{"id":553,"date":"2018-05-03T17:45:45","date_gmt":"2018-05-03T17:45:45","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/suny-osbiology2e\/chapter\/prokaryotic-cells\/"},"modified":"2018-06-27T14:17:50","modified_gmt":"2018-06-27T14:17:50","slug":"prokaryotic-cells","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/suny-osbiology2e\/chapter\/prokaryotic-cells\/","title":{"raw":"Prokaryotic Cells","rendered":"Prokaryotic Cells"},"content":{"raw":"<div class=\"textbox learning-objectives\">\r\n<h3>Learning Objectives<\/h3>\r\nBy the end of this section, you will be able to do the following:\r\n<ul>\r\n \t<li>Name examples of prokaryotic and eukaryotic organisms<\/li>\r\n \t<li>Compare and contrast prokaryotic and eukaryotic cells<\/li>\r\n \t<li>Describe the relative sizes of different cells<\/li>\r\n \t<li>Explain why cells must be small<\/li>\r\n<\/ul>\r\n<\/div>\r\n<p id=\"fs-id1961711\">Cells fall into one of two broad categories: prokaryotic and eukaryotic. We classify only the predominantly single-celled organisms Bacteria and Archaea as prokaryotes (pro- = \u201cbefore\u201d; -kary- = \u201cnucleus\u201d). Animal cells, plants, fungi, and protists are all eukaryotes (eu- = \u201ctrue\u201d).<\/p>\r\n\r\n<div id=\"fs-id2215233\" class=\"bc-section section\">\r\n<h3>Components of Prokaryotic Cells<\/h3>\r\n<p id=\"fs-id1801596\">All cells share four common components: 1) a plasma membrane, an outer covering that separates the cell\u2019s interior from its surrounding environment; 2) cytoplasm, consisting of a jelly-like cytosol within the cell in which there are other cellular components; 3) DNA, the cell's genetic material; and 4) ribosomes, which synthesize proteins. However, prokaryotes differ from eukaryotic cells in several ways.<\/p>\r\n<p id=\"fs-id1325738\">A prokaryote is a simple, mostly 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 in the cell's central part: the nucleoid (<a class=\"autogenerated-content\" href=\"#fig-ch04-02-01\">(Figure)<\/a>).<\/p>\r\n\r\n<div id=\"fig-ch04-02-01\" class=\"wp-caption aligncenter\">\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"350\"]<img src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/3206\/2018\/05\/03174538\/Figure_04_02_01.jpg\" alt=\"In this illustration, the prokaryotic cell has an oval shape. The circular chromosome is concentrated in a region called the nucleoid. The fluid inside the cell is called the cytoplasm. Ribosomes, depicted as small circles, float in the cytoplasm. The cytoplasm is encased by a plasma membrane, which in turn is encased by a cell wall. A capsule surrounds the cell wall. The bacterium depicted has a flagellum protruding from one narrow end. Pili are small protrusions that project from the capsule in all directions.\" width=\"350\" height=\"381\" \/> <strong> Figure 1.<\/strong> This figure shows the generalized structure of a prokaryotic cell. All prokaryotes have chromosomal DNA localized in a nucleoid, ribosomes, a cell membrane, and a cell wall. The other structures shown are present in some, but not all, bacteria.[\/caption]\r\n\r\n<\/div>\r\n<p id=\"fs-id1798051\">Most prokaryotes have a peptidoglycan cell wall and many have a polysaccharide capsule (<a class=\"autogenerated-content\" href=\"#fig-ch04-02-01\">(Figure)<\/a>). 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. Pili exchange genetic material during conjugation, the process by which one bacterium transfers genetic material to another through direct contact. Bacteria use fimbriae to attach to a host cell.<\/p>\r\n\r\n<div id=\"fs-id1193831\" class=\"career textbox examples\">\r\n<h3>Career Connection<\/h3>\r\n<p id=\"fs-id1056900\"><strong>Microbiologist<\/strong><\/p>\r\nThe most effective action anyone can take to prevent the spread of contagious illnesses is to wash his or her hands. Why? Because microbes (organisms so tiny that they can only be seen with microscopes) are ubiquitous. They live on doorknobs, money, your hands, and many other surfaces. If someone sneezes into his hand and touches a doorknob, and afterwards you touch that same doorknob, the microbes from the sneezer\u2019s mucus are now on your hands. If you touch your hands to your mouth, nose, or eyes, those microbes can enter your body and could make you sick.