Fructose Metabolism

There are two types of cellular respiration, aerobic and anaerobic. Aerobic respiration occurs when there is oxygen present and in the mitochondria (in eukaryotic cells) and the cytoplasm (in prokaryotic cells). Aerobic respiration requires oxygen; it proceeds through the Krebs cycle. The Krebs cycle is a cycle of producing carbon dioxide and water as waste products, and converting ADP to thirty-four ATPs. Anaerobic respiration is known as a process called fermentation. It occurs in the cytoplasm and molecules do not enter the mitochondria for further breakdown. This process helps to produce alcohol in yeast and plants, and lactate in animals. Only two ATPs are produced through this process. In yeast fermentation is used to make beer, wine, and whiskey.

One of the most significant reactions in Glycolysis is reaction one which involves the phosphorylation of glucose to form glucose-6-phosphate. Through the transfer of the hydrolysis of ATP, this supplies energy for the reaction and makes it essentially irreversible, having a negative free energy change, which allows for a spontaneous reaction in cells. Although the preparatory phase is energy consuming and uses up 2 ATP, the pay off phase synthesizes 4 molecules of ATP, with the transfer of 4e- via 2 hydride ions to 2 molecules of NAD+. Therefore, a net gain of 2 ATP is achieved through the glycolytic pathway alone. Following the glycolytic pathway, due to the absence of oxygen, as oxygen cannot be supplied fast enough to undergo aerobic respiration, the athlete will instead, undergo lactic acid fermentation. Lactic acid fermentation involves pyruvate that is formed from the glycolytic pathway to be reduced to lactate, with the aid of the enzyme, lactate dehydrogenase, while the coenzyme Nicotinamide Adenine Dinucleotide (NADH) is oxidised to NAD+. The product NAD+ then re-enters the glycolytic pathway in order to produce 2 ATP. This process of lactic acid fermentation produces 2 ATP for each cycle, and thus, rapidly supplies the body with a small amount of energy. However, with the buildup of lactic acid in the body, the athlete will eventually encounter the feeling of discomfort as this accumulation of lactate causes the body to

cycle produces two ATP molecules at a cost of six ATP molecules consumed in the

• With 6 ATPs being consumed and used, but only 2 ATPs being synthesized. 4 ATPs are being wasted and lost. Less ATP will be produced if the entire Cori cycle occurred and remained within that single cell.

4. Fructose is component of sucrose, normal table sugar, along with glucose. Whereas glucose is able to immediately enter into glycolysis, fructose is not. Fructose is broken down via fructokinase into fructose- 1-phosphate. Fructose – 1-phospate then gets converted into DHAP+ glyceraldehyde via aldolase B. DHAP+ glyceraldehyde is used in glycolysis to produce pyruvate that goes into the citric acid cycle to produce ATP

The increased production of ATP will cause the allosteric control enzyme of both anaerobic glycolysis and the allosteric control of the tricarboxylic cycle. The slowing of ATP production will cause an increase in ADP. This will allow allosteric control enzymes

Glycolysis is followed by the Krebs cycle, however, this stage does require oxygen and takes place in the mitochondria. During the Krebs cycle, pyuvic acid is broken down into carbon dioxide in a series of energy-extracting reactions. This begins when pyruvic acid produced by glycolysis enters the mitochondria. As the cycle continues, citric acid is broken down into a 4-carbon molecule and more carbon dioxide is released. Then, high-energy electrons are passed to electron carriers and taken to the electron transport chain. All this produces 2 ATP, 6 NADH, 2 FADH, and 4 CO2 molecules.

Background Research: Cellular Respiration is used by the cells to make ATP, by releasing chemical energy from sugars and other carbon based molecules. There are 3 stages to Cellular Respiration, Glycolysis, Krebs Cycle, and the Electron Transport Chain. The inputs of Glycolysis are 2 ATP’s, a Glucose molecule, and a Pyruvate. The inputs for the Krebs Cycle are oxygen, and. In animals, energy is consumed by eating food. In that food they eat, Glucose is found and broken down by the process of cellular respiration, which then converts into energy known as ATP. When there is a lot of ATP and Glucose, the liver converts it into glycogen.

(ATP must be generated continuously since muscles store only enough ATP for 1–3 secs of activity)

Although cells require sugar for energy, it is glucose the cells prefer as a source. However, much of the excess sugar consumed today is fructose. Excess fructose consumption has similar effects on the liver as excessive alcohol intake, as the liver metabolizes alcohol the same way as sugar and converting the carbohydrate into fat (Brandis, Lustig, & Schmidt, 2012). High concentrations of fructose is rare in nature and is typically found along side fiber. However, in the American diet, the fiber is

a. extra fructose in the liver gets turned into fat which gets wedged in the

Explanation of what would hypothetically happen to the amount of ATP available to a cell if the entire Cori cycle (glucose going to lactate and then back to glucose) were to occur and remain within that single cell (i.e., a muscle cell).

This means that the fructose can be converted to fructose-6-phosphate by using hexokinase and this will bypass the step for converting glucose-6-phosphate to fructose-6-phosphate, so it would be quicker for a build-up of fructose-1, 6 bisphosphate to occur. Lastly, fructose-1,6 bisphosphate is and unstable molecule that can form 2 products – dihydroxyacetone phosphate and glyceraldehyde 3-phosphate. Due to having 2 products, more of the substrate would be required and hence a relatively higher percentage of fructose-1,6 bisphosphate. 8.

pyruvate (3 carbon sugar), 2 NADH and 4 ATP (2 net) per molecule of glucose. During

Glycolysis is the predominant energy system for intense exercise lasting up to 2 minutes and is the second-fastest way to resynthesize ATP (Lethem, 2014).