1. Chapter 2: Chemical Composition of the Body (Review).
Chemical Bonds:
1.Covalent Bonds: result when atoms share their valence electrons.
can be polar or nonpolar.
2.Ionic Bonds: result when one or more valence electrons from one
atom are completely transferred to a second atom.
3. Hydrogen Bonds: when a hydrogen atom forms a polar covalent bond
with an atom of oxygen or nitrogen, the hydrogen
gains a slight positive charge as the electron is
pulled toward the other atom. This other atom is
thus described as being electronegative. Since the
hydrogen has a slight positive charge, it will have a
weak attraction for a second electronegative atom
(oxygen or nitrogen) that may be located near it.
This weak attraction is called hydrogen bond. They
are usually shown with dashed or dotted lines to
distinguish them from strong covalent bonds, which
are shown with solid lines.

2. Acid:
A molecule that can release protons (H+) into a solution; it is a “proton donor”.
Base:
A molecule that can be ionized into hydroxide (OH-) which can combine with protons (H+) to form water (H2O); it is a “proton acceptor”
pH:
The H+ concentration of a solution is usually indicated in pH units on a pH scale that runs from 0 to 14.
Acidic solutions have a pH of less than 7.
Solutions with pH 7 are neutral like that of pure water.
Basic (alkaline) solutions have a pH of more than 7.
Buffers:
Are systems of molecules and ions that act to prevent changes in H+ concentration and thus serves to stabilize the pH of a solution.
The pH of the blood (7.4 ±0.05) is stabilized, in part, by the buffering action of bicarbonate ion /carbonic acid system.
HCO H+ ◄ ► H2CO3

3. Organic Molecules: Carbohydrates Lipids Proteins Nucleic Acids
Are those molecules that contain the atoms carbon and hydrogen.
A reactive group of atoms are attached to the backbone of organic molecules known as “functional groups” (Fig page 32). These functional groups usually contain atoms of oxygen, nitrogen, phosphorus, or sulfur, and are largely responsible for the unique chemical properties of the molecule.
Organic molecules are found in living organisms as :
Carbohydrates
Lipids
Proteins
Nucleic Acids

4. Fig. 2.10 Various functional groups of organic molecules.

5. Fig. 2.14 Structural formulas for 3 hexose sugars.

6. Fig. 2. 15 The structure of glycogen
Fig The structure of glycogen. Glycogen is a polysaccharide composed of glucose subunits joined together to from a large, highly branched molecule.

7. Fig. 2.18 Structural formulas for fatty acids.

8. Fig The formation of a triglyceride (triacylglycerol) molecule from glycerol and 3 fatty acids by dehydration synthesis reactions. A water molecule is produced as an ester bond forms between each fatty acid and the glycerol. Saw tooth lines represent hydrocarbon chains, which are symbolized by an R.

9. Figure 2.22 The structure of lecithin
Lecithin is also called phosphatidylcholine, where choline is the nitrogen- containing portion of the molecule.
The circle represents the polar portion and the saw-toothed lines the nonpolar portion of the molecule.

10. Figure 2.23 The formation of a micelle structure by phospholipids such as lecithin
The hydrophilic outer layer of the micelle faces the aqueous environment.

11. Fig. 2.28 The structure of Proteins.

13. Fig. 2.33 The double-helix structure of DNA