{"id":86,"date":"2019-03-11T16:43:07","date_gmt":"2019-03-11T16:43:07","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/sunyltnutrition\/?post_type=chapter&p=86"},"modified":"2019-04-04T18:55:17","modified_gmt":"2019-04-04T18:55:17","slug":"3-2-the-basic-structural-and-functional-unit-of-life-the-cell","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/sunyltnutrition\/chapter\/3-2-the-basic-structural-and-functional-unit-of-life-the-cell\/","title":{"raw":"3.2: The Basic Structural And Functional Unit Of Life: The Cell","rendered":"3.2: The Basic Structural And Functional Unit Of Life: The Cell"},"content":{"raw":"
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Learning Objectives<\/h3>\r\n
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  • Diagram the components of a cell.<\/li>\r\n \t
  • Describe the organization of the human body.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/section><\/div>\r\n<\/header>
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    \r\n\r\nWhat distinguishes a living organism from an inanimate object? A living organism conducts self-sustaining biological processes. A cell is the smallest and most basic form of life. Robert Hooke, one of the first scientists to use a light microscope, discovered the cell in 1665. In all life forms, including bacteria, plants, animals, and humans, the\u00a0cell<\/span>\u00a0was defined as the most basic structural and functional unit. Based on scientific observations over the next 150 years, scientists formulated the\u00a0cell theory<\/span>, which is used for all living organisms no matter how simple or complex. The cell theory incorporates three principles:\r\n
      \r\n \t
    • Cells are the most basic building units of life.<\/li>\r\n \t
    • All living things are composed of cells.<\/li>\r\n \t
    • New cells are made from preexisting cells, which divide into two.<\/li>\r\n<\/ul>\r\n

      Who you are has been determined because of two cells that came together inside your mother\u2019s womb. The two cells containing all of your genetic information (DNA) united to begin making new life. Cells divided and differentiated into other cells with specific roles that led to the formation of the body\u2019s numerous body organs, systems, blood, blood vessels, bone, tissue, and skin. As an adult, you are comprised of trillions of cells. Each of your individual cells is a compact and efficient form of life\u2014self-sufficient, yet interdependent upon the other cells within your body to supply its needs.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"303\"]\"\" One cell divides into two, which begins the creation of millions of more cells that ultimately become you. Image used with permission (Public Domain; National Institutes of Health).<\/em>[\/caption]\r\n

      Independent single-celled organisms must conduct all the basic processes of life: it must take in nutrients (energy capture), excrete wastes, detect and respond to its environment, move, breathe, grow, and reproduce. Even a one-celled organism must be organized to perform these essential processes. All cells are organized from the atomic level to all its larger forms. Oxygen and hydrogen atoms combine to make the molecule water (H2<\/sub>O). Molecules bond together to make bigger macromolecules. The carbon atom is often referred to as the backbone of life because it can readily bond with four other elements to form long chains and more complex macromolecules. Four macromolecules\u2014carbohydrates, lipids, proteins, and nucleic acids\u2014make up all of the structural and functional units of cells.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"alignnone\" width=\"502\"]\"0589ca93828561b000e81251d18b5eb0.jpg\" Figure 3.2.1:\u00a0The cell is structurally and functionally complex.<\/em>[\/caption]\r\n\r\nAlthough we defined the cell as the \u201cmost basic\u201d unit of life, it is structurally and functionally complex (Figure 3.2.1). A cell can be thought of as a mini-organism consisting of tiny organs called organelles. The\u00a0organelles<\/span>\u00a0are structural and functional units constructed from several macromolecules bonded together. A typical animal cell contains the following organelles: the nucleus (which houses the genetic material DNA), mitochondria (which generate energy), ribosomes (which produce protein), the endoplasmic reticulum (which is a packaging and transport facility), and the golgi apparatus (which distributes macromolecules). In addition, animal cells contain little digestive pouches, called lysosomes and peroxisomes, which break down macromolecules and destroy foreign invaders. All of the organelles are anchored in the cell\u2019s cytoplasm via a cytoskeleton. The cell\u2019s organelles are isolated from the surrounding environment by a plasma membrane.\r\n

