Regulation of the Citric Acid Cycle by NADH Essay Example

Regulation of the Citric Acid Cycle by NADH Essay Example Regulation of the Citric Acid Cycle by NADH Paper Regulation of the Citric Acid Cycle by NADH Paper Regulation of the Citric Acid Cycle by NADH The Citric Acid Cycle is regulated mainly by the availability of substrates and by feedback inhibition by its products (http://en.wikipedia.org/wiki/Citric_acid_cycle). One such example of product inhibition is the regulation of the cycle by the reduced form of nicotinamide adenine dinucleotide (NADH), three molecules of which are formed in one turn of the cycle. NADH –specifically, a high [NADH] / [NAD+] ratio – also inhibits pyruvate dehydrogenase, which is the enzyme that converts pyruvate to the acetyl-CoA that enters the cycle in its first step. This ratio increases in conditions of fatty acid oxidation, for example, during starvation. The increase in the [NADH] / [NAD+] ratio inhibits the pyruvate dehydrogenase complex, which will then effect into a sparing of carbohydrates. In conditions such as starvation, this sparing of carbohydrates makes sense. Moreover, NADH inhibits the enzymes isocitrate dehydrogenase and ÃŽ ±-ketoglutarate dehydrogenase, which catalyze two of the reactions in which NADH is formed. Along with ATP, which also inhibits the two enzymes, levels of NADH increase when the cell has abundant energy stores. Increased NADH levels, therefore, serve to signal the cell that it does not need to produce as much energy through the citric acid cycle (Champe, Harvey, Ferrier, 2005). Regulation of Fatty Acid Catabolism The catabolism of fatty acids is regulated by several factors, depending mostly on the nutritional status of the individual. This is because fatty acids serve as the body’s major fuel storage reserve (Champe, Harvey, Ferrier, 2005). In starvation states, the low insulin/glucagon ratio favors degradation of fatty acids, usually in the muscle and in the liver. Once the fatty acids are fully oxidized, they yield acetyl-CoA, which are then further processed by the citric acid cycle to yield the energy especially needed by the body during timesof starvation. On the other hand, after a carbohydrate-rich meal, the insulin/glucagon ratio increases. This stimulates fatty acid synthesis, as a way of storing excess energy. When fatty acid synthesis is occurring in the cytosol of the cell, levels of malonyl CoA increase, and this compound inhibits the carnitine shuttle that transports long-chain fatty acids into the mitochondria. Without the carnitine shuttle, fatty acid oxidation cannot proceed and is therefore inhibited (Champe, Harvey, Ferrier, 2005). This is only logical, since the body still has enough energy derived from the carbohydrate-rich meal and does not need the acetyl-CoA that would otherwise have been formed from fatty acid catabolism. Regulation of the Urea Cycle Urea is the form in which amino groups that are derived from amino acids are disposed. When an individual ingests a protein-rich meal, levels of glutamate and arginine increase. Glutamate is added to acetyl-CoA to form N-acetylglutamate, in a reaction that is activated by arginine. In other words, a meal rich in proteins results in increased levels of N-acetylglutamate. N-acetylglutamate, for its part, is an essential activator for carbamoyl phosphate synthetase I, which is the enzyme that governs the rate-limiting step in the urea cycle. It therefore increases the production of urea. In short, a meal rich in proteins – of which amino acids are the building blocks – stimulates, through N-acetylglutamate, the production of urea. This is necessary since urea is the form in which these amino acids are disposed by the body. Thus, this helps maintain the nitrogen balance in the body. References Champe, P. C., Harvey, R. A., Ferrier, D. R. (2005). Lippincott’s Illustrated Reviews: Biochemistry. Philadelphia: Lippincott Wiliams Wilkins. Citric Acid Cycle. (2008). In Wikipedia, the free encyclopedia. Retrieved October 7, 2008, from Wikipedia: http://en.wikipedia.org/wiki/Citric_acid_cycle

