![\"\"](\"https:\/\/dr282zn36sxxg.cloudfront.net\/datastreams\/f-d%3A3ce4d84ef3f74bc9b421ff6ca1fa70eaec1ee0ff994b7b32c44d519a%2BIMAGE_THUMB_POSTCARD_TINY%2BIMAGE_THUMB_POSTCARD_TINY.1#fixme\")
Figure 1. Ultimately, most life forms get their energy from the sun. Plants use photosynthesis to capture sunlight, and herbivores eat the plants to obtain energy. Carnivores eat the herbivores, and eventual decomposition of plant and animal material contributes to the nutrient pool.[\/caption]\r\nEnergy<\/strong><\/h4>\r\n<\/div>\r\nThermodynamics<\/strong> refers to the study of energy and energy transfer involving physical matter. The matter\u00a0relevant to a particular case of energy transfer is called a system, and everything outside of that matter is\u00a0called the surroundings. For instance, when heating a pot of water on the stove, the system includes the\u00a0stove, the pot, and the water. Energy is transferred within the system (between the stove, pot, and water).\u00a0There are two types of systems: open and closed. In an open system<\/strong>, energy can be exchanged with its\u00a0surroundings. The stovetop system is open because heat can be lost to the air. A closed system<\/strong> cannot\u00a0exchange energy with its surroundings.<\/p>\r\nBiological organisms are open systems. Energy is exchanged between them and their surroundings as\u00a0they use energy from the sun to perform photosynthesis or consume energy-storing molecules and release\u00a0energy to the environment by doing work and releasing heat. Like all things in the physical world, energy is subject to physical laws. The laws of thermodynamics govern the transfer of energy in and among all\u00a0systems in the universe. In general, energy<\/strong> is defined as the ability to do work, or to create some kind of change. Energy exists in different forms: electrical energy, light energy, mechanical energy, and heat energy are all different types of energy. To appreciate the way energy flows into and out of biological systems, it is important to understand two of the physical laws that govern energy.<\/p>\r\n\r\nThermodynamics<\/strong><\/h4>\r\nThe first law of thermodynamics<\/strong> states that the total amount of energy in the universe is constant and conserved. In other words, there has always been, and always will be, exactly the same amount of energy in the universe. Energy exists in many different forms. According to the first law of thermodynamics, energy may be transferred from place to place or transformed into different forms, but it cannot be created or destroyed. The transfers and transformations of energy take place around us all the time. Light bulbs transform electrical energy into light and heat energy. Gas stoves transform chemical energy from natural gas into heat energy. Plants perform one of the most biologically useful energy transformations on earth: that of converting the energy of sunlight to chemical energy stored within organic molecules through photosynthesis (Figure 2 below).<\/p>\r\nThe challenge for all living organisms is to obtain energy from their surroundings in forms that are\u00a0usable to perform cellular work. Cells have evolved to meet this\u00a0challenge. Chemical energy stored within organic molecules such as sugars and fats is transferred and\u00a0transformed through a series of cellular chemical reactions into energy within molecules of ATP (adenosine triphosphate). Energy\u00a0in ATP molecules is easily accessible to do work. Examples of the types of work that cells need to do\u00a0include building complex molecules, transporting materials, powering the motion of cilia or flagella, and\u00a0contracting muscles to create movement.\r\n\r\n \r\n\r\n\r\n[caption id=\"\" align=\"alignnone\" width=\"400\"]![\"The](\"https:\/\/pressbooks.bccampus.ca\/environmentalissues\/wp-content\/uploads\/sites\/526\/2018\/09\/Figure_04_01_03-1.jpg\")
Figure 2. Shown are some examples of energy transferred and transformed from one system to another and from one form to another. The food we consume provides our cells with the energy required to carry out bodily functions, just as light energy provides plants with the means to create the chemical energy they need. (credit \"ice cream\": modification of work by D. Sharon Pruitt; credit \"kids\": modification of work by Max from Providence; credit \"leaf\": modification of work by Cory Zanker).[\/caption]\r\n\r\n<\/div>\r\nA living cell\u2019s primary tasks of obtaining, transforming, and using energy to do work may seem\u00a0simple. However, the second law of thermodynamics<\/strong> explains why these tasks are harder than they\u00a0appear. All energy transfers and transformations are never completely efficient. In every energy transfer,\u00a0some amount of energy is lost in a form that is unusable. In most cases, this form is heat energy.