1. Chapter 2 The Chemical Context of Life

2. The 4 Big Ideas:
Big Idea 1: The process of evolution drives the diversity and unity of life.
Big Idea 2: Biological systems utilize free energy and molecular building blocks to grow, reproduce and maintain dynamic homeostasis.
Big Idea 3: Living systems store, retrieve, transmit and respond to information essential to life processes.
Big Idea 4: Biological systems interact, and these systems and their interactions possess complex properties.

3. Who is this?
Charles Darwin
What was his contribution to science?
The Theory of Evolution.
What is Evolution?
It is the gradual changes of a population over a long period of time
Everything in Biology is a product of Evolution.

4. 5 Basic Characteristics of Life:
All living things are made of cells.
All living things grow and reproduce.
All living things strive to maintain homeostasis
All living things carry out metabolic processes (ex. Cellular respiration)
All living things contain genetic material

5. The Organization of Life
Living things function and interact with each other on many levels
The organization of life is a hierarchy of levels of increasing complexity:
1. Cellular
2. Organismal
3. Populational
The following slide sequence shows the hierarchy of transitions from one level of complexity to the next—emphasize the interconnectedness. 5

6. Cellular Level:
Atoms
Molecules
Macromolecules
Organelles
CELLS

7. Things You Must Know From Chemistry Notes
The three subatomic particles and their significance.
The types of bonds, how they form, and their relative strengths.

8. I. Matter vs. Energy Matter Energy Has mass & takes up space
Affected by gravity
Consists of elements and compounds
Energy
Moves matter
Potential, kinetic
Ability to do work
Conversions
Sound, light, heat

9. Elements of Life 25 elements Hint: Remember CHNOPS 96% : O, C, H, N
Living things are composed of the same chemical elements as non-living things in the universe.
25 elements
96% : O, C, H, N
~ 4% : P, S, Ca, K & trace elements (ex: Fe, I)
Hint: Remember CHNOPS

11. Element Compound “pure” substance
Can’t be broken down by “ordinary” means to another substance
Ex. hydrogen (H), nitrogen (N)
Compound
2 or more different elements combined in a fixed ratio
Ex. H2O, CO2

12. II. Basis for life’s chemistry is Atomic Structure
Atom = smallest unit of matter that retains properties of an element
Subatomic particles:
Mass
(dalton or AMU)
Location
Charge
neutron 1
nucleus
proton +1
electron
negligible
shell -1

13. He 4 2 Symbol for element Mass # (protons + neutrons)
Atomic # (protons or electrons)

14. Isotopes # neutrons varies, but same # of protons
Radioactive isotopes used as tracers (follow molecules, medical diagnosis)
Uncontrolled exposure causes harm

15. Example: Na + Cl  NaCl (salt)
III. Chemical Bonds
The behavior of electrons leads to the formation (bonding) of molecules.
Example: Na + Cl  NaCl (salt)
Different types of bonds leads to stability of molecules.
What is a chemical bond?
An attractive force that links 2 atoms together in a molecule. (see above)
Different types of bonds can be Ionic, Covalent, Hydrogen....

16. Bonds Covalent Ionic Hydrogen All important to life
Form cell’s molecules
Quick reactions/ responses
H bonds to other electronegative atoms
Strong bond
Weaker bond (esp. in H2O)
Even weaker
Made and broken by chemical reactions

17. Strongest Bonds: Covalent: sharing of e-
Polar: covalent bond between atoms that differ in electronegativity
Nonpolar: e- shared equally; eg. O2 or H2

18. Strongest Bonds:
Ionic: 2 ions with opposite (+/-) charges bond (givers/takers)
Na+Cl-
Affected by environment (eg. water)

19. Weaker Bonds:
Hydrogen: H of polar covalent molecule bonds to electronegative atom of other polar covalent molecules

20. Weaker Bonds:
Van der Waals Interactions: slight, fleeting attractions between atoms and molecules close together
Weakest bond
Eg. gecko toe hairs + wall surface

21. What is an Ion?
an atom or molecule with a net electric charge due to the loss or gain of one or more electrons.
What is a cation?
a positively charged ion, i.e., one that would be attracted to the cathode in electrolysis. (Na+)
What is an Anion?
a negatively charged ion, i.e., one that would be attracted to the anode in electrolysis. (Cl-)

22. All bonds affect molecule’s SHAPE  affect molecule’s FUNCTION
Similar shapes = mimic
morphine, heroin, opiates mimic endorphin (euphoria, relieve pain)

23. Water and the Fitness of the Environment

24. Things You Must Know About Water
The importance of hydrogen bonding to the properties of water.
Four unique properties of water, and how each contributes to life on Earth.
How to interpret the pH scale.
The importance of buffers in biological systems.

