{"id":662,"date":"2018-05-03T17:58:37","date_gmt":"2018-05-03T17:58:37","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/suny-osbiology2e\/chapter\/metabolism-without-oxygen\/"},"modified":"2018-06-27T17:10:32","modified_gmt":"2018-06-27T17:10:32","slug":"metabolism-without-oxygen","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/suny-osbiology2e\/chapter\/metabolism-without-oxygen\/","title":{"raw":"Metabolism without Oxygen","rendered":"Metabolism without Oxygen"},"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>Discuss the fundamental difference between anaerobic cellular respiration and fermentation<\/li>\r\n \t<li>Describe the type of fermentation that readily occurs in animal cells and the conditions that initiate that fermentation<\/li>\r\n<\/ul>\r\n<\/div>\r\n<p id=\"fs-id1982002\">In aerobic respiration, the final electron acceptor is an oxygen molecule, O<sub>2<\/sub>. If aerobic respiration occurs, then ATP will be produced using the energy of high-energy electrons carried by NADH or FADH<sub>2 <\/sub>to the electron transport chain. If aerobic respiration does not occur, NADH must be reoxidized to NAD<sup>+<\/sup> for reuse as an electron carrier for the glycolytic pathway to continue. How is this done? Some living systems use an organic molecule as the final electron acceptor. Processes that use an organic molecule to regenerate NAD<sup>+<\/sup> from NADH are collectively referred to as fermentation. In contrast, some living systems use an inorganic molecule as a final electron acceptor. Both methods are called anaerobic cellular respiration, in which organisms convert energy for their use in the absence of oxygen.<\/p>\r\n\r\n<div class=\"bc-section section\">\r\n<h3>Anaerobic Cellular Respiration<\/h3>\r\nCertain prokaryotes, including some species in the domains Bacteria and Archaea, use anaerobic respiration. For example, a group of archaeans called methanogens reduces carbon dioxide to methane to oxidize NADH. These microorganisms are found in soil and in the digestive tracts of ruminants, such as cows and sheep. Similarly, sulfate-reducing bacteria, most of which are anaerobic (<a class=\"autogenerated-content\" href=\"#fig-ch07_05_01\">(Figure)<\/a>), reduce sulfate to hydrogen sulfide to regenerate NAD<sup>+<\/sup> from NADH.\r\n<div id=\"fig-ch07_05_01\" class=\"wp-caption aligncenter\">\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"400\"]<img src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/3206\/2018\/05\/03175831\/Figure_07_05_01.jpg\" alt=\"This photo shows a bloom of green bacteria in water.\" width=\"400\" height=\"423\" \/> <strong>Figure 1. <\/strong>The green color seen in these coastal waters is from an eruption of hydrogen sulfide\u2013producing bacteria. These anaerobic, sulfate-reducing bacteria release hydrogen sulfide gas as they decompose algae in the water. (credit: modification of work by NASA\/Jeff Schmaltz, MODIS Land Rapid Response Team at NASA GSFC, Visible Earth Catalog of NASA images)[\/caption]\r\n\r\n<\/div>\r\n<div class=\"interactive textbox tryit\">\r\n<h3>Link to Learning<\/h3>\r\n<p id=\"fs-id1957291\">Visit this <a href=\"http:\/\/openstaxcollege.org\/l\/fermentation\" target=\"_window\">site<\/a> to see anaerobic cellular respiration in action.