<\/p>\r\nThermodynamically, heat energy<\/strong> is defined as the energy transferred from one system to another that\u00a0is not work. For example, when a light bulb is turned on, some of the energy being converted from\u00a0electrical energy into light energy is lost as heat energy. Likewise, some energy is lost as heat energy\u00a0during cellular metabolic reactions.<\/p>\r\nAn important concept in physical systems is that of order and disorder. The more energy that is lost\u00a0by a system to its surroundings, the less ordered and more random the system is. Scientists refer to\u00a0the measure of randomness or disorder within a system as entropy<\/strong>. High entropy means high disorder\u00a0and low energy. Molecules and chemical reactions have varying entropy as well. For example, entropy\u00a0increases as molecules at a high concentration in one place diffuse and spread out. The second law of\u00a0thermodynamics says that energy will always be lost as heat in energy transfers or transformations.\u00a0Living things are highly ordered, requiring constant energy input to be maintained in a state of low\u00a0entropy.<\/p>\r\n\r\nPotential and Kinetic Energy<\/strong><\/h4>\r\nWhen an object is in motion, there is energy associated with that object. Think of a wrecking ball. Even\u00a0a slow-moving wrecking ball can do a great deal of damage to other objects. Energy associated with\u00a0objects in motion is called kinetic energy<\/strong>. A speeding bullet, a walking person, and the\u00a0rapid movement of molecules in the air all have kinetic energy. Now what if that same motionless wrecking ball is lifted two stories above ground with a crane? If the suspended wrecking ball is not moving, is there energy associated with it? The answer is yes. The energy that was required to lift the wrecking ball did not disappear, but is now stored in the wrecking ball by virtue of its position and the force of gravity acting on it. This type of energy is called potential energy<\/strong> (Figure 3 below). If the ball were to fall, the potential energy would be transformed into kinetic energy until all of the potential energy was exhausted when the ball rested on the ground. Wrecking balls also swing like a pendulum; through the swing, there is a constant change of potential energy (highest at the top of the swing) to kinetic energy (highest at the bottom of the swing). Other examples of potential energy include the energy of water held behind a dam or a person about to skydive out of an airplane.<\/p>\r\n \r\n\r\n\r\n[caption id=\"\" align=\"alignnone\" width=\"531\"]![\"\"](\"https:\/\/dr282zn36sxxg.cloudfront.net\/datastreams\/f-d%3Ab8f5dcbf51b08c5a81d9faf5680873401f1f68f5e36fdc3d38b21839%2BIMAGE_THUMB_POSTCARD_TINY%2BIMAGE_THUMB_POSTCARD_TINY.1#fixme\")
Figure 3. Still water has potential energy; moving water, such as in a waterfall or a rapidly flowing river, has kinetic energy. (credit \"dam\": modification of work by \"Pascal\"\/Flickr; credit \"waterfall\": modification of work by Frank Gualtieri)[\/caption]\r\nPotential energy is not only associated with the location of matter, but also with the structure of matter.\u00a0Even a spring on the ground has potential energy if it is compressed; so does a rubber band that\u00a0is pulled taut. On a molecular level, the bonds that hold the atoms of molecules together exist in a\u00a0particular structure that has potential energy. The fact that energy can be released by the breakdown of certain chemical\u00a0bonds implies that those bonds have potential energy. In fact, there is potential energy stored within the\u00a0bonds of all the food molecules we eat, which is harnessed for use. The type of potential energy that exists within chemical bonds,\u00a0and is released when those bonds are broken, is called chemical energy<\/strong>. Chemical energy is responsible\u00a0for providing living cells with energy from food. The release of energy occurs when the molecular bonds\u00a0within food molecules are broken.<\/p>\r\n\r\n<\/div>\r\nAttribution<\/h4>\r\nEssentials of Environmental Science<\/a>\u00a0by Kamala Dor\u0161ner<\/a> is licensed under CC BY 4.0<\/a>. Modified from \u00a0the original.","rendered":"Virtually every task performed by living organisms requires energy. Nutrients and other molecules are imported into\u00a0the cell to meet these energy demands. For example, energy is required for the synthesis and breakdown\u00a0of molecules, as well as the transport of molecules into and out of cells. In addition, processes such\u00a0as ingesting and breaking down food, exporting wastes and toxins, and\u00a0movement of the cell all require energy.<\/p>\n
