{"id":1060,"date":"2016-04-07T19:44:02","date_gmt":"2016-04-07T19:44:02","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/biologyxwaymakerxmaster\/?post_type=chapter&p=1060"},"modified":"2017-04-18T16:18:32","modified_gmt":"2017-04-18T16:18:32","slug":"prokaryotes-and-eukaryotes","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/suny-wmopen-biology1\/chapter\/prokaryotes-and-eukaryotes\/","title":{"raw":"Prokaryotes and Eukaryotes","rendered":"Prokaryotes and Eukaryotes"},"content":{"raw":"

Identify the different kinds of cells that make up different kinds of organisms<\/h2>\r\nThere are two types\u00a0of cells: prokaryotic and eukaryotic. In this section,\u00a0we'll explore the\u00a0similarities and differences between these two types.\r\n
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Learning Objectives<\/h3>\r\n
    \r\n \t
  • Identify features common to all cells<\/li>\r\n \t
  • Contrast the composition and size of prokaryotic and eukaryotic cells<\/li>\r\n<\/ul>\r\n<\/div>\r\nCells fall into one of two broad categories: prokaryotic and eukaryotic. The single-celled organisms of the domains Bacteria and Archaea are classified as prokaryotes (pro<\/em> = before; karyon<\/em>- = nucleus). Animal cells, plant cells, fungi, and protists are eukaryotes (eu<\/em> = true).\r\n

    Components of Prokaryotic Cells<\/h2>\r\nAll cells share four common components: (1)\u00a0a plasma membrane, an outer covering that separates the cell's interior from its surrounding environment; (2)\u00a0cytoplasm, consisting of a jelly-like region within the cell in which other cellular components are found; (3)\u00a0DNA, the genetic material of the cell; and (4)\u00a0ribosomes, particles that synthesize proteins. However, prokaryotes differ from eukaryotic cells in several ways.\r\n\r\n[caption id=\"attachment_1513\" align=\"alignright\" width=\"400\"]\"In Figure 1. This figure shows the generalized structure of a prokaryotic cell.[\/caption]\r\n\r\nA prokaryotic cell<\/strong> is a simple, single-celled (unicellular) organism that lacks a nucleus, or any other membrane-bound organelle. We will shortly come to see that this is significantly different in eukaryotes. Prokaryotic DNA is found in the central part of the cell: a darkened region called the nucleoid (Figure 1).\r\n\r\nUnlike Archaea and eukaryotes, bacteria have a cell wall made of peptidoglycan, comprised of sugars and amino acids, and many have a polysaccharide capsule (Figure 1). The cell wall acts as an extra layer of protection, helps the cell maintain its shape, and prevents dehydration. The capsule enables the cell to attach to surfaces in its environment. Some prokaryotes have flagella, pili, or fimbriae. Flagella are used for locomotion, while most pili are used to exchange genetic material during a type of reproduction called conjugation.\r\n

    Eukaryotic Cells<\/h2>\r\nIn nature, the relationship between form and function is apparent at all levels, including the level of the cell, and this will become clear as we explore eukaryotic cells. The principle \"form follows function\" is found in many contexts. It means that, in general, one can deduce the function of a structure by looking at its form, because the two are matched. For example, birds and fish have streamlined bodies that allow them to move quickly through the medium in which they live, be it air or water.\r\n\r\nA eukaryotic cell<\/strong> is a cell that has a membrane-bound nucleus and other membrane-bound compartments or sacs, called organelles<\/strong>, which have specialized functions. The word eukaryotic means \"true kernel\" or \"true nucleus,\" alluding to the presence of the membrane-bound nucleus in these cells. The word \"organelle\" means \"little organ,\" and, as we learned earlier,\u00a0organelles have specialized cellular functions, just as the organs of your body have specialized functions.\r\n

    Cell Size<\/h2>\r\nAt 0.1\u20135.0 \u00b5m in diameter, prokaryotic cells are significantly smaller than eukaryotic cells, which have diameters ranging from 10\u2013100 \u00b5m (Figure 2). The small size of prokaryotes allows ions and organic molecules that enter them to quickly spread to other parts of the cell. Similarly, any wastes produced within a prokaryotic cell can quickly move out. However, larger eukaryotic cells have evolved different structural adaptations to enhance cellular transport. Indeed, the large size of these cells would not be possible without these adaptations. In general, cell size is limited because volume increases much more quickly than does cell surface area. As a cell becomes larger, it becomes more and more difficult for the cell to acquire sufficient materials to support the processes inside the cell, because the relative size of the surface area across which materials must be transported declines.\r\n\r\n[caption id=\"attachment_1514\" align=\"aligncenter\" width=\"1024\"]\"Part Figure 2. This figure shows the relative sizes of different kinds of cells and cellular components. An adult human is shown for comparison.[\/caption]\r\n\r\n
    \r\n

    In Summary: Comparing Prokaryotic and Eukaryotic Cells<\/h3>\r\nProkaryotes are single-celled organisms of the domains Bacteria and Archaea. All prokaryotes have plasma membranes, cytoplasm, ribosomes, a cell wall, DNA, and lack membrane-bound organelles. Many also have polysaccharide capsules. Prokaryotic cells range in diameter from 0.1\u20135.0 \u00b5m.\r\n\r\nLike a prokaryotic cell, a eukaryotic cell has a plasma membrane, cytoplasm, and ribosomes, but a eukaryotic cell is typically larger than a prokaryotic cell, has a true nucleus (meaning its DNA is surrounded by a membrane), and has other membrane-bound organelles that allow for compartmentalization of functions. Eukaryotic cells tend to be 10 to 100 times the size of prokaryotic cells.\r\n\r\n<\/div>\r\n

