1. Lecture 2: Chapter 2 The Chemical Level of Organization Pages: 26- 61

2. Learning Objectives
Describe an atom and compare the ways atoms combine to form molecules.
Distinguish among the types of chemical reactions that are important to physiology.
Describe the role of enzymes in metabolism.
Distinguish between organic and inorganic compounds.
Explain the importance of water, pH and buffers to living systems.
Discuss the structures and functions of carbohydrates, lipids, proteins, nucleic acids and high energy compounds.

3. Atoms, Molecules and Bonds
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

4. Hydrogen Atoms

5. Electrons occupy a series of energy levels or electron shells.
The outermost electron shell determines the reactivity of the element.

6. Atoms and Energy Levels

7. 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 = attraction between positive cations and negative anions

8. Ionic Bonding
Animation: Formation of Ions (see tutorial)

9. Covalent bonds exist between atoms that share electrons to form a molecule
Double covalent bond
Non-polar covalent bond
Polar covalent bond

10. 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

11. Polar Covalent Bonds and the Structure of Water

12. Hydrogen Bonds

13. 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
See table 2.2 for examples of chemical notation

14. A chemical reaction occurs when reactants
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

15. 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

16. 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)

17. Reversible reactions All reactions are theoretically reversible
At equilibrium the rates of two opposing reactions are in balance
Anabolism = catabolism

18. 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
Promote chemical reactions

19. Enzymes and Activation Energy

20. Nutrients and Metabolites
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

21. 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

22. Water molecules and solutions

23. Electrolytes undergo ionization
Compounds that interact readily with water are hydrophilic
Compounds that do not interact with water are hydrophobic

24. pH is a measure of the concentration of hydrogen ions solution
Neutral
Acidic
Basic

25. 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

26. pH and Hydrogen Ion Concentration

27. 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

28. Organic compounds Organic compounds generally include Carbon Hydrogen
and sometimes Oxygen

29. Organic compounds Four major classes of organic compounds are
Carbohydrates
Lipids
Proteins
Nucleic acids
High energy compounds are also organic compounds

30. Carbohydrates Important energy source for metabolism
Monosaccharides, disaccharides and polysaccharides
Di- and polysaccharides formed from monosaccharides by dehydration synthesis

31. The Formation and Breakdown of Complex Sugars
Animation: The formation and breakdown of complex sugars (see tutorial)

32. The Structure of a Polysaccharide

33. Lipids include fats, oils, and waxes
Five classes:
Fatty acids
Eicosanoids
Glycerides
Steroids
Phospholipids
Glycolipids

34. Fatty acids

35. Triglyceride Formation
Triglycerides = three fatty acids attached by dehydration synthesis to one molecule of glycerol

36. Steroids Are involved in cell membrane structure
Include sex hormones and hormones regulating metabolism
Are important in lipid digestion

37. Steroids

38. Proteins perform many vital functions in the body
Proteins perform many vital functions in the body. The six important types are:
Structural proteins
Contractile proteins
Transport proteins
Enzymes
Buffering proteins
Antibodies

39. 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

40. Amino Acids

41. Peptide Bonds

42. 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)

43. Protein Structure

44. 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

45. Figure 2.21 A simplified view of enzyme structure and function
Animation: Enzyme structure and function (see tutorial)

46. 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

47. Nucleic acids Store and process information at the molecular level
Made of purines and pyrimidines
DNA and RNA

48. Purines and Pyrimidines

49. Nucleic Acids: RNA and DNA

50. 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

51. 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

52. Biochemical compounds form functional units called cells
Chemicals and Cells
Biochemical compounds form functional
units called cells
Metabolic turnover allows cells to change and to adapt to changes in their environment

53. You should now be familiar with:
Atoms and how they combine to form compounds.
Chemical reactions and enzymes.
Organic and inorganic compounds.
Water, pH, and buffers.
The structure and function of carbohydrates, lipids, proteins, nucleic acids and high energy compounds.