Biology II
Chapter 2 The Chemical Basis of Life
Notes Outline
Introduction: Who Tends this Garden?
1. ______________________ are stuff that makes up our bodies and those of other organisms. They make up the
______________________environment as well.
2. The ordering of _____________________ into ______________________ represents the lowest level of
biological ____________________________.
3. Therefore, to understand life, it is important to understand the basic concepts of _____________________.
The Amazonian Rain Forest
4. The Amazonian rain forest is a showcase for the ________________________ of life on earth.
5. An example is the ___________________________, which prevents all trees except the
_____________________________ from growing in their gardens.
a. The ants inject a poisonous chemical into other trees that ____________________________.
b. The ants live in the _____________________________ of the lemon ant tree.
c. The scientific name for the lemon ant tree is __________________________________.
d. The scientific name for the lemon ant is ____________________________________.
e. Locals call the area covered by the lemon ant tree the “____________________________.”
f. Local legend is that this garden is home to a mythical _________________________.
i. The dwarf is half _____________________ and half ____________________ with one
_____________ and one human ________________.
ii. This creature is said to transform into that of a __________________ or _________________
and then lead lone travelers in circles until they are __________________.
g. The chemical that ants inject into the other trees in their garden is called _______________________.
h. Many species of ants produce formic acid, but it is used as a _______________________ that protects
the ants against microbial _____________________.
i. The lemon ant is the first ant species to use formic acid as an _____________________________.
Elements, Atoms, and Molecules
Section 2.1 Living organisms are composed of about 25 chemical elements
6. __________________________ are at the base level of biological hierarchy.
7. They are arranged into higher and higher levels of _______________________________________.
8. Living organisms are composed of _______________________, which is anything that has occupies
__________________ and has ___________________ (weight).
9. Matter is composed of chemical elements.
a. An ______________________ cannot be broken down to other substances.
b. There are __________ elements in nature – only a few exist in a pure state.
10. Life requires 25 essential elements; some are called _______________________________.
11. The four chemical elements that are most abundant in living matter are ____________________
a. _________________________
b. _________________________
c. _________________________
d. _________________________
Section 2.2 Trace elements are common additives to food and water
12. Some trace elements are required to prevent _______________________.
a. Without ___________________, our body cannot transport ___________________.
b. An ____________________ deficiency prevents the production of thyroid hormones, resulting in
___________________.
13. Several chemicals are added to water for a variety of reasons:
a. _____________________________________
b. _____________________________________
c. _____________________________________
Section 2.3 Elements can combine to form compounds
14. A ________________________ is a substance consisting of two or more different elements combined in a fixed
ratio.
15. ________________ compounds consist of only two elements.
a. Table salt is called _________________________________.
b. Sodium is a ____________________, and ____________________ is a poisonous gas.
c. When they combine chemically, an ___________________ compound results.
d. Table salt illustrates the theme of ________________________________ because we are able to eat
table salt, showing that it has properties that are different from those of the metal and a poisonous gas.
16. Many of the compounds in living things contain __________________, ___________________,
___________________, and ___________________.
a. ________________ contains all four of these elements.
b. ________________ contains carbon, hydrogen, and oygen.
c. Different arrangements of elements provide ________________ properties for each compound.
Section 2.4 Atoms consist of protons, neutrons, and electrons
17. An _________________ is the smallest unit of matter that still retains the properties of an element.
18. Atoms are made of over one hundred ______________________ particles, but there are only three that are
important for biological compounds.
a. ________________________ - has a single positive electrical charge
b. ________________________ - has a single negative electrical charge
c. ________________________ - is electrically neutral
19. Elements __________________ in their number of protons, neutrons, and electrons.
a. Helium has ______ protons, ______ neutrons, and ______ electrons.
b. Carbon has ______ protons, ______ neutrons, and ______ electrons.
20. Neutrons and protons are packed in the atom’s ______________________.
21. In a real atom, the electrons are very much smaller than the protons and neutrons. The electron cloud is much
bigger than the nucleus.
a. If the atom was the size of Yankee Stadium, the nucleus would be the size of a ________________ in
centerfield.
b. The electrons would be like tiny _________________ buzzing around the stadium.
22. The negative charge of electrons and the positive charge of protons keep _______________ near the nucleus.
23. The number of protons in the nucleus is called the _____________________________.
a. Helium has an atomic number of ______.
b. Carbon has an atomic number of ______.
24. The _______________________________ is the sum of the protons and neutrons in the nucleus.
a. Helium has a mass number of ______.
b. Carbon has a mass number of ______.
25. _____________________ of an element have the __________________ atomic number, some
__________________ in mass number.
26. There are three isotopes of carbon: C-12, C-13, and C-14.
a. Carbon-12 has _____ protons, _____ neutrons, and _____ electrons.
b. Carbon-13 has _____ protons, _____ neutrons, and _____ electrons.
c. Carbon-14 has _____ protons, _____ neutrons, and _____ electrons.