\r\n<p id=\"fs-id1627806\">However, not all microbes (also called microorganisms) cause disease; most are actually beneficial. You have microbes in your gut that make vitamin K. Other microorganisms are used to ferment beer and wine.<\/p>\r\n<p id=\"fs-id1904890\">Microbiologists are scientists who study microbes. Microbiologists can pursue a number of careers. Not only do they work in the food industry, they are also employed in the veterinary and medical fields. They can work in the pharmaceutical sector, serving key roles in research and development by identifying new antibiotic sources that can treat bacterial infections.<\/p>\r\n<p id=\"fs-id2028947\">Environmental microbiologists may look for new ways to use specially selected or genetically engineered microbes to remove pollutants from soil or groundwater, as well as hazardous elements from contaminated sites. We call using these microbes bioremediation technologies. Microbiologists can also work in the bioinformatics field, providing specialized knowledge and insight for designing, developing, and specificity of computer models of, for example, bacterial epidemics.<\/p>\r\n\r\n<\/div>\r\n<div id=\"fs-id1889993\" class=\"bc-section section\">\r\n<h4>Cell Size<\/h4>\r\n<p id=\"fs-id1775152\">At 0.1 to 5.0 \u03bcm in diameter, prokaryotic cells are significantly smaller than eukaryotic cells, which have diameters ranging from 10 to 100 \u03bcm (<a class=\"autogenerated-content\" href=\"#fig-ch04-02-02\">(Figure)<\/a>). The prokaryotes' small size allows ions and organic molecules that enter them to quickly diffuse to other parts of the cell. Similarly, any wastes produced within a prokaryotic cell can quickly diffuse. This is not the case in eukaryotic cells, which have developed different structural adaptations to enhance intracellular transport.<\/p>\r\n\r\n<div id=\"fig-ch04-02-02\">\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"450\"]<img src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/3206\/2018\/05\/03174541\/Figure_04_02_02.png\" alt=\"Part a: Relative sizes on a logarithmic scale, from 0.1 nm to 1 m, are shown. Objects are shown from smallest to largest. The smallest object shown, an atom, is about 1 nm in size. The next largest objects shown are lipids and proteins; these molecules are between 1 and 10 nm. Bacteria are about 100 nm, and mitochondria are about 1 greek mu m. Plant and animal cells are both between 10 and 100 greek mu m. A human egg is between 100 greek mu m and 1 mm. A frog egg is about 1 mm, A chicken egg and an ostrich egg are both between 10 and 100 mm, but a chicken egg is larger. For comparison, a human is approximately 1 m tall.\" width=\"450\" height=\"1382\" \/> <strong>Figure 2. <\/strong>This figure shows relative sizes of microbes on a logarithmic scale (recall that each unit of increase in a logarithmic scale represents a 10-fold increase in the quantity measured).[\/caption]\r\n\r\n<\/div>\r\n<p id=\"fs-id1443691\">Small size, in general, is necessary for all cells, whether prokaryotic or eukaryotic. Let\u2019s examine why that is so. First, we\u2019ll consider the area and volume of a typical cell. Not all cells are spherical in shape, but most tend to approximate a sphere. You may remember from your high school geometry course that the formula for the surface area of a sphere is 4\u03c0r<sup>2<\/sup>, while the formula for its volume is 4\u03c0r<sup>3<\/sup>\/3. Thus, as the radius of a cell increases, its surface area increases as the square of its radius, but its volume increases as the cube of its radius (much more rapidly). Therefore, as a cell increases in size, its surface area-to-volume ratio decreases. This same principle would apply if the cell had a cube shape (<a class=\"autogenerated-content\" href=\"#fig-ch04-02-03\">(Figure)<\/a>). If the cell grows too large, the plasma membrane will not have sufficient surface area to support the rate of diffusion required for the increased volume. In other words, as a cell grows, it becomes less efficient. One way to become more efficient is to divide. Another way is to develop organelles that perform specific tasks. These adaptations lead to developing more sophisticated cells, which we call eukaryotic cells.