Scientists use the term bioenergetics<\/strong> to describe the concept of energy flow through\u00a0living systems, such as cells. Cellular processes such as the building and breaking down of complex\u00a0molecules occur through step-wise chemical reactions. Some of these chemical reactions are spontaneous\u00a0and release energy, whereas others require energy to proceed. Together, all of\u00a0the chemical reactions that take place inside cells, including those that consume or generate energy, are\u00a0referred to as the cell\u2019s metabolism<\/strong>.<\/p>\nFrom where, and in what form, does this energy come? How do living cells obtain energy, and how do they use it? This section will discuss different forms of energy and the physical laws that govern energy transfer.<\/p>\n
<\/p>\n
\nFigure 1. Ultimately, most life forms get their energy from the sun. Plants use photosynthesis to capture sunlight, and herbivores eat the plants to obtain energy. Carnivores eat the herbivores, and eventual decomposition of plant and animal material contributes to the nutrient pool.<\/figcaption><\/figure>\nEnergy<\/strong><\/h4>\n<\/div>\nThermodynamics<\/strong> refers to the study of energy and energy transfer involving physical matter. The matter\u00a0relevant to a particular case of energy transfer is called a system, and everything outside of that matter is\u00a0called the surroundings. For instance, when heating a pot of water on the stove, the system includes the\u00a0stove, the pot, and the water. Energy is transferred within the system (between the stove, pot, and water).\u00a0There are two types of systems: open and closed. In an open system<\/strong>, energy can be exchanged with its\u00a0surroundings. The stovetop system is open because heat can be lost to the air. A closed system<\/strong> cannot\u00a0exchange energy with its surroundings.<\/p>\nBiological organisms are open systems. Energy is exchanged between them and their surroundings as\u00a0they use energy from the sun to perform photosynthesis or consume energy-storing molecules and release\u00a0energy to the environment by doing work and releasing heat. Like all things in the physical world, energy is subject to physical laws. The laws of thermodynamics govern the transfer of energy in and among all\u00a0systems in the universe. In general, energy<\/strong> is defined as the ability to do work, or to create some kind of change. Energy exists in different forms: electrical energy, light energy, mechanical energy, and heat energy are all different types of energy. To appreciate the way energy flows into and out of biological systems, it is important to understand two of the physical laws that govern energy.<\/p>\nThermodynamics<\/strong><\/h4>\nThe first law of thermodynamics<\/strong> states that the total amount of energy in the universe is constant and conserved. In other words, there has always been, and always will be, exactly the same amount of energy in the universe. Energy exists in many different forms. According to the first law of thermodynamics, energy may be transferred from place to place or transformed into different forms, but it cannot be created or destroyed. The transfers and transformations of energy take place around us all the time. Light bulbs transform electrical energy into light and heat energy. Gas stoves transform chemical energy from natural gas into heat energy. Plants perform one of the most biologically useful energy transformations on earth: that of converting the energy of sunlight to chemical energy stored within organic molecules through photosynthesis (Figure 2 below).<\/p>\nThe challenge for all living organisms is to obtain energy from their surroundings in forms that are\u00a0usable to perform cellular work. Cells have evolved to meet this\u00a0challenge. Chemical energy stored within organic molecules such as sugars and fats is transferred and\u00a0transformed through a series of cellular chemical reactions into energy within molecules of ATP (adenosine triphosphate). Energy\u00a0in ATP molecules is easily accessible to do work. Examples of the types of work that cells need to do\u00a0include building complex molecules, transporting materials, powering the motion of cilia or flagella, and\u00a0contracting muscles to create movement.<\/p>\n
<\/p>\n
