{"id":51,"date":"2019-06-25T15:59:28","date_gmt":"2019-06-25T19:59:28","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/nutr1100\/chapter\/basic-biology-anatomy-and-physiology\/"},"modified":"2019-07-20T10:22:44","modified_gmt":"2019-07-20T14:22:44","slug":"basic-biology-anatomy-and-physiology","status":"publish","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/nutr1100\/chapter\/basic-biology-anatomy-and-physiology\/","title":{"raw":"Basic Biology, Anatomy, and Physiology","rendered":"Basic Biology, Anatomy, and Physiology"},"content":{"raw":"

The Basic Structural and Functional Unit of Life: The Cell<\/h2>\r\nWhat distinguishes a living\u00a0<\/span>organism\u00a0from an inanimate object? A living organism conducts self-sustaining biological processes. A cell is the smallest and most basic form of life.\r\n\r\nThe cell theory incorporates three principles:\r\n\r\nCells are the most basic building units of life.<\/strong>\u00a0<\/span>All living things are composed of cells. New cells are made from preexisting cells, which divide in two. 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\u00a0<\/span>organs, systems, blood, blood vessels, bone, tissue, and skin. As an adult, you are made up 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.\r\n\r\nIndependent single-celled organisms must conduct all the basic processes of life.<\/strong>\u00a0<\/span>The single-celled organism 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\u00a0<\/span>water\u00a0<\/span>(H2O). 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,\u00a0<\/span>lipids, proteins, and nucleic acids\u2014make up all of the structural and functional units of cells.\r\n\r\nAlthough we defined the cell as the \u201cmost basic\u201d unit of life, it is structurally and functionally complex<\/strong>\u00a0<\/span>(Figure 3.2 \u201cThe Cell Structure\u201d).<\/strong>\u00a0<\/span>A cell can be thought of as a mini-organism consisting of tiny organs called organelles. The organelles are 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\r\nFigure 3.2 The Cell Structure\r\n
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The cell is structurally and functionally complex.<\/p>\r\n\r\n<\/div>\r\n

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 (see Figure 3.3 \"Organization of Life\".\r\n