Chemistry Essentials for Biology

Chemistry in Biology

Life consists of numerous ongoing chemical reactions. Understanding chemistry is fundamental to understanding biology.
Topics covered include matter, elements, atoms, compounds, molecules, chemical bonds (covalent and ionic), chemical reactions, and the kinetic theory of matter.
The focus is on essential chemistry concepts for grasping biology, not a comprehensive chemistry course.

Everything in the universe is composed of matter.
Matter is defined as anything with volume and mass (i.e., it occupies space and has mass).
All matter is made up of atoms, which are the smallest units of an element that retain its properties.
A collection of identical atoms forms an element (e.g., oxygen).

Neutrally charged particles located in the nucleus.
Contribute to the atom's mass (or weight).
To find the number of neutrons: subtract the atomic number (number of protons) from the atomic mass.
For example, Fluorine (atomic number 9, mass 19) has 19 - 9 = 10 neutrons.
Isotopes are atoms of the same element with different numbers of neutrons, leading to variations in atomic mass. These isotopes can be unstable and undergo radioactive decay.

Negatively charged particles located in the electron cloud outside the nucleus.
Responsible for chemical bonding.
Electrons have negligible mass.
In a neutral atom, the number of electrons equals the number of protons to balance the charge.
Ions are atoms that have gained or lost electrons and thus have a net electric charge.

Atoms combine to form molecules through chemical bonds.
Molecules are the building blocks of compounds (e.g., water is a molecule; a collection of water molecules is the compound water).
Atoms bond to achieve full outer electron shells, usually by sharing (covalent) or transferring (ionic) electrons.

Atoms share outermost electrons.
Example: Water (H_2O). Oxygen needs two more electrons to complete its outer shell, and each hydrogen needs one. Two hydrogen atoms share their electrons with an oxygen atom.

Atoms transfer electrons (one atom gains, one atom loses).
Example: Sodium chloride (NaCl). Sodium has one electron in its outer shell that it readily gives to chlorine, which needs one electron to complete its outer shell.
Covalent bonds are generally stronger than ionic bonds, which is crucial in biological molecules like DNA.
DNA utilizes both covalent bonds (strong, for maintaining the structural integrity) and ionic bonds, specifically hydrogen bonds (weaker, for easy access and reading of the genetic code).

Chemical reactions involve the forming and breaking of chemical bonds.
Reactants react to produce products.
Example: Water and carbon dioxide react to produce glucose and oxygen.
H2O + CO2 \rightarrow C6H{12}O6 + O2
The properties of elements change dramatically when they form compounds.
For example, sodium (flammable in water) and chlorine (poisonous gas) combine to form sodium chloride (table salt), a harmless crystalline solid.
Breaking bonds releases energy, as demonstrated by the decomposition of sucrose (table sugar) into carbon and water vapor when exposed to hydrochloric acid.

Involve the transfer of electrons between substances.
Oxidation: loss of electrons.
Reduction: gain of electrons.
OIL RIG: Oxidation Is Loss, Reduction Is Gain.
Organisms obtain energy through redox reactions by oxidizing (losing electrons from) food.

Chemical reactions require activation energy to occur.
Catalysts reduce the activation energy, making reactions more efficient.
Catalysts are not consumed in the reaction; they can be reused.
Enzymes are biological catalysts that speed up biochemical reactions in the body.
Enzymes ensure reactions occur efficiently, allowing organisms to conserve energy.

Kinetic theory of matter: all matter is made of atoms in constant motion.
The amount of kinetic energy (movement) and the proximity of particles determine the state of matter: solid, liquid, or gas.
Solids: particles vibrate in place with low kinetic energy.
Liquids: particles move and roll over each other with medium kinetic energy.
Gases: particles move rapidly and are widely dispersed with high kinetic energy.
Temperature measures kinetic energy; higher temperature indicates greater particle motion.