3 MOLECULES OF LIFE
CHAPTER OUTLINE
Forming Macromolecules (p. 50)
3.1
Polymers Are Built of Monomers (p. 50; Figs. 3.1, 3.2, 3.3; Table 3.1)
A. Organic molecules are based on long chains of carbon with functional groups on the ends
that give the molecules their unique properties.
B. Four major categories of organic molecules are found in living things; proteins, nucleic
acids, carbohydrates, and lipids.
C. Large organic molecules are called macromolecules because of their size and complexity.
D. A macromolecule is a polymer built from repeating subunits called monomers.
E. Making (and Breaking) Macromolecules
1. Subunits of macromolecules are joined together using enzymes and dehydration
synthesis.
2. Adding water to macromolecules to break them into subunits is called hydrolysis.
Types of Macromolecules (p. 53)
3.2
3.3
Proteins (p. 53; Figs. 3.4, 3.5, 3.6, 3.7, 3.8)
A. Proteins can serve as enzymes, play structural roles, and act as chemical messengers.
B. Proteins are polypeptides made up of amino acids joined together by peptide bonds.
C. Protein Structure
1. The sequence of amino acids within a protein is called the primary structure.
2. The secondary structure is the initial of the primary chain.
3. The final three-dimensional shape of a protein is called the tertiary structure of a protein.
4. When more than one polypeptide chain composes the protein, it is said to have
quaternary structure.
D. How Proteins Fold into Their Functional Shape
1. The shape of a protein can be denatured, which prevents it from functioning properly.
2. Many proteins serve as enzymes, which function as catalysts in chemical reactions.
E. Chaperone Proteins
1. Chaperone proteins help newly produced proteins to fold properly.
F. Protein Folding and Disease
1. Chaperone protein deficiencies may be involved in causing diseases such as cystic
fibrosis and Alzheimer’s disease by failing to facilitate folding of key proteins.
Nucleic Acids (p. 57; Figs.3.9, 3.10, 3.11)
A. Nucleic acids (polynucleotides) store information for cells and are made up of subunits
called nucleotides.
1. Each nucleotide has a five-carbon sugar, a phosphate group, and a nitrogen-containing
base.
2. In nucleotides, the nitrogen base can be adenine, guanine, cytosine, thymine, or uracil.
B. DNA and RNA
1. Deoxyribonucleic acid (DNA) exists as a double helix of polynucleotides, exhibiting base
pairing within the helix.
a. DNA nucleotides contain the five-carbon sugar deoxyribose
b. DNA encodes genetic instructions for the cell
2. Ribonucleic acid (RNA) is involved in protein synthesis
a. RNA nucleotides contain the five-carbon sugar ribose
b. RNA is single-stranded
c. RNA uses the nitrogen base uracil instead of thymine
C.
3.4
3.5
The Double Helix
1. The reason for DNA to assume its double helix is because only two base pairs are
possible.
a. Adenine pairs with thymine and cytosine pairs with guanine, due to the alignment of
hydrogen bonds.
2. The advantage of the double helix is that it contains two copies of the information —
one the mirror image of the other.
Carbohydrates (p. 60; Figs. 3.12, 3.13, 3.14; Table 3.2)
A. Carbohydrates are used as energy sources and are made up of polymers of simple
carbohydrates.
B. Simple Carbohydrates
1. The simplest sugars, or monosaccharides, consist of one subunit.
2. Another simple carbohydrate is a disaccharide, built of two subunits.
C. Complex Carbohydrates
1. Animals and plants store energy in polysaccharides formed from glucose.
2. Examples of complex carbohydrates include glycogen, chitin, cellulose, and starch.
Lipids (p. 62; Figs. 3.15, 3.16, 3.17)
A. Fats and all other biological molecules that are not soluble in water but are soluble in oil are
lipids.
B. Fats are employed for long-term storage of energy.
C. Fats
1. Triacylglycerol molecules (triglycerides) are made up of glycerol and three fatty acids.
2. The fatty acids may be saturated or unsaturated with hydrogen atoms along the carbon
chain.
D. Other Types of Lipids
1. Phospholipids are used to build biological membranes.
2. A third type of lipid, steroids, serves a number of functions within the cell.