beta-oxidation

Examples of beta-oxidation in the following topics:

• Connecting Lipids to Glucose Metabolism

  • Fatty acids are catabolized in a process called beta-oxidation that takes place in the matrix of the mitochondria and converts their fatty acid chains into two carbon units of acetyl groups, while producing NADH and FADH2.

• Hormonal Regulation of Metabolism

  • Insulin is produced by the beta cells of the pancreas, which are stimulated to release insulin as blood glucose levels rise (for example, after a meal is consumed).
  • These actions mediated by insulin cause blood glucose concentrations to fall, called a hypoglycemic, or "low sugar" effect, which inhibits further insulin release from beta cells through a negative feedback loop.
  • It can be caused by low levels of insulin production by the beta cells of the pancreas, or by reduced sensitivity of tissue cells to insulin.
  • In the nucleus, T3and T4activate genes involved in energy production and glucose oxidation.

• Red Blood Cells

  • Studies have found that hemoglobin also binds nitrous oxide (NO).
  • Nitrous oxide is a vasodilator: an agent that causes dilation of the blood vessels, thereby reducing blood pressure.
  • Hemoglobin is composed of four protein subunits, two alpha chains and two beta chains, and a heme group that has iron associated with it.
  • The iron reversibly associates with oxygen; in so doing, it is oxidized from Fe2+ to Fe3+.

• Electrons and Energy

  • The transfer of electrons between molecules via oxidation and reduction allows the cell to transfer and use energy for cellular functions.
  • The removal of an electron from a molecule via a process called oxidation results in a decrease in the potential energy stored in the oxidized compound.
  • These compounds can be easily reduced (that is, they accept electrons) or oxidized (they lose electrons).
  • When electrons are removed from a compound, the compound is oxidized.
  • In the above equation, NAD+ is an oxidizing agent and RH is oxidized to R.

• Hydrocarbons

  • The many covalent bonds between the atoms in hydrocarbons store a great amount of energy, which is released when these molecules are burned (oxidized).
  • Some hydrocarbons have both aliphatic and aromatic portions; beta-carotene is an example of such a hydrocarbon.

• Pancreas

  • The pancreatic islets contain two primary cell types: alpha cells, which produce the hormone glucagon, and beta cells, which produce the hormone insulin.
  • When blood glucose levels rise, such as after a meal, beta cells release insulin to lower blood glucose levels by increasing the rate of glucose uptake in most body cells, and by increasing glycogen synthesis in skeletal muscles and the liver.
  • The alpha and beta cells produce glucagon and insulin, respectively.

• The Energy-Releasing Steps of Glycolysis

  • The sixth step in glycolysis oxidizes the sugar (glyceraldehyde-3-phosphate), extracting high-energy electrons, which are picked up by the electron carrier NAD+, producing NADH.
  • The continuation of the reaction depends upon the availability of the oxidized form of the electron carrier NAD+.
  • Thus, NADH must be continuously oxidized back into NAD+ in order to keep this step going.
  • In an environment without oxygen, an alternate pathway (fermentation) can provide the oxidation of NADH to NAD+.
  • (This is an example of substrate-level phosphorylation. ) A carbonyl group on the 1,3-bisphosphoglycerate is oxidized to a carboxyl group, and 3-phosphoglycerate is formed.

• Peroxisomes

  • Peroxisomes neutralize harmful toxins and carry out lipid metabolism and oxidation reactions that break down fatty acids and amino acids.
  • They also carry out oxidation reactions that break down fatty acids and amino acids.
  • Free radicals are reactive because they contain free unpaired electrons; they can easily oxidize other molecules throughout the cell, causing cellular damage and even cell death.

• Chemiosmosis and Oxidative Phosphorylation

  • The production of ATP using the process of chemiosmosis in mitochondria is called oxidative phosphorylation.
  • In oxidative phosphorylation, the hydrogen ion gradient formed by the electron transport chain is used by ATP synthase to form ATP.

• Transforming Chemical Energy

  • The nutrients broken down through cellular respiration lose electrons throughout the process and are said to be oxidized.
  • When oxygen is used to help drive the oxidation of nutrients the process is called aerobic respiration.
  • Several prokaryotes and a few eukaryotes use an inorganic molecule other than oxygen to drive the oxidation of their nutrients in a process called anaerobic respiration.