Science class 8

Hey guys, I am Kavya swastik. And I am here today with new topic. First I request you all to subscribe this post . In first blog I had told you how you can make your own blog. Now in this blog I will give you notes 

Of science chapter 👇👇.

THE CELL : ITS FUNCTIONS AND STRUCTURE 

Notes

• Cell is the basic structural as well as functional unit of all living organisms.
• Discovery of cell -                                          1. Robert Hooke was the first scientists who observed thin slices of cork in 1665 by microscope which was designed by him.                                           2. In Latin cell means 'a little room' .
• On the basis of ' number of  cells',   living organisms are divided into two categories: Unicellular and Multicellular.
•  Example of unicellular- Euglena,Amoeba,Paramoecium.
• Example of multicellular- Humans,Birds,Animals.
• There are many different shapes of cell.
• Smallest cell PPLO ( Pleural pneumonia - like organism) also called Mycoplasma is about 0.1 micron.
• Ostrich egg is considered as largest cell is (nearly) 170mm in diameter.
• μ= 0.1 micron 
• 0.1 micron = 10^-6
• μm = micron meter 
• mm = milimeter 
• 1μ = 10^-3 mm
• 10^-6 m = 10^-3mm                                      CELL                                           SIZE 
•   Amoeba                                   1000 μm 
•   Hen's egg                                  60mm 
•   Ostrich egg                              170 mm 
•   Green laga, Chara                   10 cm   CELL OF HUMAN BODY        SIZE 
• Red blood cell                            9 μm 
• Liver cell                                     20 μm 
• Human Ovum                            0.1 mm 
• Nerve cell                                About 1m      
• Life span of RBCs  is about 120 days.
• Parts of cell-                                                   1. Cell membrane                                         2. Cytoplasm                                                 3. Nucleus                                                       4. Cell organelles       
•  Cell membrane - All living cells are bound by a membrane called the plasma membrane, or cell membrane.  It surrounds its inner gel- like material called protoplasma. The Cell of plants, fungi and bacteria have an additional outer covering called cell wall. Cell membrane controll enter and exit substance in the cell. Cell wall provide rigidity to cell.
• Cytoplasm - The portion of the cell membrane is called cytoplasm. [Kytos ( hollow) , plasma (liquid)]. It acts as ground substance. 
• Nucleus - The nucleus is a dense structure bound by a nucleus membrane.  The protoplasma of the nucleus is called  nucleoplasm. It has a thread like network called chromatin.  When cell is ready to divide this chromatin condenses to form thicker, thread  - like structure , called chromosomes.                                                                                                                       Organism                 Chromosome no.    
• Man                                        46
• Dog                                         78
• Pigeon                                    80
• Wheat                                    42
• Yeast                                       32                                       
• Nucleus is the brain of the cell.
• Cell organelles                                             1. Plastids -                                                       ● Chloroplast                                                 ● Chromoplast                                               ●  Leucoplasts                                           ■ Chloroplast are green coloured plastids. It has chlorophyll which help  in photosynthesis.                                        ■  Chromoplast give colours to fruit.      ■  Leucoplasts is colourless. It provide space for containing starch.                                                                                                2. Mitochondria -  It is known  as power house of cell.                                                                                                              3. Endoplasmic Reticulum (ER) - It provide channels for transport.                 ● Rough (ER)                                                  ● Smooth (ER)                                              ■  Rough (ER) - It  plays a vital role in synthesis  of protein.                                    ■   Smooth (ER) - It helps  in synthesis  of fats.                                                             4. Gogli Complex - They are involved in processing  and packing  of materials produce by cell.                                             5. Vacuole - It stores excess water and wastes product.                                             6. Ribosomes - They help in protein synthesis.                                                         7. Cillia and flagella - They help in locomotion and collection of food.           
• LEVEL OF ORANNISATION IN AN ORGANISMS IN ASCENDING ORDER   - Cell , Tissue ,Organ , Organ system ,  Organism  
• DIFFERENCE BETWEEN PLANT AND ANIMAL CELL                                             Character   Plant cell  Animal cell 
•   Shape             Fixed        Not Fixed 
•   Cell wall       Present          Absent  
•    Plastids        Present          Absent
• 
  
•    Vacoules     One large   Vacoules are                             vacoules is   either absent,                           present.     or are present                                               only as small                                                   vacoules.