Cell- Fundamental Unit Of Life Class 9 Chapter 5

Cell Organelles (Little Organs of Cell)

• Cytoplasm is a fluid content inside the Plasma membrane.
• Cytoplasm contain many specialized cell organelles.
• Cell organelles are enclosed by membrane.
• Each Cell organelles performs a specific function for the cell.
• Membrane bound cell organelles are only present in Eukaryotic cell. They are absent in prokaryotic cell.

 

6 MAIN CELL ORGANISMS ARE:

Endoplasmic Reticulum, Golgi Apparatus, Lysosomes, Mitochondria, Plastids and Vacuoles

 

Endoplasmic Reticulum-

• The endoplasmic reticulum (ER) is a large network of membrane- bound tubes and sheets as like Plasma membrane
• Function of the ER is to serve as channels for the transport of materials (proteins) between various regions of the cytoplasm or between the cytoplasm and the nucleus.
• Endoplasmic Reticulum also provide a surface area for various biochemical activities of the cell.

Types of Endoplasmic Reticulum [E.R]

Smooth endoplasmic Reticulum (S.E.R)- 

• When Ribosomes are not attach to the surface of ER then its surface looks smooth and hence it is called S.E.R.
• S.E.R helps in the manufacture of fat molecules and lipids.
• S.E.R present in the liver cell of vertebrates animals helps in detoxifying many poisons and drugs.

Rough Endoplasmic Reticulum (R.E.R)-

• When yellow dot-like structure Ribosomes attach to the surface of E.R, then E.R surface looks rough and hence, it is called R.E.R
• RER is the site of Protein manufacture because of the presence of Ribosomes on its surface.
• This protein made in R.E.R are then sent to various places in the cell using E.R (depending on need)

Important Note

Membrane Bio – Genesis-

• Some of the proteins and lipids made in E.R helps in building the cell membrane or plasma membrane. This process is known as Membrane Bio-Genesis.
• Some other proteins and lipids functions as enzymes and hormones.

GOLGI APPARATUS

Discovered by Camillo Golgi)

• It is a system, of membrane bound vesicles arranged approximately parallel to each other in stacks called Cistern.
• Golgi Apparatus membrane are also attach to the membrane of E.R.
• Golgi Apparatus helps in the storage, modification packing and then dispatch the material synthesized near E.R and other various products to various target organs inside and outside the cell.
• Complex sugar is made from simple sugar in Golgi apparatus.
• Golgi apparatus is also involved in the formation of lysosomes by modifying proteins into enzymes.

 

 

LYSOSOMES-

• Lysosomes are membrane-bound sacs filled with digestive enzymes,
• These enzymes are made by RER
• Lysosomes are a kind waste disposal system of the cell.
• Lysosomes clean the cell by digesting any foreign material like bacteria, worn out cell organelles, food particles etc.
• Lysosomes are known as suicide bags because: During the cellular disturbance in Metabolism, Lysosomes may burst and enzyme digest their own cell.

 

Mitochondria (Power – House of Cell)-

• It is a rod shaped structure in cytoplasm it is only present in Eukaryotic cells.
• It have two membrane covering, the outer membrane is porous and made up of proteins and the inner membrane is folded inside to form chambers known as Cristae.

Functions of Mitochondria-

• Its main function is to produce and store the energy in the form of A.T.P. (Adenosine Tri-Phosphate)
• A.T.P is known as Energy Currency of the Cell.
• Inner membrane i.e. Cristae provides a large surface area for ATP- generating chemical reaction.
• Mitochondria have their own DNA and Ribosomes so, mitochondria are able to produce their own protein.

Ribosomes- Minute particles consisting of RNA (Ribo- Nucleic Acid) Ribosomes are the main sites of protein synthesizes and transported it to E.R.

 

Plastids (Only present in Plant Cell)

• Plastics consists of numerous membrane layers embedded in a material called the stroma.
• Plastids also have their own DNA and Ribosomes like mitochondria

Functions of Various Types of Plastids

2. Leucoplast: White of colourless plastids found in of plants like roots.
Leucoplast stores materials such as Starch, Oils and Protein Granuels.

2. Chromoplast: Bed and Brown colour plastids

3. Chloroplast: Found in aerial parts of plants like leaves.-

• Green colour plastids due to the presence of green pigment chlorophyll.
• Chlorophyll helps in absorption of sunlight and by the help of sunlight plants prepare their own food by the process of photosynthesis.
• It is important for photosynthesis.

 

Vacuoles-

• Vacuoles are membrane bound storage sac like structure present in cytoplasm
• Vacuoles are small size in animals cells while plants cells have very large vacuoles i.e. 50%-90% volume of plants cells is covered by vacuole.

Functions of Vacuole-

• Storage of materials like: water, Amino Acids various organic acid, sugar and proteins.
• Helps in expelling (removing) excess of water from the cell.
• Provides turgidity and Rigidity to Plant cells.
• In single celled like Amoeba, Vacuoles contains the food items which is known as food vacuoles.