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Transcript
Chapter 2 Lecture Outline page 1 I. elements matter is made of chemical elements the most common elements in living organisms are carbon hydrogen oxygen nitrogen other important elements are calcium iodine chloride phosphorus sodium potassium iron chemical elements are represented by symbols II. energy energy is needed to change the structure or location of matter energy exists in several forms: kinetic energy is the energy of movement potential energy is stored energy when energy is converted between potential and kinetic, some is always given off as heat BIOL 2404 Strong/Fall 2006 Chapter 2 Lecture Outline page 2 III. basic chemical structures A. atoms the smallest unit of matter is the atom the atoms of each element are very similar in size but there are minor variations called isotopes examples: H C some isotopes are unstable: they give off energy waves (radiation) or subatomic particles or both in health sciences, radioactive isotopes (radioisotopes) are used in both diagnosis and treatment, but they can damage tissue and kill living organisms so they must be handled carefully I B. molecules atoms can attach to each other by chemical bonds to make larger structures called molecules examples: H2O O2 H2CO3 atoms and molecules do not have electrical charges C. ions some molecules called electrolytes are held together by fairly weak bonds that break when the molecules are placed into water when they break apart, their electrical charges are unevenly distributed BIOL 2404 Strong/Fall 2006 Chapter 2 Lecture Outline page 3 the “pieces” are called ions ions have electrical charges a solution that contains electrolytes conducts electricity examples: NaCl NaOH IV. inorganic substances A. water 1. good solvent - allows chemical reactions to occur 2. high heat capacity - the body gains and loses heat very slowly 3. used in many chemical reactions B. salts, acids and bases, pH salts, acids and bases are all ionic molecules they split apart (dissolve, dissociate) when placed in water to form ions positively charged ions are called cations negatively charged ions are called anions 1. salt molecules consist of a cation (except H+) plus an anion (except OH-) NaCl BIOL 2404 Strong/Fall 2006 Chapter 2 Lecture Outline page 4 2. acid molecules consist of the cation H+ plus an anion (not OH-) when placed into water, they release H+: HCl H+ can be dangerous because they can damage other molecules 3. base molecules consist of a cation (not H+) plus an anion when placed into water, they dissociate : NaOH the anion picks up acid (H+) 4. pH is the name of a scale used to measure how much acid is in a solution high levels of H+ (more H+ than OH-) solution is acidic pH is below 7 equal numbers of H+ and OHsolution is neutral pH is exactly 7 low levels of H+ (fewer H+ than OH-) solution is basic or alkaline pH is above 7 BIOL 2404 Strong/Fall 2006 Chapter 2 Lecture Outline page 5 V. biomolecules the most complex molecules in the body are large and are based on chains or rings of carbon (organic) most of these molecules are based on repeating units called monomers a chain of monomers is called a polymer A. carbohydrates - made of carbon, hydrogen and oxygen - 1C:2H:1O 1. monosaccharides glucose C6H12O6 main energy source for cells 2. disaccharides sucrose = glucose + fructose lactose = glucose + galactose maltose = 2 glucose 3. polysaccharides starch glycogen B. lipids 1. fatty acids - long chains of C ending in -COOH secondary energy source for cells 2. triglycerides - glycerol + 3 fatty acids storage form for fatty acids (adipose tissue) 3. phospholipids - glycerol + 2 fatty acids + 1 phosphate + 1 non-lipid membranes BIOL 2404 Strong/Fall 2006 Chapter 2 Lecture Outline page 6 4. steroids - 4 connected carbon rings examples: cholesterol, cortisol, estrogen membranes, hormones, C. proteins 1. amino acids 2. peptide - amino acids attached by peptide bonds 3. protein - peptide with 100 or more amino acids major functions: a. structure b. contraction c. transport d. buffers e. enzymes f. hormones g. antibodies function depends on 3-dimensional structure structure depends on bonds between amino acids if the bonds are broken, the shape changes and the protein loses its function loss of shape is called denaturation bonds that hold protein shape are broken by abnormal levels of ions, pH, or heat BIOL 2404 Strong/Fall 2006 Chapter 2 Lecture Outline page 7 D. nucleic acids 1. nucleotides 2. RNA - single chain of nucleotides located in nucleus, cytosol used to make proteins 3. DNA - double chain of nucleotides located in nucleus and mitochondria stores genetic information E. ATP (adenosine triphosphate) ATP is the direct energy source for cell activities ATP consists of a nucleotide (adenosine) that has three phosphates attached when one of the phosphates is removed, energy is released and can be used to do work in the cell builds or breaks down molecules moves materials into and out of cells ATP is made by the cell using glucose (or fats) as fuel BIOL 2404 Strong/Fall 2006 Chapter 2 Lecture Outline page 8 VI. enzymes A. why do we need enzymes? in chemical reactions, reactants are converted to products this conversion requires making or breaking chemical bonds in either case, activation energy is required catalysts are chemicals that reduce the amount of activation energy needed for a reaction by doing this, they speed up the reaction catalysts are not used up in the reactions-they can be used over and over again increasing the temperature of the reactants will also reduce the amount of activation energy needed, but heat damages cells, so living organisms can’t use heat to speed up reactions enzymes are proteins that act as catalysts B. how do enzymes work? enzymes bind to molecules called substrates binding occurs at a specific part of the enzyme molecule called the active site BIOL 2404 Strong/Fall 2006 Chapter 2 Lecture Outline page 9 the active site has a shape that matches the shape of the substrate molecule once the enzyme binds to the substrate, it facilitates the making or breaking of chemical bonds C. what factors affect enzyme activity? enzymes are sensitive to pH and temperature optimal pH and optimal temperature are the conditions under which the enzyme works best pH and temperatures outside the optimal range denature the enzyme and decrease its activity BIOL 2404 Strong/Fall 2006