{"id":128,"date":"2024-03-03T08:59:07","date_gmt":"2024-03-03T08:59:07","guid":{"rendered":"https:\/\/pressbooks.justwrite.in\/interactive-biology-secondary\/?post_type=chapter&p=128"},"modified":"2024-11-30T05:36:30","modified_gmt":"2024-11-30T05:36:30","slug":"1-5-cell-organelles","status":"publish","type":"chapter","link":"https:\/\/pressbooks.justwrite.in\/interactive-biology-secondary\/chapter\/1-5-cell-organelles\/","title":{"raw":"1.5. Cell Organelles","rendered":"1.5. Cell Organelles"},"content":{"raw":"Organelles are structures found within the cytoplasm of eukaryotic cell. Each organelle is enclosed within a membrane and performs a specific function.\r\n\r\n\u00a0Organelles in animal cells include the nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, vesicles, vacuoles etc .,<\/span>\r\n\r\nRibosomes are not enclosed within a membrane but are still commonly referred to as organelles in eukaryotic cells.<\/span>\r\n

Organelles\/ cell structures specific for plant cell<\/h1>\r\n\r\n

\"plant cell\"<\/a>\u00a0by\u00a0<\/span>OpenStax\u00a0<\/span><\/a><\/a><\/a>is licensed under\u00a0<\/span>CC BY 4.0<\/a><\/p>\r\nThe Cell Wall<\/span>\r\n

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The cell wall is a rigid covering that protects the cell,<\/p>\r\n

It provides structural support, and gives shape to the cell.<\/p>\r\n

Fungal and protistan cells also have cell walls.<\/p>\r\n

The plant cell wall is mainly composed of an organic constituent called [pb_glossary id=\"337\"]cellulose[\/pb_glossary]<\/strong>, a polysaccharide comprised of glucose units.<\/p>\r\nWhile the chief component of prokaryotic cell walls is peptidoglycan,\r\n

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\u00a0Cellulose is a long chain polymer of \u03b2-glucose molecules connected by a 1-4 linkage.\u00a0<\/span><\/figure>\r\n<\/div>\r\n
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Chloroplasts<\/h2>\r\nChloroplasts are plant cell organelles that carry out [pb_glossary id=\"338\"]photosynthesis[\/pb_glossary]<\/strong>\r\n\r\nThey have their own DNA.\r\n\r\nPhotosynthesis is the process by which plants through a\u00a0 series of reactions\u00a0 use carbon dioxide, water, and light energy to make glucose and oxygen.\r\n\r\nPlants\u00a0 are [pb_glossary id=\"340\"]autotrophs<\/strong>[\/pb_glossary] as they are able to make their own food, like sugars, while animals are [pb_glossary id=\"342\"]heterotrophs<\/strong>[\/pb_glossary] as they must ingest their food.\r\n\r\nThis is a major difference between plants and animals;\r\n

Chloroplasts have outer and inner membranes<\/p>\r\n

Within the space enclosed by a chloroplast\u2019s inner membrane there\u00a0 is a set of interconnected and stacked fluid-filled membrane sacs called [pb_glossary id=\"343\"]thylakoids.[\/pb_glossary]<\/strong><\/p>\r\n

Each stack of thylakoids is called a [pb_glossary id=\"345\"]granum<\/strong>[\/pb_glossary] (plural = grana).<\/p>\r\n

The fluid enclosed by the inner membrane that surrounds the grana is called the [pb_glossary id=\"347\"]stroma.[\/pb_glossary]<\/strong><\/p>\r\n\r\n

<\/figure>\r\nThe space inside the thylakoid membranes is called the thylakoid space.\r\n\r\nThe chloroplasts contain a green pigment called chlorophyll, which captures the light energy for carrying out the process of photosynthesis.\r\n\r\nThe light harvesting reactions take place in the thylakoid membranes.\r\n\r\nThe synthesis of sugar takes place in the stroma.\r\n

Like plant cells, photosynthetic protists also have chloroplasts. Some bacteria perform photosynthesis, but their chlorophyll is not relegated to an organelle.<\/p>\r\n\r\n<\/div>\r\n

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\"Chloroplast structure\"<\/a>\u00a0by\u00a0<\/span>OpenStax<\/a>is licensed under\u00a0<\/span>CC BY 4.0<\/a><\/p>\r\n\r\n