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      VIDEO 3.1: DISCOVERY VIDEO: CELLS<\/h3>\r\nThis video describes the importance of cells in the human body.\r\n
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      \r\n\r\n[embed]https:\/\/www.youtube.com\/embed\/u54bRpbSOgs[\/embed]\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
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      Tissues, Organs, Organ Systems, and Organisms<\/h2>\r\nUnicellular (single-celled) organisms can function independently, but the cells of multicellular organisms are dependent upon each other and are organized into five different levels in order to coordinate their specific functions and carry out all of life\u2019s biological processes.\r\n
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      • Cells.<\/strong>\u00a0Cells are the basic structural and functional unit of all life. Examples include red blood cells and nerve cells.<\/li>\r\n \t
      • Tissues.\u00a0<\/strong>Tissues<\/span>\u00a0are groups of cells that share a common structure and function and work together. There are four types of human tissues: connective, which connects tissues; epithelial, which lines and protects organs; muscle, which contracts for movement and support; and nerve, which responds and reacts to signals in the environment.<\/li>\r\n \t
      • Organs.\u00a0<\/strong>Organs<\/span>\u00a0are a group of tissues arranged in a specific manner to support a common physiological function. Examples include the brain, liver, and heart.<\/li>\r\n \t
      • Organ systems.\u00a0<\/strong>Organ systems<\/span>\u00a0are two or more organs that support a specific physiological function. Examples include the digestive system and central nervous system. There are eleven organ systems in the human body (Table 3.2.1).<\/li>\r\n \t
      • Organism.<\/strong>\u00a0An\u00a0organism<\/span>\u00a0is the complete living system capable of conducting all of life\u2019s biological processes.<\/li>\r\n<\/ul>\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n
        Table 3.2.1<\/strong>: The Eleven Organ Systems in the Human Body and Their Major Functions<\/em><\/caption>\r\n
        Organ System<\/th>\r\nOrgan Components<\/th>\r\nMajor Function<\/th>\r\n<\/tr>\r\n<\/thead>\r\n
        Circulatory<\/td>\r\nheart, blood\/lymph vessels, blood, lymph<\/td>\r\nTransport nutrients and waste products<\/td>\r\n<\/tr>\r\n
        Digestive<\/td>\r\nmouth, esophagus, stomach, intestines<\/td>\r\nDigestion and absorption<\/td>\r\n<\/tr>\r\n
        Endocrine<\/td>\r\nall glands (thyroid, ovaries, pancreas)<\/td>\r\nProduce and release hormones<\/td>\r\n<\/tr>\r\n
        Immune<\/td>\r\nwhite blood cells, lymphatic tissue, marrow<\/td>\r\nDefend against foreign invaders<\/td>\r\n<\/tr>\r\n
        Integumentary<\/td>\r\nskin, nails, hair, sweat glands<\/td>\r\nProtective, body temperature regulation<\/td>\r\n<\/tr>\r\n
        Muscular<\/td>\r\nskeletal, smooth, and cardiac muscle<\/td>\r\nBody movement<\/td>\r\n<\/tr>\r\n
        Nervous<\/td>\r\nbrain, spinal cord, nerves<\/td>\r\nInterprets and responds to stimuli<\/td>\r\n<\/tr>\r\n
        Reproductive<\/td>\r\ngonads, genitals<\/td>\r\nReproduction and sexual characteristics<\/td>\r\n<\/tr>\r\n
        Respiratory<\/td>\r\nlungs, nose, mouth, throat, trachea<\/td>\r\nGas exchange<\/td>\r\n<\/tr>\r\n
        Skeletal<\/td>\r\nbones, tendons, ligaments, joints<\/td>\r\nStructure and support<\/td>\r\n<\/tr>\r\n
        Urinary<\/td>\r\nkidneys, bladder, ureters<\/td>\r\nWaste excretion, water balance<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n[caption id=\"\" align=\"aligncenter\" width=\"572\"]\"\" Figure 3.2.2:\u00a0Organ Systems in the Human Body \u00a9 Networkgraphics<\/em>[\/caption]\r\n\r\n<\/div>\r\n
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        An Organism Requires Energy and Nutrient Input<\/h2>\r\nEnergy is required in order to build molecules into larger macromolecules, and to turn macromolecules into organelles and cells, and then turn those into tissues, organs, and organ systems, and finally into an organism. Proper nutrition provides the necessary nutrients to make the energy that supports life\u2019s processes. Your body builds new macromolecules from the nutrients in food.\r\n\r\n<\/div>\r\n
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        Nutrient and Energy Flow<\/h2>\r\nEnergy is stored in a nutrient\u2019s chemical bonds. Energy comes from sunlight, which plants then capture and, via photosynthesis, use it to transform carbon dioxide in the air into the molecule, glucose. When the glucose bonds are broken, energy is released. Bacteria, plants, and animals (including humans) harvest the energy in glucose via a biological process called\u00a0cellular respiration<\/span>. In this process the chemical energy of glucose is transformed into cellular energy in the form of the molecule, adenosine triphosphate (ATP). Cellular respiration requires oxygen (aerobic) and it is provided as a waste product of photosynthesis. The waste products of cellular respiration are carbon dioxide (CO2<\/sub>) and water, which plants use to conduct photosynthesis again. Thus, energy is constantly cycling between plants and animals. As energy is consumed nutrients are recycled within it.\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"740\"]\"\" Plants harvest energy from the sun and capture it in the molecule, glucose. Humans harvest the energy in glucose and capture it into the molecule, ATP.[\/caption]\r\n\r\nIn this section, we have learned that all life is composed of cells capable of transforming small organic molecules into energy. How do complex organisms such as humans convert the large macromolecules in the foods that we eat into molecules that can be used by cells to make cellular energy? In the next section, we will discuss the physiological process of digestion to answer this question.\r\n
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        Key Takeaways<\/h3>\r\n
          \r\n \t
        • The cell is the basic structural and functional unit of life. Cells are independent, single-celled organisms that take in nutrients, excrete wastes, detect and respond to their environment, move, breathe, grow, and reproduce. The macromolecules carbohydrates, proteins, lipids, and nucleic acids make up all of the structural and functional units of cells.<\/li>\r\n \t
        • In complex organisms, cells are organized into five levels so that an organism can conduct all basic processes associated with life.<\/li>\r\n \t
        • There are eleven organ systems in the human body that work together to support life, all of which require nutrient input.<\/li>\r\n \t
        • Energy is constantly cycling between plants and animals. As energy is consumed nutrients are recycled within it.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
          \r\n

