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 1
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? 2
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 3
Isotopes Differ in Neutrons Different forms of the same element Cobalt-60 Radiotherapy Sterilization 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 4
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 5
The Formation of Water Chemistry of Life I. Properties of Atoms II. Chemical Bonds III. Reactions Chemical Bonds Covalent bonds Hydrogen bonds Ionic bonds 6
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 1. Single, double, or triple covalent bond 2, 4, or 6 electrons are shared 2. Nonpolar or polar covalent bond Share electrons evenly or not 7
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 8
Chemical Bonds Covalent bonds Hydrogen bonds Ionic bonds Hydrogen Bonds Weakest chemical bond Form because of the dipole Hydrogen Bonding in Water 9
Hydrogen Bonds Weakest chemical bond Form because of the dipole Great physiological importance properties of water shape of proteins and DNA Weakness of the Hydrogen Bond Hydrogen Bonds Create Surface Tension It s why a belly flop hurts and how insects walk on water 10
Chemical Bonds Covalent bonds Hydrogen bonds Ionic bonds Ionic Bonds Electrons are donated between atoms Attraction of charged atoms (ions) Forms a salt or electrolyte Weak bonds that are readily broken Ionization One atom gives up an electron Another atom steals it Both atoms satisfy Octet Rule 11
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 12
Electrolytes/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 Dissociation of Calcium Carbonate CaCO 3 is a salt held together by ionic bonds Dissociates in H 2 O Low solubility in H 2 O Chemistry of Life I. Properties of Atoms II. Chemical Bonds III. Reactions 13
Chemical Reactions A chemical bond is formed or broken A chemical equation shows: reactants products Types of Reactions Decomposition: AB A + B Synthesis: A + B AB Exchange: AB + CD AC + BD Condensation Hydrolysis 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 electrons. Atoms can form covalent, hydrogen, or ionic bonds. Reactants can unite to form larger energy-rich molecules or decompose to form smaller energypoor molecules. 14