1. Chapter 2Chemical Basis of Life Anatomy & Physiology I (Dr. Rothschild)

2. 2 2.1: Introduction Why study chemistry in an Anatomy and Physiology class? - Body functions depend on cellular functions - Cellular functions result from chemical changes - Biochemistry helps to explain physiological processes

3. 3 Matter Atoms smallest unit of matter Elements- one type of atom Properties Mass, Volume

4. 4 Atomic Structure Atoms - composed of subatomic particles: Proton – carries a single positive charge Neutron – carries no electrical charge Electron – carries a single negative charge Nucleus Central part of atom Composed of protons and neutrons Electrons move around the nucleus Electron (e – ) Lithium (Li) Proton (p + ) Neutron (n 0 ) Nucleus 0 0 + + 0 + 0 - - - Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

5. Chemical Behavior of an Atom 1.Depends on electrons in outermost shell 2.Valence electrons (valence shell) 3.Atoms with the same number of electrons in their valence shell exhibit similar chemical behavior Consider: F and Cl –Both combine with Na 1:1 –NaF and NaCl 4.Completed valence shell atoms are unreactive (inert) 5.Orbitals describe the 3-D space occupied (90% of the time) by an electron as it orbits a nucleus. 6.Reactivity of an atom arises from the presence of unpaired electrons in one or more orbitals of an atom’s valence shell 7.Unpaired electrons of atoms interact to complete their valence shells

6. Elemental Isotopes Atoms have same number of protons Isotopes have varying numbers of neutrons in their nucleus Isotopes behave similarly in chemical reactions despite different masses. Carbon ( 6 C) Isotopes – 12 C (stable) – 13 C (stable) – 14 C (radioactive) Radioactive isotopes decay spontaneously - giving off particles and energy Atomic mass number is actually an average of the atomic masses of all the element’s isotopes

7. 7 Bonding of Atoms Bonds form when atoms combine with other atoms Electrons occupy regions of space called orbitals (subshells) Different energy levels (shells) circle the nucleus Outermost (valence) electrons responsible for bonding Atoms may lose/gain electrons Atoms may share electrons

8. 8 Bonding of Atoms: Ions Ion An atom that gains or loses electrons to become stable An electrically charged atom Cation A positively charged ion Formed when an atom loses electrons Anion A negatively charged ion Formed when an atom gains electrons 11p + 12n 0 Sodium atom (Na)Chlorine atom (Cl) (a) Separate atoms If a sodium atom loses an electron to a chlorine atom, the sodium atom becomes a sodium ion (Na + ), and the chlorine atom becomes a chloride ion (Cl – ). 17p + 18n 0

9. Ionic Compounds Highly unequally electronegative atom strips an electron from its partner’s valence shell NaCl is a compound, not a molecule Formula is a ratio

10. 10 Covalent Bonds Formed when atoms share electrons All organic (carbon) substances are formed by covalent bonds, are molecules Hydrogen atom+ H Hydrogen molecule H2H2 Hydrogen atom H ++ ++ -- - - Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

11. 11 Structural formulas show how atoms bond and are arranged in various molecules Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. H H H O O O CO 2 H2OH2O O2O2 H2H2 C O O H Polar Molecules Molecule with a slightly negative end and a slightly positive end Results when electrons are not shared equally in covalent bonds Water is an important polar molecule Slightly negative end Slightly positive ends (a)

12. Elements and Compounds Element: Cannot be broken down Bulk elements – required by the body in large amountsBulk elements – required by the body in large amounts Trace elements - required by the body in small amountsTrace elements - required by the body in small amounts Ultratrace elements – required by the body in very minute amountsUltratrace elements – required by the body in very minute amounts Compound Two or more elements in a fixed ratioTwo or more elements in a fixed ratio Chemical bonds maintain ratioChemical bonds maintain ratio Example: Sodium Chloride (NaCl)Example: Sodium Chloride (NaCl) Compound properties different than elements that form it

13. 13 Molecules and Compounds Molecule – particle formed when two or more atoms chemically combine Compound – particle formed when two or more atoms of different elements chemically combine Molecular formulas – depict the elements present and the number of each atom present in the molecule H 2 C 6 H 12 O 6 H 2 O

14. H H H H H H H H H H O O O O O Hydrogen bonds 14 Hydrogen Bonds A weak attraction between the positive end of one polar molecule and the negative end of another polar molecule Formed between water molecules Important for protein and nucleic acid structure Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

15. 15 Chemical Reactions Chemical reactions occur when chemical bonds form or break among atoms, ions, or molecules Reactants are the starting materials of the reaction - the atoms, ions, or molecules Products are substances formed at the end of the chemical reaction NaCl ’ Na + + Cl - ReactantProducts

