The Chemical Level of Organization (Chapter 2) Introduction to Chemistry All living things are composed of matter and require energy to grow and function. Matter = anything that has mass and takes up space. Mass = the amount of matter, i.e. the amount of “stuff” that makes up something. (This is not the same as weight since weight varies with gravity. Your amount of matter, how much stuff comprises you right now, remains constant regardless of where you are standing, but you weigh more here on earth and far less on the moon. This is because the gravity of the moon pulls less strongly on your matter, and weight is simply a measurement of the pull of gravity on matter. You are “weightless” when there is no net pulling force acting on your matter, and yet you clearly still have mass, i.e. you are still composed of stuff.) Chemistry = the study of matter. All matter will exist in one of three different states depending on the environmental conditions: 1.) solid – has a definite shape and volume. 2.) liquid – has a definite volume but takes the shape of its container. 3.) gas – has no definite shape or volume (both shape and volume are dependent on the container the gas resides in). Energy = the capacity to do work; the ability to put matter into motion. All energy exists in one of two forms: 1.) kinetic energy = the energy of motion. 2.) potential energy = stored energy (the “potential” to put matter into motion). (If you climb a ladder you are kinetic energy while climbing, and potential energy while standing still at the top. If you then fall off the ladder, you are kinetic energy while falling and potential energy again once you come to rest on the ground.)  Regardless of form, energy comes in four basic types depending on source: 1.) chemical energy = the energy stored in the bonds of chemical substances. (e.g. food: when you digest a food item you are breaking the chemical bonds of the food to release energy for movement and cell growth and repair.) 2.) electrical energy = energy of the movement of charged particles. (e.g. nerve impulses: we will see later that communication throughout your nervous system involves the movement of ions such as Na+ and K+ into and out of your cells.) 3.) mechanical energy = energy directly involved in moving matter. (e.g. muscles: your skeletal muscles act to physically move your appendages around in space.) 4.) radiant energy = energy that travels in waves. (e.g. light, heat: you have photoreceptors in your eye to detect light energy, and you constantly give off energy to the environment in the form of heat.) ***Energy is never created or destroyed; it just changes form and type!*** Amy Warenda Czura, Ph.D.1SCCC BIO130 Chapter 2 HandoutComposition of Matter Atom = the smallest unit of matter. Atoms are composed of either two or three types of subatomic particles. The three types of subatomic particles are: 1) protons – have a positive charge and are heavy (1 atomic mass unit [amu]). 2) neutrons – have no charge and are heavy (1 amu). 3) electrons – have a negative charge but are so light they have a negligible mass (1/2000 amu) that is often ignored. Atomic mass of an atom = sum of all its protons and neutrons: electrons are so small they are not counted in the mass number. (Atoms also have an atomic weight, which is a measure of the actual mass including electrons, and is reported as an average of all known isotopes, but this is not important to our discussion.) The mass of a human = the sum of all atoms making up the human body. Atomic Structure Nucleus - center of the atom, composed of protons and neutrons; it has a positive charge Electron orbitals / shells – organized rings or shells or orbits of electrons moving around the nucleus at different energy levels; this region has a negative charge. The opposing charges of the nucleus and electrons hold atom together. Atomic number of an atom = number of protons in an atom; this remains constant for any given atom and defines the type of atom. Element = all atoms of a particular type; they each have the same number of protons and are all thus the same type of matter. There are 92 naturally occurring elements organized into the periodic table of the elements by atomic number (number of protons in the nucleus). The table displays the elements by their one or two letter abbreviation/symbol with the atomic number written above the symbol and the atomic mass or atomic weight written below. *you are not expected to memorize this chart: its here to help with the topic! Amy Warenda Czura, Ph.D.2SCCC BIO130 Chapter 2 HandoutThe 3 most common elements found in humans are: Hydrogen (H, Atomic #1, Atomic Mass 1), Carbon (C, Atomic #6, Mass 12), and Oxygen (O, Atomic #8, Mass 16). All atoms of a particular element will all have the same number of protons, but the number of neutrons can vary between the individual atoms: Isotope = atoms with equal protons but differing numbers of neutrons; they exhibit the same properties (i.e. are the same element) but have a different mass number. (As a related side note, you can calculate the number of neutrons in any atom if you know the atomic number and atomic mass of an atom: mass = protons + neutrons, so subtracting the atomic number from the atomic mass will give you the number of neutrons.) Back to isotopes: e.g. Isotopes of Hydrogen Hydrogen-1 = 1 proton, 1 electron Hydrogen-2 = 1 proton, 1 neutron, 1 electron. (This is also known as deuterium and it is a stable but “heavy” form of the element Hydrogen) Hydrogen-3 = 1 proton, 2 neutrons, 1 electron. (This is also known as tritium and it is radioactive with a half-life of 12.3 years) Some isotopes emit subatomic particles or radiation and are called radioisotopes. There are three types of radioisotopes based on the type of particles they emit: 1) α (“alpha”) – emit 2 protons + 2 neutrons. α emissions are weak and capable of only superficial penetration and damage (they can be shielded by a single piece of paper). 2) β (“beta”) – emit electrons. β emissions are weak and capable of penetrating flesh up to 1 cm but cause only minor damage (they can be shielded by 3 mm of aluminum or Plexiglas). 3) γ (“gamma”) – emit high energy electromagnetic waves. γ emissions are very strong and penetrate completely through the body causing great damage due to the