<\/p>\r\n\r\n<\/div>\r\n<div id=\"fs-id2121627\" class=\"bc-section section\">\r\n<h4>Lactic Acid Fermentation<\/h4>\r\n<p id=\"fs-id2077122\">The fermentation method used by animals and certain bacteria, such as those in yogurt, is lactic acid fermentation (<a class=\"autogenerated-content\" href=\"#fig-ch07_05_02\">(Figure)<\/a>). This type of fermentation is used routinely in mammalian red blood cells, which do not have mitochondria, and in skeletal muscle that has an insufficient oxygen supply to allow aerobic respiration to continue (that is, in muscles used to the point of fatigue). In muscles, lactic acid accumulation must be removed by the blood circulation, and when the lactic acid loses a hydrogen, the resulting lactate is brought to the liver for further metabolism. The chemical reactions of lactic acid fermentation are the following:<\/p>\r\n\r\n<div id=\"eip-345\">[latex]\\text{Pyruvic acid}+\\text{NADH}\u2194\\text{lactic acid}+{\\text{NAD}}^{+}[\/latex]<\/div>\r\n<p id=\"fs-id2197931\">The enzyme used in this reaction is lactate dehydrogenase (LDH). The reaction can proceed in either direction, but the reaction from left to right is inhibited by acidic conditions. Such lactic acid accumulation was once believed to cause muscle stiffness, fatigue, and soreness, although more recent research disputes this hypothesis. Once the lactic acid has been removed from the muscle and circulated to the liver, it can be reconverted into pyruvic acid and further catabolized for energy.<\/p>\r\n\r\n<div id=\"fs-id2123848\" class=\"art-connection textbox examples\">\r\n<h3>Art Connection<\/h3>\r\n<div id=\"fig-ch07_05_02\" class=\"wp-caption aligncenter\">\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"320\"]<img src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/3206\/2018\/05\/03175834\/Figure_07_05_02.png\" alt=\"This illustration shows that during glycolysis, glucose is broken down into two pyruvate molecules and, in the process, two NADH are formed from NAD^{+}. During lactic acid fermentation, the two pyruvate molecules are converted into lactate, and NADH is recycled back into NAD^{+}.\" width=\"320\" height=\"697\" \/> <strong>Figure 2. <\/strong>Lactic acid fermentation is common in muscle cells that have run out of oxygen.[\/caption]\r\n\r\n<\/div>\r\nTremetol, a metabolic poison found in the white snakeroot plant, prevents the metabolism of lactate. When cows eat this plant, tremetol is concentrated in the milk they produce. Humans who consume the milk can become seriously ill. Symptoms of this disease, which include vomiting, abdominal pain, and tremors, become worse after exercise. Why do you think this is the case?\r\n\r\n[reveal-answer q=\"175191\"]Show Solution[\/reveal-answer]\r\n[hidden-answer a=\"175191\"]\r\n\r\nThe illness is caused by lactate accumulation. Lactate levels rise after exercise, making the symptoms worse. Milk sickness is rare today, but was common in the Midwestern United States in the early 1800s.\r\n\r\n[\/hidden-answer]\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-id2025525\" class=\"bc-section section\">\r\n<h4>Alcohol Fermentation<\/h4>\r\nAnother familiar fermentation process is alcohol fermentation (<a class=\"autogenerated-content\" href=\"#fig-ch07_05_03\">(Figure)<\/a>), which produces ethanol. The first chemical reaction of alcohol fermentation is the following (CO<sub>2<\/sub> does not participate in the second reaction):\r\n<div id=\"eip-10\">[latex]\\text{pyruvic acid}+{\\text{H}}^{+}\\to {\\text{CO}}_{2}+\\text{acetaldehyde}+\\text{NADH}+{\\text{H}}^{+}\\to \\text{ethanol}+{\\text{NAD}}^{+}[\/latex]<\/div>\r\n<p id=\"fs-id1986576\">The first reaction is catalyzed by pyruvate decarboxylase, a cytoplasmic enzyme, with a coenzyme of thiamine pyrophosphate (TPP, derived from vitamin B<sub>1<\/sub> and also called thiamine). A carboxyl group is removed from pyruvic acid, releasing carbon dioxide as a gas. The loss of carbon dioxide reduces the size of the molecule by one carbon, producing acetaldehyde. The second reaction is catalyzed by alcohol dehydrogenase to oxidize NADH to NAD<sup>+<\/sup> and reduce acetaldehyde to ethanol. The fermentation of pyruvic acid by yeast produces the ethanol found in alcoholic beverages. Ethanol tolerance of yeast is variable, ranging from about 5 percent to 21 percent, depending on the yeast strain and environmental conditions.