<\/p>\r\n\r\n<div>\r\n<div class=\"textbox examples\">\r\n<h3>Art Connection<\/h3>\r\n[caption id=\"\" align=\"aligncenter\" width=\"350\"]<img src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/3206\/2018\/05\/03174544\/Figure_04_02_03.png\" alt=\"On the left, a sphere 1 mm in diameter is encased in a box of the same width. On the right, the same sphere is encased in a box 2 mm in diameter.\" width=\"350\" height=\"157\" \/> <strong>Figure 3. <\/strong>Notice that as a cell increases in size, its surface area-to-volume ratio decreases. When there is insufficient surface area to support a cell\u2019s increasing volume, a cell will either divide or die. The cell on the left has a volume of 1 mm3 and a surface area of 6 mm2, with a surface area-to-volume ratio of 6 to 1; whereas, the cell on the right has a volume of 8 mm3 and a surface area of 24 mm2, with a surface area-to-volume ratio of 3 to 1.[\/caption]\r\n\r\nProkaryotic cells are much smaller than eukaryotic cells. What advantages might small cell size confer on a cell? What advantages might large cell size have?\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-id1857265\" class=\"summary textbox key-takeaways\">\r\n<h3>Section Summary<\/h3>\r\n<p id=\"fs-id1320930\">Prokaryotes are single-celled organisms of the domains Bacteria and Archaea. All prokaryotes have plasma membranes, cytoplasm, ribosomes, and DNA that is not membrane-bound. Most have peptidoglycan cell walls and many have polysaccharide capsules. Prokaryotic cells range in diameter from 0.1 to 5.0 \u03bcm.<\/p>\r\n<p id=\"fs-id1320804\">As a cell increases in size, its surface area-to-volume ratio decreases. If the cell grows too large, the plasma membrane will not have sufficient surface area to support the rate of diffusion required for the increased volume.<\/p>\r\n\r\n<\/div>\r\n<div id=\"fs-id1428749\" class=\"art-exercise\">\r\n<h3>Art Connections<\/h3>\r\n<div id=\"fs-id2339526\">\r\n<div id=\"fs-id1772038\">\r\n<p id=\"fs-id1130356\"><a class=\"autogenerated-content\" href=\"#fig-ch04-02-03\">(Figure)<\/a> Prokaryotic cells are much smaller than eukaryotic cells. What advantages might small cell size confer on a cell? What advantages might large cell size have?<\/p>\r\n\r\n<\/div>\r\n[reveal-answer q=\"fs-id1299772\"]Show Solution[\/reveal-answer]\r\n[hidden-answer a=\"fs-id1299772\"]\r\n<div id=\"fs-id1299772\">\r\n\r\n<a class=\"autogenerated-content\" href=\"#fig-ch04-02-03\">(Figure)<\/a> Substances can diffuse more quickly through small cells. Small cells have no need for organelles and therefore do not need to expend energy getting substances across organelle membranes. Large cells have organelles that can separate cellular processes, enabling them to build molecules that are more complex.\r\n\r\n<\/div>\r\n[\/hidden-answer]\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-id1981423\" class=\"multiple-choice textbox exercises\">\r\n<h3>Review Questions<\/h3>\r\n<div id=\"fs-id1617238\">\r\n<div id=\"fs-id1361215\">\r\n<p id=\"fs-id840966\">Prokaryotes depend on ________ to obtain some materials and to get rid of wastes.<\/p>\r\n\r\n<ol id=\"fs-id1521301\" type=\"a\">\r\n \t<li>ribosomes<\/li>\r\n \t<li>flagella<\/li>\r\n \t<li>cell division<\/li>\r\n \t<li>diffusion<\/li>\r\n<\/ol>\r\n<\/div>\r\n<div>\r\n<p id=\"fs-id1452099\">[reveal-answer q=\"787839\"]Show Solution[\/reveal-answer]\r\n[hidden-answer a=\"787839\"]<\/p>\r\nD[\/hidden-answer]\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-id866358\">\r\n<div id=\"fs-id1677125\">\r\n<p id=\"fs-id1222779\">Bacteria that lack fimbriae are less likely to ________.