The Chemical Level of Organization Unit I. Organization of the Human Body

Essential Concepts Matter is composed of atoms held together by chemical bonds During a chemical reaction, bonds are formed, rearranged, or broken Water is the most important and abundant inorganic compound in the body Carbohydrates, lipids, proteins, nucleic acids, and ATP are the most important organic compounds in the body

How Matter is Organized Chemical Elements Students will use their text and Handout 4 to meet learning outcomes 1-4. How Matter is Organized

Matter Matter anything that occupies space and has mass Mass the amount of matter in an object; constant Mass The force of gravity on an object; variable Weight

Chemical Elements Matter exists in three states: Solids Liquids Gases All matter is composed of chemical elements Elements - the building blocks of matter Solids (bones and teeth) are compact and have definite shape Liquids (blood plasma) have a definite volume and assume the shape of the container they are in Gases (oxygen and CO2) don’t have a definite volume or shape

Major Elements Carbon Hydrogen Oxygen Nitrogen 26 chemical elements are normally found in the human body 4 are the major elements that make up 96% of the body’s mass

Minor Elements Calcium Chlorine Phosphorus Magnesium Potassium Iodine Sulfur Sodium Chlorine Magnesium Iodine Iron These minor elements make up about 3.6% of the body’s mass

Trace Elements Examples include copper and zinc Copper works with iron to form RBCs. Keeps vessels, nerves, bones, immune system healthy. Zinc is necessary for immunity. Helps with mitosis, interphase and healing. Needed for smell and taste. There are about 13-14 of them that only add up to 0.4% of the body’s mass Functions of some trace elements is unknown

Table 2.1 Main Chemical elements in the Body

How Matter is Organized Atomic Structure Students will use their text and Handout 4 to meet learning outcomes 1-4. How Matter is Organized

Atoms Atom – the smallest unit of matter An element contains the same kind of atoms Example: a pure sample of the element carbon contains only carbon atoms

Atomic Structure Nucleus Protons Neutrons Electron shells Electrons

Figure 2.1 Two representations of the structure of an atom In the cloud model, the shading represents the chance of finding an electron outside the nucleus – not contained

Atomic Structure Protons Positively charged particles Neutrons Neutrally charged particles Neutrons Negatively charged particles Electrons

Atomic Charge The number of protons in an atom is equal to the number of electrons Therefore, atoms have no charge Example: Oxygen 8 protons are balanced by 8 electrons

How Matter is Organized Atomic Number and Mass Number Students will use their text and Handout 4 to meet learning outcomes 1-4. How Matter is Organized

Atomic Number and Atomic Mass the number of protons in an atom’s nucleus Atomic number the sum of the number of protons and neutrons in an atom’s nucleus Mass number Atomic mass Dalton = amu Neutron = 1.008 daltons Proton = 1.007 daltons Electron = 0.0005 dalton = 2000 times smaller than a neutron or proton

Figure 2.2 Atomic Structure of several stable atoms The largest element in the human body is iodine with 53 electrons – 2,8,18,18,7

Isotopes atoms of an element that have different numbers of neutrons and therefore different mass numbers Isotopes unstable isotopes that emit radiation as they decay Radioactive isotopes

Figure 2.3 Marieb 7E Isotopes of hydrogen Deuterium is a stable isotope of Hydrogen with double the atomic mass – known as heavy hydrogen Found in the oceans and in stars

How Matter is Organized Ions, Molecules, and Compounds How Matter is Organized

Ions Ion - forms when an atom loses or gains electrons

Ions An atom that has lost electrons Positively charged Cation An atom that has gained electrons Negatively charged Anion

Figure 2.4 Ions and ionic bond formation 02_01

Atoms versus Ions Atoms Ions Equal number of protons and electrons Unequal numbers of protons and electrons Uncharged Charged

Molecules and Compounds Forms when two or more atoms share electrons Molecule A type of molecule composed of two or more different atoms Compound

Molecules and Compounds H2O and O2 are molecules Why is H2O a compound? Why is O2 not a compound?

Free Radicals Free radical – an ion or electrically charged molecule with an unpaired electron in its outermost shell Are extremely unstable and highly reactive Become stable by donating or accepting electrons, which may destroy nearby molecules Like robbers deficient in energy Snatch energy from stable molecules to satisfy themselves Antioxidants help inactivate free radicals

Figure 2.3 Atomic structures of an oxygen molecule and a superoxide molecule 02_01

Students will use their text and Handout 5 to meet learning outcomes 5 and 6. Chemical Bonds

Chemical Bonds The forces that hold together a molecule’s atoms Chemical bonds occur between reacting atoms’ electrons

The Role of Electrons Electrons are found in shells Each shell has space for a specific number of electrons First shell has room for two electrons Second shell has room for eight electrons Only the outermost valence shell is important in bonding

The Octet Rule Two atoms will bond with each other if doing so leaves both with eight valence electrons Can “get to eight” by giving up, accepting, or sharing electrons Hydrogen has to “get to two”

Ionic Bonds Chemical Bonds

Ionic Bonds Ionic Bond – the force of attraction that holds a cation and anion together Formed when one atom donates an electron and another atom accepts it

Example of an Ionic Bond Sodium donates an electron Chlorine accepts the electron

Ionic Compounds Most ionic compounds exist as crystals Ionic compounds dissolve in water to form electrolytes Positive and negative ions Most ions in the body are dissolved in body fluids as electrolytes Named for the ability of the solutions to conduct electricity

Table 2.2 Common Ions and Ionic Compounds in the Body

Covalent Bonds Chemical Bonds