Prokaryotes are simple in structure with no specific organelles, just like the single cabin; whereas eukaryotic cells have well-defined organelles with each having specific roles to perform, likewise the beautiful home with separated rooms.
Eukaryotic cells are known for proper compartmentalization. These cells have true and membrane-bound nucleus and other membranous organelle and each exerts their specific functions. Fungi, protists, plants, and animals consist of the eukaryotic cells. The eukaryotic cells also have the potential to perform the metabolic activities and other reactions simultaneously inside their environment.
Though eukaryotic cells have complex structures and functions, but are highly advanced and have the potential to perform all the vital functions, required by the body.
Definition of Eukaryotic Cell
Such cell that possesses the true and well-defined nucleus (chromosomes, nuclear-membrane nucleolus) along with other organelles like the Golgi apparatus, mitochondrial endoplasmic reticulum, lysosomes, ribosomes, that are assigned to perform different functions such as, generating energy (ATP, ADP, etc.), protein production, engulfing toxic and waste products, etc. The eukaryotes are said to be evolved around 1.7 billion and 1.9 billion years ago.
Characteristics of Eukaryotic Cells
Eukaryotic Cells are characterized by:
- The size of the eukaryotic cells (ranging from 10- 100 um) is larger than the prokaryotic cells, and it can be about 10,000 times larger volume.
- The shape of the eukaryotic cells also varies according to its function, and type of organisms, and its environmental factors.
- Some eukaryotes are single-celled (that contains only one cell), while some are multicellular (having numerous cells).
- They have well-defined “true” as well as the membrane-bound nucleus.
- The nucleus has the genetic material in the form of DNA, ‘deoxyribonucleic acid’ that directs the synthesis of ribosomes and proteins.
- Eukaryotic cells have membrane-bounded organelles or compartments, each endowed with a specific role and is marked by the presence of specialized proteins.
- All the eukaryotic cells have a cell-membrane also known as the plasma membrane, which is a phospholipid bilayer having specific proteins and plays the role of a wall, that separates and protects the internal contents, from the outer environment.
- Although, all eukaryotic cells have almost the same structures, but may vary at certain organelles like animal cells have lysosomes and centrosomes, which are not present in plant cells. On the other hand, plant cells chloroplasts, plastids, large central vacuole, which are not there in animal cells.
- Some eukaryotes like yeast, reproduce asexually (fission), while others like higher animals divide sexually.
Structure of the Eukaryotic Cell and their functions
|Plasma membrane||Also known as cell or cytoplasmic membrane, it acts as the barrier or wall for the cell and separates the outer and inner environment of the cell. In the plant cell, it is present beneath the cell wall.|
|Cytoplasm||It is a fluid present all over the cell, it contains the ions, minerals, and other molecules and this cytosol provides space to all the organelles present in the cell.|
|Mitochondria and Plastids||Mitochondria is the powerhouse of the cell as it is known to generate energy for the cell. Both plastids and mitochondria have the extra-chromosomal DNA. Plastids are found in plant cells and algae. Plastids contain chlorophyll, which is required for photosynthesis.|
|Nucleus||It is the main component of the cell, as it contains the genetic or hereditary material (DNA), the chromosomes present in this are properly and linearly organized. The genome has a special protein known as histone proteins.|
|Golgi Body||It modifies the structure of the protein (protein sorting) as per the needs. It is not found in sieve cells of plants and human red blood cells.|
|Ribosomes||In eukaryotic cells, it is of 80S type, which has two subunits: 60S and 40S. It plays the vital role in the synthesis of proteins and is attached to the endoplasmic reticulum.|
|Lysosomes and peroxisomes||Their function is to engulf the toxic and waste products present in cells and thus removing the wastes and recycling the cell structures.|
|Endoplasmic Reticulum||It is of two types: Rough and Smooth. The role of rough endoplasmic reticulum is in the transporting materials in the cells to different parts, and it also separates newly produce proteins for the transport through vesicles. It is attached through the outer layer of the nuclear envelope, with ribosomes also fixed on the outer layer.|
|The smooth endoplasmic reticulum is attached with the smooth endoplasmic reticulum, though separated from the nuclear membrane, and does not have ribosomes attached. So, the main role is in the carbohydrate metabolism, lipid synthesis, transportation of material interior of the cells.|
|Cilia and Flagella||The projections like structure assist in the movement, sensation, and feeding of the cells, especially present in protists.|
|Vesicles||These are sacs, used for transporting the materials and release the contents when merge with the cell membrane.|
|Cell wall||It is present in the plant cell, protists, fungi, and is made up of cellulose and gives shape to the cell.|
|Plasmodesmata||Present in plant cells and are helpful in proving channels to carry ions, proteins, RNA, and sugar molecules to other cells.|
|Chloroplasts||These are found in plant cells and play a significant role in the process of photosynthesis.|
|Central Vacuole||It is also found in plant cells only and is known to maintain the turgor pressure as to support the cell, the large vacuole is filled with water.|
Animal cells, Plant cells, Protozoa, Fungus, Diatoms, Dinoflagellates, etc. are common examples of eukaryotic cells.