16. Chemical Reactions Do not gain/lose atoms in a reaction 6 CO 2 + 6 H 2 O  C 6 H 12 O 6 + 6 O 2 Most reactions are reversible: products can change back to the reactants 3 H 2 + N 2  2 NH 3 Chemical equilibrium: forward and reverse reactions occur at the same rate

17. 17 Types of Chemical Reactions Synthesis Reaction – more complex chemical structure is formed A + B ’ AB Decomposition Reaction – chemical bonds are broken to form a simpler chemical structure AB ’ A + B Exchange Reaction – chemical bonds are broken and new bonds are formed AB + C ’ A + CB AB + CD ’ AD + CB

18. 18 Acids, Bases, and Salts Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Ions in solution Na + Cl – Na + Cl – Salt crystal

19. 19 Acid and Base Concentration pH scale - indicates the concentration of hydrogen ions in solution Neutral – pH 7; indicates equal concentrations of H + and OH - Acidic – pH less than 7; indicates a greater concentration of H + Basic or alkaline – pH greater than 7; indicates a greater concentration of OH - OH – concentration increasesH + Acidic H + Relative Amounts of H + (red) and OH – (blue) Basic OH – 2.0 gastric juice 6.0 corn 7.0 Distilled water 8.0 Egg white 10.5 milk of magnesia 11.5 Household ammonia pH01234567891011121314 Basic (alkaline)Neutral Acidic 3.0 apple juice 4.2 tomato juice 5.3 cabbage 6.6 cow’s milk 7.4 Human blood 8.4 Sodium biocarbonate Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Each pH unit represents a 10 fold increase in hydrogen ion concentration pH = -log [H + ] Power of hydrogen

20. 20 Acids, Bases, and Salts Electrolytes – substances that release ions in water Salts –formed by the reaction between an acid & base NaCl  Na + + Cl - HCl + NaOH  H 2 O + NaCl

21. Changes in pH and Buffers 21 Blood pH Normal blood pH is 7.35 – 7.45 Alkalosis occurs when blood pH rises to 7.5 – 7.8 Acidosis occurs when blood pH drops to 7.0 – 7.3 Homeostatic mechanisms help regulate pH Buffers are chemicals which act to resist pH changes

22. Buffers Minimize pH changes Accepts or donates hydrogen ions Most are a weak acid and its conjugate base H 2 CO 3  HCO 3 - + H +

23. Water Hydrogen bonds produce a phenomenon known as cohesion Water molecules adhere to substances Water has a greater surface tension than most other liquids

24. Water and Energy Transfer Heat is the measure of the kinetic energy due to molecular motion in a body of matter Temperature measures the the heat due to the average kinetic energy Kinetic energy is transferred from a body with a higher kinetic energy to a body with a lower kinetic energy Temperature is measured using Celsius scale Calorie is a measure of heat Kilocalorie (kcal) –Unit used in for cellular reactions

25. Water: The Solvent of Life Solutions Solvents Solutes Aqueous Solutions Water forms hydration shells around dissolved ions of an ionic compound Water also surrounds organic compounds if they have ionic and polar regions

26. Dissociation of Water H 2 O  H + + OH -

27. 27 2.3: Chemical Constituents of Cells Organic v. Inorganic Molecules Organic molecules Contain C and H Usually larger than inorganic molecules Dissolve in water and organic liquids Carbohydrates, proteins, lipids, and nucleic acids Inorganic molecules Generally do not contain C Usually smaller than organic molecules Usually dissociate in water, forming ions Water, oxygen, carbon dioxide, and inorganic salts

28. 28 Inorganic Substances Water Most abundant compound in living material Two-thirds of the weight of an adult human Major component of all body fluids Medium for most metabolic reactions Important role in transporting chemicals in the body Absorbs and transports heat Oxygen (O 2 ) Used by organelles to release energy from nutrients in order to drive cell’s metabolic activities Necessary for survival

29. 29 Inorganic Substances Carbon dioxide (CO 2 ) Waste product released during metabolic reactions Must be removed from the body Inorganic salts Abundant in body fluids Sources of necessary ions (Na +, Cl -, K +, Ca 2+, etc.) Play important roles in metabolism

30. Chemistry of Living Things –C,H,O,N = 96% –All biological compounds are based on hydrocarbon chains C-C-C-C-C-C Chains are very long –4 Main types of biological compounds Proteins Carbohydrates Lipids Nucleic Acids

31. II.Proteins –Composed of amino acid building blocks COOH group NH 2 Group –Protein = Many amino acids hooked together Special covalent bond = peptide bond –Links C-N-C Only found in proteins Proteins = polypeptides Protein

