Metabolic Pathways and Isotopes

Metabolic Flux

• Metabolic flux is the movement of a metabolite through a metabolic pathway over time.
• Environmental factors, hormonal signals, and pharmacological interventions influence metabolic flux, contributing to diverse metabolic phenotypes.

Tracer-Based Methods

• Tracer-based methods utilize radioisotopes or stable isotopes to measure biosynthesis and decomposition.
• A radiotracer contains radioisotopes allowing for the detection of metabolite abundance.
• The path of the radioisotope is traced from reactant to product.
• Common radioisotopes used in metabolic pathway research include Hydrogen, Carbon, Phosphorous, Sulfur, and Iodine.

Atoms

• An atom is composed of protons, neutrons, and electrons.
• The number of protons determines the atomic number of an element.
• The atomic mass is the sum of protons and neutrons.

Isotopes

• Isotopes are atoms of the same element with differing neutron numbers.

Radioactivity

• Radioactivity is the spontaneous release of energy from an atomic nucleus.
• Radioactive elements emit radiation, a form of energy from natural and man-made sources.

Beta Decay

• In beta decay, a neutron in the nucleus decays into a proton, releasing a high-energy electron.

Positron Emission

• Positron emission occurs when a proton in the nucleus decays into a neutron, releasing a positron (antimatter electron).

Half-Life

• The half-life of a radioactive isotope is the time it takes for half of the atoms in a sample to decay.
• Decay is measured using a Geiger counter.

Medical Applications of Radioisotopes

• Medical radioisotopes are used in diagnosing and treating diseased states.
• Gamma emitters are preferred for diagnosis because gamma radiation can easily exit the body.
• "Cold" spots indicate a nonfunctioning area of tissue, while "hot" spots highlight areas with increased activity, such as rapidly dividing cancer cells.

Positron Emission Tomography (PET) Scan

• A PET scan is used to identify functional abnormalities in organs and tissues.
• Fluorine-18 is used to measure metabolic activity in the brain.
• PET scans are used to detect and diagnose neurological, cardiovascular, and cancer-related conditions.

Mass Spectrometry

• Mass spectrometry is used to quantify the abundance of specific ions fragmented by electron impact ionization.
• After ionization, fragmented ions travel through a mass analyzer and hit an electron multiplier to detect their presence.
• The intensity of the signal is directly proportional to the abundance of the ions.

Gas Chromatography (GC)

• GC separates compounds based on their volatility and affinity for a stationary phase.
• The mobile phase (carrier gas) carries the sample through the column.
• Differences in retention time allows for the separation and detection of different compounds.

Electron Ionization (EI)

• EI is used to ionize molecules by bombarding them with an electron beam.
• This method is suitable for small, stable molecules that can be vaporized.

Chromatogram

• A chromatogram is a graphical representation of the signals detected by a GC detector.
• It shows the signal intensity over time, with peaks representing the elution of individual compounds.
• The retention time is the time it takes for a compound to elute from the column.