CHAPTER 2
2.1
STUDENT NOTES
What Are Atoms?
A. Atoms Are Composed of Even Smaller Particles
1. Atom—basic structural unit of matter (Figure 2-1)
a. Atomic nucleus—Contains ______________________and_________________
b. _________________________are _____________________charged, and ________________
the nucleus
2. Elements—atoms with same number of ____________ (atomic number)
a. Each element has a different number of __________________ in the nucleus.
B. Electrons Orbit the Nucleus, Forming Electron Shells (Figure 2-2)
1. The ____________________ shell—has the lowest energy
2. First shell holds ____ electrons
3. Subsequent shells hold up to __________ electrons
2.2
How Do Atoms Form Molecules?
A. Atoms Interact When There Are _____________ in Their Outermost Electron Shells
1. __________________—hold atoms together; gain, loss, sharing of electrons
2. Chemical reactions—making and breaking of chemical bonds
3. A molecule may be depicted in different ways (Figure 2-4)
B. Charged Atoms Interact to Form Ionic Bonds (Figure 2-5)
1. Outermost electron shell is almost _____________ or almost ____________
2. Ions—atoms become stable by _________ or_____________ electrons
3. Ionic bonds—electrical attraction between ___________ and ____________ ions
C. Uncharged Atoms Share Electrons to Form Covalent Bonds (Table 2.1)
1. Most biological molecules use _____________ bonding
2. Covalent bonds are either ____________ or ________________
a. Nonpolar covalent bonds—______________ of electrons
b. Polar covalent bonds—________________ sharing of electrons (H2O)
D. Hydrogen Bonds Form Between Molecules with Polar Covalent Bonds (Figure 2-7)
1. Hydrogen bonds—bonds between parts of polar molecules
2. Responsible for unique properties of water
2.3
Why Is Water So Important to Life?
A. Water Interacts with Many Other Molecules
1. Water is involved in most chemical reactions in a cell
2. Water plays a role in _____________ and _______________
B. Many Molecules Dissolve Easily in Water (Figure 2-8)
1. A good ________________ because it is a polar molecule
2. ______________ molecules—dissolve easily in water (ex. sugars)
3. ________________ molecules—do not dissolve in water (ex. fats and oils)
C. Water Molecules Tend to Stick Together (Figure 2-9)
1. Cohesion—water molecules ___________________
2. _____________ _____________—surface of water is resistant to being broken
3. _____________—water sticks to polar surfaces
D. Water Can Form Ions (Figure 2-10)
1. Water is ___________ to form hydrogen ions (H+) and hydroxide ions (OH–)
2. Acidic solutions—more _______________(H+) than ___________ ions (OH–)
3. ___________ solutions—more hydroxide ions (OH–) than hydrogen ions (H+)
4. ____ measures acidity
a. Acids have a pH below ___ (more H+ than OH–)
b. ____________ have a pH above 7 (more OH– than H+)
c. Water has a pH of ___ (equal amount of H+ and OH–)
5. A _____________ maintains a solution at a constant pH
2.4
Why Is Carbon So Important to Life?
A. Organic Molecules vs. Inorganic Molecules
1. Organic molecules contain ___________ and ______________
2. Inorganic molecules do not contain ______________
3. Functional groups—attached to ____________ backbones; determine characteristics of different
molecules
2.5
How Are Biological Molecules Joined Together or Broken Apart?
A. Construction of Large Molecules Yields Water! REMEMBER THIS!
1. Dehydration synthesis
a. Individual subunits—linked together to make larger molecules
b. Water is formed during reaction
A + B  C + H2O
B. Breakdown of Large Molecules Uses Water (Table 2.3)
1. Hydrolysis
a. Splitting larger molecules into individual subunits
b. Water is needed to complete reaction
C + H20  A + B
2.6
What Are Carbohydrates?
A. A Variety of Simple Sugars Occurs in Organisms (Figure 2-13)
1. _________________—one sugar molecule
a. ___________—subunit of most polysaccharides
b. ________—found in corn syrup
B. _________________ Store Energy (Figure 2-14)
1. ______________—two simple sugar molecules linked together
a. ___________—table sugar (glucose + fructose)
b.____________—milk sugar (glucose + galactose)
2. Cells—can break apart disaccharides to get energy
C. Polysaccharides _________ Energy and Provide Support
1. Polysaccharides—polymers of many ______________
a. ___________—energy storage in plants
b. _____________—energy storage in animals
c. _____________—structural support in plants (Figure 2-15)
d. _____________—exoskeletons of insects, crabs, spiders
2.7
What Are Lipids?
A. Oils, Fats, and Waxes Contain Only Carbon, Hydrogen, and Oxygen (Figure 2-16)
1. Fats and oils
a. Formed by dehydration synthesis
b. Contain ___________ fatty acids and a ____________ molecule
c. Used for _______--________ storage in plants and animals
d. Store same energy with less weight than carbohydrates
2. Saturated vs. unsaturated fats
a. Saturated fats—no _____________ bonds; solid at room temperature
b. Unsaturated fats—contain _____________ bonds; liquid at room temperature
Improving on Nature? Continued
B. Phospholipids Have _______-Soluble Heads and Water-___________ Tails (Figure 2-20)
1. Phospholipids contain 2 _____ ______, 1 ________, and 1 ________ group
2. Fatty acid “tails” are ___________ (water insoluble)
3. Phosphate group “head” is polar and _____________ (water soluble)
4. Central component of cell membranes
C. Steroids Consist of Four Carbon Rings Fused Together (Figure 2-21)
1. Cholesterol is a steroid molecule
a. Important component of animal cell membranes
b. Used to synthesize other steroids
2.8
What Are Proteins?
A. Proteins Are Formed from Chains of Amino Acids (Figure 2-22)
1. Amino acids contain central ______ + four _________ groups
a. ____________-containing amino group (—NH2)
b. _______________ group (—COOH)
c. ___________ (—H)
d. ____________ group—gives each amino acid its distinctive properties
2. ______________ of amino acids dictates the function of the particular protein
B. Amino Acids Join by Dehydration Synthesis to Form Chains (Figure 2-24)
1. Peptide bond—amino group of one amino acid is joined to carboxyl group of another amino acid
2. Polypeptide chain or protein—long chain of ________ ___________
C. Three-Dimensional Shapes Give Proteins Their Functions (Figure 2-25)
1. Primary structure
a. Sequence of amino acids that make up the protein
b. Different proteins have different ____________ of amino acids
2. Secondary structure
a. Due to interactions between _____________ bonds of amino acids
b. ________ arrangement—coiled structure
c. Pleated sheet arrangement—chains that fold back upon themselves
3. Tertiary structure
a. _____________-dimensional configuration of amino acid chain
b. Interactions among different R groups of the chain
4. Quaternary structure—individual polypeptides linked together
5. Proteins whose shape is disrupted are said to be denatured
2.9
What Are Nucleic Acids?
A. DNA and RNA, the Molecules of Heredity, Are Nucleic Acids (Figure 2-26)
1. Nucleic acids—long chains of subunits known as ______________
a._____-carbon sugar
b. ____________ group
c. _____________ base
2. ___—deoxyribonucleic acid—contains deoxyribose nucleotides
3. ___—ribonucleic acid—contains ribose nucleotides
B. Other Nucleotides Perform Other Functions
1. Cyclic nucleotides—intracellular messengers (ex. cyclic AMP)
2. Adenosine triphosphate—carries energy from place to place (ex. ATP)