1. Thomas Eisner and the Chemical Language of Nature
Thomas Eisner pioneered chemical ecology
the study of the chemical language of nature
He studies how insects communicate via chemical messages

2. Rattlebox moths release a chemical that spiders don’t like
This spider caught a rattlebox moth and then let it go

3. 2.1 The emergence of biological function starts at the chemical level
ATOMS AND MOLECULES
2.1 The emergence of biological function starts at the chemical level
Everything an organism is and does depends on chemistry
Chemistry is in turn dependent on the arrangement of atoms in molecules
In order to understand the whole, biologists study the parts (reductionism)

4. Molecules and ecosystems are at opposite ends of the biological hierarchy
Each level of organization in the biological hierarchy builds on the one below it
At each level, new properties emerge not evident at lower levels

5. A biological hierarchy
D. Organ: Flight muscle of a moth
A biological hierarchy
Rattlebox moth
C. Cell and tissue: Muscle cell within muscle tissue
Myofibril (organelle)
B. Organelle: Myofibril (found only in muscle cells)
Actin
Myosin
Figure 2.1
Atom
A. Molecule: Actin

7. 2.2 Life requires about 25 chemical elements
A chemical element is a substance that cannot be broken down to other substances by ordinary chemical means.
“Atoms” are names for elemental units
About 25 different chemical elements are essential to life

8. Carbon, hydrogen, oxygen, and nitrogen make up the bulk of living matter, but there are other elements necessary for life
Trace elements are important for proper function, i.e. catalysts and enzyme cofactors
Table 2.2

9. Goiters are caused by iodine deficiency
Iodine intake is .15 mg compared to calcium which is 1000 mg. Discuss with your partner why?
Answer: Iodine = mostly metabolism and Calcium = Bone growth and muscle contraction
Figure 2.2

10. 2.3 Elements can combine to form compounds
Chemical elements combine in fixed ratios to form compounds
Different combinations determine unique properties of each compound.
Example: sodium + chlorine  sodium chloride

11. 2.4 Atoms consist of protons, neutrons, and electrons
The smallest particle of an element is an atom
Different elements have different types of atoms

12. The nucleus is surrounded by electrons
An atom is made up of protons and neutrons located in a central nucleus
The nucleus is surrounded by electrons
Protons and Neutrons with mass of 1, while electrons mass of 0 (1/2000 of a proton) 2
Protons
Nucleus 2
Neutrons 2
Electrons
Figure 2.4A
A. Helium atom

13. Neutrons are electrically neutral
Each atom is held together by attractions between the positively charged protons and negatively charged electrons
Neutrons are electrically neutral 6
Protons
Nucleus 6
Neutrons 6
Electrons
Figure 2.4B
B. Carbon atom

14. Atoms of each element are distinguished by a specific number of protons = Atomic number (define’s element’s unique properties.
The number of neutrons may vary
Atomic mass/mass number = protons plus neutrons
Variant forms of an element are called isotopes (different number of neutrons). Same atomic number but different atomic mass.
Some isotopes are radioactive
Table 2.4

15. 2.5 Connection: Radioactive isotopes can help or harm us
Radioactive isotopes can be useful tracers for studying biological processes:
PET scanners use radioactive isotopes to create anatomical images. Radiation to treat cancer or hyperthyroidism
Too much radiation can cause cancer: Chernobyl, Russia.
Figure 2.5A
Figure 2.5B

16. 2.6 Electron arrangement determines the chemical properties of an atom
Electrons are arranged in shells
The outermost shell determines the chemical properties of an atom
In most atoms, a full outer shell holds eight electrons (innermost shell holds two electrons).
Number of electrons determines chemical reactivity of an atom

17. Atoms whose shells are not full tend to interact with other atoms and gain, lose, or share electrons
Outermost electron shell (can hold 8 electrons)
Electron
First electron shell (can hold 2 electrons)
HYDROGEN (H)
Atomic number = 1
CARBON (C)
Atomic number = 6
NITROGEN (N)
Atomic number = 7
OXYGEN (O)
Atomic number = 8
Figure 2.6

18. Two major chemical bonds used by elements to build compounds: covalent and ionic bonds
For each of the bond types, two rules satisfied
The resulting compound is electrically neutral
Outer electron orbits are filled.

19. 2.7 Ionic bonds are attractions between ions of opposite charge
When atoms gain or lose electrons, charged atoms called ions are created
Loss of electron = positive charge (cation) and gain of electron = negative charge (anion)
An electrical attraction between ions with opposite charges results in an ionic bond – + Na Cl Na Cl Na
Sodium atom Cl
Chlorine atom
Na+
Sodium ion
Cl–
Chloride ion
Figure 2.7A
Sodium chloride (NaCl)

20. Sodium and chloride ions bond to form sodium chloride, common table salt (* charges are bonding, not atoms !!!)
Na+
Cl–
Figure 2.7B

21. 2.8 Covalent bonds, the sharing of electrons, join atoms into molecules
Some atoms share outer shell electrons with other atoms, forming covalent bonds
Atoms joined together by covalent bonds form molecules

