Understanding The Chemistry of Life in Biology

1. Biology Biochemistry Unit Chapter 2 The Chemistry of Life

3. The Atom – makes up all matter • The smallest particle of an element • Made of 3 “subatomic particles” Nucleus is made of: positive PROTONS (p+) and neutral NEUTRONS (n0) Forming a cloud around the nucleus are negative electrons (e-) Figure 6.2

4. Elements • Cannot be broken down into a simpler substance • 90 occur naturally; the rest are synthetic or radioactive • # of Protons gives characteristic nature – state, reactivity, etc • Many are needed by Living Orgs. for 8 characteristics….

5. Periodic Table of Elements

6. We’re more than CHNOPS 96% Living things = CHNO Look at Table 6.1

7. Elements: ~25 elements are essential to life What are trace elements? Found in the body in very small amounts, yet play vital roles!

8. Elements & Compounds • Elements • All atoms are the same • Represented by chemical symbol • Compounds • Combinations of different amounts of different atoms • Represented by Chemical formulas

9. Elements, Molecules & Compounds • ELEMENTS: • Symbols can be one capital letter or a capital letter with a lower case letter • For example: C = carbon; Ca = Calcium • MOLECULES • The combination of 2 or more elements H2O; O2 • COMPOUNDS: • A substance made of many different elements bonded together • Example: H2O = ? • Made of 2 elements – hydrogen and oxygen • NOTE: the subscripts tell # ofatoms of each element you have

10. Parts of the atom:Protons, neutrons, electrons • The atomic number tells how many Protons • Neutral atoms have = number of P & E • Example: Carbon = element 6 • Has 6 protons and 6 electrons • What about n0? • n0 number = atomic mass (rounded) – # protons • So for carbon: 12 – 6 = 6 n0 Atomic # Atomic MASS

11. Atoms that are different: ISOTOPES • Neutron (n0 ) # can vary • Atoms of the same element with different # neutrons = isotopes • Note: the p+ # NEVER CHANGES!!!

12. Atoms that are different:Isotopes • Isotopes are represented by the number of neutrons • The number of p+ and e- stay the same • Carbon-12 = 6p+;6e-;6 n • Carbon-13 = 6 p+; 6e-;7n • Carbon-14 = ?????????????

13. Ions – different # of electrons • Elements with more or less electrons than their atomic number designates • Br - = Bromine with one extra electron • Na + = Sodium with one less electron

14. The Atom:Electron clouds & “dot” diagrams

15. Look at the periodic table to clear up any confusion… 2 8 8 18

16. The Atom:Electron clouds • EXAMPLE: Carbon has 6 electrons • They are arranged as: • 2 in the first e- cloud • 4 in the second e- cloud

17. THE BOTTOM LINE • For dot diagram purposes use the rule: • 2 • 8 • 8 • 18 • Let’s try some examples… What element is this?

18. The Atom:Try these… • Which element do these atomic structures represent?

19. Why is this important? • Shows the VALENCE e-’s (outer) • Determines an elements bonding potential • its REACTIVITY! • Example: • How many valence e-’s does carbon have? • How many does it “want” to be stable?

20. Chemical bonds:Forming a compound • Bond – to join together atoms using electron energy/force • Atoms are most stable when their outer e- cloud is full • Elements can share, steal or lose electrons to fill their outer (valence) e- cloud • This causes stability • Types of Bonds: Covalent, Polar Covalent, Ionic, Hydrogen & Vander Waals Forces

21. 1. Covalent bonds EXAMPLE: Oxygen alone only has 6 electrons in its outer E level If it shares 2 more it would have 8 in its outer E level and be stable ”CO” = share Figure 6.6

22. 2. Ionic bonds • When atoms give or take electrons; not sharing • The atoms with extra (or less) e- are now not neutral = ION = bond forms Figure 6.7

23. Bond Strengths • How much energy is stored bond/How much energy it takes to break the bond 1. Triple Covalent 2. Double Covalent 3. Covalent Single 4. Ionic 5. Hydrogen*

24. Chemical Reactions • Bonds of atoms are broken and re-formed into new substances • Reactions are written as “chemical equations” which show reactants and products • All reactions in an organism = Metabolism What does balanced mean?

