What are cells?
Cells are the smallest component in all the living things. They are like basic building blocks in our bodies. There are trillions of cells in every one of our bodies. All the cellular activities occur in those tiny cells. They are the structure of our body; they carry out respiration to keep us alive; they convert nutrients into energy that we need; they can duplicate in an extraordinary speed and they can do so much more. Without cells, these little workers in our body, we are not able to stay alive.
the discovery of cells
Robert Hooke, a British scientist born in 1635, discovered cells. After working for several famous scientist, he started to work on microscopic observation between 1663 and 1664. Robert Hoke used the microscope as well as the telescope in order to study different structure of living organisms and non-living things. The observation on a cork led him to his first breakthrough in 1665. He discovered tiny pores all over the cork that he later named 'CELLS'. After his discovery on cork, he started studying different plant tissues and discovered cells in them as well. He named them cells since he thought they resemble the cells where monks live and work in. In the same year, he published the book, 'Micrographia', the first book ever in human history that was about cells.
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unicellular and multicellular
Living organisms that are made up of one cell only are called UNICELLULAR ORGANISMS.
In these organisms, only one single cell can carries out all the life process. Their cell is exposed to the environment on all sides. The organism cannot grow larger since the size of the cell is limited by the surface area to the volume ratio. The life span of these kinds of organisms are often short due to the heavy workload a single cell bare while an injury of the cell can lead to death of the organism.
Living organisms that are made up of more than one cell are called MULTICELLULAR ORGANISMS.
These organisms' bodies are composed of numerous cells and different cells have different specialized functions. Only outer cells are specialized to be exposed to the environment. The inner cells are to devoted to their specialties. A multicellular organism can grow into larger size when the number of cells are increased. Their life span is relatively longer than unicellular organisms since each cell only has limited workload and injury or death of some cell will not affect the organism in whole when they are replaceable.
In these organisms, only one single cell can carries out all the life process. Their cell is exposed to the environment on all sides. The organism cannot grow larger since the size of the cell is limited by the surface area to the volume ratio. The life span of these kinds of organisms are often short due to the heavy workload a single cell bare while an injury of the cell can lead to death of the organism.
Living organisms that are made up of more than one cell are called MULTICELLULAR ORGANISMS.
These organisms' bodies are composed of numerous cells and different cells have different specialized functions. Only outer cells are specialized to be exposed to the environment. The inner cells are to devoted to their specialties. A multicellular organism can grow into larger size when the number of cells are increased. Their life span is relatively longer than unicellular organisms since each cell only has limited workload and injury or death of some cell will not affect the organism in whole when they are replaceable.
examples of specialized cells in UNICELLULAR organisms
Specialized cells each has different functions and different adaptations. For example,
Root Hair Cell
Function: Absorbs water and mineral ions Adaptation: Long 'finger-like' shape with a very thin wall around it so that it has a large surface area to absorb more water and nutrients |
Leaf Cell
Function: Absorbs light energy for photosynthesis Adaptation: Packed with chloroplasts, all cells are tightly packed together so they can absorb efficient sunlight for photosynthesis |
the importance of specialized cells
Some of the cells in multicellular organisms are specialized to carry out particular functions. These cells have most of the features that other cells do but they also have different adaptation for them to perform better in their job. Unicellular organisms do not require specialized cells since their body is too tiny and one cell is already enough for performing all the cellular activities that the organism need. Without specialized cells, the body of multicellular organisms like us cannot perform some particular functions.
Eukaryotic cells and PROkaryotic cells
Eukaryotic cells contain membrane-bound organelles and a nucleus. They contains linear DNA and mitochondria or chloroplast. They can be unicellular or multicellular such as human, plants, fungi and insects.
Prokaryotic cells do not contain a nucleus or any membrane-bound organelle. Bacteria are an example of prokaryotic cells.
Prokaryotic cells do not contain a nucleus or any membrane-bound organelle. Bacteria are an example of prokaryotic cells.
organelle
Organelle is one of the several structures in a cell or an unicellular organism. For example, mitochondria, chloroplast, nucleus, etc.