25. 1. Polarity of H2O
O- will bond with H+ on a different molecule of H2O = hydrogen bond
H2O can form up to 4 bonds
An uneven distribution of electron density (partially + charge on one end and partially – charge on the other end.

26. Transport Universal solvent

27. 2. Properties of H2O Cohesion = H-bonding between like molecules
Surface Tension = measure of how difficult it is to break or stretch the surface of liquid due to its cohesive properties.

28. Adhesion = bonding between unlike molecules
Water will make hydrogen bonds with other substances such as glass, plants etc.

29. movement of H2O up plants
C. Transpiration (aka “Capillary Action”) =
movement of H2O up plants
H2O clings to each other by cohesion; cling to xylem tubes by adhesion

30. 3. Moderation of Temperature
Heat = Total amount of Kinetic Energy in system Heat Capacity = the amount of heat required to change water from its liquid state to a gaseous state. Temperature = measure intensity of heat due to average Kinetic Energy of molecules

31. Water’s high specific heat
Change temp less when absorbs/loses heat
Large bodies of water absorb and store more heat  warmer coastal areas
Create stable marine/land environment
Humans ~65% H2O  stable temp, resist temp. change

32. High Heat of Vaporization
Takes large amounts of heat energy to break hydrogen bonds holding water together. (that’s why when it’s outside…you’re not!)

33. Evaporative Cooling Water has high heat of vaporization
Molecules with greatest Kinetic Energy leave as gas
Stable temp in lakes & ponds
Cool plants
Human sweat

34. Insulation by ice – less dense, floating ice insulates liquid H2O below
Life exists under frozen surface (ponds, lakes, oceans)
Ice = solid habitat (polar bears)

35. 4. Solvent of life
Solution = liquid, homogeneous mixture of 2+ substances in which solute is uniformly combined with the solvent
Solvent = dissolving agent (liquid)
Water = Universal (versatile) solvent
Solute = dissolved substance

36. Hydrophilic Hydrophobic
“like dissolves like”
Hydrophilic
Hydrophobic
Affinity for H2O
Repel H2O
Polar, ions
Nonpolar
Cellulose, sugar, salt
Oils, lipids
Blood
Cell membrane

37. Hydrophobic: any substance that will repel or not mix with water.
Hydrophilic: (philic means like, water-loving) any substance that has a tendency to mix with, dissolve in, or be wetted by water.

38. Figure 3.8 A water-soluble protein

39. Polar/Solvent Properties
Water is the Universal solvent
ALL chemical reactions require water
MAIN transport system for nutrients, gases and wastes

40. Everything is carried in a solution - food, gases, hormones, vitamins, minerals

41. Building and Breaking of Molecules Need Water
AKA Condensation

42. Anabolic +Catabolic = Metabolic

43. 5. Acids and Bases
H2O H+ + OH- (gains proton) H+ + H2O H3O+ (hydronium ion) (loses proton) H2O – H+  OH- (hydroxide ion)

44. pH Scale: 7 14 Basic Acidic Acid = increases H+ concentration (HCl)
Base = reduces H+ concentration (NaOH)
Most biological fluids are pH 6-8
pH Scale: 7 14
Basic
Acidic
Neutral
(water)

45. Figure 3.10 The pH scale and pH values of some aqueous solutions

46. H2CO3 (carbonic acid)  HCO3- (bicarbonate) + H+
Buffers: minimize changes in concentration of H+ and OH- in a solution (weak acids and bases)
Buffers keep blood at pH ~7.4
If blood drops to 7 or up to 7.8, then death can occur.
Carbonic Acid – Bicarbonate System: important buffers in blood plasma
H2CO3 (carbonic acid)  HCO3- (bicarbonate) + H+

47. Examples of Benefits to Life
H2O Property
Chemical Explanation
Examples of Benefits to Life
Cohesion
polar
H-bond
like-like
↑gravity plants, trees
Adhesion
unlike-unlike
plants xylem
bloodveins
Surface Tension
diff. in stretch
break surface
bugswater
Specific Heat
Absorbs & retains E
oceanmod temp protect marine life
Evaporation
liquidgas KE
Cooling
Homeostasis
Universal Substance
Polarityionic
Good dissolver
solvent