METABOLISM Biochem Assignment

Topics: Citric acid cycle, Metabolism, Adenosine triphosphate Pages: 6 (1235 words) Published: December 12, 2014
3.0 METABOLISM

3.1 ANABOLISM AND CATABOLISM
Anabolism builds things and consumes energy by making bigger things out of smaller things and using up energy in the process. Anabolism, or biosynthesis, allows the body to grow new cells and maintain all the tissues. Catabolism breaks things down and gives out energy. Using bigger things to make smaller things and releasing energy in the process. Catabolism provides the energy our bodies need for physical activity, from a cellular level right up to whole body movements. When we eat our body breaks down the organic nutrients. This breaking down process releases energy, which is stored inside molecules of adenosine triphosphate (ATP) in the body.

3.2 The production of energy
3.2.1 Three stages:
Proteins, Carbohydrates and Fats are broken down during digestion and absorption into smaller units: amino acids, monosaccharide and fatty acids. These smaller compounds are further broken down into 2-carbon compounds. Compounds are degraded into CO2 and H20.

3.2.2 The production of adenosine triphosphate (ATP) in the body. 1. Glycolusis (pyruvate production)
There are two phases of Glycolysis. The first is known as the "priming phase," because it requires an input of energy in the form of 2 ATPs per glucose molecule. The second phase is known as the "pay off phase,"  because energy is released in the form of 4 ATPs, 2 per glyceraldehyde molecule.

The overall process of glycolysis is:
Glucose + 2 NAD+ + 2 ADP + 2 Pi → 2 Pyruvate + 2 NADH + 2 H+ + 2 ATP + 2 H2O

The end result of Glycolysis is two new pyruvate molecules which can then be fed into the Citric Acid cycle  3.2.2.Krebs cycle
In order for pyruvate from glycolysis to enter the Kreb's Cycle it must first be converted into acetyl-CoA by the pyruvate dehydrogenase complex which is an oxidative process wherein NADH and CO2 are formed

3.2.2.1 Step In Krebs Cycle
Acetyl-CoA enters the Kreb Cycle when it is joined to oxaloacetate by citrate synthase to produce citrate. Citrate is then converted into isocitrate by the enzyme aconitase. This is accomplished by the removal and addition of water to yield an isomer.Isocitrate is converted into alpha-ketogluterate by isocitrate dehydrogenase. The byproducts of which are NADH and CO2.Apha-ketogluterate is then converted into succynl-CoA by alpha-ketogluterate dehydrogenase. NADH and CO2 are once again produced.Succynl-CoA is then converted into succinate by succynl-CoA synthetase which yields one ATP per succynl-CoA.Succinate coverts into fumerate by way of the enzyme succinate dehydrogenase and [FAD] is reduced to [FADH2] which is a prosthetic group of succinate dehydrogenase. Succinate dehydrogenase is a direct part of the Electron Transport Chain.  It is also known as electron carrier II.Fumerate is then converted to malate by hydration with the use of fumerase. Malate is converted into oxaloacetate by malate dehydrogenase the byproducts of which are NADH.

3.2.3 Beta-oxidation
Beta-oxidation is a metabolic pathway that converts fatty acids into ATP. The metabolism of fats involves both catabolism to form ATP and anabolism to produce phospholipids. Proteins are broken up into their constituent amino acids in many different pathways, beginning with digestion and continuing with processing at the cellular level 3.2.3.1 Process of fatty acids entering mitochondria in Beta-Oxidation Before entering the mitochondrion, fatty acids must be activated The activation reaction happens in the cytoplasm, and it consists on the transformation of the fatty acid into its acyl-Coa derivative Thioester bonds are very energetic. Therefore, an ATP gets hydrolyzed (to AMP, which is equivalent to the hydrolysis of 2 ATP to 2 ADP) in the process The mithochondrial inner membrane is impermeable to acyl-CoAs. In order to get inside, these will react with a "special" aminoacid, carnitine, releasing CoA Sterified carnitine is transported into the mitochondial...

References: Ebenhöh O, Heinrich R (2001). "Evolutionary optimization of metabolic pathways. Theoretical reconstruction of the stoichiometry of ATP and NADH producing systems". Bull Math Biol 63 (1): 21–55
 Garrett, R.; Grisham, C. M. (2005). Biochemistry (3rd ed.). Belmont, CA: Thomson Brooks/Cole. p. 584.
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