Chapter 2: The Chemical Basis Of Life

Summary

2.1 Atoms 
Biology is the study of life. In order to truly understand biology, one must understand basic chemistry, which is the study of matter. This is because matter is anything that contains mass and shape. Life-forms contain mass and shape, and therefore are composed of matter. The smallest functional unit of matter is the atom. Atoms cannot be broken down into smaller substances by ordinary chemical or physical means. However, atoms are made up of subatomic particles. When two atoms bond together a molecule is formed.
 Each specific type of atom is called an element.  The subatomic particles that compose atoms are protons, neutrons, and electrons. Protons carry a positive charge, neutrons carry no charge, and electrons carry no charge. Protons and neutrons are found in the middle of the atom in the atomic nucleus. Electrons are found  in orbitals around an atom's nucleus. Orbitals occupy energy shells or energy levels. Energy is the capacity to do work. Different energy shells may contain one or more orbitals. Most atoms have outer shells that are not filled. This outer shell is known as the valence shell.
Each element has a unique number of protons. This is what distinguishes one element from another. The number of protons an atom has is its atomic number. For example, carbon has 6 protons, and therefore its atomic number is 6. Atoms are quite small, but they still have mass. The atomic mass scale shows an atom's mass relative to the mass of other atoms. Atomic mass is measured in daltons or atomic mass units (amu). A mole of any substance contains the same number of particles as there are atoms in 12g of carbon. (I was going to include information about Avogadro's number but it confused me so...) Elements can exist in many forms. When the number of neutrons differ in an atom, it is called an isotope. Unstable isotopes are called radioisotopes. The mass of all living organisms is largely composed of oxygen, carbon, hydrogen, and nitrogen. These four elements make up about 95% of a living organism.

2.2 Chemical Bonds and Molecules
When two or more atoms bond together, a molecule is formed. A compound is a molecule of two or more elements. Electronegativity is the measure of an atoms ability to attract electrons in a bond with other atoms.  One type of bond is a covalent bond. In a covalent bond, atoms share a pair of electrons. Covalent bonds are the strongest types of bonds. In a polar covalent bond, atoms with different electronegativities bond causing a difference in electric charge for the atoms. In a nonpolar covalent bond, atoms with similar electronegativities bond, causing no difference in charge for the atoms. Ionic bonds are the next strongest strongest bond. In ionic bonds, one or more atoms completely give up electrons to other atoms. A hydrogen bond is the weakest bond. In a hydrogen bond, a hydrogen atom from a polar molecule is attracted to an electronegative atom.
A free radical is a molecule containing an atom with a single, unpaired electron in its outer shell. When one or more substances are changed into other substance a chemical reaction has occurred. Reactants are what go into the chemical reaction and products are what are produced.

2.3 Properties of Water
Water is known as the universal solvent. A solute is a substance dissolved in a liquid and a solvent is the liquid the solutes dissolve into. When solutes dissolve in water, a solution is formed. Solutions containing water are known as aqueous solutions. Molecules that dissolve in water are said to be hydrophylic (like salt), while substances that do not dissolve in water are said to be be hydrophobic (like oil). Hydrophilic substances are polar, hydrophobic substances are nonpolar, and molecules containing both polar and nonpolar regions are known as amphipathic.
Water exists in three states. When water boils it goes into the gaseous state of water vapor. When water goes into water vapor at normal temperatures, it is known as evaporation. When water is in it's regular state it is a liquid. When water goes below the freezing point, it is becomes ice which is a solid.
Hydrolysis  reactions is when long chains of molecules are broken apart by water molecules. Dehydration synthesis is when water is removed from separate chains of molecules and thus joins them together. Cohesion is the phenomenon of water molecules sticking together. Adhesion is the phenomenon of water molecules sticking to surfaces that are electrically neutral. Surface tension is the measure of the attraction between molecules at the surface of a liquid.
The H+ concentration of a solution is what determines its pH. Pure water has a neutral pH of 7. A solution with a pH lower than 7 is said to be acidic, and a solution with a pH higher than 7 is said to be alkaline or basic. A buffer is made up of a weak acid and its related base. Buffers help to to neutralize solutions.

Helpful Hints!

Now this video is kind of old school but it's still helpful! I found this video helpful because it starts out with a nice explanation and then shows experiments and other displays to put a visual to cohesion, adhesion, and surface tension. It also, makes a clear difference between cohesion and adhesion which I often confused for one another. Lastly, the video shows how cohesion, adhesion, and surface tension are all working together.

Alright now this video is a claymation about electronegativity! This would constitute as being sooo fetch! So I like this video because it tells you all of the different atoms before each scene starts so you know what you're looking at. It also gives different scenarios involving electronegativity. Lastly, the song in the background is nice and calming. One can enjoy it and still enjoy the video because it definitely somewhat relates to electronegativity. So basically, this claymation helps to electronegativity in simpler terms.

Article
In this article, the morphology of gelatin with three different substances was discussed. Tizanidine hydrochloride, Gatifloxacin and Fluconazole were entrapped and then released from gelatin nanoparticles. The particles were prepared by nanoprecipitation. Water and ethanol were used as a solvent and a nonsolvent, respectively. The 80% of loaded Tizanidine hydrochloride was released after about 15 hours. The 20% of loaded Gatifloxacin was released more rapidly than the loaded Tizanidine hydrochloride and generally sustained slow release during the remaining period of its release experiment. This study relates to chapter 2 because it is about soluts, solvents, and solutions.