Question

summary of the cell : the fundamental unit of life (class 9th biology )

Answer 1

ʜᴇʟʟᴏ ᴍᴀᴛᴇ!

Summary of "Cell"

Cell was discovered by Rober Hooke, where he examined a thin slice if cork. There he concluded that the shape of cork slice was similar to Honey Comb shape. They consisted of several empty compartment and he named each "cell"

What is a cell?

A cell is basic fundamental and structural unit of life.

Fundamental = A cell is capable to perform various activities of life and hence called functional unit.

Structural = A cell is a building block which combines to form a structure. Hence, also known as structural unit of life.

As we know that several components move in and out of cell. They move by two process :-
Osmosis, diffusion.

Osmosis = Movement of water molecules through plasma membrane from region of higher concentration to lower concentration.

Diffusion = Movement of gases through plasma membrane from region of higher concentration to lower concentration.

On basis of Osmosis, cell shows variation, whwn kept in
1. Hypotonic solutions
2. Hypertonic solutions
3. Isotonic solution.

Hypotonic solution = When water inside os less the cell than to outside of cell then wayer moves inside the cell and cell swell. Such solutions are called hypotonic solutions.

Hypertonic = When water inside the cell is more than outside the cell, then wayer moves outside the cell and the cell shrinks. Such solutions is called hypertonic solution.

Isotonic solution = When water content is equal both the sides then no change occur.

Note: Plasmolysis is process when plant cell shrinks as kept in hypertonic solutions and content moves outside the cell.

1. Plasma Membrane :- The outer most covering of cell which allows passage of material in and out of cell. Its also called selectively preamble membrane as it allows only some substance to move in and out.

2. Cell Wall :- Plant cell has to survive in jarah conditions and has more chances to catch disease. To prevent it, a non living cell wall made of cellulose, calcium pectate and magnesium pectate is lresent only in plant and bacterial cell.

3. Nucleus :- The brain of cell, which consist genetic materials, chromosome needed for inheritance of characteristics from one generation to other.

a) Chromatic Fibers = A thin network thread like structure that is made up of DNA or RNA.

b) Chromosome = Condensed form of chromatin fibers which can be seen only while cell division.

c) Genes = They are segments of linear fashion. Each gene performs more than one function. The contain genetic codes.

Nuclues of Prokaryotic Cell and Eukaryotic cell.

Procaryotic cell are 1 miu to 10 miu where as Eukaryotic cell has size 5 miu to 100 miu. The nucleus region of Prokaryotic isn't well difined due to absence of nuclear membrane and known as nucleoid. Prokaryotes have on chromosome and no membrane bond cell organelles where as Eukaryotes have more than 1 chromosome and membrane bound cell organelles.

4. Cytoplasm : A thik transparent jelly like structure where all cell organnelles are suspended.

5. Cell Organelles :

↔️Endoplasmic Reticulum = Divided into
RER and SER.
RER = Have ribosomes attached to them. Synthesize protein.
SER = Are smooth amd synthesize fats and lipids.

The Endoplasmic Reticulum also make cell membrane when it get damaged and this process is known as Memberane Biogenisis.

↔Golgi Apparatus = The have a system of membrane bound vesicle arranged on each other like sacks called cisterns.

There function is to pacakge, modify, store and transport substance.

️↔️ Lysosomes = They burst when cell hets damage and digest the whole cell. Lysosome contain digestive enzyme made by Endoplasmic Reticulum where as lysosomes are formed in Goldi Apparatus.

↔️Mitochondrial = They produce energy molecules ( ATP = Adenosine Triphosphate )

Here, resporation takes place and produce energy for cell hence known as power house of cell.

↔Plastids : Coloured organelles only found in plant cell.

a. Chromoplast = Contain Carotenoid ans Xynophyll. They give colour to leaves, flower etc. Green colored pigments known as chlorophyll ae present in Chloroplast help in photosynthesis.

b. Luceoplast = Store oil, starch granules and are colour less

️↔️Vacuole = They give turgidity and rigidity to cell. They store amino acids, starch, protein etc in plant cell. They also store food in unicellular organism like Amoeba. They ae found less in animal cell and more and centered in plant cell.

Hope it will help you ☺️