<\/p>\r\n\r\n<ol id=\"fs-id1684505\" type=\"a\">\r\n \t<li>adhere to cell surfaces<\/li>\r\n \t<li>swim through bodily fluids<\/li>\r\n \t<li>synthesize proteins<\/li>\r\n \t<li>retain the ability to divide<\/li>\r\n<\/ol>\r\n<\/div>\r\n[reveal-answer q=\"fs-id2017833\"]Show Solution[\/reveal-answer]\r\n[hidden-answer a=\"fs-id2017833\"]\r\n<div id=\"fs-id2017833\">\r\n<p id=\"fs-id1322813\">A<\/p>\r\n\r\n<\/div>\r\n[\/hidden-answer]\r\n\r\n<\/div>\r\n<div id=\"fs-idm71000708\">\r\n<div id=\"fs-idp81418435\">\r\n<p id=\"fs-idm74380420\">Which of the following organisms is a prokaryote?<\/p>\r\n\r\n<ol id=\"fs-idm67922759\" type=\"a\">\r\n \t<li>amoeba<\/li>\r\n \t<li>influenza A virus<\/li>\r\n \t<li>charophyte algae<\/li>\r\n \t<li><em>E. coli<\/em><\/li>\r\n<\/ol>\r\n<\/div>\r\n[reveal-answer q=\"fs-idm40512363\"]Show Solution[\/reveal-answer]\r\n[hidden-answer a=\"fs-idm40512363\"]\r\n<div id=\"fs-idm40512363\">\r\n<p id=\"fs-idm200102069\">D<\/p>\r\n\r\n<\/div>\r\n[\/hidden-answer]\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-id1585726\" class=\"free-response textbox exercises\">\r\n<h3>Free Response<\/h3>\r\n<div>\r\n<div id=\"fs-id1421134\">\r\n<p id=\"fs-id1981261\">Antibiotics are medicines that are used to fight bacterial infections. These medicines kill prokaryotic cells without harming human cells. What part or parts of the bacterial cell do you think antibiotics target? Why?<\/p>\r\n\r\n<\/div>\r\n[reveal-answer q=\"fs-id1194561\"]Show Solution[\/reveal-answer]\r\n[hidden-answer a=\"fs-id1194561\"]\r\n<div id=\"fs-id1194561\">\r\n<p id=\"fs-id1194361\">The cell wall would be targeted by antibiotics as well as the bacteria\u2019s ability to replicate. This would inhibit the bacteria\u2019s ability to reproduce, and it would compromise its defense mechanisms.<\/p>\r\n\r\n<\/div>\r\n[\/hidden-answer]\r\n\r\n<\/div>\r\n<div id=\"fs-id1195128\">\r\n<div>\r\n<p id=\"fs-id1310945\">Explain why not all microbes are harmful.<\/p>\r\n\r\n<\/div>\r\n[reveal-answer q=\"fs-id1407738\"]Show Solution[\/reveal-answer]\r\n[hidden-answer a=\"fs-id1407738\"]\r\n<div id=\"fs-id1407738\">\r\n<p id=\"fs-id1214893\">Some microbes are beneficial. For instance, <em>E. coli <\/em>bacteria populate the human gut and help break down fiber in the diet. Some foods such as yogurt are formed by bacteria.<\/p>\r\n\r\n<\/div>\r\n[\/hidden-answer]\r\n\r\n<\/div>\r\n<\/div>\r\n<div class=\"textbox shaded\">\r\n<h3>Glossary<\/h3>\r\n<dl id=\"fs-id1330398\">\r\n \t<dt>nucleoid<\/dt>\r\n \t<dd id=\"fs-id1227229\">central part of a prokaryotic cell's central part where the chromosome is located<\/dd>\r\n<\/dl>\r\n<dl id=\"fs-id1703590\">\r\n \t<dt>prokaryote<\/dt>\r\n \t<dd id=\"fs-id1338820\">unicellular organism that lacks a nucleus or any other membrane-bound organelle<\/dd>\r\n<\/dl>\r\n<\/div>","rendered":"<div class=\"textbox learning-objectives\">\n<h3>Learning Objectives<\/h3>\n<p>By the end of this section, you will be able to do the following:<\/p>\n<ul>\n<li>Name examples of prokaryotic and eukaryotic organisms<\/li>\n<li>Compare and contrast prokaryotic and eukaryotic cells<\/li>\n<li>Describe the relative sizes of different cells<\/li>\n<li>Explain why cells must be small<\/li>\n<\/ul>\n<\/div>\n<p id=\"fs-id1961711\">Cells fall into one of two broad categories: prokaryotic and eukaryotic. We classify only the predominantly single-celled organisms Bacteria and Archaea as prokaryotes (pro- = \u201cbefore\u201d; -kary- = \u201cnucleus\u201d). Animal cells, plants, fungi, and protists are all eukaryotes (eu- = \u201ctrue\u201d).<\/p>\n<div id=\"fs-id2215233\" class=\"bc-section section\">\n<h3>Components of Prokaryotic Cells<\/h3>\n<p id=\"fs-id1801596\">All cells share four common components: 1) a plasma membrane, an outer covering that separates the cell\u2019s interior from its surrounding environment; 2) cytoplasm, consisting of a jelly-like cytosol within the cell in which there are other cellular components; 3) DNA, the cell&#8217;s genetic material; and 4) ribosomes, which synthesize proteins. However, prokaryotes differ from eukaryotic cells in several ways.