\nFigure 2. Shown are some examples of energy transferred and transformed from one system to another and from one form to another. The food we consume provides our cells with the energy required to carry out bodily functions, just as light energy provides plants with the means to create the chemical energy they need. (credit “ice cream”: modification of work by D. Sharon Pruitt; credit “kids”: modification of work by Max from Providence; credit “leaf”: modification of work by Cory Zanker).<\/figcaption><\/figure>\n<\/div>\nA living cell\u2019s primary tasks of obtaining, transforming, and using energy to do work may seem\u00a0simple. However, the second law of thermodynamics<\/strong> explains why these tasks are harder than they\u00a0appear. All energy transfers and transformations are never completely efficient. In every energy transfer,\u00a0some amount of energy is lost in a form that is unusable. In most cases, this form is heat energy.<\/p>\nThermodynamically, heat energy<\/strong> is defined as the energy transferred from one system to another that\u00a0is not work. For example, when a light bulb is turned on, some of the energy being converted from\u00a0electrical energy into light energy is lost as heat energy. Likewise, some energy is lost as heat energy\u00a0during cellular metabolic reactions.<\/p>\nAn important concept in physical systems is that of order and disorder. The more energy that is lost\u00a0by a system to its surroundings, the less ordered and more random the system is. Scientists refer to\u00a0the measure of randomness or disorder within a system as entropy<\/strong>. High entropy means high disorder\u00a0and low energy. Molecules and chemical reactions have varying entropy as well. For example, entropy\u00a0increases as molecules at a high concentration in one place diffuse and spread out. The second law of\u00a0thermodynamics says that energy will always be lost as heat in energy transfers or transformations.\u00a0Living things are highly ordered, requiring constant energy input to be maintained in a state of low\u00a0entropy.<\/p>\nPotential and Kinetic Energy<\/strong><\/h4>\nWhen an object is in motion, there is energy associated with that object. Think of a wrecking ball. Even\u00a0a slow-moving wrecking ball can do a great deal of damage to other objects. Energy associated with\u00a0objects in motion is called kinetic energy<\/strong>. A speeding bullet, a walking person, and the\u00a0rapid movement of molecules in the air all have kinetic energy. Now what if that same motionless wrecking ball is lifted two stories above ground with a crane? If the suspended wrecking ball is not moving, is there energy associated with it? The answer is yes. The energy that was required to lift the wrecking ball did not disappear, but is now stored in the wrecking ball by virtue of its position and the force of gravity acting on it. This type of energy is called potential energy<\/strong> (Figure 3 below). If the ball were to fall, the potential energy would be transformed into kinetic energy until all of the potential energy was exhausted when the ball rested on the ground. Wrecking balls also swing like a pendulum; through the swing, there is a constant change of potential energy (highest at the top of the swing) to kinetic energy (highest at the bottom of the swing). Other examples of potential energy include the energy of water held behind a dam or a person about to skydive out of an airplane.<\/p>\n <\/p>\n
\nFigure 3. Still water has potential energy; moving water, such as in a waterfall or a rapidly flowing river, has kinetic energy. (credit “dam”: modification of work by “Pascal”\/Flickr; credit “waterfall”: modification of work by Frank Gualtieri)<\/figcaption><\/figure>\nPotential energy is not only associated with the location of matter, but also with the structure of matter.\u00a0Even a spring on the ground has potential energy if it is compressed; so does a rubber band that\u00a0is pulled taut. On a molecular level, the bonds that hold the atoms of molecules together exist in a\u00a0particular structure that has potential energy. The fact that energy can be released by the breakdown of certain chemical\u00a0bonds implies that those bonds have potential energy. In fact, there is potential energy stored within the\u00a0bonds of all the food molecules we eat, which is harnessed for use. The type of potential energy that exists within chemical bonds,\u00a0and is released when those bonds are broken, is called chemical energy<\/strong>. Chemical energy is responsible\u00a0for providing living cells with energy from food. The release of energy occurs when the molecular bonds\u00a0within food molecules are broken.<\/p>\n<\/div>\nAttribution<\/h4>\n
