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Classical Cell Theory was proposed by Theodor Schwann in 1839. He proposed three conclusions on his theory. The first one states that all living organisms are made of cells. Theodor Schwann compared his discovery that animals are composed of cells to the discovery of Matthias Schleiden that plants are also composed of cells. Given these two conclusions, Schwann proposed the second part of his classical cell theory, which states that cells are the basic unit of life. The third part states that cells came from preexisting cells that have multiplied, after the description of Rudolf Virchow in 1858. Since then, the technology evolved that allows scientists to have a broader and detailed observation that led to modern cell theory. Modern Cell theory has three main additions to the classical cell theory. The first is that DNA passed between cells during cell division; second, that the cells of all organisms within a similar species are mostly the same, both structurally and chemically; and finally that energy flow occurs within cells. Some organisms are made up of a single cell, while others are made up of millions of cells. Cells are categorized into Prokaryotic and Eukaryotic. Both cell types have DNA that contains the genetic code of the cell, plasma membrane that surrounds the entire cell, cytoplasm - a gelatine like liquid that fills inside the cell and ribosomes that make proteins. Prokaryotic Cells are small cells that range from zero point one to two micrometers. It has no true nucleus and membrane bound organelles are absent. Organisms based from prokaryotic cells are known for being unicellular organisms; an organism made up of only one cell that carries out all of the functions needed by the organism. Examples are Bacteria and Archaea. Organisms like plants and animals are based on eukaryotic cells. This type of cell generally has a nucleus, an organelle that contains the DNA of the cell. It has various organelles that differ on different organisms. Most organisms based on eukaryotic cells are multicellular, that means they use many different cells to function. Its size is quite bigger than a Prokaryotic Cell that ranges from 10-100 micrometers. A eukaryotic cell has three parts, the nucleus, cytoplasm and cell membrane or plasma membrane. The cell membrane is a thin membrane which forms the outer boundary of the cell. The cytoplasm contains protoplasm where other organelles are found. Nucleus is the control center of the cell. It houses the DNA; the hereditary material of cells as well as various proteins and nucleolus and covered by a nuclear membrane. Most organelles are present on both animal and plant cells like nucleus, mitochondria, golgi apparatus, Smooth and Rough Endoplasmic Reticulum, and ribosomes. Ribosomes are the tiny dots found on cells known as the protein factory. It manufactures protein using RNA and amino acids. Mitochondria is a rod-shaped organelle that stores, transfers and converts energy into adenosine triphosphate or ATP. Endoplasmic Reticulum known as the manufacturer and shipper of cells. It is the organelle that forms an interconnected network of flattened sacs. It is divided into two parts that differ in structure and function called smooth and rough endoplasmic reticulum. Smooth Endoplasmic Reticulum lacks ribosomes on its surface resulting in its smooth appearance. It involves lipid synthesis and carbohydrates that are used to build the cell membrane. Rough Endoplasmic Reticulum on the other hand has ribosomes attached to its surface. It is involved in the manufacture of proteins, production of antibodies and insulin and transport of proteins into the smooth endoplasmic reticulum. Golgi Apparatus or Golgi body are highly folded into flattened sacs. It is known as the packaging counter of the cell because it packages the secretory proteins and other products from the endoplasmic reticulum. Some organelles are only present or prominent in plant cells and others are on an animal cell. Cell wall is one of the most important components of plant cells. The cell wall surrounds the cell membrane and serves to strengthen and protect the cell. Vacuole may be described as a space inside the cell that does not contain cytoplasm. It is surrounded by a membrane and filled with a fluid. Vacuoles store various molecules including enzymes, waste products of the cell, water, and even food material depending on the type of cell. Plastids are a type of organelle found in plant cells and algae. Like mitochondria, plastids are membrane-bound organelles that contain nucleoids. As such, they are also semi-autonomous organelles. There are different types of plastids that include chloroplasts, chromoplasts, gerontoplasts, and leucoplasts. Chloroplasts contain the pigment chlorophyll that captures energy from sunlight for photosynthesis. It is the site of photosynthesis, the process of making food of plants. Chromoplasts are present in certain photosynthetic eukaryotes. They are primarily involved in the production and storage of pigments. Gernotoplasts play an important role in salvaging nutrients and other important material as a cell dies. Leucoplasts are unpigmented organelles. Leucoplast is specialized for such functions as the storage of starch, lipids and proteins. The cytoskeleton is the framework of the cell, and is made up of microtubules and microfilaments. By spreading throughout the cell. It helps maintain the shape of the cell while also ensuring its elasticity. Centrioles are cylindrical organelles found in most eukaryotic cells. They contain tube-shaped molecules known as microtubules that help separate chromosomes and move them during cell division. A lysosome is commonly referred to as sacs of enzymes. They are membranous organelles that contain acidic enzymes that serve to digest various macromolecules in the cell. Be updated with new topics weekly by subscribing to our youtube channel! Don’t forget to like and leave us a comment about this video. See you next week!