List and describe, in your laboratory journal, the four forces acting on amino acids placed in water. These four forces ultimately determine the shape of a protein.

Write definitions, in your laboratory journal, for the words hydrophobic and hydrophilic.

Describe, in your laboratory journal, how hydrophobic and hydrophilic amino acids react to water and to oil.

The following are the four forces acting on the amino acids placed in water:

1. Van der Waals forces: The natural stickiness of every single atom, resulting due to the movement of its electron cloud.

2. Electrostatic charge: The ions of a side chain, which have either minus or plus charge.

3. S-S bonds: Many sulfur-containing amino acids like cysteine situated in the distinct parts of the protein chain, associated with each other, forming a covalent bond, which connects together the two distinct parts of a protein molecule.

4. Hydrogen bonds: As the oxygen of the water molecule is strong, it pulls the electron cloud away from its two hydrogens, making its hydrogen somewhat positive and thus possessing the tendency to associate with the negative poles on the adjacent molecules.

Hydrophobic is defined as the tendency to repel or fail to mix with water. While hydrophilic is defined as possessing the tendency to mix with or dissolve in water.

Hydrophilic amino acids are water-loving, while hydrophobic amino acids are water-hating. Hydrophilic amino acids will react in a manner, which is contrasting from their response to water. When positioned in oil, they will be more fascinated with each other in comparison to the surrounding molecules. The non-polar hydrophobic amino acids will not be herded in combination by the oil, as they were by water, so they will get dissolve efficiently.

The forces are:

1. Hydrophobic forces: Major forces that drives protein folding. The non-polar amino acids are hydrophobic, that is, they repel (or 'dislike') water and are forced to be buried inside globular protein where they will pack and form strong hydrophobic interactions.

2. Hydrogen bonding: Hydrogen bonding (occurs between a partially negative charge with a partialy positive Hydrogen) occurs upon burial of Non-polar residues between the backbone of the polypeptide chains. This stabilizes the helices and beta-sheets of the proteins secondary structure.

3. Van der Waals interactions: They are dependent on the proximity or overlap of the amino acid's atoms due to the electron cloud. They are also transient since occur between the negative and positive charges induced by the electron's dipole moment. Although weak they play an important role in stability of the protein since they are accumulative

4. Ionic interactions: Occurs between oppositely charged residues. The surface of proteins has charged residues and water forms shells around them causing solubility of the protein.

Definitions:

Hydrophobic: Water repelling

Hydrophilic: Water attracting

Hydrophobic amino acids will repel Water and become insoluble. Will form hydrophobic interactions with oil since it is also non-polar.

Hydrophilic amino acids will hydrogen bond or form ionic interactions with water becoming soluble. And repel the non-polar oil becoming insoluble.