Essentials of Environmental Science<\/a>\u00a0by Kamala Dor\u0161ner<\/a> is licensed under CC BY 4.0<\/a>. Modified from \u00a0the original.<\/p>\n","protected":false},"author":515,"menu_order":2,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[48],"contributor":[],"license":[],"class_list":["post-469","chapter","type-chapter","status-publish","hentry","chapter-type-numberless"],"part":476,"_links":{"self":[{"href":"https:\/\/pressbooks.bccampus.ca\/environmentalissues\/wp-json\/pressbooks\/v2\/chapters\/469","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.bccampus.ca\/environmentalissues\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.bccampus.ca\/environmentalissues\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/environmentalissues\/wp-json\/wp\/v2\/users\/515"}],"version-history":[{"count":8,"href":"https:\/\/pressbooks.bccampus.ca\/environmentalissues\/wp-json\/pressbooks\/v2\/chapters\/469\/revisions"}],"predecessor-version":[{"id":900,"href":"https:\/\/pressbooks.bccampus.ca\/environmentalissues\/wp-json\/pressbooks\/v2\/chapters\/469\/revisions\/900"}],"part":[{"href":"https:\/\/pressbooks.bccampus.ca\/environmentalissues\/wp-json\/pressbooks\/v2\/parts\/476"}],"metadata":[{"href":"https:\/\/pressbooks.bccampus.ca\/environmentalissues\/wp-json\/pressbooks\/v2\/chapters\/469\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.bccampus.ca\/environmentalissues\/wp-json\/wp\/v2\/media?parent=469"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/environmentalissues\/wp-json\/pressbooks\/v2\/chapter-type?post=469"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/environmentalissues\/wp-json\/wp\/v2\/contributor?post=469"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/environmentalissues\/wp-json\/wp\/v2\/license?post=469"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
Biological organisms are open systems. Energy is exchanged between them and their surroundings as\u00a0they use energy from the sun to perform photosynthesis or consume energy-storing molecules and release\u00a0energy to the environment by doing work and releasing heat. Like all things in the physical world, energy is subject to physical laws. The laws of thermodynamics govern the transfer of energy in and among all\u00a0systems in the universe. In general, energy<\/strong> is defined as the ability to do work, or to create some kind of change. Energy exists in different forms: electrical energy, light energy, mechanical energy, and heat energy are all different types of energy. To appreciate the way energy flows into and out of biological systems, it is important to understand two of the physical laws that govern energy.<\/p>\r\n\r\n The first law of thermodynamics<\/strong> states that the total amount of energy in the universe is constant and conserved. In other words, there has always been, and always will be, exactly the same amount of energy in the universe. Energy exists in many different forms. According to the first law of thermodynamics, energy may be transferred from place to place or transformed into different forms, but it cannot be created or destroyed. The transfers and transformations of energy take place around us all the time. Light bulbs transform electrical energy into light and heat energy. Gas stoves transform chemical energy from natural gas into heat energy. Plants perform one of the most biologically useful energy transformations on earth: that of converting the energy of sunlight to chemical energy stored within organic molecules through photosynthesis (Figure 2 below).<\/p>\r\nThe challenge for all living organisms is to obtain energy from their surroundings in forms that are\u00a0usable to perform cellular work. Cells have evolved to meet this\u00a0challenge. Chemical energy stored within organic molecules such as sugars and fats is transferred and\u00a0transformed through a series of cellular chemical reactions into energy within molecules of ATP (adenosine triphosphate). Energy\u00a0in ATP molecules is easily accessible to do work. Examples of the types of work that cells need to do\u00a0include building complex molecules, transporting materials, powering the motion of cilia or flagella, and\u00a0contracting muscles to create movement.\r\n\r\n \r\n A living cell\u2019s primary tasks of obtaining, transforming, and using energy to do work may seem\u00a0simple. However, the second law of thermodynamics<\/strong> explains why these tasks are harder than they\u00a0appear. All energy transfers and transformations are never completely efficient. In every energy transfer,\u00a0some amount of energy is lost in a form that is unusable. In most cases, this form is heat energy.<\/p>\r\n Thermodynamically, heat energy<\/strong> is defined as the energy transferred from one system to another that\u00a0is not work. For example, when a light bulb is turned on, some of the energy being converted from\u00a0electrical energy into light energy is lost as heat energy. Likewise, some energy is lost as heat energy\u00a0during cellular metabolic reactions.