Chemistry of Life: Organisation of Matter

**Chemistry of Life: Organization of Matter** **Matter:** Anything that occupies space and has mass. **Mass:** Amount of matter in a substance. **Weight:** Force of gravity on mass. **Element:** Cannot be split into smaller substances by ordinary means. **Main Elements of the Body:** * 112 elements on Earth * In the body: * 96% from 4 elements (C, H, O, N) * 3% from 8 elements * 1% from 14 trace elements **Atomic Structure:** * Atom: Smallest unit of an element * Nucleus: Centrally located, contains protons (+) and neutrons (no charge). * Electrons (-): Revolve around nucleus in energy shells. * Neutral element: # of protons = # of electrons **Atomic Number and Mass Number:** * Atomic number: # of protons in nucleus * Mass number: protons + neutrons * Isotope: Different atoms of same element. - # of protons NOT equal to # of neutrons **Matter Combined:** * Atoms can gain or lose electrons → ions * Atoms can be combined: - 2 atoms of SAME ELEMENT bonded together → MOLECULE - 2 atoms of DIFFERENT ELEMENTS bonded together → COMPOUND * Free radicals: Unpaired electrons in outer shell **Mixtures:** * Mixture: Blend of elements or compounds not bonded together * Solution: 2+ components, small particles, will not settle out * Suspension: 2+ components, large particles, will settle out * Colloid: 2+ components, small particles, will not settle out * Concentration: Amount of solute dissolved in solvent (g/L); clear **Chemical Bonds:** * Chemical bonds: Forces holding atoms together. * Bond formation depends on # of electrons in outer shell * Ionic bonds: Formed when cations (positive) and anions (negative) attract each other. * Ionic compounds: Exist as solids, dissociate easily in water Covalent Bonds: Strongest chemical bonds in the body Formed when atoms share 1, 2, or 3 pairs of electrons Equal sharing of electrons = nonpolar covalent bond Unequal sharing of electrons = polar covalent bond Hydrogen bond: weak, useful for linking molecules to each other Types of Chemical Reactions: Occur when bonds are formed or broken Synthesis (anabolism): A + B → AB Decomposition (catabolism): AB → A + B Exchange: AB + CD → AC + BD Energy and Chemical Reactions: Energy (capacity to do work) Exergonic reactions: Release energy (using ATP) Endergonic reactions: Require energy (forming ATP) Activation energy: Energy required for a reaction to occur Catalysts: Lower activation energy needed and speed up reactions Enzymes: Act as catalysts to speed up rate of reaction Specific to a substrate type in reaction Aren't changed by the reaction Depends on enzyme shape Inorganic vs Organic Compounds Inorganic No chains of C-H bonds Ionic or covalent bonds Water, salts, acids, bases (rocks, lemon juice) Organic Always have chains of C-H bonds Usually contain O, N, P Covalent bonded Proteins, lipids, carbs, nucleic acids Inorganic Compounds Water Polar covalent bonds (ionic compounds are hydrophilic) Solvent: Key to solutions and suspensions High specific heat: helps regulate body temperature High heat of vaporization: helps cool the body **Acids, Bases, and Salts:** * **Dissociation:** Compounds separate into ions in a solution * **Acids:** Dissociate into H+ ions and anions * **Bases:** Dissociate into OH- ions and cations * **Salts:** Dissociate into cations and anions (no H+ or OH- ions formed) **pH and Buffer Systems:** * **pH:** Measure of H+ ions in a solution * **Buffers:** Convert strong acids or bases to weak acids or bases * **Body uses buffers to maintain pH homeostasis** **Organic Compounds:** * Carbon forms up to 4 covalent bonds * **Dehydration Synthesis:** Anabolic, bonds monomers into polymers * **Hydrolysis:** Catabolic, breaks polymers apart **Carbohydrates:** * Contain C, H, and O (1:2:1 ratio) * Provide most of the energy needed for life * **Monosaccharides:** Single sugar molecule (pentose, hexose form) * **Disaccharides:** Two monosaccharides bonded together * **Polysaccharides:** Many monosaccharides * Starch: Storage form in plants * Glycogen: Storage form in animals * Fiber (cellulose): Structural form in plants **Lipids:** * Contain C, H, and O * Do not have a 1:2:1 ratio * Hydrophobic (mostly nonpolar covalent bonds) * **Triglycerides:** 3 fatty acid chains + glycerol * **Phospholipids:** * 2 fatty acid chains + phosphate group * Bilayer forms cell membranes * **Cholesterol:** * 4 rings of carbon atoms * Used in membranes, some hormones