Chemical Composition of the Body


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Chemical Composition of the Body

  1. 1. Chapter 2 Chemical Composition of the Body
  2. 2. Objectives <ul><li>Explain how covalent bonds are formed and distinguish between nonpolar and polar covalent bonds. </li></ul><ul><li>Describe the nature of hydrogen bonds and explain their significance. </li></ul><ul><li>Describe the structure of DNA and RNA, and explain the law of complementary base pairing. </li></ul>
  3. 3. Chemical Bonds, Molecules, and Ionic Compounds <ul><li>Chemical bonds: </li></ul><ul><ul><li>Interaction of valence electrons between 2 or more atoms. </li></ul></ul><ul><li>Number of bonds determined by number of electrons needed to complete outermost shell. </li></ul>
  4. 4. Covalent Bonds <ul><li>Atoms share their valence electrons. </li></ul><ul><li>Nonpolar covalent bonds: </li></ul><ul><ul><li>Electrons are equally distributed between the two identical atoms. </li></ul></ul><ul><ul><li>Strongest bond. </li></ul></ul><ul><ul><ul><li>H 2 and 0 2 . </li></ul></ul></ul>Figure 2.2
  5. 5. Covalent Bonds (continued) <ul><li>Polar bonds: </li></ul><ul><ul><li>Electrons are shared between two different atoms. </li></ul></ul><ul><ul><ul><li>Electrons may be pulled more toward one atom. </li></ul></ul></ul><ul><ul><li>Has + and – poles. </li></ul></ul><ul><ul><li>Oxygen, nitrogen, phosphorous have tendency to pull electrons towards themselves. </li></ul></ul>Figure 2.4
  6. 6. Ionic Bonds <ul><li>One or more valence electrons from one atom are completely transferred to a second atom. </li></ul><ul><li>Cation and anion attract, form ionic compound. </li></ul><ul><ul><li>Weaker than polar covalent bonds. </li></ul></ul><ul><li>Dissociate easily when dissolved in H 2 0. </li></ul><ul><ul><li>Form hydration spheres. </li></ul></ul><ul><li>Make an ion/molecule more soluble. </li></ul><ul><li>NaCl Na + + Cl - </li></ul>Figure 2.6 Figure 2.5
  7. 7. Ionic Bonds (continued) <ul><li>Glucose, amino acids, are H 2 0 soluble. </li></ul><ul><ul><li>Hydration spheres form around atoms of oxygen, nitrogen, phosphorous. </li></ul></ul><ul><ul><ul><li>Hydrophilic molecules. </li></ul></ul></ul><ul><li>Molecules composed of nonpolar covalent bonds are not H 2 0 soluble. </li></ul><ul><ul><li>Cannot form hydration spheres. </li></ul></ul><ul><ul><ul><li>Hydrophobic molecules. </li></ul></ul></ul>
  8. 8. Hydrogen Bond <ul><li>Hydrogen forms a polar bond with another atom, giving hydrogen has a slight + charge. </li></ul><ul><li>Weak attraction for a second electronegative atom. </li></ul><ul><ul><li>Surface tension. </li></ul></ul>Insert fig. 2.7 Figure 2.7
  9. 9. Acid/Base <ul><li>Acid: </li></ul><ul><ul><li>Molecule that can release protons (H + ). </li></ul></ul><ul><ul><ul><li>Proton donor. </li></ul></ul></ul><ul><li>Base: </li></ul><ul><ul><li>Negatively charged ion that can combine with H + , and remove it from solution. </li></ul></ul><ul><ul><ul><li>Proton acceptor. </li></ul></ul></ul>
  10. 10. pH <ul><li>pH = log _1__ [H + ] </li></ul><ul><ul><li>[H + ] = molar concentration of H + . </li></ul></ul><ul><ul><li>pH inversely related to [H + ]. </li></ul></ul><ul><li>Because of logarithmic relationship, a solution with 10 times [H + ] of H 2 0 has a pH = 6; solution with 0.1 the [H + ] has a pH = 8. </li></ul>
  11. 11. Organic MACROMolecules <ul><li>Molecules that contain carbon and hydrogen. </li></ul><ul><li>Carbon has 4 electrons in outer shell and covalently bonds to fill its outer shell. </li></ul><ul><li>Functional groups: </li></ul><ul><ul><li>Inactive “backbone” to which more reactive atoms are attached. </li></ul></ul><ul><li>Carbonyl group: </li></ul><ul><ul><li>Aldehydes and ketones. </li></ul></ul><ul><li>Carboxyl group: </li></ul><ul><ul><li>Organic acids (lactic and acetic acids). </li></ul></ul><ul><li>Hydroxyl group: </li></ul><ul><ul><li>Alcohol. </li></ul></ul>Figure 2.10
  12. 12. Carbohydrates <ul><li>Organic molecules that contain carbon, hydrogen and oxygen. </li></ul><ul><ul><li>C n H 2n 0 n . </li></ul></ul><ul><li>Monosaccharides: </li></ul><ul><ul><li>Simple sugars. </li></ul></ul><ul><ul><ul><li>Glucose, fructose, galactose. </li></ul></ul></ul><ul><li>Disaccharide: </li></ul><ul><ul><li>2 monosaccharides joined covalently. </li></ul></ul><ul><ul><ul><li>Sucrose (glucose and fructose), lactose (glucose and galactose), maltose (2 glucose). </li></ul></ul></ul><ul><li>Polysaccharide: </li></ul><ul><ul><li>Numerous monosaccharides joined covalently. </li></ul></ul><ul><ul><ul><li>Starch (thousands of glucose joined), glycogen (repeating glucose joined that are highly branched). </li></ul></ul></ul><ul><ul><li>Mechanism for storing energy with less osmotic H 2 0 movement. </li></ul></ul>Figure 2.13