27. ___________________________________ - an isotope on which the nucleus decays spontaneously, giving off
particles and energy
a. Carbon- _____ is a radioactive isotope that emits radiation that can damage cellular molecules and pose
a risk to living organisms.
b. Radioactive isotopes can be helpful as in __________________________, research, and medicine.
28. A radioactive nitrogen atom has 7 protons, and 9 neutrons.
a. The atomic number of the radioactive nitrogen is _____.
b. The mass number of the radioactive nitrogen is _____.
Section 2.5 Radioactive isotopes can help or harm us
29. Living cells cannot distinguish between isotopes of the same element.
a. Therefore, when radioactive compounds are used in metabolic processes, they act as _______________.
b. Radioactivity can be detected by __________________________.
30. With instruments, the fate of radioactive tracers can be _______________________ in living organisms.
31. Biologists use radioactive tracers in research.
a. Radioactive carbon-14 was used to show the route of _________ in the formation of _______________
during plant _____________________________________.
32. Radioactive tracers are frequently used in medical ___________________________.
33. Sophisticated imaging instruments are used to detect radioactive tracers
a. An imaging instrument that used positron-emission tomography (PET) detects the
_____________________ of injected radioactive materials.
b. PET is useful for diagnosing __________________ disorders and _________________ and in
___________________ research.
34. In addition to benefits, there are also ____________________ associated with radioactive substances.
a. Uncontrolled ____________________ can cause damage to some molecules in a living cell,
especially ______________________.
b. Chemical _________________ are broken by the emitted energy, which causes _________________
bonds to form.
c. Ex. The explosion of a _________________________ at Chernobyl, Ukraine, in 1986 released large
amounts of radioactive isotopes into the environment.
i. _____ people died within a few weeks.
ii. Survivors have suffered from increased rates of __________________ cancer and increased
rates of ______________________ in their children.
iii. _____________________ may be at risk for future cancers.
Section 2.6 Electron arrangement determines the chemical properties of an atom
35. Only ___________________ are involved in chemical activity.
36. Electrons _______________________ from the nucleus have ___________________ amounts of energy.
37. Electrons occur only at certain energy levels, called ___________________________.
a. An atom may have ___________________ electron shells.
b. The number of electrons in the _______________ shell determines the chemical properties of the atom.
c. The number of electrons that fills a shell varies.
i. The first shell, closest to the nucleus, holds _____ electrons.
ii. The second shell holds up to _____ electrons.
38. Atoms are most _________________ when the outermost electron shell is ________________.
a. To accomplish this, the atom can __________________, __________________, or _________________
electrons.
b. These interactions result in atoms being attracted to each other forming a ________________________.
39. Sodium is in group 1 and period 3 of the periodic table. It is element number 11.
a. Sodium has _____ total electrons.
b. Sodium has _____ electron shells.
c. Sodium had _____ electrons in its outermost shell.
Section 2.7 Ionic bonds are attractions between ions of opposite charges
40. An ____________ is an atom or molecule with an electrical charge resulting from the gain or loss of electrons.
a. When an electron is lost, a _____________________ charge results.
b. When an electron is gained, a ____________________ charge results.
41. Two ions with _____________________ charges _____________________ each other.
a. When the attraction holds the ions together, it is called an _____________________________.
b. Compounds formed by ionic bonds are called ______________________.
42. Ionic bonds typically form between a ___________________ and a ___________________.
Section 2.8 Covalent bonds join atoms into molecules through electron sharing
43. A ________________________ results when atoms ___________________ outer-shell electrons.
44. A _______________________ is formed when atoms are held together by covalent bonds.
45. Types of Covalent Bonds
a. A __________________ covalent bonds forms when one pair of electrons is shared.
b. A __________________ bond forms when two pair of electrons is shared.
c. A triple bond shares _____ pair of electrons.
46. Outermost electrons are called ____________________ electrons.
Section 2.9 Unequal electron sharing creates polar molecules
47. Atoms in a covalently bonded molecule continually ________________ for shared electrons.
a. The attraction, or ______________, for shared electrons is called _______________________.
b. More electronegative atoms pull ___________________.
48. In molecules of only one element, the pull toward each atom is __________________, because each atom has
the _____________________ electronegativity.
a. The bonds formed are called ___________________ covalent bonds.
49. Water has atoms with _____________________ electronegativities.
a. Oxygen attracts the shared electrons more ___________________ than hydrogen,
b. Therefore, the shared electrons are pulled closer to the ______________________.
c. The bond formed is called a ___________________ covalent bond.
50. In water, H2O, the oxygen atom has a slight ______________________ charge, and the hydrogens have a slight
_____________________ charge.
a. Molecules with an unequal distribution of charges are called _______________________________.