Biography of Mata Hari, Infamous World War I Spy

Biography of Mata Hari, Infamous World War I Spy Mata Hari (August 7, 1876–October 15, 1917) was a Dutch exotic dancer and courtesan who was arrested by the French and executed for espionage during World War I. After her death, her stage name Mata Hari became synonymous with spying and espionage. Fast Facts: Mata Hari Known For: Working as a  spy  for  Germany  during  World War IAlso Known As: Margaretha Geertruida Zelle; Lady MacLeodBorn: August 7, 1876 in Leeuwarden,  The NetherlandsParents: Adam Zelle, Antje van der MeulenDied: October 15, 1917 in Paris,  FranceSpouse: Rudolf John MacLeod (m.  1895- 1906)Children: Norman-John MacLeod, Louise Jeanne MacLeodNotable Quote: Death is nothing, nor life either, for that matter. To die, to sleep, to pass into nothingness, what does it matter? Everything is an illusion. Early Life Mata Hari was born Margaretha Geertruida Zelle in Leeuwarden, Netherlands, on August 7, 1876, as the first of four children. Zelles father was a hat maker by trade, but having invested well in oil, he had enough money to spoil his only daughter. At only 6 years old, Zelle became the talk of the town when she traveled in a goat-drawn carriage that her father had given her. In school, Zelle was known to be flamboyant, often appearing in new, flashy dresses. However, Zelles world changed drastically when her family went bankrupt in 1889 and her mother died two years later. Family Breakup After her mothers death, the Zelle family was split up and Zelle, now 15, was sent to Sneek to live with her godfather, Mr. Visser. Visser decided to send Zelle to a school that trained kindergarten teachers so that shed have a career. At the school, the headmaster Wybrandus Haanstra became enchanted by Zelle and pursued her. When a scandal broke out, Zelle was asked to leave the school, so she went to live with her uncle, Mr. Taconis, in The Hague. Marriage  and Divorce In March 1895, while still staying with her uncle, 18-year-old Zelle became engaged to Rudolph John MacLeod after answering a personal ad in the newspaper. (The ad had been placed as a joke by MacLeods friend.) MacLeod was a 38-year-old officer on home leave from the Dutch East Indies, where he had been stationed for 16 years. On July 11, 1895, the two were married. They spent much of their married life living in the tropics of Indonesia where money was tight, isolation was difficult, and Johns rudeness and Zelles youth caused serious friction in their marriage. Zelle and John had two children together, Norman-John MacLeod and Louise Jeanne MacLeod. Both children became quite ill in June 1899. Norman-John died at age 2, but Louise Jeanne survived and lived until 1919. Zelle and John suspected the children may have been poisoned by a disgruntled servant. In 1902, the couple moved back to The Netherlands and soon separated. Their divorce became final in 1906. Off to Paris Zelle decided to go to Paris for a new start. Without a husband, career, and money, Zelle used her experiences in Indonesia to create a new persona, one who donned jewels, smelled of perfume, spoke occasionally in Malay, danced seductively, and often wore very few clothes. She made her dancing debut in a salon and instantaneously became a success. When reporters and others interviewed her, Zelle continually added to the mystique that surrounded her by spinning fantastic, fictionalized stories about her background, including being a Javanese princess and daughter of a baron. To sound more exotic, she took the stage name Mata Hari, Malayan for eye of the day (the sun). Famous Dancer and Courtesan Zelle became famous. All things oriental were in fashion in Paris, and Zelles exotic looks added to her mystique. Zelle danced at both private salons and later at large theaters. She danced at ballets and operas. She was invited to large parties and traveled extensively. She also took a number of lovers (often military men from various countries) who were willing to provide her financial support in exchange for her company. Espionage, Capture, and Execution Zelle was no longer a sleek dancer when in 1916 she started to spy for France during World War I. She was actually 40 years old at the time, and her time as a dancer was long behind her. She fell in love with a Russian captain, Vladimir de Masloff, who was sent to the front and became injured. Zelle wanted to support him financially, so she accepted an offer to spy for France in mid-1916. France thought her courtesan contacts would be of use to its intelligence operation. She began to meet with German contacts. She provided the French with little useful information and may have begun to work for Germany as a double agent. The French eventually intercepted a German cable that named a spy code-named H-21, clearly a code name for Mata Hari. The French became convinced that she was a spy and arrested her on Feb. 13, 1917. She was accused of spying for Germany, causing the deaths of at least 50,000 soldiers, and was put on trial in July 1917. After a short trial conducted in private in front of a military court, she was found guilty of spying for Germany and sentenced to death by firing squad. The French executed Zelle on Oct. 15, 1917. She was 41 years old. Legacy During World War I, Zelles frequent traveling across international borders and her varied companions caused several countries to wonder if she was a spy or even a double-agent. Many people who met her say that she was sociable but just not smart enough to pull off such a feat. The notion that Zelle was an exotic dancer who used her powers of seduction to extract military secrets was false. She was years past her prime as a dancer by the time she agreed to serve as a spy for France- and possibly for Germany. Zelle maintained her innocence up until the time of her death. Sources Shipman, Pat. â€Å"Why Mata Hari Wasnt a Cunning Spy After All.†Ã‚  The History Behind the Killing of Mata Hari, 14 Oct. 2017. NationalGeographic.com.â€Å"Mata Hari.†Ã‚  Biography.com, AE Networks Television, 19 Apr. 2019.The Execution of Mata Hari, 1917. Eyewitnesstohistory.com.