Mitochondria are 'power house of the cell' whereas chloroplasts are the 'kitchen of the cell'.
18) Endoplasmic reticulum provides internal support to the cytoplasm; RER helps in protein synthesis ; SER helps in lipid synthesis.
19) Golgi bodies help in the formation of cell plate and synthesis of lysosomes.
20) Lysosomes are suicide bags. They also help in intracellular digestion.
21) Ribosomes help in protein synthesis.
22) Centrosomes contain centrioles which help in spindle formation. It is absent in plants.
23) Vacuoles are involved in the maintenance of water balance. They also separate variety of substances (in cell sap) from the cytoplasm.
24) Nucleus is the largest cell structure. It controls all the vital activities of the cell. It also contains all the information necessary for structure, metabolism, growth and reproduction.
25) Plants cells contain cell wall, plastids and lack centrioles, whereas animal cells lack cell wall and plastids but possess centrioles.
SCIENCE || CLASS 09TH || CHAPTER 05 || INTEXT QUESTIONS AND ANSWERS || CBSE AND MP BOARD CLICK HERE
