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THE CHEMISTRY OF LIFE Review/Background Information Important Words Elements – pure substances that cannot be broken down any further. Atom – the smallest unit of an element. Important Words Molecule – a substance made up of more than one atom. Compound – a substance made up of two or more different Important Words Ion – an atom that has a different number or electrons (and thus has a charge). Isotope – an atom that has a different number of neutrons. Important Words Covalent Bond – a molecule where atoms share electrons. Ionic Bond – a compound where atoms transfer electrons. The Atom “Parts” of the atom Neutron (0 charge) Proton (+ charge) Electron (- charge) The basic structure of an atom The Nucleus Central core Consists of protons and neutrons Contains most of the mass of the atom The Protons Positively charged IN the nucleus Weigh 1 dalton The Neutrons Are neutral (no charge) In the nucleus Weigh 1 dalton The Electrons Negatively charged Weigh 1/2000 dalton (super tiny!) little or no mass Travel at very high speeds at various distances (energy levels) from the nucleus Atomic Number - the # of protons Atomic Mass – the # of protons + Neutrons Energy Levels Atoms have energy levels The 1st level holds 2 electrons The next 6 levels hold 8 electrons (octet rule) There are more than 100 elements (92 naturally occurring) The Periodic Table Common Elements in Biology Calcium Carbon Chlorine Copper Fluorine Hydrogen Iodine Iron Magnesium Ca C Cl Cu F H I Fe Mg Phosphorus Nitrogen Oxygen Potassium Silicon Sodium Sulfur Tin Zinc P N O K Si Na S Sn Zn The most frequently occurring elements in living things are: Oxygen (65%) Carbon (19%) hydrogen (10%) Nitrogen (3%) Other important elements Sulfur Calcium Phosphorous Iron sodium Sulfur Can be found in some amino acids. Phosphorous A component of ATP Forms DNA Calcium Cell structure in prokaryotes and plants Necessary for healthy bones Involved in the transmission of nerve messages Iron Helps form chlorophyll in plants Makes up hemoglobin (helps oxygen transport in red blood cells) Sodium Can help in photosynthesis Helps transport glucose across the membrane Water Water is Important to Life! Water covers ¾ of the Earth. It is the most abundant compound in living things. It is essential to life! What makes water special? Water is POLAR – the oxygen atom attracts more of the electrons than the hydrogen atoms do. POLARITY The structure of the water molecule Covalent bond The nucleus of oxygen is larger and has a greater charge (+8) than the hydrogen nucleus (+1). The electrons that are shared are found “closer” to the oxygen nucleus. This creates a polar molecule – the oxygen side is lightly negative and the hydrogen side is slightly positive. This polarity results in hydrogen bonds Weak bond between the H of one molecule and the C of another molecule. Hydrogen bonds Because of the bonds, water has some unique properties! Water “mini-lab” Properties of Water 1. Cohesive properties 2. Thermal properties 3. Solvent properties Cohesive properties Cohesion - Water molecules Sticking together Cohesive properties The way plants transport water through their tissues is called transpiration and depends on the cohesive nature of water. Thermal properties Water has a high specific heat capacity (the amount of heat required to change a substance’s temperature). Thermal properties A body of water is thermostable. Water maintains its temperature relatively well and has less variation in temperature than air and land. Thermal properties Water acts as a coolant. It absorbs heat before it evaporates and in doing so reduces body temperature. Heat from chemical reactions can be removed, to protect enzymes. Blood can carry heat to cold parts of the body. Solvent properties Because water is polar, it is strongly attracted to ions. This has the effect of isolating one ion from another (which is commonly known as solubility). Dissolving Salt Water is the solvent of blood, tissue fluid and cytoplasm. It allows the transport of soluble minerals, carbohydrates, amino acids, etc. that organisms need to survive. Other unique things about water Water expands as it freezes (ice floats) The universal solvent (lots of things can dissolve in it) Adhesive Part of biogeochemical cycles Essential to life