FUNDAMENTAL UNIT OF LIFE CLASS 9
Ch5 - The Fundamental unit of life
Cell: (i) the structural and Fundamental unit of life
(ii) the basic unit of life
(iii) The fundamental unit of life
✥ Study of cell: [cytology]
All the living organism are made up of cells and the product of cells.
* Discovery of cell
✥ Robert Hooke discovered the [first] dead cell of cork slice with the help of primitive microscope in 1665.
✥ Structure of cells like a honeycomb and there were many small/little – boxes / rooms. then robert hooke named it cell.
✥ Anton van Leeuwenhoek discovered the first living cell of pond water in 1674 with the help of improved microscope
✥ Robert Brown discovered the nucleus in 1831.
✥ purkinje named the term 'protoplasm' for the fluid substance of the cell in 1839.
✥ The theory of the cell that all organism are made up of cells is given by two biologists schleiden (1838) and Schwann (1839).
✥ The cell theory was further expanded by Virchow (1856) by suggestion that all cells arise from pre-existing cells.
✥ Most plant and animals cells are fixed in shape but WBC and amoeba keep changing their shape and size.
* Components of Cell
a) Cell wall : (i) It is found only in plant cell
(ii) It is made up of cellulose
✥ It particles the plant cell from extreme hot and cold climate.
b) Cell membrane / Plasma membrane :-
(i) It is formed in both plant and animal cell.
(ii) It is made up of protiens and Lipids.
Functions
✥ This is the outermost covering of the cell that separates the contents of cell from the external environment.
✥ It is called selectively permeable membrane because it allows the entry and exit of some material in and out of cell from cell plasma membrane.
✥ It helps in maintaining the shape of cell.
✥ Diffusion:- The spontaneous movement of ions or substance from a region of higher concentration to lower concentration.
Cell ---> [Less O2] <---- High O2
Cell ---> [High O2] ----> Low O2
✥ Osmosis :- Movement of water molecules through a selectively permeable membrane.
✥ Movement of water is always from high concentration of water to low concentration of water.
✥ Hypotonic Solution ✥ Isotonic Solution ✥ Hypertonic Solution
H2O will be to cell. Cell neither swell H2O will be to cell
nor shrink.
c) Nucleus: Nucleus is the most important cell organelle which live in the center of cell.
Functions :-
• Nucleus transfers the characters from parent to their offspring in the form of DNA (Deoxyribose Nucleic Acid) chromosome are composed of DNA and protein.
• It controls all the metabolic activities of the cell.
• It contains genes in the form of DNA
• It regulates the cell cycle.
Prokaryotic cell Eukaryotic cell
• Very small in size • Fairly large in size
• Nucleus membrane is • Nucleus membrane is
absent here present here
• Nucleolus absent • Nucleolus present
• Membrane bound cell • Membrane bound
organells are absent cell organells present
d) Cytoplasm :- The liquid part in which the other organelles floats. It is mainly composed of water, salt and proteins.
• Endocytosis: The flexibility of the cell membrane also enables the cell to engulf in food and other materials from its external environment such process are known as endocytosis.
# All cell organelles
(i) Endoplasmic reticulum: It is the network of membranes present in cytoplasm.
# Functions of ER
• Gives mechanical support.
• Help in transporting the material between cytoplasm and nucleus.
• Synthesis proteins.
• It provide space for biochemical activities.
• It helps in detoxification of poisonous products.
SER RER
• It made of tubules • It made of vesicles
• It manufactures fat • It manufactures protein
molecules etc. • Ribosomes are present
• Ribosomes are absent
(ii) Golgi appartus :- Functions :-
Discovery :- Camillo golgi
• Golgi appartus stores, modifies and paks product in vesicles.
• It is involved in the formation of lysosome
• It forms complex sugar from simple sugars in some cases.
• It is involved in synthesis of cell wall and plasma membrane.
(iii) Lysosomes:
Discovery :- Deduve
# These are tiny like granules containing digestive enzymes these are bounded by a single membrane.
Functions:-
• The main function is digestion.
• They are kind of waste disposal.
• Helps in digestion foreign and cell material.
(iv) Mitochondria
Discovery: Albert von Rolliker
• It is also known as "Power house of the cell" or "storage Battery".
• It has double membrane.
• Mitochondria has its own DNA and ribosomes
* Functions
• Its main function is to produce the energy in the form of ATP (Adinosine Tri Phosphate)
✥ Energy currency of the cell
• They provide intermediates for the synthesis of various chemicals.
Ex - Fatty acids, steroids, etc
(v) Plastids
• These are present only in plant cell. It has its own DNA.
* Three types of plastids
• Leucoplast:- Color white found in underground parts.
• Chromoplast: Red. Brown.
• Chloroplast: Green in color, found in arial pants.
Functions
• Chloroplast and chromoplast: They are important for Photosynthesis.
• Leucoplast: It is storage of material Such as starch, oils, proteins granules.
vi) Vacuoles
• These are membrane bounded regions in the cytoplasm containing water, amino acids, sugar, various organic acid and some proteins.
• Vacuoles are small sized in animal cells while plant cells have very large vacuoles.
Functions
• Storage of materials.
• Important role in expelling excess water.
• It is a minute particle consisting of RNA Ribosomes are the main sites of proteins synthesis and also the protein transported to Endoplasmic Reticulum.
* Cell division
• Division of cell into new cells.
Reason of Division:-
→ Growth of organism
→ Replace old, dead and injured cells
→ For gamete formation
* Difference between plant and animal cell
Plant cell Animal cell
• Larger in size • Smaller in size
• Larger Nucleus • Smaller Nucleus
• Cell wall is present • cell wall is absent
• Plastids are present • plastids are absent
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