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Chapter 2 The Chemical Basis of Life 1 Basic Chemistry • Matter and Energy –Matter, Mass, and Weight • Matter: everything that occupies space and has mass. You, your chair, your car, the air. • Mass: the amount of matter in an object. • Weight: the gravitational force acting on an object of a given mass (on earth, mass = weight). 2 Basic Chemistry • Elements and Atoms – Element: • the simplest type of matter with unique chemical properties. • composed of atoms of only one kind (gold, helium, carbon, oxygen). – Atom: • smallest particle of an element that has chemical characteristics of that element. • Individual atoms are too small to see, even with a microscope. 3 Atomic Structure • Everything (all matter) is made of Atoms. • Atoms: composed of subatomic particles – Neutrons: no electrical charge (0) – Protons: one positive charge (+) – Electrons: one negative charge (-) • Nucleus: formed by protons and neutrons. Most of the mass of atom. • Most of the volume of an atom occupied by electrons in orbit. 4 Atomic Number and Mass Number • Atomic Number (P) : number of protons in each atom – Determines element and it characteristics. – Usually equal to the number of electrons. – Atom is neutrally charged. – Periodic table shows the atomic number of each element. 5 Electron orbits or shells • Electrons are thought of as circling the nucleus in orbits or shells. – The inner shell can hold 2 electrons. – The next shell holds 8 electrons. The next 18, then 32. – The inner shells fill up first. – The outermost shell containing electrons is called the valence shell. 6 Electrons and Chemical Bonding • Intramolecular bonding occurs when outermost (valence) electrons are either shared with or transferred to another atom. – Ionic Bonding: atoms exchange electrons. – Covalent Bonding: two or more atoms share electron pairs. 7 Ionic Bonding • Ion: an atom that loses or gains one or more electrons and becomes charged. – Cation: positively charged ion, Written as Na+, Ca2+ – Anion: negatively charged ion, Written as Cl- • In an ionic bond, cations and anions are attracted to each other and remain close to each other. 8 Play Video Covalent Bonding Atoms share one or more pairs of electrons – Single covalent: two atoms share one pair of electrons. – Double covalent: Two atoms share 2 pairs of electrons. – Nonpolar covalent: Electrons shared equally because nuclei attract the electrons equally. – Polar covalent: Electrons not shared equally because one nucleus attracts the electrons more than the other does. 9 Molecules • 2 or more atoms bonded together form a Molecule. • Water= 2 hydrogens bound to an oxygen • Written as a formula: H2O • Some molecules (like glucose) are very complex and we simplify with line drawings. 10 Hydrogen Bonds • When an oxygen has polar covalent bonds with 2 hydrogen atoms, the oxygen pulls the electrons to itself. • Oxygen side of the molecule is partly negative. • Hydrogen side is partly positive. • Water is a polar molecule. • The hydrogen of one molecule is attracted to the oxygen of another molecule • This makes water sticky. • Hydrogen bonds occur in other molecules, too. 11 Intermolecular Forces: Hydrogen Bonds • Occur when the positively charged H of one molecule is attracted to the negatively charged O, N or F of another molecule. – For example, in water the positively charged hydrogen atoms of one water molecule bond with the negatively charged oxygen atoms of other water molecules. – Hydrogen bonds play an important role in determining the shape of complex molecules. 12 13 Solubility and Dissociation • Solubility: ability of one substance to dissolve in another. – For example, sugar or salt dissolves in water • Dissociation or Separation: – In ionic compounds, • positive ions are attracted to negative end of water molecules. • negative ions attracted to positive end of water molecules. – The ions separate and each becomes surrounded by 14 water molecules. Functional Groups • Organic molecules may have one or more functional groups. • All functional groups are polar because their oxygen or nitrogen atoms exert a strong pull on shared electrons. • Their polarity makes them hydrophilic (water loving) and therefore soluble in water, the solvent of life. • 15 16 Chemical Reactions • Atoms, ions, molecules or compounds interact to form or break chemical bonds. – Reactants: substances that enter into a chemical reaction. – Products: substances that result from the reaction – Synthesis = anabolism = making chemical bonds – Decomposition = catabolism = breaking chemical bonds • Metabolism: collective term used for the sum of all of the anabolic and catabolic reactions in the body. 17 Synthetic Reactions • Two or more reactants chemically combine to form a new and larger product. Anabolism. – – – – When chemical bonds are made; energy is stored in the bonds. Responsible for growth, maintenance and repair Dehydration: synthetic reaction where water is a product. Produce chemicals of life: carbohydrates, proteins, lipids, and nucleic acids. 18 Decomposition Reactions • A large reactant is broken down to form smaller products. Catabolism. – When chemical bonds are broken, energy is released. – Hydrolysis: water is split into two parts that contribute to the formation of the products. – Example: the breakdown of starch to sugars with a release of energy that the body can use. 19 Reversible Reactions • Chemical reactions in which the reaction can proceed either from reactants to products or from products to reactants. • Equilibrium: rate of product formation is equal to rate of reactant formation. • Equilibrium is like Substituting Players in a Sports Game. • H2O H+ + OH20 Oxidation-Reduction Reactions • Oxidation-Reduction Reactions: the complete or partial loss of an electron by one atom is accompanied by the gain of that electron by another atom – Na + Cl Na+ Cl- • Oxidation: loss of an electron by an atom • Reduction: gain of an electron by an atom • Which atom is oxidized? 