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Transcript
ANPS019 09/02/2011 COVALENT BOND Atoms share electrons to form a molecule Very strong If atoms share electrons equally, nonpolar covalent bond -equal pull, nonpolar bonds If atoms share electrons unequally, polar covalent bond THE STRUCTURE OF WATER MOLEULCES Polar covalent bond Two hydrogen atoms each form a covalent bond with the same oxygen atom Electronegativity: more pull The oxygen atom is bigger and exerts more pull on the electrons The electrons spend more time around the oxygen nucleus than around the hydrogen nucleus, thus are not share equally. -The oxygen acts more positively, and the hydrogen acts more negatively The is a polar covalent HYDROGEN BONDS (formed all over the body) Occur when hydrogen bonds covalently with other elements Unequal sharing of electrons creates a polar molecule The weakly positive hydrogen atom of a molecule may be attracted to negatively charged atoms of other molecules Hydrogen bonds create weak forces that affect the shape and properties of compounds THE STRUCTURE OF WATER IS BASED ON HYDROGEN BONDING Individual water molecules are attracted to one another by hydrogen bonds between the oxygen atom (slight negative charge) of one molecule and the hydrogen atom (slight positive charge) of another water molecule Each water molecule is held together by polar covalent bonds One water molecule is attracted to another by HYDROGEN BONDS WATER MOLECULES AND SOLUTIONS The polar water molecule is attracted to any solute with charged atoms Most ions exist in the body with a shell of water surrounding them Anything with a charge exists well with water PROPERTIES OF WATER Solubility: -most molecules in body dissolved in water (but not all) Reactivity -water is involved in many of the reactions in the body High Heat Capacity -water can absorb and retain a great deal of heat Lubrication: -little friction between water molecules so water is protective for many interactions between organs IMPORTANT TERMS Compounds that interact readily with water hydrophilic Compounds that do not interact with water are hydrophobic --example, fatty substances A CHEMICAL REACTION OCCURS WHEN REACTANTS COMBINE TO GENERATE ONE OR MORE PROFUCTS (Chemical reactions should go both ways) All chemical reactions in the body constitutes metabolism Metabolism provides for the capture, storage and release of energy All reactions are theoretically reversible Anabolism = building larger molecules from smaller ones Catabolism = breaking larger molecules into smaller one At equilibrium the rates of two opposing reactions are in balance: anabolism = catabolism ENZYMES Most enzymes are proteins: organic molecules Reactants (substrate interact to yield a product by binding to the active site of the enzyme Enzymes are catalysts that promote chemical reactions Active site: substrate binds to enzyme --active sites are unique for each substrate Enzymes can do reaction repeatedly ENZYMES AND ACTIVATION ENERGY Activation energy is the amount of energy needed to begin a reaction Enzymes make reaction more likely Most reactions require enzymes Enzymes reduce energy of activation, making it more likely a reaction will occur Enzymes are not changed or used up in the reaction, so one enzyme can catalyze the same reaction over and over in the cell pH A measure of concentration of hydrogen ions in a solution Solutions can be classified by their pH as neutral, acidic (more H+), or basic (less H-) Lower # is more acidic 7 is neutral High number is basic BUFFERS 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 completely *BUFFERS ARE VERY IMPORTANT TO SUSTAINING BODY AND BLOOD pH: Blood pH is maintained over a very small range (7.35-7.45) because compounds in blood act as weak acids and bases, releasing or removing small numbers of H+ ions to keep pH stable NUTRIENTS AND METABOLITES Nutrients are essential chemical compounds obtained from their diet Metabolites are molecules synthesized or broken down inside the body These can be classified as organic or inorganic compounds: ORGANIC: have carbon and hydrogen as their primary structural component INORGANIC: not primarily carbon and hydrogen ORGANIC COMPOUNDS Usually large, complex molecules containing carbon and usually hydrogen and oxygen Four major classes of organic compounds 1. Carbohydrates 2. Lipids 3. Proteins 4. Nucleic acids (Found in small amounts) The structure of the carbon atom gives it unique bonding properties: VERSATILE Maybe form single bonds, double bonds, triple bond Bonding pattern influences the shape of molecule: complexity in sizes and shapes due to bending of bonding Carbon based molecules can have wide range of sized and shapes CARBOHYDRATES *most simple Key example: GLUCOSE Sugars and starches, glycogen Hydrophilic molecules Important energy source for metabolism Occur as monosaccharides, disaccharides and polysaccharides -di and polysaccharides formed from monosaccharides by dehydration synthesis (removal of water molecule) THE FORMATION AND BREAKDOWN OF COMPLEX SUGARS Water is very important with the interaction of sugar molecules Dehydration synthesis: two molecules, such as two monosaccharides, are joined together by the removal of a water molecule, to form a disaccharide. Hydration synthesis: a complex molecule is broke down by the addition of a water molecule. Disaccharide to 2 monosaccharides. POLYSACCHARIDES ARE VERY LARGE CARBOHYDRATES -straight or high branched Hydrophilic Large size makes them ideal molecules to ‘hold” water in the body LIPIDS Less oxygen, but same about of carbon as carbohydrates Includes fats, oils, and waxes Set of compounds Hydrophobic Five classes: 1. Phospholipids and glycolipids: uses in cell membrane 2. Fatty acids: uses in building blocks, energy 3. Glyceridses: uses: fatty acids + glycerol = body fat 4. Steroids: uses cholesterol, some hormones 5. Eicosanoids: uses prostaglandins, etc cell messages -produced acid released by cell FATTY ACIDS Long carbon chains with hydrogen atoms attached *** -COOH (Carboxylic Acid group) 1. Saturated: all single bonds 2. Unsaturated: double bonds which form kinks TRIGLYCERIDES Formed storage fats Triglycerides = three fatty acids attached by dehydration synthesis to one molecule of glycerol -energy source -insulation -protection STEROIDS Cholesterol is critical in cell membrane structure: “structural lipid” -Four ring structure Include sec hormones (“sex steroids”) and hormones regulating metabolism (“corticosteroids”) --help suppress immune system PROTEINS Most abundant organic compounds in human body 20% totally body weight Proteins perform vital functions in the body 1. Structural proteins 2. Contractile proteins: muscles 3. Transport proteins: shovel or move other things in body 4. Enzymes: metabolic activity 5. Buffering proteins: maintain pH 6. Antibodies: fight disease AMINO ACIDS ARE THE BUILDING BLOCKS OF PROTEINS Amino acids contain: -a central carbon atom -an amino group -a carboxylic group -a radical group --differs between amino acids --20 different combinations Amino acids join with peptide bonds to form linear stands of molecules Hydrophilic THE FORMATION OF A PEPTIDE BOND INVOLES THE REMOVAL OF A WATER MOLEUCLES BETWEEN TWO ADJACENT AMINO ACID MOLECULES INTERACTIONS BETWEEN MOLECULES IN THE CHAIN CUAE THE CHAIN TO BEND, SPIRAL OR FOLD INTO A UNIQUE SHAPE 1. Primary structure: linear chain of amino acids 2. Second structure: amino acid interactions of either an alpha helix or pleated sheet 3. Tertiary structure: complex folding 4. Quaternary structure: hemoglobin: globular protein or keratin or collage (fibrous protein) PROTEINS Long chain of amino acids (1000-100,000) -short chains are called peptides Form complex shapes as amino acids in chain react with one another *Most importantly: Shape of final protein determines its function --proteins pushed outside their optimal temperature and pH range become temporarily or permanently denatured and ill ceases to function-shape changes make proteins nonfunctional!