Cell organelles are specialized structures or you can say tiny organs of a cell which are coordinated together to perform necessary functions to keep the cell in living state. There are diferent types of cell organelles in a cell possessing different morphologies and are composed of unique sets of macromolecules such as lipids, proteins and nucleic acids. Due this distinctness these organelles are able to perform different functions in order to maintain a cellular homeostasis and carrying out various cellular processes. If any dysfunctions occurs to these organelles, results in cellular dysfunctions which leads to various types of diseases in a cell.
Cell organelles
Cell organelles are broadly divided into two categories:-1) non membrane bound cell organelles
2) membrane bound cell organelles
Membrane bound cell organelles are further divided into two types:-
i) single membrane bound cell organelles
ii) double membrane bound cell organelles
A) Non membrane bound cell organelles:
these are tiny cellular entities or organs which do not have any surrounding membrane or coverings. They are made up of protein complexes that are dispersed throughout the cytoplasm of the cell.
Some examples of non membrane bound organelles are:- Ribosomes, centrosomes, cytoskeleton, Nucleolus and proteosomes.
1) Ribosomes: these organelles consists of large ribonucleoproteins consists of RNA and proteins. As we discussed earlier it can either 70S type or 80S type depending upon the type of cell.
It is resposible for synthesizing proteins by translating the genetic information encoded in the messenger RNA into polypeptide. Ribosomes are found throughout the cytoplasm and also on the endoplasmic reticulum of a cell.
2) cytoskeleton: it is an intracellular network of minute, fibrous and tubular proteins structures present in cytoplasm of a cell. All these fibrous are polymers of proteins acts as monomers units held together by non covalent bonds.
It consists of 3 types of cytoskeleton fibres:-
1) microfilament
2) intermediate filaments
3) microtubules
It involved in many functions such as mechanical support, maintenance shape and cellular integrity, motility etc.
3) centrosomes: these organelles are present in almost all eukaryotic cells except in higher plant cells.animal cell, consist of a pair of centioles perpendicular arranged to each other and surrounded by cloudy amorphous centriolar matrix.
This organelle is important because it is involved in spindle Fibre formation during cell division.
It is the site for ribosomal RNA synthesis. It can be one or more than one in a eukaryotic cell, thus actively involved in protein synthesis.
5) proteosomes: these are also non membrane bound organelle present in a cell. These are the large protein complex resposible for degradation of proteins that are no longer needed or get damaged or may be harmful for the cell. Degradation of proteins is essential for maintaining the homeostasis of a cell.
READ MORE: Prokaryotic and eukaryotic cells
B) single membrane bound organelles:-
These are the entities surrounded by a single bilipid membrane. This membrane separates the organelles internal environment from the surrounding cytoplasm and allows in and out of specific molecules.
Some of the examples of single membrane bound organelles are :- Endoplasmic reticulum, golgi apparatus, lysosomes, microbodies and vacuoles.
1) endoplasmic reticulum: largest single membrane bound organelle. Network of flattened tiny tubular structures in cytoplasm.
ER divides intracellular space into 2 compartments.
i) luminal compartment- internal space of ER.
ii) Extra luminal compartment- space outside the ER in cytoplasm.
It is differentiated into rough endoplasmic reticulum and smooth endoplasmic reticulum on the basis of presence or absence of ribosome.
2) Golgi body or golgi apparatus: it is also a single membrane bound organelle consist of 4 to 8 flattened sac like cisternae stacked on one another. Each stack of cisternae termed as Golgi stack or dictyosome. In plant the Golgi body is termed as dictyosomes.
i) luminal compartment- internal space of ER.
ii) Extra luminal compartment- space outside the ER in cytoplasm.
It is differentiated into rough endoplasmic reticulum and smooth endoplasmic reticulum on the basis of presence or absence of ribosome.
2) Golgi body or golgi apparatus: it is also a single membrane bound organelle consist of 4 to 8 flattened sac like cisternae stacked on one another. Each stack of cisternae termed as Golgi stack or dictyosome. In plant the Golgi body is termed as dictyosomes.
Golgi apparatus has two distinct faces:-
A cis face or forming face
A trans face or maturing face.
Both cis and trans face are closely associated with special compartments. It is also considered as the distribution and shipping department for cells.
3) lysosomes: it is a single membrane bound organelle present in animal cells.Lysosomes have acidic internal PH and are filled with hydrolytic enzymes called hydrolyases. These enzymes are capable of digesting carbohydrates, proteins, lipids and nucleic acids. It is form by the process of packing in the Golgi apparatus.