21 Energy: the capacity to do work • Potential Energy: – stored energy – energy that could do work if it were released. • Kinetic Energy: – does work and moves matter – energy of motion 22 Energy: the capacity to do work • Mechanical Energy: energy resulting from the position or movement of objects • Heat Energy: energy that flows between objects of different temperatures • Chemical Energy: form of potential energy in the chemical bonds of a substance 23 Heat Energy • When a chemical bond is broken and energy is released, only some of that energy is stored. • Energy that is released but not captured is released as heat. • That heat is used by humans to maintain body temperature. 24 Speed of Chemical Reactions • Temperature affects rate of reaction. – Increase in temperature means increase of kinetic energy. – Molecules move faster, collide harder and more frequently. • Concentration of reactants affects rate of reaction. – As concentration of reactants increases, rate of reaction increases. • Catalysts: substances that increase the rate of chemical reactions without being permanently changed or depleted 25 Activation Energy and Enzymes • Activation Energy: minimum energy reactants must have to start a chemical reaction. • Enzymes: protein catalysts that increase the rate of chemical reactions by lowering the activation energy necessary for reaction to begin. 26 Solutions and Concentration • Solution: mixture of liquids, gasses, or solids that are uniformly distributed – Solvent: substance that dissolves the solute. – Solute: substance that is dissolved by the solvent. – Like dissolves like; polar substances dissolve in water, nonpolar substances dissolve in oils. • Concentration: measure of number of particles of solute per volume of solution (particles/ml). – Unit used by physiologists is osmole. – Concentration = osmolality. – Concentration of body fluids influences movement of fluid into and out of cells. 27 Chemistry • Inorganic Chemistry: generally, substances that do not contain carbon – Water, oxygen – Exceptions: CO, CO2, and HCO3- • Organic Chemistry: study of carboncontaining substances. 28 Oxygen and Carbon Dioxide: Important Inorganic Compounds • Oxygen (O2): – Two oxygen molecules with double covalent bond (O=O) – Important reactant in metabolism. • Carbon dioxide (CO2): – produced during the catabolism of organic compounds. – Metabolic waste product. 29 Organic Chemistry: Macromolecules • Carbohydrates: cellulose, starches, sugars – Strings of sugar molecules – Example: sucrose – Energy sources and structure • Proteins: muscle – Example: insulin – Functions: regulate processes, aid transport, protection, muscle contraction, structure, energy • Lipids: fats, oils, waxes – Relatively insoluble in water. – Example: anabolic steroids – Functions: protection, insulation, physiological regulation, component of cell membranes, energy source • Nucleic Acids: – Examples: ATP, DNA, RNA – Functions: store energy, genetic information 30 Carbohydrates: Monosaccharides • Simple sugars. • Six-carbon sugars like glucose, fructose, and galactose are important in the diet as energy sources. • Five-carbon sugars are components of ATP, DNA and RNA 31 Carbohydrates: Disaccharides • Two simple sugars bound together by dehydration • Examples: sucrose, lactose, maltose 32 Carbohydrates: Polysaccharides • Long chains of many monosaccharides. • Storage molecules for monosaccharides and form part of cell surface markers • Glycogen formed by animals. • Starch and cellulose formed by plants – Starch in food is used as a source of monosaccharides – Cellulose in food acts as fiber (bulk) in the diet 33 Lipids: Fats • • • • • • 95% triglycerides composed of glycerol and fatty acids Glycerol linked by dehydration synthesis to 3 fatty acids Saturated = contains only single covalent bonds (lard) Unsaturated = 1 double covalent bonds (vegetable oils) Trans fats – artificially saturated (hydrogenated) Functions: protection, insulation, energy source 34 Lipids: Phospholipids • Polar (hydrophilic) at one end • Nonpolar (hydrophobic) at the other. • Function: important structural component of cell membranes 35 Lipids: Steroids • • • • Cholesterol, bile salts, hormones Carbon atoms arranged in four rings Functions: physiological regulators and component of cell membranes Anabolic-androgenic steroids are derivatives of the male hormone, testosterone 36 Proteins • Large polar compounds • Amino acids: – monomer – building blocks of protein • Peptide bonds: covalent bonds formed between amino acids during protein synthesis ProteinVideo 37 Protein Structure • Primary: sequence of amino acids in the polypeptide chain • Secondary: formation of helices or of pleated sheets; caused in part by H bonds between amino acids 38 Protein Structure • Tertiary: folding and bending of chain caused by hydrogen bonding • Quaternary: two or more proteins associate as a functional unit 39 Denaturation of proteins • Denaturation - the alteration of a protein shape through some form of external stress (for example, heat, acid or alkali), so that it will no longer be able to carry out its cellular function. • Extreme changes in body temperature or blood pH can cause inactivation of proteins. 40 Enzymes: Protein Catalysts • Lower the activation energy necessary for a reaction to occur • bring reactants into close proximity • Three-dimensional shape contains an active site where reactants attach. • Enzyme names usually end in – ase and often have the same word stem as the reactant, example: lipase. 41 Nucleic Acids • Include the nucleic acids: DNA and RNA and ATP. • Nucleotides – monomer – Composed of a fivecarbon sugar, a nitrogenous base, and a phosphate 42 DNA and RNA DNA • deoxyribonucleic acid • Genetic material of cells copied from one generation to next • Composed of 2 strands of nucleotides in a double helix RNA • ribonucleic acid • Similar to a single strand of DNA • Responsible for interpreting the code within DNA into the primary structure of proteins 43 Adenosine Triphosphate (ATP) • • • • Energy currency of the body Provides energy for other chemical reactions as anabolism or drive cell processes as muscle contraction All energy-requiring chemical reactions stop when there is inadequate ATP 3 phosphate bonds (PO4) with energy stored in last PO4 44 bond ATP and Potential Energy 45