  13. 13. Lipids <ul><li>Diverse group of molecules. </li></ul><ul><li>Differ greatly in chemical structure. </li></ul><ul><li>Insoluble in polar solvents (H 2 0). </li></ul><ul><li>Consist primarily of hydrocarbon chains and rings. </li></ul><ul><ul><li>Hydrophobic. </li></ul></ul>
  14. 14. LIPIDS: Triglycerides (triacylglycerol) <ul><li>Formed by condensation of glycerol and 3 fatty acids. </li></ul><ul><ul><li>Fatty acids consist of nonpolar hydrocarbon chain with carboxyl end. </li></ul></ul><ul><li>Saturated: </li></ul><ul><ul><li>Hydrocarbon chains joined by single covalent bonds. </li></ul></ul><ul><li>Unsaturated: </li></ul><ul><ul><li>Double covalent bonds within hydrocarbon chain. </li></ul></ul>Figure 2.17 Figure 2.18
  15. 15. LIPIDS:Ketone Bodies <ul><li>Hydrolysis of triglycerides in adipose tissue release free fatty acids. </li></ul><ul><ul><li>Free fatty acids can be converted in the liver to ketone bodies. </li></ul></ul><ul><li>Ketoacidosis: </li></ul><ul><ul><li>Increased ketone bodies in the blood which lowers pH. </li></ul></ul>Figure 2.19
  16. 16. LIPIDS: Phospholipids <ul><li>Phospholipids: </li></ul><ul><ul><li>Number of different categories of lipids that contain phosphate group. </li></ul></ul><ul><ul><ul><li>Nonpolar end is hydrophobic, polar end is hydrophilic. </li></ul></ul></ul><ul><ul><li>Lecithin: </li></ul></ul><ul><ul><ul><li>Phosphate attached to a nitrogen-containing choline molecule. </li></ul></ul></ul>Figure 2.20
  17. 17. LIPIDS: Steroids <ul><li>All have same basic structure; three 6-carbon rings joined to a 5-carbon ring. </li></ul><ul><ul><li>Nonpolar and insoluble in H20. </li></ul></ul><ul><li>Cholesterol is precursor for steroid hormones. </li></ul>Figure 2.22
  18. 18. LIPIDS: Prostaglandins <ul><ul><li>Fatty acid with cyclic hydrocarbon group. </li></ul></ul><ul><ul><ul><li>Derived from arachidonic acid. </li></ul></ul></ul><ul><ul><li>Serve a variety of regulatory functions. </li></ul></ul><ul><ul><ul><li>Blood vessel diameter, ovulation, uterine contractions, inflammation, blood clotting. </li></ul></ul></ul>Figure 2.23
  19. 19. Proteins <ul><li>Large molecules composed of long chains of amino acids. </li></ul><ul><ul><li>20 different amino acids can be used in constructing a given protein. </li></ul></ul><ul><ul><li>Each amino acid contains an amino group (NH2) at one end and carboxyl group (COOH) at the other end. </li></ul></ul><ul><li>Differences between amino acids are due to differences in functional groups (“R”). </li></ul>Figure 2.24
  20. 20. Protein Structure Level <ul><li>Primary structure: </li></ul><ul><ul><li>Sequence of the amino acids in the protein is described. </li></ul></ul><ul><li>Secondary structure: </li></ul><ul><ul><li>Weak hydrogen bonds form between hydrogen of 1 amino acid and the and oxygen of a different amino acid nearby. </li></ul></ul><ul><ul><ul><li>a-helix or b-sheet. </li></ul></ul></ul><ul><li>Tertiary structure: </li></ul><ul><ul><li>Polypeptide chains bend and fold to produce 3 -dimensional shape. </li></ul></ul><ul><ul><li>Formed and stabilized by weak chemical bonds between functional groups. </li></ul></ul><ul><li>Quaternary structure: </li></ul><ul><ul><li>Number of polypeptide chains covalently linked together. </li></ul></ul>Figure 2.26
  21. 21. Nucleic Acids <ul><li>Include DNA and RNA. </li></ul><ul><li>Nucleotides: </li></ul><ul><ul><li>Subunits of nucleic acids bonded together to form long polynucleotide chains. </li></ul></ul><ul><ul><ul><li>Each composed of 3 smaller units: </li></ul></ul></ul><ul><ul><ul><ul><li>5-carbon sugar. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Phosphate group attached to one end of sugar. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Nitrogenous base attached to other end of sugar. </li></ul></ul></ul></ul><ul><ul><ul><li>Nitrogenous bases: </li></ul></ul></ul><ul><ul><ul><ul><li>Pyrimidines: single ring of carbon and nitrogen. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Purines: two rings of carbon and nitrogen. </li></ul></ul></ul></ul>Figure 2.29
  22. 22. NUCLEIC ACIDS: DNA and RNA <ul><li>DNA: </li></ul><ul><li>Basis of genetic code. </li></ul><ul><li>Deoxyribose covalently bonded to 1 of 4 bases: </li></ul><ul><ul><li>Purines: guanine and adenine. </li></ul></ul><ul><ul><li>Pyrimidines: cytosine and thymine. </li></ul></ul><ul><ul><li>Sugar-phosphate bonds form the chain. </li></ul></ul><ul><li>Each base can form hydrogen bonds with other bases. </li></ul><ul><ul><li>Two strands are are produced by hydrogen bonding. </li></ul></ul><ul><li>RNA: </li></ul><ul><li>Consists of a single long chain of nucleotides joined together by sugar-phosphate bonds. </li></ul><ul><ul><li>Ribose covalently bonds to 4 bases. </li></ul></ul><ul><ul><ul><li>Uracil replaces thymine. </li></ul></ul></ul>Figure 2.32