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AP Biology, Chapter 4
Carbon and the Molecular Diversity of Life
INTRODUCTION
THE IMPORTANCE OF CARBON
Intro
Organic chemistry is the study of organic compounds
1. Distinguish organic and inorganic compounds and give examples of each.
a. Organic contain carbon, inorganic do not
b. Organic: methane, urea, octane; inorganic: ammonia, NaCl, H 2S
2. Describe the Miller experiment and its implications for chemical evolution.
a. Miller simulated the chemistry of the early Earth
i. Gases: H2O, H2, NH3, CH4
ii. Liquid water
iii. Sparks
iv. Got complex organic goo
b. Complex organic chemicals may appear from non-living sources
3. Summarize the philosophies of vitalism and mechanism and explain how they
influenced the development of organic chemistry and mainstream biological thought.
a. Vitalism: a life force exists separate from physics and chemistry
b. Mechanism: physical and chemical laws explain life
c. Artificial organic molecules functioned as natural; no life force
Carbon atoms are the most versatile building blocks of molecules
4. Explain how the tetravalence of the carbon atom contributes the structural complexity
of organic compounds.
a. Carbon has 4 valence electrons, forms 4 covalent bonds
b. Is not very electronegative, the bonds are relatively stable
c. Can serve as branch points in complex molecules
5. Review the valences of CHON.
a. C, 4; H, 1; O, 2; N, 3
6. Draw a structural formula for C3H8N2O.
Variation in carbon skeleton contributes to the diversity of organic molecules
7. Describe how carbon skeletons vary, and explain how this variation contributes to the
diversity and complexity of organic molecules.
a. May be straight, branched, ringed
b. Ex.: fatty acid, isopropanol, benzene
8. Contrast alkanes, alkenes, and alkynes.
a. Alkanes: no C-C double bonds
b. Alkenes: at least one C-C double bond
c. Alkynes: at least one C-C triple bond
9. Draw a structural formula for a 15-carbon hydrocarbon.
10. Why are hydrocarbons hydrophobic?
a. Only have C and H
b. C and have very similar electronegativities (C, 2.20; H, 2.55)
c. C-H bonds are relatively non-polar, no hydrogen bonding
d. When mixed with water, water molecules bind strongly to each other
11. Draw structural formulas for all isomers of pentene.
12. Distinguish the three types of isomers: structural, geometric, and enantiomer.
a. Structural: different arrangement of the same atoms
b. Geometric: same atoms bound but a different arrangement across a double
bond
c. Enantiomers
i. Also called stereoisomers, chiral compounds and optical isomers
ii. Mirror image arrangement of groups on the asymmetric carbon
iii. Opposite forms called (+)- and (-)-, D- and L-, and left-and righthanded
iv. Mixture of the two is a racemic mixture
v. Separated enantiomers rotate polarized light in opposite directions
13. Why are enantiomers important in biology?
a. One or the other is active
i. L-amino acids are synthesized by cells and used in proteins
ii. D-glucose can be used for energy, L- cannot
b. Drugs may be mixtures
i. Thalidomide: one active, the other teratogenic
ii. Mixtures can be patented and the pure active enantiomer
FUNCTIONAL GROUPS
Intro
Functional groups also contribute to the molecular diversity of life
13. Draw the structural formula for a 10-carbon molecule containing one of each of the 6
major functional groups.
14. Differentiate the chemical properties of thiols, alcohols, organic phosphates, amines,
aldehydes, carboxylic acids, and ketones.
a. Hydroxyl, -OH, alcohols
i. Polar
ii. Forms ester linkage with carboxyl
b. Carbonyl, -C=O, aldehydes and ketones
i. Polar
ii. Aldehyde if on a terminal C, ketone if in the middle
c. Carboxyl, -COOH, carboxylic acids
i. Acidic
ii. Forms amide bond with amino group
iii. Forms ester with carbonyl
d. Amino, -NH2, amines
i. Base
ii. Forms amide bonds with carboxyl
e. Sulfhydryl, -SH, thiols
i. Polar
ii. Forms disulfide bridges to stabilize proteins
f. Phosphate, -PO4, organic phosphates
i. Acid
ii. Stores energy when linked as ester
The chemical elements of life: a review