Water, pH, and

Biological Molecules

I. The Importance of Water to Life (Sections 3.1 and 3.2)A. 71 % of Earth’s surface;

66 % of weight of human body

B. Important properties of water1. Required/generated by many cellular reactions

(breaking down food)

2. Important solvent—hydrogen bonds with polar or charged molecules (NaCl): Figure 3.1

3. Solid versus liquid

densities,importance for

marine organisms

4. Important for insulating Earth, and for cooling living organisms by sweating

5. Cohesion and surface tension – allows water to move up a tree in cells; allows insects to walk on water.

6. Hydrophobic versus hydrophilic molecules – control certain cellular activities

C. Acids and Bases

1.Common acids (vinegar) and common bases (lye, ammonia)

2.Definition of an acid—substance that yields hydrogen ions in solution (HCl): Figure 3.5

3.Definition of a base—substance that accepts hydrogen ions (NaOH): Figure 3.5

C. Acids and Bases

4.pH scale (lower pH = more acidic; raise pH = less acidic, more basic, or alkaline): Figure 3.6

5.pH and health; diabetes, cardiac arrest, vomiting as result of acidosis

6.pH and the environment—acid rain (Interactive Activity 1)

7.Normal pH and buffering – body keeps a balance so that pH is relatively constant at different parts of the body – if it changes, the body will try to correct it by buffering the solution (ex – stomach pH = 2, small intestine pH = 6; both acidic, but buffers neutralize acid from stomach when materials move to small intestine.

II. Carbon Is a Central Element in Life (Section 3.3)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.Isomers4.Double bonds5.Rings

III. The Molecules of Life: Carbohydrates. Lipids, Proteins, and Nucleic Acids (A. A. Carbohydrates

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 (also called dehydration synthesis)

a) Simplest polymer is disaccharide; examples: sucrose, lactose, maltose

3.Condensation reactions can be reversed; hydrolysis (digestion in our guts -Interactive Activity 2)

4.Simple sugars on food labels are mono and disaccharides: Figure 3.11 (Interactive Activity 3 or 4)

5.Complex carbohydrates on food labels: long chains of monomers called polysaccharides: Figure 3.12

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) (Interactive Activity 4)

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: UA 3.10 and Figure 3.13).

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 semi-permanent energy stores in animals: Figure 3.15. Why not use carbohydrates like plants? (Interactive Activity 4, 5 & 6)

4.Steroids

a) Composition: Figure 3.16

b) Function: Figure 3.17 (Interactive Activity 7 & 8)

5. Phospholipids

a) Composition: Figure 3.18a

b) Function: Figure 3.18b. Under the resources for Chapter 3, there is a nice animation showing the behavior of phospholipids in water and oil: file named figure 3_20.

C. Proteins

1.Huge range of functions: Table 3.2

2.Composition: monomers = amino acids

a) Similarities of amino acids: Figure 3.19a

b) Differences: Figure 3.19b (Interactive Activity 9)

3. Polymers = polypeptides

4.Linkage by condensation; this is nicely animated in the resources for Chapter 3, file named figure 3_22 -Interactive Activity 4.

5.Shape and function6. Four levels of protein structure: Figure 3.22

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: Figure 3.24a (ATP)

• DNA = deoxyribonucleic acid– In nucleus– Controls cell activities– Directs production of proteins– Makes up genes on chromosomes– Controls heredity

• RNA – ribonucleic acid– Helps DNA make proteins– Found all around the cell