The Chemical Level of Organization 2.1-2.3 August 8, 2012 August 9, 2012 Agenda General Housekeeping Assignments Review Chapter 2 2.1 2.2 2.3 Research Paper Overview Process Review Are the ribs superficial to the lungs? How do you know? In which cavity is the thymus located? Locate the nine abdominopelvic regions on yourself and list some of the organs found in each Use four strips of tape to mark yourself Which forms of medical imagery would be used to show a blockage of an artery of the heart? Chapter 2: The Chemical Level of Organization 2.1 How Matter is Organized 2.2 Chemical Bonds 2.3 Chemical Reactions 2.4 Inorganic Compounds & Solutions 2.5 Organic Compounds The Big Idea Chemistry and Homeostasis Maintaining the proper assortment and quantity of thousands of different chemicals in your body, and monitoring the interactions of these chemicals with one another, are two important aspects of homeostasis 2.1 How Matter is Organized Objectives Identify the main chemical elements of the human body Describe the structures of atoms, ions, molecules, free radicals, and compounds Chemical Elements Matter exists in three states Solid Compact, definite shape and volume Bones and teeth Liquid Definite volume, shape of their container Blood plasma Gas No definite shape or volume Oxygen and carbon dioxide How Matter is Organized All forms of matter are composed of chemical elements which are substances that cannot be split into simpler substances by ordinary chemical means Elements are given letter abbreviations called chemical symbols Major Elements constitute about 96% of the body s mass O, C, H, N Lesser Elements contribute about 3.6% of the body s mass Ca, P, K, S, Na, Cl, Mg, Fe Trace elements are elements in our bodies, present in tiny amounts and account for the remaining 0.4% of the body s mass Several trace elements have important functions in the body
Structure of Atoms Units of matter of all chemical elements are called atoms. An element is a quantity of matter composed of atoms of the same type. Atoms contain three types of subatomic particles Electrons (e - ) are very small and light (mass about 1/2000 th that of proton or neutron), often represented as orbiting around the nucleus In reality, they are found in a cloud of probability surrounding the nucleus Protons (p + ) and neutrons (n 0 ) form the nucleus of an atom Protons are large, positively-charged particles The number of protons in the nucleus (called the atomic number) determines the element Neutrons are the second largest particle that make-up the nucleus of atoms Unlike protons, neutrons have no charge They do add mass, however, and determine the variety, or isotope of a certain element Isotopes are atoms of an element that have different numbers of neutrons Carbon-12 vs. Carbon-14, which has 2 extra neutrons in nucleus Radioactive isotopes are unstable and their nuclei decay into stable configurations As they decay, the isotopes emit radiation and in the process, often transform into different elements C-14 decays into N-14 The half-life of an isotope is the time required for half of the radioactive atoms in a sample of that isotope to decay into a more stable form Half-life of C-14 is about 5730 years Half-life of I-131 is 8 days Mass is measured as a dalton (atomic mass unit) Certain numbers are used to describe different properties of elements - Atomic number is the number of protons in an atom - Mass number is the sum of protons and neutrons in an atom - Atomic mass (atomic weight) is the average mass of all naturally occurring isotopes Elements in the Human Body Ions Atoms that have given up or gained an electron in their outer electron shell (also called the valence shell) Written with its chemical symbol and (+) or ( )
Molecules Molecules are formed when atoms share electrons Written as a molecular formula showing the number of atoms of each element (H2O) The oxygen gas in the atmosphere we breath is really not oxygen the atom, but a pair of oxygen atoms linked together into an oxygen molecule (O2) 2.2 Chemical Bonds Objectives Describe how valence electrons form chemical bonds Distinguish among ionic, covalent, and hydrogen bonds Compounds A substance that contains atoms of two or more different elements Most of the atoms in the body are joined into compounds H2O NaCl O2 is not a compound. Why? The atoms of a molecule are held together by forces of attraction called chemical bonds The likelihood that an atom will form a chemical bond with another atom depends on the number of electrons in its outermost or valence shell Atoms will interact in ways that produce a chemically stable arrangement of eight valence electrons in each atom (Octet Rule) Covalent Bonds Formed by the atoms of molecules sharing one, two, or three pairs of their valence electrons Covalent bonds are the strongest chemical bonds Single, double, or triple covalent bonds are formed by sharing one, two, or three pairs of electrons, respectively Free Radicals Is an electrically charged atom or group of atoms with an unpaired electron in its outermost shell They are unstable and highly reactive They can become stable by giving up an electron or taking an electron from another molecule, often breaking apart important body molecules Antioxidants are substances that inactivate oxygenderived free radicals Ionic Bonds Ions form when an atom loses or gains a valence electron Positively and negatively charged ions are attracted to one another Cations are positively charged ions that have given up one or more electrons (they are electron donors) Anions are negatively charged ions that have picked up one or more electrons that another atom has lost (they are electron acceptors) Ionic compounds that break apart into positive and negative ions in solution are called electrolytes Covalent bonds may be nonpolar or polar In a nonpolar covalent bond, atoms share the electrons equally Nonpolar covalent bonds are the most common types of covalent bonds
