Download Ch03Water,pH,Biological Molecules

Chapter 4
Water, and
Biological Molecules
3.1 The Importance of Water to Life
3.2 Acids and Bases Are Important to Life
3.3 Carbon Is a Central Element in Life
3.4 The Molecules of Life: Carbohydrates, Lipids, Proteins, and Nucleic Acids
Required reading from Textbook:
LECTURE OUTLINE
I.
The Importance of Water to Life
A. 71 percent of Earth’s surface, 66 percent of weight of human body.
B. Important properties of water:
1. Required/generated by many cellular reactions (breaking down food).
2. Important solvent—hydrogen bonds with polar or charged molecules (NaCl).
3. Solid versus liquid densities, importance for marine organisms
4. Specific heat (importance for insulating Earth, and for cooling living organisms by
sweating)
5. Cohesion and surface tension
6. Hydrophobic versus hydrophilic molecules
C. Acids and Bases
1. Common acids (vinegar) and common bases (lye)
2. Definition of an acid—substance that yields hydrogen ions in solution (HCl):
3. Definition of a base—substance that accepts hydrogen ions (NaOH):
4. pH scale (logarithmic, lower pH = more acidic; raise pH = less acidic, more basic, or
alkaline.
5. pH and the environment—acid rain
6. Normal pH and buffering
II.
Carbon Is a Central Element in Life
A. Carbon is starting point for biological molecules.
1. Four electrons in outer shell; can make four bonds (covalent, stable)
2. Ball-and-stick models demonstrating covalent bonds: CH4 (methane)
3. Isomers
4. Double bonds
5. Rings
III. The Molecules of Life: Carbohydrates. Lipids, Proteins, and Nucleic Acids
[Concept of polymer and monomer:
A. Carbohydrates (introduce concept of why animals eat)
1. Monomer—rings of C, H, and O (glucose, C6H12O6) called monosaccharides
a. Examples: glucose, fructose, galactose, ribose, deoxyribose
2. Polymers are chains of monomers created by chemical reaction called
condensation or dehydration synthesis
a. Simplest polymer is disaccharide; examples: sucrose, lactose, maltose
3. Condensation reactions can be reversed; hydrolysis (digestion in our guts)
4. Simple sugars on food labels are mono and disaccharides:
5. Complex carbohydrates on food labels: long chains of monomers called
polysaccharides:
a. Starch, main form of energy storage
b. Glycogen, primary short-term energy storage in animals, released as glucose
into the bloodstream when needed
c. Cellulose, functions to provide structure to plants; indigestible to mammals
(fiber on food label)
d. Chitin, functions in external skeleton of arthropods
B. Lipids
1. Common characteristics of lipids: composed of C, H, and O, but insoluble in
water.
2. Major function: Energy storage and insulation, but also function as hormones
and the outer lining of all cells.
3. Glycerides—composed of glycerol and fatty acids (For example, triglycerides: )
a. Make up 90 percent of lipid in food
b. Difference between saturated and unsaturated fatty acids:
c. Saturated fatty acids and health
d. Main semipermanent energy stores in animals: . Why not use carbohydrates
like plants?
e. Essay: From Trans Fats to Omega 3s: Fats and Health?
4. Steroids
a. Composition: four interlocking rings
b. Function:
5. Phospholipids
a. Composition: phosphorous head (polar) and fatty acid (non-polar) tail
b. Function:
C. Proteins
1. Huge range of functions:
2. Composition: monomers = amino acids
a. Similarities of amino acids:
b. Differences
3. Polymers = polypeptides
4. Linkage by condensation; this is nicely animated in the resources for Chapter 3,
file named
5. Shape and function
6. Four levels of protein structure:
a. Primary—unique to every type of protein
b. Secondary—hydrogen bonds in alpha helix and beta pleated sheet
c. Tertiary
d. Quaternary
7. Denatured proteins (albumin in egg whites)
8. Lipoproteins and glycoproteins
D. Nucleic Acids
1. Function—provides information for structure of proteins
2. Composition—nucleotides (ATP)