32. 32 Four Levels of Protein Structure (b ) Secondary structure — The polypeptide chain of a protein molecule is often either pleated or twisted to form a coil. Dotted lines represent hydrogen bonds. R groups (see fig. 2.17) are indicated in bold. (a) Primary structure—Each oblong shape in this polypeptide chain represents an amino acid molecule. The whole chain represents a portion of a protein molecule. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Three-dimensional folding HH (c ) Tertiary structure — The pleated and coiled polypeptide chain of a protein molecule folds into a unique three- dimensional structure. ( d) Quaternary structure —Two or more polypeptide chains may be connected to form a single protein molecule.

33. 33 Animation: Protein Denaturation Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer.

34. C.Functions of proteins 1)Enzymes 2)Muscles 3)Cell Membranes 4)Structure of cells 5)Some Hormones a)insulin

35. III.Carbohydrates = sugars and starches –Composed of monosaccharides (single sugars) m.s.+m.s.  disaccharide + HOH –Dehydration synthesis –(m.s.+m.s.  polysaccharide+many HOH (polysaccharide = starch) Examples of monosaccharides –Glucose –Fructose –Galactose Examples of disaccharides –Sucrose –Lactose –Maltose

36. 36 Functions Provide energy to cells Supply materials to build cell structures Water-soluble Contain C, H, and O Ratio of H to O close to 2:1 (C 6 H 12 O 6 ) Monosaccharides – glucose, fructose Disaccharides – sucrose, lactose Polysaccharides – glycogen, cellulose

37. 37 Carbohydrate shapes (a) Some glucose molecules (C 6 H 12 O 6 ) have a straight chain of carbon atoms. C C C C C C H O H O O O HH OH H H H H O H H H H C H O O H H O H O H H HH C O H C C C O C H (b) More commonly, glucose molecules form a ring structure. O (c) This shape symbolizes the ring structure of a glucose molecule. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

38. 38 Lipids Soluble in organic solvents; insoluble in water Fats (triglycerides) Used primarily for energy; most common lipid in the body Contain C, H, and O but less O than carbohydrates (C 57 H 110 O 6 ) Building blocks are 1 glycerol and 3 fatty acids per molecule Saturated and unsaturated Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

39. 39 Lipids Steroids Four connected rings of carbon Widely distributed in the body, various functions Component of cell membrane Used to synthesize hormones Cholesterol (a) General structure of a steroid C C C H 2 C H 2 CC H (b) Cholesterol C CH 2 2 3 2 H C HC H 2 H 2 CH 2 2 3 3 C H 2 C H 3 HOC CH 3 2 C

40. 40 Organic Substances Lipids Phospholipids Building blocks are 1 glycerol, 2 fatty acids, and 1 phosphate per molecule Hydrophilic and hydrophobic Major component of cell membranes C H C OH CH H Glycerol portion (a) A fat molecule O O Fatty acid H C H H H H C H H N O O O POCH O – Phosphate portion (b) A phospholipid molecule (the unshaded portion may vary) H CH C H H O (c) Schematic representation of a phospholipid molecule Water-insoluble (hydrophobic) “tail” Water-soluble (hydrophilic) “head” Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

41. V.Nucleic Acids = DNA + RNA Made of 3 components –5-C sugar –Phosphate –Nitrogen Base –Together these make 1 nucleotide –Nucleotides = Building Blocks Functions –Carries genetic code/blueprint –Cell fuel (ATP) –Important in cell cycles

42. 42 Nucleic Acids Carry genes Encode amino acid sequences of proteins Building blocks are nucleotides DNA (deoxyribonucleic acid) – double polynucleotide RNA (ribonucleic acid) – single polynucleotide S P B Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

43. 43 Nucleic Acids S P S P S P S P S P S P B B B B B B S S S S S S P P P P P P B B B B B B (b) S P S P S P S P S P S P B B B B B B (a) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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45. 45 Important Points in Chapter 2: Outcomes to be Assessed 2.1: Introduction Give examples of how the study of living materials requires and understanding of chemistry. 2.2: Structure of Matter Describe how atomic structure determines how atoms interact. Describe the relationships among matter, atoms, and molecules. Explain how molecular and structural formulas symbolize the composition of compounds. Describe three types of chemical reactions. Explain what acids, bases, and buffers are. Define pH.

46. 46 Important Points in Chapter 2: Outcomes to be Assessed Continued 2.3: Chemical Constituents of Cells List the major groups of inorganic chemicals common in cells. Describe the general functions of the main classes of organic molecules in cells.