<\/p>\n<p id=\"fs-id1325738\">A prokaryote is a simple, mostly 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 in the cell&#8217;s central part: the nucleoid (<a class=\"autogenerated-content\" href=\"#fig-ch04-02-01\">(Figure)<\/a>).<\/p>\n<div id=\"fig-ch04-02-01\" class=\"wp-caption aligncenter\">\n<div style=\"width: 360px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/3206\/2018\/05\/03174538\/Figure_04_02_01.jpg\" alt=\"In this illustration, the prokaryotic cell has an oval shape. The circular chromosome is concentrated in a region called the nucleoid. The fluid inside the cell is called the cytoplasm. Ribosomes, depicted as small circles, float in the cytoplasm. The cytoplasm is encased by a plasma membrane, which in turn is encased by a cell wall. A capsule surrounds the cell wall. The bacterium depicted has a flagellum protruding from one narrow end. Pili are small protrusions that project from the capsule in all directions.\" width=\"350\" height=\"381\" \/><\/p>\n<p class=\"wp-caption-text\"><strong> Figure 1.<\/strong> This figure shows the generalized structure of a prokaryotic cell. All prokaryotes have chromosomal DNA localized in a nucleoid, ribosomes, a cell membrane, and a cell wall. The other structures shown are present in some, but not all, bacteria.<\/p>\n<\/div>\n<\/div>\n<p id=\"fs-id1798051\">Most prokaryotes have a peptidoglycan cell wall and many have a polysaccharide capsule (<a class=\"autogenerated-content\" href=\"#fig-ch04-02-01\">(Figure)<\/a>). 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. Pili exchange genetic material during conjugation, the process by which one bacterium transfers genetic material to another through direct contact. Bacteria use fimbriae to attach to a host cell.<\/p>\n<div id=\"fs-id1193831\" class=\"career textbox examples\">\n<h3>Career Connection<\/h3>\n<p id=\"fs-id1056900\"><strong>Microbiologist<\/strong><\/p>\n<p>The most effective action anyone can take to prevent the spread of contagious illnesses is to wash his or her hands. Why? Because microbes (organisms so tiny that they can only be seen with microscopes) are ubiquitous. They live on doorknobs, money, your hands, and many other surfaces. If someone sneezes into his hand and touches a doorknob, and afterwards you touch that same doorknob, the microbes from the sneezer\u2019s mucus are now on your hands. If you touch your hands to your mouth, nose, or eyes, those microbes can enter your body and could make you sick.<\/p>\n<p id=\"fs-id1627806\">However, not all microbes (also called microorganisms) cause disease; most are actually beneficial. You have microbes in your gut that make vitamin K. Other microorganisms are used to ferment beer and wine.<\/p>\n<p id=\"fs-id1904890\">Microbiologists are scientists who study microbes. Microbiologists can pursue a number of careers. Not only do they work in the food industry, they are also employed in the veterinary and medical fields. They can work in the pharmaceutical sector, serving key roles in research and development by identifying new antibiotic sources that can treat bacterial infections.<\/p>\n<p id=\"fs-id2028947\">Environmental microbiologists may look for new ways to use specially selected or genetically engineered microbes to remove pollutants from soil or groundwater, as well as hazardous elements from contaminated sites. We call using these microbes bioremediation technologies. Microbiologists can also work in the bioinformatics field, providing specialized knowledge and insight for designing, developing, and specificity of computer models of, for example, bacterial epidemics.