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Download Atoms are the smallest stable units of matter Electrons occupy a
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Atoms are the smallest stable units of matter • Subatomic particles • Protons = positive charge; weight of approximately 1 Dalton • Neutrons = no charge; weight similar to protons • Electrons = negative charge; weigh 1/1836th Dalton • Protons and neutrons are found in the nucleus; electrons occupy electron cloud • Atomic number = proton number; atomic mass = protons and neutrons • Isotopes are elements with similar numbers of protons but different numbers of neutron Electrons occupy a series of energy levels or electron shells. • The outermost electron shell determines the reactivity of the element. Atoms combine through chemical reactions • Molecule = a chemical structure consisting of molecules held together by covalent bonds • Compound = a chemical substance composed of atoms of two or more elements • There are three types of bond: Ionic, covalent, and hydrogen Ionic Bonding • Exchange of electrons from one atom to another Ionic = attraction between positive cations and negative anions Covalent bonds exist between atoms that share electrons to form a molecule • Double covalent bond • Non-polar covalent bond • Polar covalent bond Hydrogen bonds are weak forces that affect the shape and properties of compounds • Polar covalent bonds that occur when hydrogen covalently bonds with another element Matter and chemical notation • Matter can exist as a solid, liquid or gas • Depends on the interaction of the component atoms or molecules • Molecular weight is the sum of the atomic weights of the component atoms • Chemical notation • Short-hand that describes chemical compounds and reactions Chemical Reactions A chemical reaction occurs when reactants combine to generate one or more products • All chemical reactions in the body constitutes metabolism • Metabolism provides for the capture, storage and release of energy Basic energy concepts • • • • Work = movement of an object or change in its physical structure Energy = the capacity to perform work Kinetic energy is energy of motion Potential energy is stored energy resulting from position or structure • Conversions are not 100% efficient, resulting in release of heat Metabolism • Types of reaction • Decomposition • Synthesis • Exchange • Metabolism is the sum of all reactions • Through catabolism cells gain energy (break down of complex molecules) • Anabolism uses energy (synthesis of new molecules) Reversible reactions • All reactions are theoretically reversible • At equilibrium the rates of two opposing reactions are in balance • Anabolism = catabolism Enzymes, energy and chemical reactions • Activation energy is the amount of energy needed to begin a reaction • Enzymes are catalysts • Reduce energy of activation without being permanently changed or used up Inorganic Compounds Nutrients and Metabolites • Nutrients are essential chemical compounds obtained from the diet • Metabolites are molecules synthesized or broken down inside the body • These can be classified as organic or inorganic compounds • Organic compounds have carbon and hydrogen as their primary structural component • Inorganic compounds are not primarily carbon and hydrogen Water and its properties • Water is the most important constituent of the body • Solution is a uniform mixture of two or more substances • Solvent is the medium in which molecules of solute are dispersed • Water is the solvent in aqueous solutions Electrolytes undergo ionization • Compounds that interact readily with water are hydrophilic • Compounds that do not interact with water are hydrophobic pH is a measure of the concentration of hydrogen ions solution • Neutral • Acidic • Basic Acids and Bases • Acids release hydrogen ions into solution • Bases remove hydrogen ions from solution • Strong acids and strong bases ionize completely • Weak acids and weak bases do not ionize Salts and buffers • Salt = an electrolyte whose cation is not hydrogen and whose anion is not hydroxide • Buffers remove or replace hydrogen ions in solution • Buffer systems maintain the pH of body fluids Organic Compounds Organic compounds • Organic compounds generally include • Carbon • Hydrogen • and sometimes Oxygen • Four major classes of organic compounds are • Carbohydrates • Lipids • Proteins • Nucleic acids • High energy compounds are also organic compounds Carbohydrates • Important energy source for metabolism • Monosaccharides, disaccharides and polysaccharides • Di- and polysaccharides formed from monosaccharides by dehydration synthesis Lipids include fats, oils, and waxes • Five classes: • Fatty acids • Eicosanoids • Glycerides • Steroids • Phospholipids • Glycolipids • Triglycerides = three fatty acids attached by dehydration synthesis to one molecule of glycerol Steroids • Are involved in cell membrane structure • Include sex hormones and hormones regulating metabolism • Are important in lipid digestion Proteins perform many vital functions in the body. The six important types are: • • • • • • Structural proteins Contractile proteins Transport proteins Enzymes Buffering proteins Antibodies Proteins are chains of amino acids • Amino acids contain an amino group, a carboxylic group and a radical group • Polypeptides are linear sequences of amino acids held together by peptide bonds The four levels of protein structure are: • • • • Primary structure (amino acids sequence) Secondary structure (amino acid interactions) Tertiary structure (complex folding) Quaternary structure (protein complexes) Enzyme reactions • Reactants (substrate) interact to yield a product by binding to the active site of the enzyme • Cofactors must bond to the enzyme before substrate binding can occur • Coenzymes are organic cofactors commonly derived from vitamins The shape of a protein determines its function • Proteins pushed outside their optimal temperature and pH range become temporarily or permanently denatured and will cease to function Nucleic acids • Store and process information at the molecular level • Made of purines and pyrimidines • DNA and RNA Nucleic acids are chains of nucleotides • Nucleotides are composed of a sugar, a phosphate and a nitrogenous base • Sugar = deoxyribose (DNA) or ribose (RNA) • DNA Bases = adenine, thymine, cytosine, guanine • RNA bases = adenine, uracil, cytosine, guanine High energy compounds store cellular energy in high energy bonds • Adenosine triphosphate (ATP) • Made by adding a phosphate group to adenosine diphosphate (ADP) • Process referred to as phosphorylation Chemicals and Cells Biochemical compounds form functional units called cells • Metabolic turnover allows cells to change and to adapt to changes in their environment
