Definition of Cells, Cell Structure and Function, Read Here

Cell is the smallest unit of living things. Every organism in this world is composed of cells that integrate with each other to form a certain function in the body of living things. Both cellular level organisms ( Unicellular ) and Multicellular organisms . Cells were first introduced by Robert Hooke in 1665 who observed cork tissue in plants using a magnifying lens. Cork is a building with small holes like a honeycomb arrangement separated by a " diaphragm ". This honeycomb-like building is hereinafter referred to as a cell . The cell name is taken from the Greek " Kytos ".” which means empty space, while the Latin empty space is “ cella ”.
The development of the theory of cells began in 1839 until the end of the XIX century.
Schleiden and T. Schwann . The cell is the smallest structural unit of living things. This theory explains that every living thing is composed of cells. Cells are the smallest part of living things that make up living things.
Max Schultze . The cell is the smallest functional unit of living things. This theory explains that the cell is the smallest part of a living thing that performs the functions of life. The functions of life in cells can be demonstrated by the presence of cell metabolism and cell regulation by the nucleus.
Rudolf Virchow . The cell is the smallest unit of growth in living things. Cells as the smallest constituent of living things in addition to carrying out a function of life also experience growth. Cells can experience an elongation in size or an increase in cell volume.
The end of the XIX century . The cell is the smallest unit of heredity in living things. Cells have a structure called the nucleus. The nucleus has a role as a carrier of genetic material (stored as DNA molecules) which have traits that are passed on to the next generation of cells.
Cells can be classified into two based on the presence or absence of a nuclear membrane (nuclear membrane ), namely prokaryotic cells , cell types that are not equipped with a nuclear membrane for example bacteria and blue algae ( Cyanophita ); and eukaryotic cells , which are types of cells that have a nuclear membrane such as animal cells, plants, fungi.
Prokaryotic cells
Bacteria as prokaryotic organisms which are unicellular organisms have a cell structure that does not have a nuclear membrane. The general cell structure possessed by prokaryotic cells can be seen in bacterial cells.

Bacterial Cell Structure

The nucleoid ( nucleus ) or the cell nucleus functions as a controller and regulator of the cell. All cell activity is regulated by the nucleus. The nucleus also functions as a carrier of genetic information, namely chromosomes , which are passed on to the next generation. Chromosomes are structures composed of DNA molecules and proteins ( histones ). The nucleus of a bacterial cell is exposed or in direct contact with the cytoplasm because it does not have a nuclear membrane.
Cytoplasm ( Cytoplasm ) is the part of the cell that contains fluid where cell metabolism takes place. The largest content in the cytoplasm is water (80-90%).
Ribosome ( Ribosome ) is a structure in the form of small granules which is the site of protein synthesis . Proteins are synthesized or made by combining several amino acids according to the genetic information present in the DNA molecule. Ribosomes are in the cytoplasm.

Cytoplasmic membrane ( plasma membrane ) is the outer layer of the cytoplasm which is composed of . The function of the plasma membrane is to protect and regulate cell transport . Cell transport regulation is intended to regulate the entry and exit of substances into and out of the cell. The plasma membrane also plays a role in receiving stimuli that come from outside the cell.
The cell membrane in prokaryotic cells undergoes an inward indentation to form a structure called the mesosome (mesosomes) . Mesosomes function as a place for cellular respiration to produce energy that will be used for activities in the cell.
Cell wall ( Cell Wall ) It is the second protective structure after the plasma membrane.

Capsule ( Capsule l ) is the third protective structure of the cell after the plasma membrane and cell wall.
Pili (hair feathers) function as a means of attachment of bacterial cells to a substrate or object surface.
Flagella ( Flagella ) function in cell movement. Both flagella and pili are composed by microtubules.
Eukaryotic cells
Eukaryotic cells have a more complex structure than prokaryotic cells. Eukaryotic cells have a nuclear membrane that separates the nucleus from the cytoplasm. These cells also have endomembrane structures called organelles . The organelles of eukaryotic cells have certain functions that support the life of eukaryotic cells. Types of organelles that are owned by eukaryotic cells include:
Lysosomes , organelles that play a role in cell digestion. This organelle contains the enzyme lysozyme which will lyse parts of cells that are dead, damaged or old.
Mitochondria , organelles that play a role in cellular respiration. Cellular respiration aims to produce energy that will be used in cellular activities.
Golgi apparatus , organelle that plays a role in the secretion of products, both proteins, polysaccharides and fats .
Endoplasmic Reticulum (ER) , an organelle that plays a role in product synthesis. There are two types of ER, namely rough ER (ER which has ribosomes on its surface) and smooth ER (ER which does not have ribosomes). The rough ER functions to synthesize proteins, while the smooth ER functions in the synthesis of fats and sterols .
Plastids , organelles that contain pigment (color).
Vacuoles , organelles that function in the storage of food reserves, essential oils and the rest of cell metabolism.
Microtubules , organelles that have a tube structure. for example flagella (for cell movement), cilia (cell attachment tool) and spindle (for cell division).
Microfilaments , organelles that have a filament (thread) structure. functions in cytoplasmic movement and muscle contraction .
Micro Bodies There are two kinds of micro bodies, namely Peroxisomes (containing catalase enzymes ) and Glyoxisomes (containing catalase and oxidase enzymes ).
Cell wall , cellulolytic structure and chitin which functions to give cell shape and as a cell protector.
Centrioles , organelles that play a role in cell division. Centrioles function to pull chromosomes towards opposite poles.
Eukaryotic cells are divided into animal cells and plant cells . The basic difference between the two types of cells is that there are some parts of the cell that are only owned by animal cells ( centrosomes and lysosomes) and which are only owned by plant cells (plastids and cell walls). The following is an animated video that explains the difference between plant cells and animal cells. E


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