If you missed the first post in this series, there is still time to catch up. This is week 2 of a 6 week college biology course prep plan. Last week’s focus was on homeostasis. This week’s focus is general chemistry.
Why are we talking about chemistry for biology?
Chemistry is the basis of biology. When we look at the hierarchy of organization, chemistry is the non-living base that biology starts from. Chemistry is examining the molecules, atoms, and even sub-atomic particles that are making up the large parts of a living organism.
Why are there two weeks on chemistry?
I have divided up general chemistry (the basics) and organic chemistry (more advanced) because chemistry can be such an area of struggle for students that I wanted to make sure that we dedicated more time in this area for review. This is a review and designed to help activate your memory. This is not a substitute for course work.
Disclaimer: This is the mere basics and does not in any way negate what your professor may tell you. This is a basic concept review.
General Chemistry – The Atom
All things that take up space are made up of matter. Matter is composed of atoms of elements. Atoms are the smallest complete unit of an element. Elements are the basic materials of chemistry. Elements are then broken down into units called atoms. You can have an atom of Helium for instance. Atoms have subunits (called sub-atomic particles) that are known as protons, neutrons, and electrons. For reference, we usually use the periodic table to help up visualize some of the trends that we see in the way atoms behave with one another. For instance the last column are all inert gases, which means that the atoms of these elements don’t typically interact with other atoms (therefore they are called inert).
Why does an atom interact with other atoms?
To be satisfied. Atoms will interact with other atoms to have a full number of one of their parts (electrons) on the outer most part of the atom. A full outer shell is considered 8 electrons, but there are exceptions. This is sometimes referred to as the octet rule. Atoms can get a fuller outer layer (valence) by giving away electrons, accepting electrons are sharing electrons. A reaction occurs when atoms participate in activity that results in the movement or sharing of electrons. Chemical reactions are the result of atoms needing to fill their outer layer with electrons. Inert gases have a full outer layer and therefore don’t need to react with other atoms (that is the reason we use Helium in balloons). Chemical reactions result in atoms that are held together through some type of bond.
What type of bonds?
The three types of subunits for atoms have charges and mass. The protons have positive charges, the neutrons have neutral charges, and the electrons have negative charges. A neutral atom has an equal number of positive and negative charges. There are two basic types of chemical bonds: ionic and covalent.
Ionic bonds are bonds between atoms that have moved electrons (one atom accepts electrons and another atoms gives away electrons). The result is that by moving atoms they are now full on the outer layer (valence), but they have an overall charge. When reactions happen, we only move electrons. That means that the atom that gains electrons now has more negative (it is now a negative ion) and the one with less electrons is now positively charged (it is now a positive ion). The attraction between the positive and negative charges is what holds the atoms together. Ionic bonds are pretty easy to break due to the fact that they are held together by mere attraction.
Covalent bonds occur between atoms that share electrons. They can share the electrons equally (we call those non polar covalent bonds) or unequally (we call those polar covalent bonds). Electrons that are shared unequally means that one atom has the electrons closer to it most of the time. These types of covalent bonds are more common and more important in biology.
The third type of bond is not really a bond at all. Hydrogen bonding is the attraction between a hydrogen in a polar covalent bond to a negative ion or negative side of a polar covalent bonded molecule. I only mention hydrogen bonding because it is important in maintaining structures in biology like protein and DNA.
Other stuff you might need to refresh on…
Isotopes are atoms with a different number of neutrons. An isotope has a different atomic mass than depicted on the periodic table. Isotopes are used in nuclear medicine.
Water is a polar covalent molecule. As a result of this chemical nature, it participates in hydrogen bonding. These properties make water behave in a way that cause it to be very important biologically.