<\/p>\n<\/div>\n<div id=\"fs-id1889993\" class=\"bc-section section\">\n<h4>Cell Size<\/h4>\n<p id=\"fs-id1775152\">At 0.1 to 5.0 \u03bcm in diameter, prokaryotic cells are significantly smaller than eukaryotic cells, which have diameters ranging from 10 to 100 \u03bcm (<a class=\"autogenerated-content\" href=\"#fig-ch04-02-02\">(Figure)<\/a>). The prokaryotes&#8217; small size allows ions and organic molecules that enter them to quickly diffuse to other parts of the cell. Similarly, any wastes produced within a prokaryotic cell can quickly diffuse. This is not the case in eukaryotic cells, which have developed different structural adaptations to enhance intracellular transport.<\/p>\n<div id=\"fig-ch04-02-02\">\n<div style=\"width: 460px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/3206\/2018\/05\/03174541\/Figure_04_02_02.png\" alt=\"Part a: Relative sizes on a logarithmic scale, from 0.1 nm to 1 m, are shown. Objects are shown from smallest to largest. The smallest object shown, an atom, is about 1 nm in size. The next largest objects shown are lipids and proteins; these molecules are between 1 and 10 nm. Bacteria are about 100 nm, and mitochondria are about 1 greek mu m. Plant and animal cells are both between 10 and 100 greek mu m. A human egg is between 100 greek mu m and 1 mm. A frog egg is about 1 mm, A chicken egg and an ostrich egg are both between 10 and 100 mm, but a chicken egg is larger. For comparison, a human is approximately 1 m tall.\" width=\"450\" height=\"1382\" \/><\/p>\n<p class=\"wp-caption-text\"><strong>Figure 2. <\/strong>This figure shows relative sizes of microbes on a logarithmic scale (recall that each unit of increase in a logarithmic scale represents a 10-fold increase in the quantity measured).<\/p>\n<\/div>\n<\/div>\n<p id=\"fs-id1443691\">Small size, in general, is necessary for all cells, whether prokaryotic or eukaryotic. Let\u2019s examine why that is so. First, we\u2019ll consider the area and volume of a typical cell. Not all cells are spherical in shape, but most tend to approximate a sphere. You may remember from your high school geometry course that the formula for the surface area of a sphere is 4\u03c0r<sup>2<\/sup>, while the formula for its volume is 4\u03c0r<sup>3<\/sup>\/3. Thus, as the radius of a cell increases, its surface area increases as the square of its radius, but its volume increases as the cube of its radius (much more rapidly). Therefore, as a cell increases in size, its surface area-to-volume ratio decreases. This same principle would apply if the cell had a cube shape (<a class=\"autogenerated-content\" href=\"#fig-ch04-02-03\">(Figure)<\/a>). If the cell grows too large, the plasma membrane will not have sufficient surface area to support the rate of diffusion required for the increased volume. In other words, as a cell grows, it becomes less efficient. One way to become more efficient is to divide. Another way is to develop organelles that perform specific tasks. These adaptations lead to developing more sophisticated cells, which we call eukaryotic cells.<\/p>\n<div>\n<div class=\"textbox examples\">\n<h3>Art Connection<\/h3>\n<div style=\"width: 360px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/3206\/2018\/05\/03174544\/Figure_04_02_03.png\" alt=\"On the left, a sphere 1 mm in diameter is encased in a box of the same width. On the right, the same sphere is encased in a box 2 mm in diameter.\" width=\"350\" height=\"157\" \/><\/p>\n<p class=\"wp-caption-text\"><strong>Figure 3. <\/strong>Notice that as a cell increases in size, its surface area-to-volume ratio decreases. When there is insufficient surface area to support a cell\u2019s increasing volume, a cell will either divide or die. The cell on the left has a volume of 1 mm3 and a surface area of 6 mm2, with a surface area-to-volume ratio of 6 to 1; whereas, the cell on the right has a volume of 8 mm3 and a surface area of 24 mm2, with a surface area-to-volume ratio of 3 to 1.<\/p>\n<\/div>\n<p>Prokaryotic cells are much smaller than eukaryotic cells. What advantages might small cell size confer on a cell? What advantages might large cell size have?