Science of
Redox Signaling Molecules

Fundamentals of Redox
Redox — The scientific shorthand for reduction-oxidation
Reduction-Oxidation — A chemical reaction common in biological processes, involving the transfer of electrons from one atom to another. When a redox reaction occurs, atoms become bonded as molecules.
Reduction — When an atom gains electrons
Oxidation — When an atom loses electrons
Reducers (reducing agents) — Substances that cause another substance to gain electrons. They do this by donating their own electrons (thus becoming oxidized). Therefore reducers are also called electron-donors.
Oxidants (oxidizing agents) — Substances that cause another substance to lose electrons. They do this by removing electrons from another substance and incorporating them (thus becoming reduced). Therefore oxidants are also known as electron-acceptors.
※ Oxygen is an oxidant, but the term includes other substances because of similarities to the way oxygen often behaves in chemical reactions.

Fundamentals of Biology
Metabolism — How we process fuel for our bodies! These are chemical reactions that convert energy stored in food into energy usable for cells. Meanwhile, food is also broken down into smaller components that become building blocks for compounds essential to life, such as carbohydrates, proteins, lipids, and nucleic acids. Lastly, any waste products of metabolism are then eliminated as part of the process.
Cellular Respiration — A set of metabolic redox reactions that uses oxygen to break down food into smaller components, generating a large amount of energy in the form of ATP (adenosine triphosphate). This is a primary way to fuel cellular activities.
Biological Pathway — Interactions between molecules within a cell that enable changes or production of new molecules. The main biological pathways are the metabolic pathway, the transcription regulatory pathway, and the signal transduction pathway.
Cell Signaling Pathways — Involves both the transcription regulatory pathway and the signal transduction pathway. Also known as cellular communication, these are biological pathways that enable cells to receive signals through receptors, process signals, and then propogate those signals. Signals can come from within the body or from the environment.
※ The transcription regulatory pathway allows cells to respond to a variety of signals by altering the way it converts DNA to RNA, thereby altering the way genes can be expressed.
      Gene Expression determines what encoded info becomes functional products, such as protein.
      Enzymes are important proteins that catalyze/accelerate the rates of chemical reactions, so affecting the gene expression of enzymes enables the body to adapt to changes from a genetic level.
      Epigenetics describes how behavioral and environmental factors can affect gene expression without changing the DNA sequence itself.
※ The signal transduction pathway involves converting (transducting) all signals received by the receptors into chemical signals capable of activating channels or triggering second messenger systems.
Second Messenger System — Molecules within a cell that amplify signals initially received from outside the cell (from the first messengers). Second messengers amplify signals by propogating them to other cells in a signal transduction cascade. This downstream effect allows messages to be transmitted across large distances, enabling uniform responses and physiological changes.
Redox Signaling Molecules — These are reactive oxygen species (ROS) molecules (notably, H2O2) that act as second messengers for cell signaling, and pathway activators for numerous biological functions.

Redox Biology
Reactive Oxygen Species (ROS) — These molecules are naturally formed in the body from metabolizing oxygen through redox reactions. The most common species include superoxide (O2-), hydroxyl radical (OH), and hydrogen peroxide (H2O2), which is the most significant molecule for redox cell signaling. Under normal, healthy conditions ROS are produced and eliminated in balanced concentrations. However various factors could disrupt ROS levels, and different concentrations of ROS yield different health effects:
※ Reduced concentration: Since H2O2 is essential for activating pathways and propogating signals, diminished levels of ROS inhibit cellular communication and impair bodily functions
※ Extreme high concentration: But because oxygen is very a reactive element, high levels of ROS can disrupt biological systems by oxidizing components unintentionally, causing a type of cell damage known as oxidative stress
※ Slightly elevated concentration: Thus the sweet spot for optimal functioning is a slightly elevated level of ROS, allowing proper pathway activation and cell signaling, without potential oxidative harm. The way our bodies mitigate oxidative stress is by counterbalancing ROS with antioxidants. Your health depends on a balance of both!
Oxidative Stress — A type of cell/tissue damage that results from extreme concentrations of unstable peroxides and free radicals, of which some ROS (especially O2 and OH) are a subspecies. It reflects an imbalance such that there are too many reactive molecules interferring with body systems, incorrectly binding to proteins, lipids, breaking strands in DNA, and interrupting cell signaling. Antioxidants are necessary to balance out oxidants. 
Antioxidants — Substances that inhibit oxidation. These can be industrial, dietary (such as vitamins A, C, E), or cellular compounds like glutathione, that prevent oxidative stress by deactivating ROS. Your body has a natural supply of antioxidants, similar to ROS, but of course the balance can be upset. High concentrations of antioxidants means too many ROS molecules are deactivated, resulting in depleted concentrations and impaired signaling.
Redox Homeostasis — The proper balance of ROS and antioxidants, so that redox signaling molecules can do their vital work without negative health risks
NADPH Oxidase — A white blood cell enzyme that serves as one of the primary generators of ROS. It supports immune function by killing bacteria in a sudden release of ROS known as a respiratory burst
Respiratory Burst — A sudden release of ROS for immune, cell signaling, and reproductive purposes