Cells were first discovered by Robert Hooke in Anton Von Leeuwenhoek discovered the free living cells in pond water for the first time. It was Robert Brown in who discovered the nucleus in the cell. Cell Theory: The cell theory, that all the plants and animals are composed of cells and that the cell is the basic unit of life, was prese nted by two biologists, Schleiden and Schwann They did not explain how new cells formed. The cell theory was further expanded by Virchow by suggesting that all cells arise from pre-existing cells.
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Cells were first discovered by Robert Hooke in Anton Von Leeuwenhoek discovered the free living cells in pond water for the first time. It was Robert Brown in who discovered the nucleus in the cell.
Cell Theory: The cell theory, that all the plants and animals are composed of cells and that the cell is the basic unit of life, was prese nted by two biologists, Schleiden and Schwann They did not explain how new cells formed. The cell theory was further expanded by Virchow by suggesting that all cells arise from pre-existing cells. It states that: i. Substances that can be used for staining cells: iodine solution, safranin solution or methylene blue solution.
Net transfer of water is positive into cell. Absorption of water by plant roots is also an example of osmosis. Different molecules move in and out of the cell through a type of transport requiring use of energy in the form of ATP. Such processes are known as endocytosis. Amoeba acquires its food through such processes. This phenomenon is known as plasmolysis. It has pores to allow the transfer of materials to and fro from nucleus to cytoplasm. Chromatin material is visible as entangled mass of thread like structures.
Whenever the cell is about to divide, the chromatin material gets organised into chromosomes. Such an undefined nuclear region containing only nucleic acids is called a nucleoid. Many of the functions of such organelles are also performed by poorly organised parts of the cytoplasm.
Cytoplasm: The cytoplasm is the fluid content inside the plasma membrane. It also contains many specialized cell organelles. On the other hand, the eukaryotic cells have nuclear membrane as well as membrane-enclosed organelles. Viruses lack any membranes and hence do not show characteristics of life until they enter a living body and use its cell machinery to multiply. This is one of the features of the eukaryotic cells that distinguish them fro m prokaryotic cells.
This process is known as membrane biogenesis. These membranes often have connections with the membranes of ER and therefore constitute another portion of a complex cellular membrane system. However, the work of greatest importance, which Golgi carried out was a revolutionary method of staining individual nerve and cell structures.
This method uses a weak solution of silver nitrate and is particularly valuable in tracing the processes and most delicate ramifications of cells. All through his life, he continued to work on these lines, modifying and improving this technique. Golgi received the highest honours and awards in recognition of his work. He shared the Nobel prize in with Santiago Ramony Cajal for their work on the structure of the nervous system.
These enzymes are made by RER. Lysosomes help to keep the cell clean by digesting any. Lysosomes help to keep the cell clean by digesting any foreign material as well as worn-out cell organelles. ATP is known as the energy currency of the cell. The outer membrane is very porous while the inner membrane is deeply folded. These folds create a large surface area for ATP-generating chemical reactions.
Therefore, mitochondria are able to make some of their own proteins. Chloroplasts are important for photosynthesis in plants. Chloroplasts also contain various yellow or orange pigments in addition to chlorophyll.
Accordingly they will be called - Amyloplasts, Elaioplasts, Proteinoplasts. Like the mitochondria, plastids also have their own DNA and ribosomes. These include amino acids, sugars, various organic acids and some proteins. Did You Know? The cells in the outermost layer of our skin are dead. An average adult carries around about 2 kg of dead skin. Billions of t iny fragments of the skin are lost every day. Every time you run your finger on a dusty table, you shed a lot of old skin.
Visit an agriculture extension centre in your area. Find out about genetically modified GM crops. Prepare a short speech for your class on this topic. You may visit www. Find out about Bt cotton from an agriculture expert or from envfor.
Cytoplasmic inclusion From Wikipedia, the free encyclopedia Inclusions are considered to be nonliving components of the cell that do not possess metabolic activity and are not bounded by membranes.
The most common inclusions are glycogen, lipid droplets, crystals and pigments. It appears in electron micrograph as clusters, or rosette of beta particles that resemble ribosomes, located near the smooth endoplasmic reticulum. Lipid yields more than twice as many calories per gram as does carbohydrate. On demand, they serve as a local store of energy and a potential source of short carbon chains that are used by the cell in its synthesis of membranes and other lipid containing structural components or secretory products.
Furthermore, cardiac tissue and central nervous system neurons shows yellow to brown pigment called lipofuscin, some believed that they have lysosomal activity. Learn more about Scribd Membership Home. Much more than documents. Discover everything Scribd has to offer, including books and audiobooks from major publishers. Start Free Trial Cancel anytime.
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Furthermore, cardiac tissue and central nervous system neurons shows yellow to brown pigment called lipofuscin, some believed that they have lysosomal activity Biology Page 6. Samson Baughman. Jason Ng. Nu Club. Teofilius Kilmonis. Muhammad Usman. Moni Villalba. Gette Acupan. Viva la Vida. Zhel Nieves Maravillas. Ryan Freud Cuadrazal.
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