<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div id=\"fs-id1857265\" class=\"summary textbox key-takeaways\">\n<h3>Section Summary<\/h3>\n<p id=\"fs-id1320930\">Prokaryotes are single-celled organisms of the domains Bacteria and Archaea. All prokaryotes have plasma membranes, cytoplasm, ribosomes, and DNA that is not membrane-bound. Most have peptidoglycan cell walls and many have polysaccharide capsules. Prokaryotic cells range in diameter from 0.1 to 5.0 \u03bcm.<\/p>\n<p id=\"fs-id1320804\">As a cell increases in size, its surface area-to-volume ratio decreases. If the cell grows too large, the plasma membrane will not have sufficient surface area to support the rate of diffusion required for the increased volume.<\/p>\n<\/div>\n<div id=\"fs-id1428749\" class=\"art-exercise\">\n<h3>Art Connections<\/h3>\n<div id=\"fs-id2339526\">\n<div id=\"fs-id1772038\">\n<p id=\"fs-id1130356\"><a class=\"autogenerated-content\" href=\"#fig-ch04-02-03\">(Figure)<\/a> Prokaryotic cells are much smaller than eukaryotic cells. What advantages might small cell size confer on a cell? What advantages might large cell size have?<\/p>\n<\/div>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"qfs-id1299772\">Show Solution<\/span><\/p>\n<div id=\"qfs-id1299772\" class=\"hidden-answer\" style=\"display: none\">\n<div id=\"fs-id1299772\">\n<p><a class=\"autogenerated-content\" href=\"#fig-ch04-02-03\">(Figure)<\/a> Substances can diffuse more quickly through small cells. Small cells have no need for organelles and therefore do not need to expend energy getting substances across organelle membranes. Large cells have organelles that can separate cellular processes, enabling them to build molecules that are more complex.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div id=\"fs-id1981423\" class=\"multiple-choice textbox exercises\">\n<h3>Review Questions<\/h3>\n<div id=\"fs-id1617238\">\n<div id=\"fs-id1361215\">\n<p id=\"fs-id840966\">Prokaryotes depend on ________ to obtain some materials and to get rid of wastes.<\/p>\n<ol id=\"fs-id1521301\" type=\"a\">\n<li>ribosomes<\/li>\n<li>flagella<\/li>\n<li>cell division<\/li>\n<li>diffusion<\/li>\n<\/ol>\n<\/div>\n<div>\n<p id=\"fs-id1452099\">\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q787839\">Show Solution<\/span><\/p>\n<div id=\"q787839\" class=\"hidden-answer\" style=\"display: none\">\n<p>D<\/p><\/div>\n<\/div>\n<\/div>\n<\/div>\n<div id=\"fs-id866358\">\n<div id=\"fs-id1677125\">\n<p id=\"fs-id1222779\">Bacteria that lack fimbriae are less likely to ________.<\/p>\n<ol id=\"fs-id1684505\" type=\"a\">\n<li>adhere to cell surfaces<\/li>\n<li>swim through bodily fluids<\/li>\n<li>synthesize proteins<\/li>\n<li>retain the ability to divide<\/li>\n<\/ol>\n<\/div>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"qfs-id2017833\">Show Solution<\/span><\/p>\n<div id=\"qfs-id2017833\" class=\"hidden-answer\" style=\"display: none\">\n<div id=\"fs-id2017833\">\n<p id=\"fs-id1322813\">A<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div id=\"fs-idm71000708\">\n<div id=\"fs-idp81418435\">\n<p id=\"fs-idm74380420\">Which of the following organisms is a prokaryote?<\/p>\n<ol id=\"fs-idm67922759\" type=\"a\">\n<li>amoeba<\/li>\n<li>influenza A virus<\/li>\n<li>charophyte algae<\/li>\n<li><em>E. coli<\/em><\/li>\n<\/ol>\n<\/div>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"qfs-idm40512363\">Show Solution<\/span><\/p>\n<div id=\"qfs-idm40512363\" class=\"hidden-answer\" style=\"display: none\">\n<div id=\"fs-idm40512363\">\n<p id=\"fs-idm200102069\">D<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div id=\"fs-id1585726\" class=\"free-response textbox exercises\">\n<h3>Free Response<\/h3>\n<div>\n<div id=\"fs-id1421134\">\n<p id=\"fs-id1981261\">Antibiotics are medicines that are used to fight bacterial infections. These medicines kill prokaryotic cells without harming human cells. What part or parts of the bacterial cell do you think antibiotics target? Why?<\/p>\n<\/div>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"qfs-id1194561\">Show Solution<\/span><\/p>\n<div id=\"qfs-id1194561\" class=\"hidden-answer\" style=\"display: none\">\n<div id=\"fs-id1194561\">\n<p id=\"fs-id1194361\">The cell wall would be targeted by antibiotics as well as the bacteria\u2019s ability to replicate. This would inhibit the bacteria\u2019s ability to reproduce, and it would compromise its defense mechanisms.