The Chemical & Physical Basis of Life

1. The Chemical & Physical Basis of Life Chapter 2

2. Life is a series of complex chemical reactions. Chemical reactions are the basis of physiology. Chemistry follows the laws of Physics. Physics is, fundamentally, the study of matter & energy.

3. Matter • Matter is “stuff”. • It occupies space and has mass. • Mass is measured in grams. • Mass and “weight” are often used interchangeably but are really two different things • Weight is a measure of the effect of force on an object. It changes. • Mass does not change. • Example: The Moon’s gravitational force is 1/6th that of Earth’s. If you weigh 155 pounds on Earth (70 kg), you will only weigh 26 pounds on the Moon. But you will still have 70 kilograms of mass! • (The BE or British Engineering unit of mass is the “slug”.)

4. Energy Potential = stored energy. The amount energy contained in an object of a given mass that can be used to do work. Kinetic Energy = energy of work. This is energy that is actually being released and doing work.

5. Other Forms of Energy Electrical Mechanical Chemical Radiant Nuclear

6. Energy is governed by the Laws of Thermodynamics

7. The 1st Law of Thermodynamics: Energy cannot be created nor can it be destroyed. Also known as “the Conservation Statement”

8. The 2nd law of Thermodynamics: Energy flows from an area of high density to an area of low density. This is also referred to as “the Entropy Statement”. The 2nd LTD is perhaps the most relevant concept to us for our understanding biological systems, chemistry and physiology.

9. Another way to look at the 2nd LTD:Since energy is what holds matter together, or maintains “order”, then the 2nd LTD dictates that systems go from order to disorder.

10. Example of Entropy

11. The 3rd Law of Thermodynamics: You cannot reach absolute zero in a finite number of steps. This is implied from the first two LTDs.

12. Absolute zero That’s really cold!

13. The Zeroth Law: There is no net flow of energy between to systems that are in equilibrium. (The “well duh!” statement.)

14. Atoms:The Building Blocks of Matter

15. There are 26 elements essential to most living systems. Humans are composed of the the following: Trace elements (in alphabetical order) Aluminum Boron Chromium Cobalt Copper Fluorine Iodine Manganese Molybdenum Selenium Silicon Tin Vanadium Zinc Oxygen - 65% Carbon - 18.5% Hydrogen - 9.5% Nitrogen - 3.3% Calcium - 1.5% Phosphorus- 1.0% Potassium - 0.4% Sulfur - 0.3% Sodium - 0.2% Chlorine - 0.2% Magnesium - 0.1% Iron - 0.005%

16. Composition of the Human body

17. Atomic structure Atomic number = the number of protons Mass number = protons + neutrons Atomic mass = mass of protons (1.008 amu) + mass of neutrons (1.007 amu) + mass of electrons (0.0005 amu)

18. More elements

19. Isotopes The number of protons defines the element. The number of neutrons and electrons can vary. Isotopes are different forms of elements with different numbers of neutrons. Some are stable, some decay and release energy. This energy is nuclear radiation!

20. There are 3 basic types of atomic radiation •  particles = a He nucleus (2 protons + 2 neutrons) • Easily stopped. Dangerous if ingested or inhaled. Produced by the decay of Polonium, Radon, Radium and Uranium • particles = are electrons and are negatively charged • More energetic and therefore, more dangerous. Given off in the opposite direction of particle. Produced by Krypton, Strontium, Carbon and Indium. •  rays = high energy electromagnetic radiation • Most deadly, mutagenic and toxic. Produced by Polonium, Krypton, Radon, Radium, and Uranium

21. Chemical reactivity:It’s all about electrons

22. Unfilled valence shells lead to reactivity

23. The Octet Rule • Atoms with eight electrons in their valance shell are most stable. • When a reaction between two atoms leads to full valance shells then the two are more likely to interact. • Atoms or molecules with partially filled valance shells are more reactive.

24. Free Radicals

25. Superoxide free radical is highly reactive

26. Chemical bonds and the combining of matter • Atoms can combine by chemical reactions to form molecules. • Two or more atoms of the same element bound together form a molecule. • Two or more atoms of different elements bound together form a compound. This is different than a mixture, which is when substances are physically combined but are not chemically bonded. Mixtures include: Solutions, Colloids, and Suspensions.

27. Ionic compounds

28. An important Ionic compound: NaCl Or “table salt”!

29. Covalent bonds:the sharing of electrons

30. Covalent molecules

31. Two covalent compounds

32. Weak strong Important characteristics & relative strength of chemical bonds

33. Water:its structure gives it special properties

34. Hydrogen Bonds Hydrogen bonds are too weak to form compounds but are an important influence on chemical structure. The electrical attraction between the partial charge on the hydrogen of one water molecule and the oxygen of another gives water its special properties.

35. Important properties of H2O • It is polar, which gives rise to the following: • Cohesion - it clings to itself • Adhesion I it clings to other things • These properties account of its high surface tension and capillary action. • It is the “universal solvent”. • It has high heat capacity, latent heat of vaporization and specific heat.

36. How water works to dissolve an ionic compound(this is actually a chemical reaction)

37. Solutions • Colloid: • a solution of very large organic molecules • Suspension: • a solution in which particles settle (sediment) • Concentration: • the amount of solute in a solvent (mol/L, mg/mL)

38. Electrolytes Table 2–3

39. Chemical Reactions:Water is formed by a chemical reaction

40. Reactions & energy • Reactions that absorb more energy than they release are endergonic • Reactions that release more energy than they absorb are exergonic • Life is a series of these reactions that are coupled together • Reactions require energy to initiate them – Activation energy

41. Activation Energy

42. Catalyst activity

43. Enzymes are organic catalysts that speed up chemical reactions by lower the energy needed to activate them. They are not changed by the reaction, nor are they a product or a reactant.

44. Chemical Reactions:Synthesis Synthesis reactions build more complex molecules from individual building blocks. Biological molecules are synthesized by removing producing water molecules.

45. Decomposition Decomposition reactions break large molecules into their constituent components. Biological molecules are generally broken down by addition of water molecules. This type of reaction is called hydrolysis.

46. Oxidation-reduction reactionsor “redox” • When something is reduced, something else is always oxidized • Electrons are exchanged between reactants. • The electron donor is oxidized. (It is the reducing agent). • The electron acceptor is reduced. (It is the oxidizing agent). • Also defined as the loss of hydrogens (and electrons) or the addition of oxygen. Example of a simple redox reaction

47. Exchange reactions

48. Aerobic respiration:A very important redox reaction! ADP + Pi ATP C6H12O6 + 6 O2 6 CO2 + 6 H2O Stored energy

49. Some other important redox reactions

50. Influences on reaction rates • Concentration • Temperature • pH • Catalysts