4) vacoules: it is a single membrane bound structure which is filled with fluid the single membrane is called tonoplast. In plant cells the vacuole occupies up to 90% of the volume of the cell. It stores dissolved inorganic ions, organic acid, sugar, enzymes, pigments and secondary metabolites.
There are types of vacuoles
1) contractile vacoule- in Amoeba
2) food vacoule- in protists.
5) Microbodies: it is a single membrane bound structures that contains different types of enzymes responsible for Oxidation reaction. It is present in both plants and animal cells. Microbodies include peroxysomes, sphaerosomes and glyoxysomes.
READ MORE: What is a cell
4) vacoules: it is a single membrane bound structure which is filled with fluid the single membrane is called tonoplast. In plant cells the vacuole occupies up to 90% of the volume of the cell. It stores dissolved inorganic ions, organic acid, sugar, enzymes, pigments and secondary metabolites.
There are types of vacuoles
1) contractile vacoule- in Amoeba
2) food vacoule- in protists.
5) Microbodies: it is a single membrane bound structures that contains different types of enzymes responsible for Oxidation reaction. It is present in both plants and animal cells. Microbodies include peroxysomes, sphaerosomes and glyoxysomes.
READ MORE: What is a cell
C) double membrane bound organelles:-
1) mitochondria: mitochondria is a double membrane Bound structure with outer and inner membrane. The space between the outer and inner membrane is called inter membrane space. It is a site of aerobic respiration and produce cellular energy in the form of ATP so they are called power houses of the cell.In aerobic respiration the energy liberated in the process stored in the form of ATP which is utilised in oxidation of Carbohydrates proteins and fats.
2) plastids: plastids are double membrane bound organelle present in all living plants and photosynthetic protists. Depending upon the pigmentation they are of three types leucoplast, chromoplast, and chloroplast.
i) Leucoplast: are colourless plastids generally occur in non green cells and store food.
ii) chromoplast: these are of various colours due to the presence of pigment called carotenoid.
iii) chloroplast: it is a green colour plasted which is present in majority of green plants.
We will discuss all the cell organelles in detail In upcoming articles.
Conclusion:-
1) All eukaryotic cells have 3 types of cell organelles. Non membrane bound organelle, single membrane bound organelle and double membrane bound organelle.2) These organelles are coordinated together to do work to keep the cell in living state and perform all the necessary functions.
3) non membrane bound organelle do not have membrane around it.
4) single membrane bound organelle have single membrane arounde it.
5) double membrane bound organelle have Double membrane around it.
FAQ:-
Ques-1 what is the largest organelle in the cell?Ans- the largest organelle is the nucleus of a cell. It contains genetic material such as DNA. It covers the central space in animals and peripheral space in plants. But in case of plants it is the 2nd largest because vacoule is the largest organelle, as it occupies more than 90% of cell volume and it shifts the nucleus to the periphery.
Ques-2 which is the smallest organelle?
Ans- ribosomes are the smallest cell organelle. These organelles are called as protein factories because they synthesize proteins necessary for the cells. Ribosomes are of two types measured on the basis of density and size these are 70s and 80s.
Ques-3 where DNA found?
Ans- in majority did DNA is found in the nucleus of the cell and it is called the nuclear DNA or genetic material but DNA can also be found in mitochondria and chloroplast that's why mitochondria and chloroplast are called as semi autonomous organelle because they are capable of self duplication as they have circular DNA.
Ques-4 what is golgi bodies?
Ans- Golgi body or golgi apparatus is a single membrane bound organelle consist of 4 to 8 flattened sac like cisternae stacked on one another. Each stack of cisternae termed as Golgi stack or dictyosome. In plant the Golgi body is termed as dictyosomes.
Golgi apparatus has two distinct faces:-
A cis face or forming face
A trans face or maturing face.
Both cis and trans face are closely associated with special compartments. It is also considered as the distribution and shipping department for cells.
Ques-5 where are ribosomes are made?
Ans- Ribosomes are made by the process of Transcription of DNA in the Nucleolus. It is the site for ribosomal RNA synthesis. It can be one or more than one in a eukarotic cell, thus actively involved in protein synthesis.
A trans face or maturing face.
Both cis and trans face are closely associated with special compartments. It is also considered as the distribution and shipping department for cells.
Ques-5 where are ribosomes are made?
Ans- Ribosomes are made by the process of Transcription of DNA in the Nucleolus. It is the site for ribosomal RNA synthesis. It can be one or more than one in a eukarotic cell, thus actively involved in protein synthesis.
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