<\/p>\r\n\r\n<div id=\"fig-ch07_05_03\" 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\/03175836\/Figure_07_05_03.jpg\" alt=\"This photo shows large cylindrical fermentation tanks stacked one on top of the other.\" width=\"350\" height=\"432\" \/> <strong>Figure 3. <\/strong>Fermentation of grape juice into wine produces CO2 as a byproduct. Fermentation tanks have valves so that the pressure inside the tanks created by the carbon dioxide produced can be released.[\/caption]\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-id811872\" class=\"bc-section section\">\r\n<h4>Other Types of Fermentation<\/h4>\r\n<p id=\"fs-id2317124\">Other fermentation methods take place in bacteria. We should note that many prokaryotes are <em>facultatively<\/em> anaerobic. This means that they can switch between aerobic respiration and fermentation, depending on the availability of free oxygen. Certain prokaryotes, such as <em>Clostridia<\/em>, are obligate anaerobes. Obligate anaerobes live and grow in the absence of molecular oxygen. Oxygen is a poison to these microorganisms and kills them on exposure. We should also note that all forms of fermentation, except lactic acid fermentation, produce gas. The production of particular types of gas is used as an indicator of the fermentation of specific carbohydrates, which plays a role in the laboratory identification of the bacteria. Various methods of fermentation are used by assorted organisms to ensure an adequate supply of NAD<sup>+<\/sup> for the sixth step in glycolysis. Without these pathways, this step would not occur, and ATP could not be harvested from the breakdown of glucose.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<div id=\"fs-id1342929\" class=\"summary textbox key-takeaways\">\r\n<h3>Section Summary<\/h3>\r\n<p id=\"fs-id2235232\">If NADH cannot be oxidized through aerobic respiration, another electron acceptor is used. Most organisms will use some form of fermentation to accomplish the regeneration of NAD<sup>+<\/sup>, ensuring the continuation of glycolysis. The regeneration of NAD<sup>+<\/sup> in fermentation is not accompanied by ATP production; therefore, the potential of NADH to produce ATP using an electron transport chain is not utilized.<\/p>\r\n\r\n<\/div>\r\n<div id=\"fs-idp361376\" class=\"art-exercise\">\r\n<h3>Art Connections<\/h3>\r\n<div id=\"fs-idp22236752\">\r\n<div id=\"fs-idp26658304\">\r\n<p id=\"fs-idp61363968\">(<a class=\"autogenerated-content\" href=\"#fig-ch07_05_02\">(Figure)<\/a>) Tremetol, a metabolic poison found in the white snake root plant, prevents the metabolism of lactate. When cows eat this plant, tremetol is concentrated in the milk they produce. Humans who consume the milk can become seriously ill. Symptoms of this disease, which include vomiting, abdominal pain, and tremors, become worse after exercise. Why do you think this is the case?<\/p>\r\n\r\n<\/div>\r\n<div id=\"fs-idp63639536\">\r\n<p id=\"fs-idp125692288\">[reveal-answer q=\"541672\"]Show Solution[\/reveal-answer]\r\n[hidden-answer a=\"541672\"]<\/p>\r\n<a href=\"#fig-ch07_05_02\">(Figure)<\/a> The illness is caused by lactate accumulation. Lactate levels rise after exercise, making the symptoms worse. Milk sickness is rare today but was common in the midwestern United States in the early 1800s.\r\n\r\n[\/hidden-answer]\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div class=\"multiple-choice textbox exercises\">\r\n<h3>Review Questions<\/h3>\r\n<div>\r\n<div>\r\n\r\nWhich of the following fermentation methods can occur in animal skeletal muscles?