The Fundamental Unit of Life- Blog 2

CLASS 9 CHAPTER 5 
THE FUNDAMENTAL UNIT OF LIFE
Day 2
" Whenever you feel sad, just remember that there are trillions of cells in your body & all they care about is you!!"
Dear Students, 
Welcome Back!😊

I hope you have completed your yesterday's assignment.

This is our second class for this chapter. After this class, you will be able to:
  • List the basic structural components of a cell.
  • Explain the structure and function of the cell membrane.
  • Distinguish between Hypotonic, Hypertonic & Isotonic solutions.
  • Explain the structure and function of the cell wall.
Note: Content written in blue should be recorded as notes in the Biology Notebook.
Happy Learning!😊

Structural Organisation of Cell:

General components present in every cell are:
( To be drawn in bio notebook) 

Plasma /Cell Membrane

  • It is the outermost covering of the cell that separates cell contents from its external environment. 
  • It allows entry or exit of certain substances only in & out of the cell, thus it is also called a semi-permeable membrane (SPM).
  • Movement of substances takes place in and out of the cell by a process called Diffusion.
  • Plasma Membrane is flexible and is made up of Lipids (includes, fats, oils, etc. ) and Protein.

Diffusion: A spontaneous movement of a substance from a region of high concentration to a region of low concentration.

Exchange of materials between Cells as well as cell and its environment:

Carbon Dioxide: It is a byproduct of cellular respiration, which needs to be excreted out by cell. As there is a difference in the concentration of carbon dioxide inside and outside of a cell, it moves out of the cell by the process of diffusion.

Oxygen: Oxygen enters the cell by the process of diffusion as its concentration is high outside the cell as compared to inside.

Water: The movement of water molecules across an SPM is called Osmosis.

Osmosis: The passage of water from a region of high concentration, through an SPM to a region of low concentration. It is a special case of Diffusion through SPM.

Movement of water across the plasma membrane is affected by the amount of substance dissolved in water. On the basis of these solutions are classified as:
  1. Hypertonic Solution
  2. Hypotonic Solution
  3. Isotonic Solution

( Not to be drawn in bio notebook)

https://youtu.be/rMa9MzP19zI (Check this video to know about solutions & its types)

Note:

  • Flexibility enables the cell to engulf in food & other material from its external environment by a process called ENDOCYTOSIS. Amoeba acquires its food by this process.

Cell Wall:

  • Plant cells in addition to the plasma membrane have another rigid outer covering called Cell wall, which lies outside the Cell Membrane.
  • It is made up of cellulose which provides structural strength to plants.
  • When a plant cell loses water through osmosis, there is a shrinkage/contraction of contents of the cell. This phenomenon is PLASMOLYSIS.
Plant cells can withstand much greater changes in the surrounding medium than animal cells!!

https://youtu.be/RrFVAz56vQk (check this video to know more about cell membrane & cell wall) 

Assignment:

  1. Tabulate points of difference between Hyper, hypo & isotonic solutions. ( Refer to pg.60 of N.C.E.R.T)
  2. Read activity 5.3 & 5.4 on pg.60 of N.C.E.R.T.
  3. Solve IQ's on pg. 61.
That's it for today's class.
See you for the next class.
Stay Fantastic! Stay Safe!😊

Comments

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