CHAPTER - 8 CELL - STRUCTURE AND FUNCTIONS CLASS :- VIII MADE BY :- RAVI PRAKASH SINGH SUBJECT :- BIOLOGY Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017RAVI PRAKASH SINGH 1

The cell is the smallest unit of life. Cell is basic structural and functional unit of living organisms. New cells arise from pre-existing cells. All organisms are composed one or more cells. Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017RAVI PRAKASH SINGH 2

 Robert Hooke was the first scientist to discover existence of cells with the help of a microscope in  He observed thin slices of cork (a part bark of a tree) under a microscope and saw honeycomb structures.  The slices of cork appeared like small compartments which were further separated by a wall. Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017RAVI PRAKASH SINGH 3

 Cell Number: On basis of no. of cell, living organisms can be classified into two categories:- 1)Unicellular- Living organism consist of single cell. Example- Amoeba, Euglena 2)Multicellular- Living organism consist of more than one cell. Example- Earthworm, Human being. Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017RAVI PRAKASH SINGH 4

 Cell Shape: The shape of cell differ not only in different organisms, but also in different organs of same organism Shape may be oval spherical cuboidal, fibre like or polygonal  Cell size: The difference in size of organism is due to the number of cells present in them The smallest cell PPLO (Plero Pneumonia –like organism) are called mycoplasma is about 0.1 micron in diameter The largest cell is ostrich cell with 170 mm in diameter Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017RAVI PRAKASH SINGH 5

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Cell Membrane (plasma membrane) Outer membrane of cell that controls the entry and exit of substances according to the requirement of cell the cell. Cell Wall It provide rigidity, Supports & protection to cell. It also give shape, size. Found in plants, fungi, bacteria. Surrounds plasma membrane Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017RAVI PRAKASH SINGH 7

Cytoplasm The portion of the protoplasm lying inner to cell membrane, but outside the nuclear membrane. It comprises of Gel-like substances that fills the inside of the cell. Contains hereditary material Nucleus Separated from cytoplasm by nuclear membrane Directs all cell activities. Contains genetic material - DNA Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017RAVI PRAKASH SINGH 8

NUCLEAR MEMBRANE Surrounds nucleus Made of two layers Openings allow material to enter and leave nucleus It is made of DNA and present in nucleus It is responsible for the inheritance of characters (genes) from one generation to other CHROMOSOMES Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017 RAVI PRAKASH SINGH 9

Cell Organelles Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017 RAVI PRAKASH SINGH 10 The cell organelles are: Plastids:Plastids: Plastid are large organelles & characteristic of plant cell. ⇒ Chloroplasts: provide green color and Manufacture food for plant by the process of photosynthesis ⇒ Chromoplasts: for providing color other than

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Mitochondria They are rod shape or spherical structures. Responsible for cellular respiration & produces energy for different activities. So, it is called power house of cell Controls level of water and other materials in cell Recycles and decomposes proteins, fats, and carbohydrates Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017RAVI PRAKASH SINGH 12

Endoplasmic Reticulum It is network of membranes. It provides a skeletal framework to the cell. Moves materials around in cell. Ribosomes Each cell contains thousands Make proteins Present in the cytoplasm & float throughout the cell Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017RAVI PRAKASH SINGH 13

Golgi Complex Sac-like structure stacked one above the other Store the material produced by cell So they are called store house of the cell Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017RAVI PRAKASH SINGH 14

Vacuoles Empty space in the cytoplasm It store excess of water and Waste product In amoeba, it held food for digestion. Cilia and flagella They are small extensions on their cell membrane They help in locomotion & collection of food. Paramecium have numerous cilia while Euglena has a single flagellum. Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017RAVI PRAKASH SINGH 15

Euglena Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017RAVI PRAKASH SINGH 16

Cells Types On the basis of their nuclear organization, cells are of types:  Prokaryotic: In Greek, pro : primitive; karyon : nucleus. 1)No Nucleus 2)No membrane-bound organelles like mitochondria or chloroplasts. 3)Bacteria and Blue-Green algae 4)Reproduce asexually by budding and fission 5)First type of cell on the earth 6)Very small ( µm)  Eukaryotic: In Greek, Eu : True; karyon : nucleus. 1)True Nucleus 2)Membrane bound organelles 3)All other organisms except Bacteria and Blue-Green algae 4)Cell size generally µm 5)Some are larger 6)Include fungi, protists, plant, and animal cells. Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017RAVI PRAKASH SINGH 17

“Typical” Animal Cell /~ acarpi/NSC/images/cell.gif Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017RAVI PRAKASH SINGH 18

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“Typical” Plant Cell Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017RAVI PRAKASH SINGH 20

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Cell Components / organelles Plant CellAnimal Cell Cell wallpresentAbsent Cell membranePresent PlastidPresentAbsent MitochondriaPresentpresent NucleusPresentpresent VacuolesLarge size & more in number Small size or Absent ChloroplastPresentAbsent RibosomesPresent ShapeFixedIrregular Golgi ApparatusPresent sizeLargerComparatively Smaller Differences Between Plant and Animal Cells Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017RAVI PRAKASH SINGH 22

Levels of organization of living being CELLTISSUE ORGAN ORGAN SYSTEM ORGANISM 1)CELL: cell is the smallest unit of life. 2)TISSUE: Group of similar cells that perform specific function. 3)ORGAN: Group of different tissues form an organ. Ex – liver, kidney, stomach 4)ORGAN SYSTEM: Group of organ that work together to perform specific functions. Ex- Digestive System, circulatory system etc. 5)ORGANISM: Different organ systems work together to form organism. Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017RAVI PRAKASH SINGH 23

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Cell Division And cell Growth Cell Growth : When a cell is formed it is small but it gradually grow in size by taking nutrients and after reaching certain size, it divides into two new cells. Cell Division : Cell division is the process by which a parent cell divides into two or more daughter cells Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017Wednesday, December 20, 2017RAVI PRAKASH SINGH 25

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