22. Molecules can be represented in many ways
Table 2.8

23. 2.9 Water is a polar molecule
THE PROPERTIES OF WATER
2.9 Water is a polar molecule
Atoms in a covalently bonded molecule may share electrons equally, creating a nonpolar molecule
If electrons are shared unequally, a polar molecule is created

24. In a water molecule, oxygen exerts a stronger pull on the shared electrons than hydrogen
This makes the oxygen end of the molecule slightly negatively charged
The hydrogen end of the molecule is slightly positively charged
Water is therefore a polar molecule
(–)
(–) O H H
(+)
(+)
Figure 2.9

25. 2.10 Overview: Water’s polarity leads to hydrogen bonding and other unusual properties
The charged regions on water molecules are attracted to the oppositely charged regions on nearby molecules
This attraction forms weak bonds called hydrogen bonds
Hydrogen bond
Figure 2.10A

26. Like no other common substance, water exists in nature in all three physical states:
as a solid
as a liquid
as a gas
Figure 2.10B

27. 2.11 Hydrogen bonds make liquid water cohesive
Cohesion is water molecules sticking together.
Adhesion is water sticking to a surface.
Due to hydrogen bonding, water molecules can move from a plant’s roots to its leaves (transpiration)
Insects can walk on water due to surface tension created by cohesive water molecules.
Jesus Lizard
Figure 2.11

28. 2.12 Water’s hydrogen bonds moderate temperature
It takes a lot of energy to disrupt hydrogen bonds
Therefore water is able to absorb a great deal of heat energy without a large increase in temperature – overall temperature rises slowly when heated due to hydrogen bonds breaking
As water cools, a slight drop in temperature releases a large amount of heat from the hydrogen bonds forming
Cooler at the beach then at SRHS during summer and vice-versa during winter.

29. This leads to evaporative cooling
A water molecule takes a large amount of energy with it when it evaporates
This leads to evaporative cooling
Figure 2.12

30. 2.13 Ice is less dense than liquid water
Molecules in ice are farther apart than those in liquid water
Hydrogen bond
ICE
Hydrogen bonds are stable
LIQUID WATER
Hydrogen bonds constantly break and re-form
Figure 2.13

31. Big picture:
Why is it so important for the evolution of life to have ice less dense then water? Discuss with partner.

32. Ice is therefore less dense than liquid water, which causes it to float (a given volume of ice has fewer water molecules than an equal volume of liquid water.
If ice sank, it would seldom have a chance to thaw
Ponds, lakes, and oceans would eventually freeze solid

33. 2.14 Water is a versatile solvent
Solutes whose charges or polarity allow them to stick to water molecules dissolve in water
They form aqueous solutions
Na+ – –
Na+ + +
Cl–
Cl– – – + + –
Ions in solution
Salt crystal
Figure 2.14

34. What is pure water?
Hint: what is water made of and what is constantly going on?

36. 2.15 The chemistry of life is sensitive to acidic and basic conditions
A compound that releases H+ ions in solution is an acid, and one that accepts H+ ions in solution is a base
Acidity is measured on the pH scale:
0-6.9 is acidic
is basic
Pure water and solutions that are neither basic nor acidic are neutral, with a pH of 7

37. (Higher concentration of H+) (Lower concentration of H+)
pH scale
The pH scale
Biological pH ranges from 1-9 H+
OH–
Lemon juice; gastric juice
(Higher concentration of H+)
Increasingly ACIDIC
Grapefruit juice
Acidic solution
Tomato juice
Urine
NEUTRAL
[H+] = [OH–]
PURE WATER
Human blood
Seawater
Neutral solution
(Lower concentration of H+)
Increasingly BASIC
Milk of magnesia
Household ammonia
Household bleach
Oven cleaner
Basic solution
Figure 2.15

38. So what is acid indigestion?
Have you had it? Discuss with your partner what is going on. You may have to go back to your 7th grade digestion activity!!!

39. Cells are kept close to pH 7 (neutral) by buffers
Buffers are substances that resist pH change
They accept H+ ions when they are in excess and donate H+ ions when they are depleted
Buffers are not foolproof (Mucus in the stomach is alkaline!! Other mucus produced in the body may have varying pH, including cervical mucus)
Too many wings, you have a sour stomach. Wing sauce a pH of 5. What kind of buffer do you need?

40. 2.16 Connection: Acid precipitation threatens the environment
Some ecosystems are threatened by acid precipitation
Acid precipitation is formed when air pollutants from burning fossil fuels combine with water vapor in the air to form sulfuric and nitric acids
Figure 2.16A

41. These acids can kill fish, damage buildings, and injure trees
Regulations, new technology, and energy conservation may help us reduce acid precipitation
Figure 2.16B

42. 2.17 Chemical reactions rearrange matter
REARRANGEMENTS OF ATOMS
2.17 Chemical reactions rearrange matter
In a chemical reaction:
reactants interact
atoms rearrange
products result
Figure 2.17A
2 H2 + O2 
2 H2O

43. Living cells carry out thousands of chemical reactions that rearrange matter in significant ways
Beta-carotene
Vitamin A
(2 molecules)
Figure 2.17B

44. Balancing Equations
See Chem review Worksheet.