25. Chemical Reactions • EXAMPLE 6CO2 + 6H2O  C6H12O6 + 6O2 This is the chemical equation for the reaction that occurs…. Notice the COEFFICENTS WHAT IS THEIR PURPOSE?

26. Macromolecules What are living things made of?

27. Carbon – A special element • All of “life’s substances” are carbon based • Compounds that contain the element carbon = Organic compounds • The structure of carbon allows it to make 4 covalent bonds with other molecules • This makes it a GREAT building block!

28. Carbon – A special element • It can even share 2 or 3 electrons at one time • Double or triple bonds

29. Some typical carbon compound “drawings” • Carbon can form chain molecules • Or “ring” structures

30. Linear and ring forms of glucose

31. Carbon Molecules • Counting carbons can be tricky • How many carbons are in the ribose ring structure? • How many carbons are in the ribose straight-chain structure? • In the short-hand version, “crossroads” represent carbon molecules

32. Lets Count Some Others…

33. Molecular Chains of Carbon • Carbon can form very long chains of molecules called MACROMOLECULES

34. Macromolecules • Monomer vs. Polymer • What’s the difference?

35. How are Polymers Made from Monomers?Dehydration Synthesis!How are polymers broken down into monomers?Hydrolysis!

36. Life Substances/Macromolecules • There are 4 principle organic compounds that make up living things • i.e., the 4 most important “life substances” are… • a. Carbohydrates • b. Proteins • c. Nucleic acids • d. Lipids

37. Summarizing • Read section 2.3 in the textbook • Answer Questions 1-4 on page 48 • Fill in the following sections of your Macromolecules chart • Elements • Drawings • Examples

38. CARBOHYDRATES • Sugars/starches • give us (animals) quick energy • provide plants with structural support (cellulose) AND energy

39. Three Types ofcarbohydrates • Monosaccharides = 1 sugar • Disaccharides = 2 sugars • Polysaccharides = many sugars

40. Monosaccharides • Monomer • “one” sugar; the smallest [C6H12O6] • simplest type of sugar • building blocks of all other sugar types • examples: fruit sugar (fructose) blood sugar (glucose)

41. Disaccharides • “two” simple sugars attached with a covalent bond [C12H22O11] • (2 monosacs put together) * What reaction puts them together? • examples: milk sugar (lactose) table sugar (sucrose) byproduct of starch digestion (maltose)

42. Polysaccharides • “many” simple sugars attached with covalent bonds • (just like making disaccharides) • examples: starches: pasta, bread, corn starch (amylose) plant cell walls (cellulose)

43. Chitin, a structural polysaccharide:exoskeleton and surgical thread

44. Chemical ID Test • Benedict’s Test – Monosaccharide • Positive = orange/yellow/red • Negative = blue • Iodine Test – Polysaccharide • Positive = blue/black • Negative = rusty yellow • What about Disaccharide?

45. Isomers:same formula, different structure • Mono- glucoseand fructose Both: [C6H12O6] • Di- sucrose, lactose, maltose Both: [C12H22O11]

46. Recap for carbohydrates: • made of C, H, O in a 1:2:1 ratio • in animals: used for quick energy • in plants: used for energy storage/ structural support • There are three types (mono, di, poly) • The building block of any carb is a monosacharride • isomers are everywhere

47. Fats, Phospholipids, Waxes and Steriods Structure – consist mostly of hydrocarbons Contains C H O…very little O Lipids

48. The facts on fats: Fats are also known as lipids. They are very important in the makeup of the cell membrane. They are a stored energy source in animals.

49. Are lipids “Bad?” • Major function is energy storage Ex. Gram of fat stores more than TWICE the energy of a gram of carb • Adipose tissue provides cushioning for organs and insulation for body • Form Phospholipid bilayer of ALL cell membranes! • Send messages – steriod hormones • Cholesterol – in cell membranes – cells won’t freeze!!

50. The monomer of lipids: fatty acids and a glycerol This one is called a “triglyceride”