- Explain how enzymes are involved in processes such as the breakdown of fructose
Enzymes are organic catalysts. In this context, organic denotes the matter in question is generated or is obtained from a living life form. The word Catalyst indicates a matter that has the aptitude to boost a chemical reaction’s rate, and is neither transformed nor damaged by the reaction that it speeds up.
Many chemical reactions occur but a slow rate that their progress would seem to be imperceptible at normally encountered environmental temperature. However, the enzymes are specific to certain functions. Generally, they may speed up a reaction, but the reactions differ. For example in the case in fructolysis (breakdown of fructose), several enzymes have different specific actions. For instance, fructokinase is involved in phosphorylation of fructose-to-fructose 1-phosphate, which is helpful in the trapping of fructose for metabolism in the liver, and Hexokinase IV that phosphorylates the fructose-to-fructose 6-phosphate. Another enzyme, fructose-1-phosphate aldolase also known as aldolase B is also helpful in the hydrolysis of fructose 1-phosphate to dihydroxyacetone phosphate (DHAP) and glyceraldehydes. DHAP and glyceraldehydes are the fates of fructose in the liver but they can still undergo more reactions by the help of more enzymes. For example, DHAP can be isomerised by triosephosphate isomerise or reduced by glycerol 3-phosphate dehydrogenase to glycerol 3-phosphate. The glyceraldehydes can be converted by glyceraldehydes kinase or by glyceraldehydes 3-phosphate dehydrogenase to glyceraldehydes 3-phosphate and glycerol 3-phosphate respectively (McGrane, 2006).
- Explain how a deficiency in aldolase B can be responsible for hereditary fructoseintolerance
Aldolase B takes part in a very vital role in carbohydrate metabolism. This is because it catalyzes one of the main glycolytic-gluconeogenic pathway steps. It takes part in a predominantly significant task in fructose metabolism, which happens principally in renal cortex, the liver and small intestinal mucosa. After fructose is absorbed into the body, fructokinase enzyme phosphorylates it to form useable fructose 1-phosphate. The Aldolase B enzyme then catalyzes fructose 1-phosphate metabolism into glyceraldehydes and DHAP. Subsequent to glyceraldehydes triose kinase phosphorylation to create G3P, both the produces can be utilized in the glycolytic-gluconeogenic trail, explicitly, they can be tailored to turn into either glucose or pyruvate. Deficiency in efficient aldolase B, individuals cannot appropriately metabolize F1P, which results in a build up of F1P in body tissues (Ali et.al, 2008).
As well as being poisonous to cellular tissues, elevated F1P intensities ensnare phosphate in an inoperative structure that does not go back to the universal phosphate pool, resultant in the exhaustion of both phosphate and ATP storages. The deficiency in readily obtainable phosphate entails the termination of glycogenolysis in the liver. This encourages hypoglycaemia. The subsequent gathering also restrains gluconeogenesis, further decreasing the quantity of readily obtainable glucose. Apparently, the loss ATP results in a massive amount of predicaments as well as inhibition of protein production and hepatic and renal dysfunction. Thus resulting in hereditary fructose intolerance.
- Provide clearly labelled diagrams to demonstrate:
- Diagram lock and key models of enzymatic activity
- Diagram the effect of enzymes on activation energy
- Discuss the specific substrate and reactant involved in the enzymatic activity ofaldolase B.
The Aldolase B enzyme catalyzes fructose 1-phosphate metabolism into glyceraldehydes and DHAP. Therefore, the substrate involved in the enzymatic activity of aldolase B is fructose 1-phosphate.
- Role of aldolase B enzyme in fructose metabolism
Aldolase B takes part in a very vital role in carbohydrate metabolism. This is because it catalyzes one of the main glycolytic-gluconeogenic pathway steps. It takes part in a predominantly significant task in fructose metabolism, which happens principally in renal cortex, the liver and small intestinal mucosa. After fructose is absorbed into the body, fructokinase enzyme phosphorylates it to form useable fructose 1-phosphate. The Aldolase B enzyme then catalyzes fructose 1-phosphate metabolism into glyceraldehydes and DHAP (Segebarth et.al, 2007)..
- Explain what would happen if the interconversions of the Cori cycle occurred and remained within a single cell.
If the interconversions of the Cori cycle were to take place within a single cell, it would constitute a futile cycle with glucose being consumed and resynthesised at the expense of ATP and GTP hydrolysis (McGrane, 2006).
- Construct a dynamic model to show the doctor why the citric acid cycle is central to aerobic metabolism.
- Explain where in the citric acid cycle a defect can occur that prevents an increased conversion of adenosine diphosphate (ADP) to adenosine triphosphate (ATP) in response to an increased energy need and how the products of the citric acid cycle are converted into ATP
- Explain the role of coenzyme Q10 in ATP synthesis.
Ali M, Rellos P, and Cox, T., (2008). Hereditary fructose intolerance. J Med Genet. May;35(5):353-65.
McGrane, M., (2006). Carbohydrate Metabolism: Synthesis and Oxidation. Missouri: Saunders, Elsevier. pp. 258–277.
Michael W,.(2008) "citric acid cycle." A Dictionary of Plant Sciences.. Retrieved July 09, 2011 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O7-citricacidcycle.html
Segebarth, C; Grivegnée AR, Longo R, Luyten PR, den Hollander JA. (2007). "In vivo monitoring of fructose metabolism in human liver by means of 32P magnetic resonance spectroscopy". Biochimie 73 (1): 105–108