<\/p>\r\n An important concept in physical systems is that of order and disorder. The more energy that is lost\u00a0by a system to its surroundings, the less ordered and more random the system is. Scientists refer to\u00a0the measure of randomness or disorder within a system as entropy<\/strong>. High entropy means high disorder\u00a0and low energy. Molecules and chemical reactions have varying entropy as well. For example, entropy\u00a0increases as molecules at a high concentration in one place diffuse and spread out. The second law of\u00a0thermodynamics says that energy will always be lost as heat in energy transfers or transformations.\u00a0Living things are highly ordered, requiring constant energy input to be maintained in a state of low\u00a0entropy.<\/p>\r\n\r\n When an object is in motion, there is energy associated with that object. Think of a wrecking ball. Even\u00a0a slow-moving wrecking ball can do a great deal of damage to other objects. Energy associated with\u00a0objects in motion is called kinetic energy<\/strong>. A speeding bullet, a walking person, and the\u00a0rapid movement of molecules in the air all have kinetic energy. Now what if that same motionless wrecking ball is lifted two stories above ground with a crane? If the suspended wrecking ball is not moving, is there energy associated with it? The answer is yes. The energy that was required to lift the wrecking ball did not disappear, but is now stored in the wrecking ball by virtue of its position and the force of gravity acting on it. This type of energy is called potential energy<\/strong> (Figure 3 below). If the ball were to fall, the potential energy would be transformed into kinetic energy until all of the potential energy was exhausted when the ball rested on the ground. Wrecking balls also swing like a pendulum; through the swing, there is a constant change of potential energy (highest at the top of the swing) to kinetic energy (highest at the bottom of the swing). Other examples of potential energy include the energy of water held behind a dam or a person about to skydive out of an airplane.<\/p>\r\n \r\n Potential energy is not only associated with the location of matter, but also with the structure of matter.\u00a0Even a spring on the ground has potential energy if it is compressed; so does a rubber band that\u00a0is pulled taut. On a molecular level, the bonds that hold the atoms of molecules together exist in a\u00a0particular structure that has potential energy. The fact that energy can be released by the breakdown of certain chemical\u00a0bonds implies that those bonds have potential energy. In fact, there is potential energy stored within the\u00a0bonds of all the food molecules we eat, which is harnessed for use. The type of potential energy that exists within chemical bonds,\u00a0and is released when those bonds are broken, is called chemical energy<\/strong>. Chemical energy is responsible\u00a0for providing living cells with energy from food. The release of energy occurs when the molecular bonds\u00a0within food molecules are broken.<\/p>\r\n\r\n<\/div>\r\n Virtually every task performed by living organisms requires energy. Nutrients and other molecules are imported into\u00a0the cell to meet these energy demands. For example, energy is required for the synthesis and breakdown\u00a0of molecules, as well as the transport of molecules into and out of cells. In addition, processes such\u00a0as ingesting and breaking down food, exporting wastes and toxins, and\u00a0movement of the cell all require energy.<\/p>\n Scientists use the term bioenergetics<\/strong> to describe the concept of energy flow through\u00a0living systems, such as cells. Cellular processes such as the building and breaking down of complex\u00a0molecules occur through step-wise chemical reactions. Some of these chemical reactions are spontaneous\u00a0and release energy, whereas others require energy to proceed. Together, all of\u00a0the chemical reactions that take place inside cells, including those that consume or generate energy, are\u00a0referred to as the cell\u2019s metabolism<\/strong>.<\/p>\n From where, and in what form, does this energy come? How do living cells obtain energy, and how do they use it? This section will discuss different forms of energy and the physical laws that govern energy transfer.<\/p>\n <\/p>\n Thermodynamics<\/strong> refers to the study of energy and energy transfer involving physical matter. The matter\u00a0relevant to a particular case of energy transfer is called a system, and everything outside of that matter is\u00a0called the surroundings. For instance, when heating a pot of water on the stove, the system includes the\u00a0stove, the pot, and the water. Energy is transferred within the system (between the stove, pot, and water).