The Human Body and the Chemistry of Life

Overview These introductory chapters will provide you with a general understanding of anatomy and physiology, by investigating the relationship between structure and function within the human organism. You will observe that physiologically, the human body can be broken down into eleven organ systems, or groups of organs that have a common set of functions. Throughout this course we will look at the unique structure and function of many of these organ systems in great detail. When we eat, exercise, or move outside into the cold, our body is able to respond to these demands by altering the physiological functioning of a variety of different systems. The goal of many physiological responses is to return our body to the balanced state in which it functions most efficiently. In order to maintain our body’s core temperature at 37 degrees Celsius in the cold, we will shiver, producing heat and raising our core temperature. This state of balance that applies to many different aspects of physiology is called homeostasis. Our physiological systems help maintain homeostasis by keeping body temperature, fluid volume, and the chemical content of our cells and fluid compartments near a homeostatic or optimal set point. Most systems are regulated by negative feedback mechanisms; when a variable rises, physiological mechanisms turn on in response to the change, bringing that variable back down towards the set point or balanced state at which the body functions most efficiently. In order to understand physiological functioning of the human body, it is important to have basic knowledge of the chemical composition of its structures, and the many chemical reactions that are required for its function. Chapter 2 serves as a basic introduction to the chemistry of life and should be utilized as reference throughout the course when chemical composition or reactions are discussed. Objectives After completing this module you will be able to: Define anatomy and physiology. Explain the importance of understanding the relationship between structure and function. Recognize and briefly describe the organ systems that will be discussed in this course. List and describe the six characteristics of life. Define homeostasis and explain why it is important. Describe negative feedback and its relationship to homeostasis. Describe ionic and covalent chemical bonds. Define hydrogen bond and its importance. Describe a compound. Describe the process of dissociation. Using symbols, explain synthesis, decomposition, and exchange reactions. Explain how reversible reactions produce chemical equilibrium. List the factors that affect the rate of chemical reactions. Describe the pH scale and its relationship to acidity and alkalinity. Explain why buffers are important in the human body. Describe the four properties of water that make it important for living organisms. Describe the four important types of organic molecules (carbohydrates, lipids, proteins and nucleic acids) and their functions. Explain how enzymes work and their importance in the chemical reactions within the body. Terminology The section number displayed beside each term indicate related textbook section. 1. anatomy (Section 1.1) 2. physiology (Section 1.1) 3. cell (Section 1.2) 4. metabolism (Section 1.3) 5. homeostasis (Section 1.4) 6. negative feedback (Section 1.4) 7. dissociation (Section 2.1) 8. ionic bond (Section 2.1) 9. covalent bond (Section 2.1) 10. reactants (Section 2.2) 11. products (Section 2.2) 12. equilibrium (Section 2.2) 13. acid (Section 2.3) 14. base (Section 2.3) 15. buffers (Section 2.3) 16. enzyme (Section 2.4, Figures 2.17 and 2.18) 17. carbohydrate (Section 2.4) 18. lipid (Section 2.4) 19. proteins(Section 2.4) 20. nucleic acid(Section 2.4) Study Guide The study guide is intended to help familiarize you with important and difficult sections of each module. It is intended to introduce the corresponding figures and discussion found within the ebook and supplementary materials. Module 1 serves to introduce you to the basics of anatomy (structure) and physiology (function). A good basic understanding of the molecules of life and how they can interact within the human body will be important throughout this course. When required, I will refer you to sections of the introductory chapters so that you can refresh your memory before applying these concepts in more detailed study of the physiological systems. Structural and Functional Organization Beginning at the microscopic level, the body can be studied at increasingly complex structural levels (chemical, cell, tissue, organ, organ system, organism). Chapter 2 will give you a detailed introduction to the properties of the chemical compounds from which our bodies are constructed. The construction of organelles and cells requires the contribution of the special properties of each of the chemical compounds. Tissues are groups of cells that have a similar function (structure). It takes more than one cell to provide enough of a particular function for something the size of an organism to function properly. By associating together into tissues, this grouping of cells help one another to perform a specialized function. Organs are constructed from many tissue types that come together to facilitate the performance of a large function. The eye, for example, requires a lens, photoreceptors, muscles, and many other tissue types to perform the function of vision. Organ systems are groups of organs that come together to perform even larger functions. In the cardiovascular system, the heart, blood, and blood vessels are separate organs that combine their functions for the cardiovascular system to provide its various roles to the human body or organism. Our course will focus on the Muscular, Nervous, Endocrine, Cardiovascular, Lymphatic, Respiratory, Digestive, and Urinary Systems. Homeostasis Homeostasis, the maintenance of a relatively constant internal environment, is an extremely important concept in physiology. It is introduced here, but will come up again as we study the various organ systems throughout the course. Many of the responses we can observe in our body are attempts to maintain a state of equilibrium or balance in our internal environment. When we exercise, our muscles produce more carbon dioxide as a result of an increased rate of metabolism. This in turn increases the level of carbon dioxide in the blood. Our respiratory system is stimulated to increase breathing rate and depth in order to remove this carbon dioxide and return the blood levels to normal. This is an example of homeostasis in action. Ionic Bonding and Dissociation An atom, the smallest particle that retains the chemical properties of an element, can gain or lose an electron (one negative charge). When this occurs it becomes a positive ion (after the loss of electron) or negative ion (after the gain of an electron). One of the two types of chemical bonding between atoms is ionic bonding. This is a loose association of oppositely charged ions. These associate because opposite charges (positive and negative) attract one another. Figure 2.7 illustrates the dissociation of an ionic compound when it dissolves in water. Water is a polarized covalent molecule, and the weak negatively charged aspect of water attracts the positively changed component of the ionic bond (e.g., Sodium, Na+). As our bodies are mostly water, ions are dissociated when in solution in our bodies. Ions that have dissociated in water are often called electrolytes. This is because they have the capacity to conduct an electrical signal. When we discuss excitable tissues such as nerve and muscle, we will look at the importance of electrolytes in nerve signal transmission and muscle contraction. Table 2.2 lists important ions found in the body and their chemical symbols. These ions and their importance in physiological function will come up in every organ system we study throughout the course. It is important to become familiar with the concept of an ion, the idea of charge (+ or -), and a general idea of the functions of these important ions. Review Please visit the section of the Course Syllabus called “How to Succeed in this Course” for recommendations of how to spend your time learning and reviewing the material for each module. There are customized practice questions and ebook notes in CONNECT to assist you with the course material. At the end of each chapter there are “Review and Comprehension” questions that require you to summarize content in your own words. Answer Questions 1 to 8 in Chapter 1 and 1 to 20 in Chapter 2 on your own, then check the readings to ensure that you have mastered the important concepts in the chapter. To assist you in reflecting on the importance of the material in these chapters, please utilize the “Apply it” questions indicated by the purple triangles throughout the chapters. To confirm your understanding of these concepts you can refer to the explanations provided for the odd numbered questions in Appendix E. To further develop your understanding and problem solving skills answer the “Critical Thinking” questions at the end of Chapter 1 (Questions 1 and 3 only) and Chapter 2. These questions help you apply the content in new situations, developing your critical thinking skills. To confirm your understanding of these problems you can refer to the explanations provided in Appendix D.