\r\n<ol id=\"fs-id2186884\" type=\"a\">\r\n \t<li>lactic acid fermentation<\/li>\r\n \t<li>alcohol fermentation<\/li>\r\n \t<li>mixed acid fermentation<\/li>\r\n \t<li>propionic fermentation<\/li>\r\n<\/ol>\r\n<\/div>\r\n<div id=\"fs-id2571119\">\r\n\r\n[reveal-answer q=\"820149\"]Show Solution[\/reveal-answer]\r\n[hidden-answer a=\"820149\"]\r\n\r\nA[\/hidden-answer]\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div class=\"free-response textbox exercises\">\r\n<h3>Free Response<\/h3>\r\n<div id=\"fs-id2574316\">\r\n<div>\r\n\r\nWhat is the primary difference between fermentation and anaerobic respiration?\r\n\r\n<\/div>\r\n<div id=\"fs-id1798390\">\r\n\r\n[reveal-answer q=\"794122\"]Show Solution[\/reveal-answer]\r\n[hidden-answer a=\"794122\"]\r\n\r\nFermentation uses glycolysis only. Anaerobic respiration uses all three parts of cellular respiration, including the parts in the mitochondria like the citric acid cycle and electron transport; it also uses a different final electron acceptor instead of oxygen gas.[\/hidden-answer]\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div class=\"textbox shaded\">\r\n<h3>Glossary<\/h3>\r\n<dl id=\"fs-id1707504\">\r\n \t<dt>anaerobic cellular respiration<\/dt>\r\n \t<dd id=\"fs-id2200333\">process in which organisms convert energy for their use in the absence of oxygen<\/dd>\r\n<\/dl>\r\n<dl id=\"fs-id1769884\">\r\n \t<dt>fermentation<\/dt>\r\n \t<dd>process of regenerating NAD<sup>+<\/sup> with either an inorganic or organic compound serving as the final electron acceptor; occurs in the absence of oxygen<\/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>Discuss the fundamental difference between anaerobic cellular respiration and fermentation<\/li>\n<li>Describe the type of fermentation that readily occurs in animal cells and the conditions that initiate that fermentation<\/li>\n<\/ul>\n<\/div>\n<p id=\"fs-id1982002\">In aerobic respiration, the final electron acceptor is an oxygen molecule, O<sub>2<\/sub>. If aerobic respiration occurs, then ATP will be produced using the energy of high-energy electrons carried by NADH or FADH<sub>2 <\/sub>to the electron transport chain. If aerobic respiration does not occur, NADH must be reoxidized to NAD<sup>+<\/sup> for reuse as an electron carrier for the glycolytic pathway to continue. How is this done? Some living systems use an organic molecule as the final electron acceptor. Processes that use an organic molecule to regenerate NAD<sup>+<\/sup> from NADH are collectively referred to as fermentation. In contrast, some living systems use an inorganic molecule as a final electron acceptor. Both methods are called anaerobic cellular respiration, in which organisms convert energy for their use in the absence of oxygen.<\/p>\n<div class=\"bc-section section\">\n<h3>Anaerobic Cellular Respiration<\/h3>\n<p>Certain prokaryotes, including some species in the domains Bacteria and Archaea, use anaerobic respiration. For example, a group of archaeans called methanogens reduces carbon dioxide to methane to oxidize NADH. These microorganisms are found in soil and in the digestive tracts of ruminants, such as cows and sheep. Similarly, sulfate-reducing bacteria, most of which are anaerobic (<a class=\"autogenerated-content\" href=\"#fig-ch07_05_01\">(Figure)<\/a>), reduce sulfate to hydrogen sulfide to regenerate NAD<sup>+<\/sup> from NADH.<\/p>\n<div id=\"fig-ch07_05_01\" class=\"wp-caption aligncenter\">\n<div style=\"width: 410px\" 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\/03175831\/Figure_07_05_01.jpg\" alt=\"This photo shows a bloom of green bacteria in water.