\u00a0There are two types of systems: open and closed. In an open system<\/strong>, energy can be exchanged with its\u00a0surroundings. The stovetop system is open because heat can be lost to the air. A closed system<\/strong> cannot\u00a0exchange energy with its surroundings.<\/p>\n Biological organisms are open systems. Energy is exchanged between them and their surroundings as\u00a0they use energy from the sun to perform photosynthesis or consume energy-storing molecules and release\u00a0energy to the environment by doing work and releasing heat. Like all things in the physical world, energy is subject to physical laws. The laws of thermodynamics govern the transfer of energy in and among all\u00a0systems in the universe. In general, energy<\/strong> is defined as the ability to do work, or to create some kind of change. Energy exists in different forms: electrical energy, light energy, mechanical energy, and heat energy are all different types of energy. To appreciate the way energy flows into and out of biological systems, it is important to understand two of the physical laws that govern energy.<\/p>\n The first law of thermodynamics<\/strong> states that the total amount of energy in the universe is constant and conserved. In other words, there has always been, and always will be, exactly the same amount of energy in the universe. Energy exists in many different forms. According to the first law of thermodynamics, energy may be transferred from place to place or transformed into different forms, but it cannot be created or destroyed. The transfers and transformations of energy take place around us all the time. Light bulbs transform electrical energy into light and heat energy. Gas stoves transform chemical energy from natural gas into heat energy. Plants perform one of the most biologically useful energy transformations on earth: that of converting the energy of sunlight to chemical energy stored within organic molecules through photosynthesis (Figure 2 below).<\/p>\n The challenge for all living organisms is to obtain energy from their surroundings in forms that are\u00a0usable to perform cellular work. Cells have evolved to meet this\u00a0challenge. Chemical energy stored within organic molecules such as sugars and fats is transferred and\u00a0transformed through a series of cellular chemical reactions into energy within molecules of ATP (adenosine triphosphate). Energy\u00a0in ATP molecules is easily accessible to do work. Examples of the types of work that cells need to do\u00a0include building complex molecules, transporting materials, powering the motion of cilia or flagella, and\u00a0contracting muscles to create movement.<\/p>\n <\/p>\n A living cell\u2019s primary tasks of obtaining, transforming, and using energy to do work may seem\u00a0simple. However, the second law of thermodynamics<\/strong> explains why these tasks are harder than they\u00a0appear. All energy transfers and transformations are never completely efficient. In every energy transfer,\u00a0some amount of energy is lost in a form that is unusable. In most cases, this form is heat energy.<\/p>\n Thermodynamically, heat energy<\/strong> is defined as the energy transferred from one system to another that\u00a0is not work. For example, when a light bulb is turned on, some of the energy being converted from\u00a0electrical energy into light energy is lost as heat energy. Likewise, some energy is lost as heat energy\u00a0during cellular metabolic reactions.<\/p>\n An important concept in physical systems is that of order and disorder. The more energy that is lost\u00a0by a system to its surroundings, the less ordered and more random the system is. Scientists refer to\u00a0the measure of randomness or disorder within a system as entropy<\/strong>. High entropy means high disorder\u00a0and low energy. Molecules and chemical reactions have varying entropy as well. For example, entropy\u00a0increases as molecules at a high concentration in one place diffuse and spread out. The second law of\u00a0thermodynamics says that energy will always be lost as heat in energy transfers or transformations.\u00a0Living things are highly ordered, requiring constant energy input to be maintained in a state of low\u00a0entropy.