    Check Your Understanding<\/strong><\/h2>\r\nAnswer the question(s) below to see how well you understand the topics covered in the previous section. This short quiz does\u00a0not<\/strong>\u00a0count toward your grade in the class, and you can retake it an unlimited number of times.\r\n\r\nUse this quiz to check your understanding and decide whether to (1) study the previous section further or (2) move on to the next section.\r\n\r\nhttps:\/\/assessments.lumenlearning.com\/assessments\/3306","rendered":"

    Identify the different kinds of cells that make up different kinds of organisms<\/h2>\n

    There are two types\u00a0of cells: prokaryotic and eukaryotic. In this section,\u00a0we’ll explore the\u00a0similarities and differences between these two types.<\/p>\n

    \n

    Learning Objectives<\/h3>\n
      \n
    • Identify features common to all cells<\/li>\n
    • Contrast the composition and size of prokaryotic and eukaryotic cells<\/li>\n<\/ul>\n<\/div>\n

      Cells fall into one of two broad categories: prokaryotic and eukaryotic. The single-celled organisms of the domains Bacteria and Archaea are classified as prokaryotes (pro<\/em> = before; karyon<\/em>– = nucleus). Animal cells, plant cells, fungi, and protists are eukaryotes (eu<\/em> = true).<\/p>\n

      Components of Prokaryotic Cells<\/h2>\n

      All cells share four common components: (1)\u00a0a plasma membrane, an outer covering that separates the cell’s interior from its surrounding environment; (2)\u00a0cytoplasm, consisting of a jelly-like region within the cell in which other cellular components are found; (3)\u00a0DNA, the genetic material of the cell; and (4)\u00a0ribosomes, particles that synthesize proteins. However, prokaryotes differ from eukaryotic cells in several ways.<\/p>\n

      \"In<\/p>\n

      Figure 1. This figure shows the generalized structure of a prokaryotic cell.<\/p>\n<\/div>\n

      A prokaryotic cell<\/strong> is a simple, single-celled (unicellular) organism that lacks a nucleus, or any other membrane-bound organelle. We will shortly come to see that this is significantly different in eukaryotes. Prokaryotic DNA is found in the central part of the cell: a darkened region called the nucleoid (Figure 1).<\/p>\n

      Unlike Archaea and eukaryotes, bacteria have a cell wall made of peptidoglycan, comprised of sugars and amino acids, and many have a polysaccharide capsule (Figure 1). The cell wall acts as an extra layer of protection, helps the cell maintain its shape, and prevents dehydration. The capsule enables the cell to attach to surfaces in its environment. Some prokaryotes have flagella, pili, or fimbriae. Flagella are used for locomotion, while most pili are used to exchange genetic material during a type of reproduction called conjugation.<\/p>\n

      Eukaryotic Cells<\/h2>\n

      In nature, the relationship between form and function is apparent at all levels, including the level of the cell, and this will become clear as we explore eukaryotic cells. The principle “form follows function” is found in many contexts. It means that, in general, one can deduce the function of a structure by looking at its form, because the two are matched. For example, birds and fish have streamlined bodies that allow them to move quickly through the medium in which they live, be it air or water.<\/p>\n

      A eukaryotic cell<\/strong> is a cell that has a membrane-bound nucleus and other membrane-bound compartments or sacs, called organelles<\/strong>, which have specialized functions. The word eukaryotic means “true kernel” or “true nucleus,” alluding to the presence of the membrane-bound nucleus in these cells. The word “organelle” means “little organ,” and, as we learned earlier,\u00a0organelles have specialized cellular functions, just as the organs of your body have specialized functions.<\/p>\n

      Cell Size<\/h2>\n

      At 0.1\u20135.0 \u00b5m in diameter, prokaryotic cells are significantly smaller than eukaryotic cells, which have diameters ranging from 10\u2013100 \u00b5m (Figure 2). The small size of prokaryotes allows ions and organic molecules that enter them to quickly spread to other parts of the cell. Similarly, any wastes produced within a prokaryotic cell can quickly move out. However, larger eukaryotic cells have evolved different structural adaptations to enhance cellular transport. Indeed, the large size of these cells would not be possible without these adaptations. In general, cell size is limited because volume increases much more quickly than does cell surface area. As a cell becomes larger, it becomes more and more difficult for the cell to acquire sufficient materials to support the processes inside the cell, because the relative size of the surface area across which materials must be transported declines.<\/p>\n

      \"Part<\/p>\n

      Figure 2. This figure shows the relative sizes of different kinds of cells and cellular components. An adult human is shown for comparison.<\/p>\n<\/div>\n

      \n

      In Summary: Comparing Prokaryotic and Eukaryotic Cells<\/h3>\n

      Prokaryotes are single-celled organisms of the domains Bacteria and Archaea. All prokaryotes have plasma membranes, cytoplasm, ribosomes, a cell wall, DNA, and lack membrane-bound organelles. Many also have polysaccharide capsules. Prokaryotic cells range in diameter from 0.1\u20135.0 \u00b5m.<\/p>\n

      Like a prokaryotic cell, a eukaryotic cell has a plasma membrane, cytoplasm, and ribosomes, but a eukaryotic cell is typically larger than a prokaryotic cell, has a true nucleus (meaning its DNA is surrounded by a membrane), and has other membrane-bound organelles that allow for compartmentalization of functions. Eukaryotic cells tend to be 10 to 100 times the size of prokaryotic cells.<\/p>\n<\/div>\n

      Check Your Understanding<\/strong><\/h2>\n

      Answer the question(s) below to see how well you understand the topics covered in the previous section. This short quiz does\u00a0not<\/strong>\u00a0count toward your grade in the class, and you can retake it an unlimited number of times.<\/p>\n

      Use this quiz to check your understanding and decide whether to (1) study the previous section further or (2) move on to the next section.<\/p>\n

      \t