1. CHAPTER 2 The Chemical Basis of Life

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

3. Water in three different states: 5 States of matter

4. The emergence of biological function starts at the chemical level
ATOMS AND MOLECULES
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)

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

6. About ____ different chemical elements are essential to _____
A chemical _____ is a substance that cannot be broken down to other substances by ordinary chemical means
About ____ different chemical elements are essential to _____
lead

7. Carbon, hydrogen, oxygen, and nitrogen make up the bulk of living matter, but there are other elements necessary for life
_________
Table 2.2

8. Goiters are caused by iodine deficiency
Figure 2.2

9. 2.4 Atoms consist of protons, ________, and electrons
The smallest particle of an element is an _____
Different ______ have different types of atoms

10. 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 2
Protons
Nucleus 2
Neutrons 2
Electrons
A. Helium atom

11. Neutrons are electrically _______
Each atom is held together by attractions between the positively charged protons and ________charged electrons
Neutrons are electrically _______ 6
Protons
Nucleus 6
Neutrons 6
Electrons
B. Carbon atom

12. Atoms of each element are distinguished by a specific number of protons
The number of neutrons may vary
Variant forms of an element are called ________
Some isotopes are ________

13. 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
Figure 2.5A
Figure 2.5B

14. 2.3 Elements can combine to form compounds
Chemical elements combine in fixed ratios to form _________
Example: sodium + chlorine  sodium chloride
Reactants Products

15. 2.6 Electron arrangement determines the chemical properties of an atom
Electrons are arranged in _______
The outermost shell determines the chemical properties of an atom
In most atoms, a full outer shell holds _____ electrons

16. Atoms whose shells are not full tend to interact with other atoms and ___, ____, or ______ 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

17. 2.7 Ionic bonds are attractions between ions of opposite charge
When atoms gain or lose electrons, charged atoms called ions are created
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)

18. 2.8 Covalent bonds, the _____ 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

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

20. 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 is acidic
8-13 is basic OH- Hydroxide Ion Alkaline
Pure water and solutions that are neither basic nor acidic are neutral, with a pH of 7

21. (Higher concentration of H+) (Lower concentration of H+)
pH scale
The pH scale 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

22. Cells are kept close to pH 7 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