Section 2.10 Hydrogen bonds are weak bonds important in the chemistry of life
51. Some chemical bonds are ________________ than covalent bonds.
52. Hydrogen, as a part of a polar covalent molecule, will share electrons with other electronegative atoms, like
_____________________ and _____________________.
53. Water molecules are electrically attracted to oppositely charged regions on __________________ molecules.
54. Because the positively charged region is always a hydrogen atom, the bond is called a ____________________.
Water’s Life Supporting Properties
Section 2.11 Hydrogen bonds make liquid water cohesive
55. Hydrogen bonds between molecules of liquid water last for only a few ____________________ of a second.
56. Hydrogen bonding causes molecules to ___________________________.
57. ________________________ - the tendency of like molecules to stick together
a. Cohesion is much ____________________ for water than other liquids.
b. Ex. Cohesion is useful in plants for ______________________ water and nutrients ________ the plant.
58. ________________________ - the clinging of one substance to another substance
a. Ex. Adhesion between water and the cell walls of a plant helps __________________ the pull of gravity.
59. ________________________ - the measure of how difficult it is to stretch or break the surface of a liquid
a. ____________________ bonds are responsible for surface tension
b. Ex. a dragonfly can sit on the surface of water without sinking because of the surface tension
Section 2.12 Water’s hydrogen bonds moderate temperature
60. Due to hydrogen bonding, water has a greater ability to _____________ temperature change than other liquids.
61. ______________________ - the amount of energy associated with movement of atoms and molecules in matter
62. ______________________ - measure of the intensity of heat (average ____________ of molecules rather than
the _______________ amount of heat)
63. Heat must be _______________________ in order to break hydrogen bonds, and heat must be
____________________ in order to form hydrogen bonds.
a. Ex. When heating water, heat must be _______________ to break the hydrogen bonds so that the
molecules can move faster. In order to cool water, heat is _________________ as molecules move
slower, and more hydrogen bonds form
b. Ex. Cooling occurs when water _____________________ from the surface of a liquid.
Section 2.13 Ice is less dense than liquid water
64. Water exists in nature as a ____________________, ____________________, and __________________.
65. As water _________________, each molecule forms a stable bond with _____ neighboring molecules, holding
them at “arm’s length” creating a three-dimensional _________________.
66. An ice crystal has more ________________ between its molecules.
67. Ice is less _____________ than water; therefore, ice ______________ in water.
Section 2.14 Water is the solvent of life
68. ________________________ - liquid consisting of a uniform mixture of two or more substances
a. ___________________________ - dissolving agent
b. ___________________________ - substance that is dissolved
69. ________________________ - a solution in which water is the solvent
70. Water is a __________________________ solvent that is fundamental to life’s processes.
a. Water’s versatility results from its _________________________.
b. Example, ___________________________ is a solute that will go into solution in water
i. Sodium and chloride ions and water are attracted to each other because of their
____________________________.
71. A compound does not need to be ____________________ to dissolve in water. Polar molecules like
______________________ and some ______________________ can dissolve in water.
Section 2.15 The chemistry of life is sensitive to acidic and basic conditions
72. Water molecules can break apart into ________________.
a. Some are _______________________ ions (H+).
b. Some are _______________________ ions (OH-).
c. Both types of ions are extremely _______________________.
73. _______________________ - chemicals other than water can contribute H+ to a solution
a. Example, HCl is hydrochloric acid. It aids ______________________ in your stomach.
b. An acidic solution has a _____________________ concentration of H+ than OH-.
74. _______________________ - chemicals that accept ions and remove them from solution
a. Example, NaOH is sodium hydroxide. The OH- ion combines with H+ to produce ____________.
b. A basic solution has a ____________________ concentration of H+ than OH-.
75. _______________________ - used to describe whether a solution is acidic or basic
a. pH ranges from ______ (most acidic) to ______ (most basic).
b. A solution that is neutral has a pH of ______.
c. The pH of human blood is ______. A person cannot survive more than a few minutes if the blood pH
drops to ______ or rises to ______. Buffers in the blood prevent a drastic change in pH.
d. _______________________ - substance that minimizes changes in pH
Section 2.16 Acid precipitation and ocean acidification threaten the environment
76. When we burn ____________________________ (gasoline and heating oil), air-polluting compounds and CO2
are released into the atmosphere
a. Sulfur and nitrous oxides react with water in the air to form ________________________.
i. These acids fall to Earth as ___________________________________, which is rain, snow, or
fog with a pH lower than _________.
b. Additional CO2 in the atmosphere contributes to the “________________________” effect and alters
ocean _____________________.
Section 2.17 EVOLUTION CONNECTION: The search for extraterrestrial life centers on the search for water
77. Question: Has life evolved elsewhere?
a. _____________________ is necessary for life as we know it.
78. NASA (National Aeronautics and Space Administration) has evidence that water was once abundant on _______.
a. Scientists believe that reservoirs of water beneath the surface of Mars could hold __________________.
CHEMICAL REACTIONS
Section 2.18 Chemical Reactions make and break bonds, changing the composition of matter
79. The ______________________ of atoms and molecules determines the way they behave.
80. __________________________ - making and breaking of chemical bonds that leads to changes on the
composition of matter
81. __________________________ - the starting materials of a reaction
82. __________________________ - the ending materials in a reaction