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Chemistry of Life Objectives • Define the terms atom, element, molecule, and compound. • Describe the structure of an atom. • Compare and contrast ionic and covalent types of chemical bonding. • Distinguish between organic and inorganic chemical compounds. Objectives • Discuss the chemical characteristics of water. • Explain the concept of PH. • Discuss the structure and function of the following types of organic molecules: – Carbs – Lipids – Proteins – Nucleic acid Levels of Chemical Organization • Matter – Anything that occupies space and has mass. • Molecules are particles of matter, made up of atoms. Atoms • Nucleus – Central core of the atom – Contains subatomic particles: • Protons = positively charged –Number of protons determines type of atom. (atomic number) • Neutrons = no charge Atoms • Orbiting around the nucleus are negatively charged particles called electrons. – Energy levels (shells) – Outer level may hold up to 8 electrons. – Energy increases with distance from the nucleus. – Number of electrons in the outer shell affects the atoms ability to unite with other atoms. Elements, Molecules, and Compounds • Element – Pure substance; made up of only one kind of atom. • Molecule – Group of atoms bound together. • Compound – Substances whose molecules have more than one kind of atom. Elements, Molecules, and Compounds • Compounds are written in formulas containing symbols and number of atoms in subscript. • Example: Carbon Dioxide –CO2 Elements, Molecules, and Compounds • Four kinds of atoms make up approx. 96% of the human body. – Oxygen – Carbon – Hydrogen – Nitrogen • 20 or more trace elements. Chemical Bonding • Chemical bonds form to make atoms more stable. – Considered stable when the outer energy level is full. (8 electrons) • Atoms will share, donate, or borrow electrons to fill the outermost energy level. Ionic Bonds • Ions form when atoms gain or lose electrons in the outer energy levels. • Positive Ions – Have lost electrons becoming positively charged. • Negative Ions – Have gained electrons becoming negatively charged. Ionic Bonds • Example: (Fig 2-2) – Sodium – Na • Containing 1 electron in outer shell. – Chlorine – Cl • Contains 7 electrons in outer shell. • Donating or borrowing electrons make sodium positively charged and chlorine negatively charged forming a bond NaCl or Sodium Cloride. Electrolytes • Ionic molecules dissociate easily in water forming electrolytes. • Examples: – Sodium – Na+ – Chloride – Cl– Calcium – Ca++ – Potassium – K+ Covalent Bonds • Atoms that share electrons, rather than donate or receive them form covalent bonds. • Bonds are not easily broken and do not break apart in water. Organic/Inorganic Compounds • Living organisms contain both organic and inorganic compounds. • Organic compounds contain: – Carbon to Carbon covalent bonds And/Or – Carbon to Hydrogen covalent bonds • Inorganic compounds lack these bonds. Inorganic Compounds • Water – Most abundant compound in the body. – Solvent that other solutes are dissolved. • Aqueous solution – Essential in many important chemical reactions. Chemical Reactions Fig 2-4 • Dehydration synthesis – Water is removed from smaller molecules so larger ones can be created. • Hydrolysis – Water is added to larger molecules to break them apart into smaller ones. Chemical Reactions • Chemical reactions involve energy transfers. • Some of the energy used to build the molecules are stored as potential energy and released when broken apart. • Example: – Adenosine Triphosphate (ATP) – Needed for muscle contraction. Chemical Reactions • Chemical equations show how reactants interact to form products. • Written with “arrows” to separate and show products. • Example: – K+ + ClKCL The pH Scale Acids, Bases, and Salts • Water molecules dissociate to form equal amounts of Hydrogen Ions/Hydroxide Ions. – Neutral pH 7.0 • Acids are higher in Hydrogen Ions (< 7.0) • Bases/Alkalines are lower in Hydrogen Ions (>7.0) Acids, Bases, and Salts • Strong acids or strong bases are neutralized when mixed with each other and form salts. • Buffers are chemical systems that absorb excess acids or bases and thus maintain a relatively stable pH. Organic Compounds • More complex than inorganic compounds. – Carbohydrates – Lipids – Proteins – Nucleic acids Organic Compounds • Carbohydrates – Sugars and complex carbohydrates • Monosaccharide (Glucose/Dextrose) • Disaccharide (Sucrose/Lactose) • Polysaccharides (Glycogen/Starches) – Contains Carbon, Hydrogen, Organic Compounds • Lipids - Fats and oils – Triglycerides • Glycerol and 3 fatty acids. • Stores energy. – Phospholipids • Phosphorus unit with 2 fatty acids • Forms cell membranes – Cholesterol • Transports lipids • Basis for making steroid hormones Organic Compounds • Proteins – Very large molecules composed of amino acids held together in long folded chains by peptide bonds. • Structural proteins • Functional proteins – Can bond with other compounds to form mixed molecules: • Glycoproteins • Lipoproteins Organic Compounds • Structural Proteins – Form structures in the body. – Collagen is a fibrous protein that holds many tissues together. – Keratin forms tough, waterproof fibers in the outer layer of the skin. Organic Compounds • Functional Proteins – Participate in chemical processes. – Examples: • Hormones • Cell membrane channels/receptors • Enzymes Organic Compounds • Enzymes – Catalysts • Assist with chemical reactions – Lock and Key model • Each enzyme fits a particular molecule that it acts on as a key fits into a lock. Organic Compounds • Nucleic acids – Direct proteins for overall body structure and function. – Basic building blocks are called nucleotides. • Phosphate, sugar, and nitrogen base. – Deoxyribonucleic Acid (DNA) – Ribonucleic Acid (RNA) Nucleic Acids • Deoxyribonucleic Acid (DNA) • Nucleotide bases: – Adensine – Thymine – Guanine – Cytosine • Used as a master code for assembling proteins. Nucleic Acids • Ribonucleic Acid (RNA) • Nucleotide bases: – Adensine – Uracil – Guanine – Cytosine • Used as a temporary working copy of a gene. • Portion of DNA code Are you as confused as I am? Any Questions?