<\/p>\n When an object is in motion, there is energy associated with that object. Think of a wrecking ball. Even\u00a0a slow-moving wrecking ball can do a great deal of damage to other objects. Energy associated with\u00a0objects in motion is called kinetic energy<\/strong>. A speeding bullet, a walking person, and the\u00a0rapid movement of molecules in the air all have kinetic energy. Now what if that same motionless wrecking ball is lifted two stories above ground with a crane? If the suspended wrecking ball is not moving, is there energy associated with it? The answer is yes. The energy that was required to lift the wrecking ball did not disappear, but is now stored in the wrecking ball by virtue of its position and the force of gravity acting on it. This type of energy is called potential energy<\/strong> (Figure 3 below). If the ball were to fall, the potential energy would be transformed into kinetic energy until all of the potential energy was exhausted when the ball rested on the ground. Wrecking balls also swing like a pendulum; through the swing, there is a constant change of potential energy (highest at the top of the swing) to kinetic energy (highest at the bottom of the swing). Other examples of potential energy include the energy of water held behind a dam or a person about to skydive out of an airplane.<\/p>\n <\/p>\n Potential energy is not only associated with the location of matter, but also with the structure of matter.\u00a0Even a spring on the ground has potential energy if it is compressed; so does a rubber band that\u00a0is pulled taut. On a molecular level, the bonds that hold the atoms of molecules together exist in a\u00a0particular structure that has potential energy. The fact that energy can be released by the breakdown of certain chemical\u00a0bonds implies that those bonds have potential energy. In fact, there is potential energy stored within the\u00a0bonds of all the food molecules we eat, which is harnessed for use. The type of potential energy that exists within chemical bonds,\u00a0and is released when those bonds are broken, is called chemical energy<\/strong>. Chemical energy is responsible\u00a0for providing living cells with energy from food. The release of energy occurs when the molecular bonds\u00a0within food molecules are broken.<\/p>\n<\/div>\n Essentials of Environmental Science<\/a>\u00a0by Kamala Dor\u0161ner<\/a> is licensed under CC BY 4.0<\/a>. Modified from \u00a0the original.<\/p>\n","protected":false},"author":515,"menu_order":2,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[48],"contributor":[],"license":[],"class_list":["post-469","chapter","type-chapter","status-publish","hentry","chapter-type-numberless"],"part":476,"_links":{"self":[{"href":"https:\/\/pressbooks.bccampus.ca\/environmentalissues\/wp-json\/pressbooks\/v2\/chapters\/469","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.bccampus.ca\/environmentalissues\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.bccampus.ca\/environmentalissues\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/environmentalissues\/wp-json\/wp\/v2\/users\/515"}],"version-history":[{"count":8,"href":"https:\/\/pressbooks.bccampus.ca\/environmentalissues\/wp-json\/pressbooks\/v2\/chapters\/469\/revisions"}],"predecessor-version":[{"id":900,"href":"https:\/\/pressbooks.bccampus.ca\/environmentalissues\/wp-json\/pressbooks\/v2\/chapters\/469\/revisions\/900"}],"part":[{"href":"https:\/\/pressbooks.bccampus.ca\/environmentalissues\/wp-json\/pressbooks\/v2\/parts\/476"}],"metadata":[{"href":"https:\/\/pressbooks.bccampus.ca\/environmentalissues\/wp-json\/pressbooks\/v2\/chapters\/469\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.bccampus.ca\/environmentalissues\/wp-json\/wp\/v2\/media?parent=469"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/environmentalissues\/wp-json\/pressbooks\/v2\/chapter-type?post=469"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/environmentalissues\/wp-json\/wp\/v2\/contributor?post=469"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/environmentalissues\/wp-json\/wp\/v2\/license?post=469"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}Thermodynamics<\/strong><\/h4>\r\n
Figure 2. Shown are some examples of energy transferred and transformed from one system to another and from one form to another. The food we consume provides our cells with the energy required to carry out bodily functions, just as light energy provides plants with the means to create the chemical energy they need. (credit \"ice cream\": modification of work by D. Sharon Pruitt; credit \"kids\": modification of work by Max from Providence; credit \"leaf\": modification of work by Cory Zanker).[\/caption]\r\n\r\n<\/div>\r\nPotential and Kinetic Energy<\/strong><\/h4>\r\n
Attribution<\/h4>\r\nEssentials of Environmental Science<\/a>\u00a0by Kamala Dor\u0161ner<\/a> is licensed under CC BY 4.0<\/a>. Modified from \u00a0the original.","rendered":"
Energy<\/strong><\/h4>\n<\/div>\n
Thermodynamics<\/strong><\/h4>\n
Potential and Kinetic Energy<\/strong><\/h4>\n
Attribution<\/h4>\n