Cells / General / Micro organisms


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Cells, cells cells…We have come across many different types of cells in biology – plant cells, animal cells, fungi, and even bacterial cells. Are they all the same? Do they function the same? Are there any similar features? Let us dive into the basic facts about cells and their organizations. The cell is the fundamental unit of any living system be it the teeny weeny bacteria to the gigantic dinosaur.

Cells can be divided into 2 major classes based on their structure – The Prokaryotes and the Eukaryotes.

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Prokaryotes are simple cells that form organisms like bacteria. They are very rudimentary and have an outer wall (called the membrane), appendages for movement of the single-celled organism (like cilia or flagella – the small hair like structures you may have seen in a cartoon or a picture of any bacteria), and the actual ‘inside’ of the cell also called the cytoplasm. The cytoplasm is home to various components which perform different functions in the living cell. The genetic material also called the chromosomes are found loosely organized in the cytoplasm in a unit called the nucleoid. They have other units for protein synthesis and energy production etc but all of them are loosely scattered within the cytoplasm. They have a simple way of life moving around freely by whipping their hairy appendages.

The other class of cells called the eukaryotes have a more complex organization than their prokaryotic counterparts. They form the basic units of most other living organisms right from fishes to mammals.

The major difference between the prokaryotes and the eukaryotes is the presence of a highly organized cytoplasm with distinct units each executing a different function within the cell. The genetic material organized in structures called chromosomes is housed in a distinct compartment called the nucleus which has a separate membrane to limit its contents inside the unit. This membrane called the nuclear membrane along with other membranous structures is one of the means to differentiate a prokaryote and a eukaryote.

PC: Genome Research Limited

Eukaryotic cells are much larger than prokaryotes and have these distinct membrane-bound units in their cytoplasm called organelles to execute every function of a living cell. These include the mitochondria which is the powerhouse of the cell producing ATP which is otherwise called the currency of the cell and can be ‘burnt’ to meet the energy demands of the cell. Ribosomes constitute another important organelle where proteins are made. Lysosomes possess enzymes which can do a quick clean-up of the unwanted substances within a cell by digesting them within its unit. Free units called vacuoles are places of storage within the cell. Organelles called the Golgi apparatus help in providing the finishing touch to proteins synthesized by the ribosomes by packaging them neatly with a tag such that it reaches its destination. The endoplasmic reticulum forms a channel within the cell for intracellular transport and is of two types the smooth and the rough endoplasmic reticulum. The rough endoplasmic reticulum is the one dotted with ribosomes while the smooth is devoid of that.

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Plant cells have in addition a unit called the chloroplast which has the green pigment chlorophyll that the leaves use to make the food of the plants – starch. Plant cells also have another additional protection called the cell wall over the cell membrane.

So these are the basic differences between prokaryotes and eukaryotes that one ought to know. While at the molecular level most fundamental processes remain the same, at the cellular level there is a lot of difference between the rudimentary prokaryotes and the more evolved eukaryotic cells.

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