Characteristics of Life Part 2: Chemistry of Life

Chemistry of Life matter elements 92 Carbon (C) Hydrogen (H) II. THE CHEMISTRY OF LIFE (pp. 148 - 155) Organisms are composed of _________, which is anything that takes up space and has mass. All matter is composed of ____________, pure substances composed entirely of one type of atom and cannot be broken down by chemical reactions. A. Elements – There are ___ naturally occurring elements in nature, 25 of which are essential to life. Four elements make up approx. 96% of living matter. They are: matter elements 92 Carbon (C) Hydrogen (H) Oxygen (O) Nitrogen(N)

Chemistry of Life trace elements matter element protons + neutrons Sulfur and Phosphorus make up 3 %. These 6 elements are known as: “SPONCH”. S – sulfur P – phosphorus O – oxygen N – nitrogen C – carbon H – hydrogen 3. Remaining 1% is composed of ________ ___________which are required by an organism in minute amounts. Ex. Iron (Fe), Iodine (I), Copper (Cu), Zinc (Zn) trace elements Atoms – An atom is the smallest unit of __________that still retains the properties of that __________. 1. Nucleus a. center of atom. Composed of b. _________ which have a __ charge. c. ___________ which are _________. d. overall charge of nucleus is __. Why? matter element protons + neutrons neutral +

Chemistry of Life electron shells electrons - valence Atomic # protons 2. Electron cloud: contains orbitals aka. __________ _______. a. area surrounding nucleus b. ___________ are in constant motion in this space. electrons have a __ charge; therefore attracted to the positively charged nucleus. The reactivity of an atom and the type of bond that it forms are determined by the number of ___________ electrons it has. electron shells electrons - valence 3. Charge of Atoms a. Have equal # of protons & electrons which makes the atom neutral b. __________: # of _________ that the element contains. Ex. Atomic # of carbon (C) = 6 Atomic # protons

Chemistry of Life elements chemical bonds incomplete sharing C. Compounds 1. Any substance consisting of two or more ___________ combined in a fixed ratio. 2. Held together by ___________________. elements chemical bonds D. Chemical Bonds – Atoms with ______________ valence shells can interact with one another by either __________ or ______________valence electrons. The ___________ kinds of chemical bonds are covalent and ionic. incomplete sharing transferring strongest

sharing molecules transferred ions negative charge gains loses 1. Covalent Bonds a. Formed by the __________ of valence electrons of two atoms. b. Results in very stable compounds called ______________. c. Ex: H2O, glucose, DNA sharing molecules 2. Ionic Bonds a. One or more electrons are _____________ from one atom to another. b. Results in two oppositely charged particles called ______. * an atom that _______ electrons has a ___________________. * an atom that ________electrons has a ___________________. * attraction between _____________ charged ions forms ionic bonds. transferred ions gains negative charge loses positive charge oppositely * Ex: NaCl or table salt 3. Hydrogen Bonds Bonds found ___________water molecules Aka: __________________ bonds Very ______ bonds between intermolecular weak