\" width=\"400\" height=\"423\" \/><\/p>\n<p class=\"wp-caption-text\"><strong>Figure 1. <\/strong>The green color seen in these coastal waters is from an eruption of hydrogen sulfide\u2013producing bacteria. These anaerobic, sulfate-reducing bacteria release hydrogen sulfide gas as they decompose algae in the water. (credit: modification of work by NASA\/Jeff Schmaltz, MODIS Land Rapid Response Team at NASA GSFC, Visible Earth Catalog of NASA images)<\/p>\n<\/div>\n<\/div>\n<div class=\"interactive textbox tryit\">\n<h3>Link to Learning<\/h3>\n<p id=\"fs-id1957291\">Visit this <a href=\"http:\/\/openstaxcollege.org\/l\/fermentation\" target=\"_window\">site<\/a> to see anaerobic cellular respiration in action.<\/p>\n<\/div>\n<div id=\"fs-id2121627\" class=\"bc-section section\">\n<h4>Lactic Acid Fermentation<\/h4>\n<p id=\"fs-id2077122\">The fermentation method used by animals and certain bacteria, such as those in yogurt, is lactic acid fermentation (<a class=\"autogenerated-content\" href=\"#fig-ch07_05_02\">(Figure)<\/a>). This type of fermentation is used routinely in mammalian red blood cells, which do not have mitochondria, and in skeletal muscle that has an insufficient oxygen supply to allow aerobic respiration to continue (that is, in muscles used to the point of fatigue). In muscles, lactic acid accumulation must be removed by the blood circulation, and when the lactic acid loses a hydrogen, the resulting lactate is brought to the liver for further metabolism. The chemical reactions of lactic acid fermentation are the following:<\/p>\n<div id=\"eip-345\">[latex]\\text{Pyruvic acid}+\\text{NADH}\u2194\\text{lactic acid}+{\\text{NAD}}^{+}[\/latex]<\/div>\n<p id=\"fs-id2197931\">The enzyme used in this reaction is lactate dehydrogenase (LDH). The reaction can proceed in either direction, but the reaction from left to right is inhibited by acidic conditions. Such lactic acid accumulation was once believed to cause muscle stiffness, fatigue, and soreness, although more recent research disputes this hypothesis. Once the lactic acid has been removed from the muscle and circulated to the liver, it can be reconverted into pyruvic acid and further catabolized for energy.<\/p>\n<div id=\"fs-id2123848\" class=\"art-connection textbox examples\">\n<h3>Art Connection<\/h3>\n<div id=\"fig-ch07_05_02\" class=\"wp-caption aligncenter\">\n<div style=\"width: 330px\" 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\/03175834\/Figure_07_05_02.png\" alt=\"This illustration shows that during glycolysis, glucose is broken down into two pyruvate molecules and, in the process, two NADH are formed from NAD^{+}. During lactic acid fermentation, the two pyruvate molecules are converted into lactate, and NADH is recycled back into NAD^{+}.\" width=\"320\" height=\"697\" \/><\/p>\n<p class=\"wp-caption-text\"><strong>Figure 2. <\/strong>Lactic acid fermentation is common in muscle cells that have run out of oxygen.<\/p>\n<\/div>\n<\/div>\n<p>Tremetol, a metabolic poison found in the white snakeroot plant, prevents the metabolism of lactate. When cows eat this plant, tremetol is concentrated in the milk they produce. Humans who consume the milk can become seriously ill. Symptoms of this disease, which include vomiting, abdominal pain, and tremors, become worse after exercise. Why do you think this is the case?<\/p>\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q175191\">Show Solution<\/span><\/p>\n<div id=\"q175191\" class=\"hidden-answer\" style=\"display: none\">\n<p>The illness is caused by lactate accumulation. Lactate levels rise after exercise, making the symptoms worse. Milk sickness is rare today, but was common in the Midwestern United States in the early 1800s.