          Discussion Starter<\/h3>\r\n
            \r\n \t
          1. Discuss the importance of organization in the human body. If the body becomes disorganized by a disease or disorder what happens to its function? Can you think of a good example (what about leg fracture and movement)?<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/section>","rendered":"
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            Learning Objectives<\/h3>\n
            \n
            \n
            \n
            \n
              \n
            • Diagram the components of a cell.<\/li>\n
            • Describe the organization of the human body.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<\/div>\n<\/section>\n<\/div>\n<\/header>\n
              \n
              \n

              What distinguishes a living organism from an inanimate object? A living organism conducts self-sustaining biological processes. A cell is the smallest and most basic form of life. Robert Hooke, one of the first scientists to use a light microscope, discovered the cell in 1665. In all life forms, including bacteria, plants, animals, and humans, the\u00a0cell<\/span>\u00a0was defined as the most basic structural and functional unit. Based on scientific observations over the next 150 years, scientists formulated the\u00a0cell theory<\/span>, which is used for all living organisms no matter how simple or complex. The cell theory incorporates three principles:<\/p>\n

                \n
              • Cells are the most basic building units of life.<\/li>\n
              • All living things are composed of cells.<\/li>\n
              • New cells are made from preexisting cells, which divide into two.<\/li>\n<\/ul>\n

                Who you are has been determined because of two cells that came together inside your mother\u2019s womb. The two cells containing all of your genetic information (DNA) united to begin making new life. Cells divided and differentiated into other cells with specific roles that led to the formation of the body\u2019s numerous body organs, systems, blood, blood vessels, bone, tissue, and skin. As an adult, you are comprised of trillions of cells. Each of your individual cells is a compact and efficient form of life\u2014self-sufficient, yet interdependent upon the other cells within your body to supply its needs.<\/p>\n

                \"\"<\/p>\n

                One cell divides into two, which begins the creation of millions of more cells that ultimately become you. Image used with permission (Public Domain; National Institutes of Health).<\/em><\/p>\n<\/div>\n

                Independent single-celled organisms must conduct all the basic processes of life: it must take in nutrients (energy capture), excrete wastes, detect and respond to its environment, move, breathe, grow, and reproduce. Even a one-celled organism must be organized to perform these essential processes. All cells are organized from the atomic level to all its larger forms. Oxygen and hydrogen atoms combine to make the molecule water (H2<\/sub>O). Molecules bond together to make bigger macromolecules. The carbon atom is often referred to as the backbone of life because it can readily bond with four other elements to form long chains and more complex macromolecules. Four macromolecules\u2014carbohydrates, lipids, proteins, and nucleic acids\u2014make up all of the structural and functional units of cells.<\/p>\n

                \"0589ca93828561b000e81251d18b5eb0.jpg\"<\/p>\n

                Figure 3.2.1:\u00a0The cell is structurally and functionally complex.<\/em><\/p>\n<\/div>\n

                Although we defined the cell as the \u201cmost basic\u201d unit of life, it is structurally and functionally complex (Figure 3.2.1). A cell can be thought of as a mini-organism consisting of tiny organs called organelles. The\u00a0organelles<\/span>\u00a0are structural and functional units constructed from several macromolecules bonded together. A typical animal cell contains the following organelles: the nucleus (which houses the genetic material DNA), mitochondria (which generate energy), ribosomes (which produce protein), the endoplasmic reticulum (which is a packaging and transport facility), and the golgi apparatus (which distributes macromolecules). In addition, animal cells contain little digestive pouches, called lysosomes and peroxisomes, which break down macromolecules and destroy foreign invaders. All of the organelles are anchored in the cell\u2019s cytoplasm via a cytoskeleton. The cell\u2019s organelles are isolated from the surrounding environment by a plasma membrane.<\/p>\n

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                VIDEO 3.1: DISCOVERY VIDEO: CELLS<\/h3>\n

                This video describes the importance of cells in the human body.<\/p>\n

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