Transcript Slides
The maintenance of a relatively constant internal environment in is termed: A. Positive Feedback B. Homeostasis C. Negative Feedback D. Homeopathy E. Osmosis Which of the following is an organ? A. Mitochondria B. Blood C. Fat D. Skin E. Cardiac Muscle A collection of cells that work together to perform a function is termed a(n): A. Organelle B. Organ C. Cell D. Tissue E. Prison Chemistry of Life I . Properties of Atoms II. Chemical Bonds III. Reactions Why do I have to learn Chemistry? Answer: Physiology is applied chemistry Topics requiring knowledge of chemistry: - metabolism - nerve impulses - blood pH - protein structure The Elements of the Human Body • We are mostly Carbon, Hydrogen, Oxygen, Nitrogen • What substance makes up 65% of your mass? The Elements of the Human Body Carbon Hydrogen Oxygen Nitrogen Why are these particular elements so common? Planetary Models of an Atom Review of Atomic Structure • Nucleus – protons: positive charge, mass of 1 unit – neutrons: neutral charge, mass of 1 unit Review of Atomic Structure • Electrons orbit the nucleus – negative charge, mass negligible Review of Atomic Structure • Electrons can occur in many shells – Valence electrons are in outermost shell Review of Atomic Structure • Electrons can occur in many shells – Valence electrons are in outermost shell • form bonds with other atoms • one bond formed for each shared, donated, or received electron What Determines the Number of Bonds? • The Duet Rule – Hydrogen wants 2 electrons in shell What Determines the Number of Bonds? • The Duet Rule – Hydrogen wants 2 electrons in shell • The Octet Rule – Atoms want to fill their outer shell – Shells 2 & 3 hold up to 8 electrons The Formation of Water Chemistry of Life I . Properties of Atoms II. Chemical Bonds III. Reactions Chemical Bonds • Covalent bonds • Hydrogen bonds • Ionic bonds Covalent Bonds • Sharing of valence electrons • Types of covalent bonds 1. Single, double, or triple covalent bond • 2, 4, or 6 electrons are shared Single Covalent Bond One pair of electrons are shared Covalent Bonds • • Sharing of valence electrons Types of covalent bonds 2. Nonpolar or polar covalent bond • Share electrons evenly or not Types of Covalent Bonds • electrons spend equal time around each nucleus • electrons spend more time around one nucleus • Creates a Dipole Water is formed by polar covalent bonds Dipole is the partial negative charge on the O and the partial positive charge on the H Covalent Bonds are Really Strong Bond…… Covalent Bond Chemical Bonds • Covalent bonds • Hydrogen bonds • Ionic bonds Hydrogen Bonds • Weakest of the bonds • Form because of the dipole • Greatest physiological importance – properties of water – shape of proteins and DNA Hydrogen Bonding in Water The Weakness of the Hydrogen Bond Hydrogen Bonds Create Surface Tension It’s why a belly flop hurts… …and how insects walk on water Chemical Bonds • Covalent bonds • Hydrogen bonds • Ionic bonds Ionic Bonds • Attraction of charged atoms (ions) • Weak bonds that are readily broken Ionization • One atom gives up an electron • Another atom “steals” it • Both atoms satisfy Octet Rule Ionization • Chloride is now an anion (net negative charge) • Sodium is now a cation (net positive charge) Hydrogen & ionic bonds are like a Hollywood marriage: Weak Don’t Hassel the Hoff What’s the big deal with weak bonds? Sodium Chloride Crystals Salts Dissolve in Water • Ionic bonds are weak and break in water • Hydrogen bonds form between water and ions. • Many H-bonds can overpower ionic bonds Chemistry of Life I . Properties of Atoms II. Chemical Bonds III. Reactions Chemical Reactions • A chemical bond is formed or broken • A chemical equation shows: reactants products • Types of Reactions Decomposition: Synthesis: Exchange: AB A + B A + B AB AB + CD AC + BD Summary • Life is composed mainly of Carbon, Hydrogen, Oxygen, and Nitrogen. Carbon serves as the structural backbone for most biological molecules. • An atom’s reactive properties are determined by its valence. • Atoms can form covalent, hydrogen, or ionic bonds. • Reactants can unite to form larger energy-rich molecules or decompose to form smaller energypoor molecules.