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div id=\"fs-id2025525\" class=\"bc-section section\">\n<h4>Alcohol Fermentation<\/h4>\n<p>Another familiar fermentation process is alcohol fermentation (<a class=\"autogenerated-content\" href=\"#fig-ch07_05_03\">(Figure)<\/a>), which produces ethanol. The first chemical reaction of alcohol fermentation is the following (CO<sub>2<\/sub> does not participate in the second reaction):<\/p>\n<div id=\"eip-10\">[latex]\\text{pyruvic acid}+{\\text{H}}^{+}\\to {\\text{CO}}_{2}+\\text{acetaldehyde}+\\text{NADH}+{\\text{H}}^{+}\\to \\text{ethanol}+{\\text{NAD}}^{+}[\/latex]<\/div>\n<p id=\"fs-id1986576\">The first reaction is catalyzed by pyruvate decarboxylase, a cytoplasmic enzyme, with a coenzyme of thiamine pyrophosphate (TPP, derived from vitamin B<sub>1<\/sub> and also called thiamine). A carboxyl group is removed from pyruvic acid, releasing carbon dioxide as a gas. The loss of carbon dioxide reduces the size of the molecule by one carbon, producing acetaldehyde. The second reaction is catalyzed by alcohol dehydrogenase to oxidize NADH to NAD<sup>+<\/sup> and reduce acetaldehyde to ethanol. The fermentation of pyruvic acid by yeast produces the ethanol found in alcoholic beverages. Ethanol tolerance of yeast is variable, ranging from about 5 percent to 21 percent, depending on the yeast strain and environmental conditions.<\/p>\n<div id=\"fig-ch07_05_03\" 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\/03175836\/Figure_07_05_03.jpg\" alt=\"This photo shows large cylindrical fermentation tanks stacked one on top of the other.\" width=\"350\" height=\"432\" \/><\/p>\n<p class=\"wp-caption-text\"><strong>Figure 3. <\/strong>Fermentation of grape juice into wine produces CO2 as a byproduct. Fermentation tanks have valves so that the pressure inside the tanks created by the carbon dioxide produced can be released.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<div id=\"fs-id811872\" class=\"bc-section section\">\n<h4>Other Types of Fermentation<\/h4>\n<p id=\"fs-id2317124\">Other fermentation methods take place in bacteria. We should note that many prokaryotes are <em>facultatively<\/em> anaerobic. This means that they can switch between aerobic respiration and fermentation, depending on the availability of free oxygen. Certain prokaryotes, such as <em>Clostridia<\/em>, are obligate anaerobes. Obligate anaerobes live and grow in the absence of molecular oxygen. Oxygen is a poison to these microorganisms and kills them on exposure. We should also note that all forms of fermentation, except lactic acid fermentation, produce gas. The production of particular types of gas is used as an indicator of the fermentation of specific carbohydrates, which plays a role in the laboratory identification of the bacteria. Various methods of fermentation are used by assorted organisms to ensure an adequate supply of NAD<sup>+<\/sup> for the sixth step in glycolysis. Without these pathways, this step would not occur, and ATP could not be harvested from the breakdown of glucose.<\/p>\n<\/div>\n<\/div>\n<div id=\"fs-id1342929\" class=\"summary textbox key-takeaways\">\n<h3>Section Summary<\/h3>\n<p id=\"fs-id2235232\">If NADH cannot be oxidized through aerobic respiration, another electron acceptor is used. Most organisms will use some form of fermentation to accomplish the regeneration of NAD<sup>+<\/sup>, ensuring the continuation of glycolysis. The regeneration of NAD<sup>+<\/sup> in fermentation is not accompanied by ATP production; therefore, the potential of NADH to produce ATP using an electron transport chain is not utilized.<\/p>\n<\/div>\n<div id=\"fs-idp361376\" class=\"art-exercise\">\n<h3>Art Connections<\/h3>\n<div id=\"fs-idp22236752\">\n<div id=\"fs-idp26658304\">\n<p id=\"fs-idp61363968\">(<a class=\"autogenerated-content\" href=\"#fig-ch07_05_02\">(Figure)<\/a>) Tremetol, a metabolic poison found in the white snake root plant, prevents the metabolism of lactate. When cows eat this plant, tremetol is concentrated in the milk they produce. Humans who consume the milk can become seriously ill. Symptoms of this disease, which include vomiting, abdominal pain, and tremors, become worse after exercise. Why do you think this is the case?