Chapter 2: Introduction to Chemistry A review

The basics: Chemistry is the science of the structure and interactions of matter. Matter is anything that occupies space and has mass. Mass is the amount of matter in an object. There are112 recognized chemical elements, each designated by a chemical symbol. Elements are made up of atoms, the smallest units of matter. Atoms are composed of protons (+), neutrons (0) and electrons (-).

The main elements in the human body: Oxygen (O) 65% Carbon (C) 18.5% Hydrogen (H) 9.5% Nitrogen (N) 3.2% Calcium (Ca) 1.5% Phosphorus (P) 1.0 % Other elements include: K, S, Na, Cl, Mg and Fe

Atomic number vs. Mass number The atomic number is the number of protons in an atom. A Cl atom has 17 protons, it has an atomic number of 17. The mass number is the number of protons plus the number of neutrons. Ex. Na has 11 p and 12 n, it has a mass number of 23.

Chemical Bonds Ionic bonds – Positively charged ions and negatively charged ions are attracted to each other. Ex. Na and Cl ions. Covalent bonds – When neither of the combining atoms loses are gains electrons, but share them. Ex. H20 Hydrogen bonds – Polar covalent bonds between H atoms and other atoms. But, are considered weak. Join nitrogen bases together in DNA.

Chemistry and the Human Body Synthesis reactions: The production of new and larger molecules. Anabolism is the collective term that refers to the combining of simple molecules (amino acids) to form larger molecules (proteins)

2 Types of Chemical Compounds Inorganic & Organic

Inorganic Compounds Lack Carbon Are held together by ionic or covalent bonds. Examples include water, salts and acids. The exceptions are 2-carbon containing compounds CO2 and HCO3-

Organic Compounds Always contain carbon and usually hydrogen. Always have covalent bonds. Examples include lipids, proteins, nucleic acids, carbohydrates and ATP ( all macromolecules )

Water

Water makes up 55 to 60 percent of lean adults and is an excellent solvent.

Participates in chemical reactions. Ex Participates in chemical reactions. Ex. Hydrolysis, the process of breaking down large nutrient molecules into smaller molecules. (digestion)

Water requires large amounts of heat to change from liquid to gas Water requires large amounts of heat to change from liquid to gas. This makes water an excellent cooling mechanism, evaporation.

Water serves as a lubricant. It is a major part of saliva and mucus Water serves as a lubricant. It is a major part of saliva and mucus. Lubrication allows organs of the thoracic and abdominal cavities to slide over one another. Lubrication is also needed at the joints where bones, tendons and ligaments rub against one another.

Water absorbs and releases heat slowly, this helps to maintain homeostasis.

Acids, Bases and Salts Acids, bases and salts dissociate into ions in water. Acids ionize into H ions (H+) Bases ionize into hydroxide ions (OH-) Salts ionize into either H+ or OH- ions

The pH Scale Acids range from 0–6 on the pH scale. Bases (alkaline) range from 8-14. 7 on the pH scale is considered neutral.

The body is sensative to even the slightest changes in pH The body is sensative to even the slightest changes in pH. Anything outside of the normal limits greatly disrupts the body’s function.

Buffer systems are chemical compounds that convert strong acids and bases into weak acids and bases.