Chapter 2

The Body’s Chemical Makeup

Applied Learning Objectives Use the terminology associated with the body’s chemical makeup Learn about: atomic structure and bonding molecular structure characteristics of the biochemical groups composing the human body the chemical environment in which human biochemicals function Understand the aging and pathology of the body’s chemical makeup

Introduction Chemistry is a branch of the natural sciences dealing with the composition of substances, and their properties and reactions. Biochemistry, or molecular biology, is the chemistry of the body’s structures and functions. The body is composed of two substances: energy and matter. Energy is usually explained as the ability for chemical systems to do work or carry out some type of change.

Introduction... Cont. Much of the energy taken in by the human body through food ingestion is used to operate chemical pumps that make nerves and muscles work. Matter is defined as a material that has mass and occupies space. Mass is the property of a material that causes it to have weight in the presence of gravity.

Forms of Energy Chemical energy—stored in bonds of chemical substances Electrical energy—results from movement of charged particles Mechanical energy—directly involved in moving matter Radiant or electromagnetic energy—exhibits wavelike properties (i.e., visible light, ultraviolet light, and X-rays)

Major Elements of the Human Body Oxygen (O) Carbon (C) Hydrogen (H) Nitrogen (N) About 96% of body mass

Atoms and Molecules All organisms are composed of energy and matter. All matter is composed of atoms. Atoms have a central core called the nucleus, which is composed of protons and neutrons that determine the atomic mass. The proton number or atomic number determines the properties of an atom. Atoms with a particular proton number are called elements. Elements that vary in neutron number are called isotopes. Ions are elements that have more or fewer electrons than protons and carry an electric charge. Elements can form ionic, covalent, and hydrogen bonds. An isomer is a molecule that has the same elemental makeup, but a different elemental arrangement. Organisms are primarily composed of organic molecules called biochemicals. All biochemicals are composed of a carbon skeleton and a functional group.

Acids and Bases Acid solutions have a high hydrogen ion concentration. Base or alkaline solutions have a low hydrogen ion concentration. pH (the “potential for hydrogen atoms”) is a measure of the hydrogen ion concentration in a solution. pH is represented by the pH scale, which ranges from pH 1 through 14. pH numbers 1 through 6 are acids, 7 is neutral, and bases are pH 8 through 14. Buffers are used in the body to prevent pH fluctuations. A more detailed version of this image is available in the Visual Aids section on the instructor’s side of the Internet Resource Center (IRC).

Human Molecules Thousands of molecules are needed to keep the human body intact and running. A majority of the molecules are organic molecules that build body structure and regulate physiology. Biochemicals can be categorized into four organic chemical groups: lipids, carbohydrates, peptides, and nucleic acids. Each group has a unique chemistry that determines its role in the body. Lipids (or Fats): Simple molecules that provide the body with chemical signals, insulation, padding, and stored energy Carbohydrates: Compound molecules that provide the body with energy Peptides: Linear polymers of amino acids Nucleic Acid: Molecules involved in converting food energy and an essential component of genetic material

Molecules and Nutrition The right amounts of biochemicals must be absorbed to maintain homeostasis. In the health fields, homeostasis implies the natural tendency of an organism to maintain physiological and psychological stability. At the molecular level, homeostasis means taking in a constant supply of energy and raw materials needed to keep each body component in a continuous state of well-being. The body’s physiology continually monitors its needs for energy and raw materials. It does this through a variety of methods, including chemical messengers that coordinate all of the body’s systems.

Discussion Questions How does the body use food and other nutrients? What would result from the body not obtaining the necessary nutrition needed to maintain homeostasis? The body utilizes food as a source of energy to power and support body functions. Students should understand diets lacking a balanced molecular composition create a condition called malnutrition. Undernutrition describes a condition when the diet lacks all of the needed molecules for energy and raw materials. Without proper nutrition, the body cannot maintain homeostasis.

Wellness and Illness over the Life Span Molecular aging – also called senescence – is due to the destruction of essential biochemicals. The human body is continuously decaying at the chemical level. Factors such as oxidation and exposure to ultraviolet light can contribute to molecular decay. Senescence The aging process in organisms Oxidation The process of joining oxygen with another molecule; a chemical change in which an atom loses electrons Functional molecules, such as enzymes, break down as a result of the work they carry out. (Compare to a machine breaking down after years of use.) Structural molecules decay of their own accord, or are destroyed by injury or disease.

Summary All organisms are composed of energy and matter. Matter and energy work together to build and run the human body. Elements are bonded together to form a wide array of structural and functional molecules.

Summary... Cont. Molecules need a constant supply of energy to carry out their roles. Humans are primarily composed of organic molecules called biochemicals. It is necessary to take in appropriate portions of the biochemicals needed to replace those that are used.