Polar covalent bonds are formed by the unequal sharing of electrons between atoms Polar covalent bonds are extremely important because the all-important water molecule makes use of this bond In water, oxygen attracts the hydrogen electrons more strongly, making oxygen slightly electronegative as indicated by the negative Greek delta sign Hydrogen Bonds Are weak interactions (approximately 5% as strong as covalent bonds) between hydrogen and adjacent electronegative atoms like oxygen or sulfur Result from attraction of oppositely charged parts of molecules they should not be confused with covalent bonding to hydrogen which involves actual sharing of electrons Hydrogen bonds are useful in establishing links between molecules or between distant parts of a very large molecule. Large 3-D molecules (like proteins) are often held together by a great many hydrogen bonds In water, hydrogen bonding provides considerable cohesion which creates a very high surface tension A measure of difficulty of stretching or breaking the surface of a liquid 2.3 Chemical Reactions Objectives Define a chemical reaction Describe the various forms of energy Compare exergonic and endergonic chemical reactions Describe the role of activation energy and catalysts in chemical reactions Describe synthesis, decomposition, exchange, and reversible reactions Chemical reactions occur when electrons in the valence shell are shared or transferred Old bonds are broken in the reactants and new bonds are formed in the product(s) Metabolism is the sum of all the chemical reactions in the body Law of Conservation of Mass The total mass of reactants equals the total mass of the products Energy Energy (the capacity to do work) is transferred in a chemical reaction Kinetic Energy is the energy of matter in motion Potential Energy is energy stored by matter - due to an object s position in space, or stored in chemical bonds (Chemical Energy) Law of Conservation of Energy Energy can be neither created nor destroyed, it can be converted from one form to another An exergonic reaction releases energy (usually in the form of heat during catabolism of food) by breaking a bond with more energy than the one being formed An endergonic reaction requires that energy be added, usually from a molecule called ATP, to form a bond Activation Energy is the energy required to break chemical bonds in the reactant molecules so a reaction can start
Chemical concentration and temperature influence the chance that a collision will occur and cause a chemical reaction The more particles of matter present in a confined space, the greater the chance that they will collide As temperature rises, particles of matter move more rapidly increasing the chance of collisions between particles Catalysts Factors that cause a collision (and a chemical reaction to take place) include the temperature and the concentration of the reactants, and the presence or absence of a catalyst Catalysts are chemical compounds that speed up chemical reactions by lowering the activation energy needed for a reaction to occur Catalysts are neither consumed nor produced in the reaction They are used over-and-over again, often several million times per second In a chemical reaction, a catalyst helps to properly orient the colliding particles of matter so that a reaction can occur at a lower collision speed A catalyst does not alter the difference in potential energy between the reactants and products (it only lowers the amount of energy needed to get the reaction started) Types of Chemical Reactions Synthesis Reactions Anabolism - A + B AB - Two or more atoms, ions, or molecules combining to form a new, larger molecule - Usually endergonic because they absorb more energy than they release N 2 + 3H 2 2NH 3 Decomposition Reactions Catabolism - AB A + B - Large molecule breaks down into smaller atoms, ions, or molecules - Usually exergonic because they release more energy than they absorb 2H 2 O 2 2H 2 O + O 2 Exchange Reactions - AB + CD AD + CB - The ions in both compounds have switched partners HCl + NaHCO 3 H 2 CO 3 +NaCl Reversible Reactions - AB A + B - Products can revert back to the original reactants - Some reactions are only reversible under special conditions - Many reversible reactions in the body require specific enzymes to guide the reaction in opposite directions Oxidation-Reduction Reactions Involves the transfer of electrons between atoms and molecules Oxidation: the loss of electrons, and in the process the oxidized substance releases energy Reduction: the gain of electrons, and in the process the reduced substance gains energy Reactions are parallel; when one substance is oxidized, another is reduced at the same time Involved the in the break down of food molecules to produce energy Clinical Connections Harmful and Beneficial Effects of Radiation Some radioactive isotopes release radiation that can break apart molecules, producing tissue damage and/or causing different types of cancer Radon-222, produced during the break down or uranium, may seep out of the soil and accumulate in buildings. It has been linked to cases of lung cancer Other radioisotopes can be used as tracers to follow the movement of certain substances through the body Thallium-201 is used to monitor blood flow through the heart during exercise stress tests
Free Radicals & Antioxidants Sources include exposure to UV radiation, x-rays, and some reactions that occur during normal metabolic processes Certain harmful substances, such as carbon tetrachloride can give rise to free radicals when they are metabolized in the body Linked to cancer, athrosclerosis, Alzheimer s, emphysema, diabetes, cataracts, and arthritis (among other disorders and diseases) Antioxidants, substances that inactivate oxygen-derived free radicals, is thought to slow the pace of damage caused by free radicals. Dietary antioxidants include selenium, zinc, beta-carotene, and vitamins C and E Red, blue, and purple fruits and vegetables also contain high levels of antioxidants Assignments Finish Chapter 1 Review WS Begin Chapter 2 Review WS Read Sections 2.4-2.5 Choose five pieces of technology used in science and brainstorms improvements you would like to see made to it Terminology Quiz next class (1.5)