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div id=\"fs-id1195128\">\n<div>\n<p id=\"fs-id1310945\">Explain why not all microbes are harmful.<\/p>\n<\/div>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"qfs-id1407738\">Show Solution<\/span><\/p>\n<div id=\"qfs-id1407738\" class=\"hidden-answer\" style=\"display: none\">\n<div id=\"fs-id1407738\">\n<p id=\"fs-id1214893\">Some microbes are beneficial. For instance, <em>E. coli <\/em>bacteria populate the human gut and help break down fiber in the diet. Some foods such as yogurt are formed by bacteria.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"textbox shaded\">\n<h3>Glossary<\/h3>\n<dl id=\"fs-id1330398\">\n<dt>nucleoid<\/dt>\n<dd id=\"fs-id1227229\">central part of a prokaryotic cell&#8217;s central part where the chromosome is located<\/dd>\n<\/dl>\n<dl id=\"fs-id1703590\">\n<dt>prokaryote<\/dt>\n<dd id=\"fs-id1338820\">unicellular organism that lacks a nucleus or any other membrane-bound organelle<\/dd>\n<\/dl>\n<\/div>\n\n\t\t\t <section class=\"citations-section\" role=\"contentinfo\">\n\t\t\t <h3>Candela Citations<\/h3>\n\t\t\t\t\t <div>\n\t\t\t\t\t\t <div id=\"citation-list-553\">\n\t\t\t\t\t\t\t <div class=\"licensing\"><div class=\"license-attribution-dropdown-subheading\">CC licensed content, Shared previously<\/div><ul class=\"citation-list\"><li>Biology 2e. <strong>Provided by<\/strong>: OpenStax. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"https:\/\/openstax.org\/details\/books\/biology-2e\">https:\/\/openstax.org\/details\/books\/biology-2e<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY: Attribution<\/a><\/em>. <strong>License Terms<\/strong>: Download for free at http:\/\/cnx.org\/contents\/8d50a0af-948b-4204-a71d-4826cba765b8@8.19<\/li><\/ul><\/div>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t <\/div>\n\t\t\t <\/section>","protected":false},"author":311,"menu_order":3,"template":"","meta":{"_candela_citation":"[{\"type\":\"cc\",\"description\":\"Biology 2e\",\"author\":\"\",\"organization\":\"OpenStax\",\"url\":\"https:\/\/openstax.org\/details\/books\/biology-2e\",\"project\":\"\",\"license\":\"cc-by\",\"license_terms\":\"Download for free at http:\/\/cnx.org\/contents\/8d50a0af-948b-4204-a71d-4826cba765b8@8.19\"}]","CANDELA_OUTCOMES_GUID":"","pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-553","chapter","type-chapter","status-publish","hentry"],"part":542,"_links":{"self":[{"href":"https:\/\/courses.lumenlearning.com\/suny-osbiology2e\/wp-json\/pressbooks\/v2\/chapters\/553","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/courses.lumenlearning.com\/suny-osbiology2e\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/courses.lumenlearning.com\/suny-osbiology2e\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-osbiology2e\/wp-json\/wp\/v2\/users\/311"}],"version-history":[{"count":3,"href":"https:\/\/courses.lumenlearning.com\/suny-osbiology2e\/wp-json\/pressbooks\/v2\/chapters\/553\/revisions"}],"predecessor-version":[{"id":2443,"href":"https:\/\/courses.lumenlearning.com\/suny-osbiology2e\/wp-json\/pressbooks\/v2\/chapters\/553\/revisions\/2443"}],"part":[{"href":"https:\/\/courses.lumenlearning.com\/suny-osbiology2e\/wp-json\/pressbooks\/v2\/parts\/542"}],"metadata":[{"href":"https:\/\/courses.lumenlearning.com\/suny-osbiology2e\/wp-json\/pressbooks\/v2\/chapters\/553\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/courses.lumenlearning.com\/suny-osbiology2e\/wp-json\/wp\/v2\/media?parent=553"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-osbiology2e\/wp-json\/pressbooks\/v2\/chapter-type?post=553"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-osbiology2e\/wp-json\/wp\/v2\/contributor?post=553"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-osbiology2e\/wp-json\/wp\/v2\/license?post=553"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}