<\/p>\n<\/div>\n<div id=\"fs-idp63639536\">\n<p id=\"fs-idp125692288\">\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q541672\">Show Solution<\/span><\/p>\n<div id=\"q541672\" class=\"hidden-answer\" style=\"display: none\">\n<p><a href=\"#fig-ch07_05_02\">(Figure)<\/a> The illness is caused by lactate accumulation. Lactate levels rise after exercise, making the symptoms worse. Milk sickness is rare today but was common in the midwestern United States in the early 1800s.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"multiple-choice textbox exercises\">\n<h3>Review Questions<\/h3>\n<div>\n<div>\n<p>Which of the following fermentation methods can occur in animal skeletal muscles?<\/p>\n<ol id=\"fs-id2186884\" type=\"a\">\n<li>lactic acid fermentation<\/li>\n<li>alcohol fermentation<\/li>\n<li>mixed acid fermentation<\/li>\n<li>propionic fermentation<\/li>\n<\/ol>\n<\/div>\n<div id=\"fs-id2571119\">\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q820149\">Show Solution<\/span><\/p>\n<div id=\"q820149\" class=\"hidden-answer\" style=\"display: none\">\n<p>A<\/p><\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"free-response textbox exercises\">\n<h3>Free Response<\/h3>\n<div id=\"fs-id2574316\">\n<div>\n<p>What is the primary difference between fermentation and anaerobic respiration?<\/p>\n<\/div>\n<div id=\"fs-id1798390\">\n<div class=\"qa-wrapper\" style=\"display: block\"><span class=\"show-answer collapsed\" style=\"cursor: pointer\" data-target=\"q794122\">Show Solution<\/span><\/p>\n<div id=\"q794122\" class=\"hidden-answer\" style=\"display: none\">\n<p>Fermentation uses glycolysis only. Anaerobic respiration uses all three parts of cellular respiration, including the parts in the mitochondria like the citric acid cycle and electron transport; it also uses a different final electron acceptor instead of oxygen gas.<\/p><\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"textbox shaded\">\n<h3>Glossary<\/h3>\n<dl id=\"fs-id1707504\">\n<dt>anaerobic cellular respiration<\/dt>\n<dd id=\"fs-id2200333\">process in which organisms convert energy for their use in the absence of oxygen<\/dd>\n<\/dl>\n<dl id=\"fs-id1769884\">\n<dt>fermentation<\/dt>\n<dd>process of regenerating NAD<sup>+<\/sup> with either an inorganic or organic compound serving as the final electron acceptor; occurs in the absence of oxygen<\/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-662\">\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":6,"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-662","chapter","type-chapter","status-publish","hentry"],"part":641,"_links":{"self":[{"href":"https:\/\/courses.lumenlearning.com\/suny-osbiology2e\/wp-json\/pressbooks\/v2\/chapters\/662","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\/662\/revisions"}],"predecessor-version":[{"id":2471,"href":"https:\/\/courses.lumenlearning.com\/suny-osbiology2e\/wp-json\/pressbooks\/v2\/chapters\/662\/revisions\/2471"}],"part":[{"href":"https:\/\/courses.lumenlearning.com\/suny-osbiology2e\/wp-json\/pressbooks\/v2\/parts\/641"}],"metadata":[{"href":"https:\/\/courses.lumenlearning.com\/suny-osbiology2e\/wp-json\/pressbooks\/v2\/chapters\/662\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/courses.lumenlearning.com\/suny-osbiology2e\/wp-json\/wp\/v2\/media?parent=662"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-osbiology2e\/wp-json\/pressbooks\/v2\/chapter-type?post=662"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-osbiology2e\/wp-json\/wp\/v2\/contributor?post=662"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-osbiology2e\/wp-json\/wp\/v2\/license?post=662"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}