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 CarbonHydrogenOxygen 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 …and how insects walk on water It’s why a belly flop hurts…

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

Sodium Chloride Crystals What’s the big deal with weak bonds?

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: AB  A + B Synthesis: A + B  AB Exchange: 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 energy- poor molecules.