Prokaryotic and eukaryotic cells (video) | Khan Academy

Prokaryotic cells Parts and Functions

Function / April 16, 2019

Prokaryotic cells are simpler and smaller than the eukaryotic cells. The term prokaryote is derived from the Greek word- “prokaryote” meaning before nuclei. These cells lack membrane bound organelles. Prokaryotic cells are unicellular organisms, which reproduce through binary fission. In some cases few prokaryotic organisms also reproduce by budding. Prokaryotic cells have a cell envelope, which generally consists of a capsule, cell wall, cytoplasm, plasma membrane, cytoplasm region or nucleiod region, ribosome, plasmids, pili and flagella. Prokaryotic Cell Example: Bacteria, blue green algae, E.coli, etc.

Parts of Prokaryotic Cell and their Functions

Capsule: It is composed of a thick polysaccharide. It is a kind of slime layer, which covers the outside of the cell wall. It is used to stick cells together and works as a food reserve and it also protects the cell from dryness and from chemicals.Cell wall: It is made from the glycoprotein murein. Cell wall provides strength and rigidity to the cell and it is permeable to solutes.Cytoplasm: It helps in cellular growth, metabolism and replication. Cytoplasm is the storehouses for all types of chemicals and components that are used to sustain the life of a bacterium.Plasma membrane: It is also known as a cell membrane.It is mainly composed of proteins, phospholipids and carbohydrates, which forms into a fluid-mosaic. Plasma membrane surrounds the bacteria and it is a most important organelle and plays a vital role in controlling the movement of substances in the cell.Cytoplasm region (or) nucleiod region: An area of the cytoplasm that contains the single bacterial DNA molecule.Ribosome: They are the smallest part of cell organelle. Ribosome plays a vital role in protein synthesis as they consist of protein and RNA. They are located freely in the cytoplasm of attached to the rough endoplasmic reticulum.Mesosomes: They are the folding, present inside the plasma membrane. Mesosome plays a vital role in cellular respirations, replication of DNA, cell division, separation of chromosomes during cell division and also performs the role of Golgi bodies and mitochondria.Plasmids: They are a small circle of DNA. Plasmid plays a vital role in exchanging DNA between the bacterial cells. Bacterial cells have many plasmids.Pili: They are short protein appendages, which fixes bacteria to surfaces. These pili are smaller than those flagella and are used in conjugation to exchange the genetic information.

Flagella: They are rigid rotating tail. The clockwise rotation moves the cell forward and anticlockwise rotation helps the cell to spin. The rotation is powered by H+ gradient across the cell membrane.

Eukaryotic cells are those cells, which are complex and larger than the prokaryotic cells. The term eukaryote is derived from the Greek word- “eukaryote” meaning true or good nuclei. This cell includes all life kingdoms except monera. Eukaryotic cells can be easily distinguished through a membrane-bound nucleus. The life, which is present and visible by our naked eye, is all made up of these cells. Eukaryotic cells are membrane-bound organelles, which have a multiple membrane-bound organelles to carry out specific cell tasks. They have different internal membranes, which are known as organelles. These organelles play a vital role in cell maintenance and other functions. These organelles generally consist of cell wall, plasma membrane, nucleus, mitochondria, chloroplasts (plastids), endoplasmic reticulum, ribosome, Golgi apparatus, lysosomes, vacuoles, cytoplasm and chromosomes.

Cell wall: It helps in protecting the plasma membrane and plays a vital role in supporting and protecting the cells. It is a thick outer layer made of tough cellulose. Cell walls are present in plant cells and are absent in animal cells.

Plasma membrane: The plasma membrane is present in animal cells, plant cells and even in eukaryotic cells. It is a double layered, thin barrier, surrounding the cell that controls the entry and exit of certain substances. It also refers to a thin, fluid entity that manages to be very flexible and it is stable. It is also called as cell membrane. It is the living ultra thin biological membrane ranging from 6 to 8nm and composed of a dynamic layer that chemically comprises a molecule of lipids and proteins that are arranged in a fluid mosaic pattern. It acts as a protective barrier. This membrane plays a vital role in:

It acts as a boundary and separates the internal and external organelles of a cell.

  • Transportation of materials.
  • Cell to cell recognition.
  • Enzymatic activity.
  • Signal transduction.

Nucleus: It is present both in animal cell and in plant cells. It is large and present in the center of a cell. It contains DNA and stores all the necessary information, which is required to control all the activities within the cell. Hence it is also called as a brain of the cell.

Nuclear membrane: It is a double layered, which surrounds the nucleus and helps in the entry and exits of material into the nucleus. It also separates the nucleus from the other parts of the cell.

Nucleolus: It is present in nucleus of both plant cell and animal cell. It plays a vital role in the synthesis of RNA and in the formation of the ribosome.

Mitochondria: The organelles that convert energy into usable forms, which are used by the cell to perform their cellular functions. They are double membranes, semi-autonomous organelles. This organelle plays a vital role in generating and transforming the energy. Albert von Kolliker recognized the structure of the mitochondria in the year 1880. It is a powerhouse of the cell, which produces energy by breaking down fats and carbohydrates. Mitochondria play a vital role in:

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