Watch the Video on Chloroplast structure and Function.<\/div>\r\n \r\n\r\nhttps:\/\/youtu.be\/c8wA_0pfBu8?si=1GKC_2sBdEhbEgHm\r\n

The Central Vacuole<\/h2>\r\nThe central vacuole is an unique and essential component of plant cell and occupies most of the space of the cell.\r\n\r\nThe\u00a0<\/span>central vacuole<\/span> plays a key role in regulating the concentration of water in the cell against the changing environmental conditions. <\/span>\r\n\r\nThe the liquid inside the central vacuole provides turgor pressure<\/strong>, which is the outward pressure caused by the fluid inside the cell.<\/span>\r\n\r\nThe wilting of a plant when we forget to water it for few days is because of shrinking of the central vacuole caused due to the movement of water out of the central vacuole ,as the water concentration in the soil becomes lower than the water concentration in the plant.\r\n\r\nThis loss of support to the cell walls of plant cells results in the wilted appearance of the plant.\r\n\r\nOn the contrary when the\u00a0\u00a0central vacuole holds more water, the cell gets larger without having to invest a lot of energy in synthesizing new cytoplasm.\r\n\r\nThe\u00a0 fluid inside the central vacuole has a very bitter taste, which discourages consumption by insects and animals. <\/span>\r\n\r\nThe central vacuole also functions to store proteins in developing seed cells.<\/span>\r\n\r\nIn plant cells, the digestive processes take place in vacuoles.\r\n

Plasmodesmata<\/span><\/h1>\r\n

Plasmodesmata<\/span>(singular = plasmodesma) are junctions between plant cells,<\/p>\r\nNeighboring plant cells cannot touch one another because they are separated by the cell walls\r\n\r\nThe Plasmodesmata are numerous channels that pass between the cell walls of adjacent plant cells,\r\n\r\nThey serve to connect the cytoplasm , signal molecules and\u00a0 transport the nutrients\u00a0 from one plant cell to another.\r\n\r\n \r\n\r\nOrganelles\/ cell structures specific for Animal cell<\/span>\r\n\r\n<\/div>\r\n

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The Centrosome<\/h2>\r\n

The centrosome is a microtubule-organizing center. It is\u00a0 found near the nuclei of animal cells and contains \u00a0a pair of centrioles,<\/p>\r\n

The two centrioles\u00a0 lie perpendicular to each other.<\/p>\r\n

Each centriole is a cylinder of nine triplets of microtubules. Non tubulin serves to hold the microtubule triplets .<\/p>\r\nThe microtubule originate from the centrosome .\r\n

The centrosome replicates itself before a cell division.<\/p>\r\n

The centrioles\u00a0 pull the duplicated chromosomes to opposite ends of the dividing cell.<\/p>\r\n

The exact function of the centrioles in cell division is however not\u00a0 clear as cells that have had the centrosome removed can still divide; and plant cells, which lack centrosomes, are capable of cell division.<\/p>\r\n

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\"Centriole structure\"<\/a>\u00a0<\/span>by\u00a0<\/span>Libre Text biology<\/a><\/a><\/a>\u00a0<\/span>is licensed under\u00a0<\/span>CC BY-SA 4.0<\/a><\/a><\/span><\/span><\/p>\r\n\r\n<\/div>\r\n

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Lysosomes<\/h2>\r\n

\u00a0The lysosomes are the cell\u2019s \u201cgarbage disposal units \u201d .<\/p>\r\nThe lysosomes contain enzymes that\u00a0 aid the breakdown of proteins, polysaccharides, lipids, nucleic acids, and even worn-out organelles.\r\n\r\nThese enzymes are active at a much lower pH than that of the cytoplasm. Therefore, the pH within lysosomes is more acidic than the pH of the cytoplasm.\r\n\r\nMany reactions that take place in the cytoplasm could not occur at a low pH,\r\n\r\nthis is the advantage of compartmentalizing the eukaryotic cell into organelles .\r\n\r\n\"In\r\n

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Extracellular Matrix of Animal Cells<\/h2>\r\nMost animal cells release materials into the extracellular space. <\/span>\r\n\r\nThe primary components of the extra cellular matrix\u00a0 are glycoproteins and the protein collagen. Collectively, these materials are called the <\/span>extracellular matrix<\/span> <\/span>.<\/span>\r\n\r\nTheir function\u00a0 include :<\/span>\r\n