catabolism

Examples of catabolism in the following topics:

• Metabolic Pathways

  • An anabolic pathway requires energy and builds molecules while a catabolic pathway produces energy and breaks down molecules.
  • The second process produces energy and is referred to as catabolic.
  • Some catabolic pathways can capture that energy to produce ATP, the molecule used to power all cellular processes.
  • Other energy-storing molecules, such as lipids, are also broken down through similar catabolic reactions to release energy and make ATP.
  • Catabolic pathways are those that generate energy by breaking down larger molecules.

• Connecting Lipids to Glucose Metabolism

  • Lipids can be both made and broken down through parts of the glucose catabolism pathways.
  • Like sugars and amino acids, the catabolic pathways of lipids are also connected to the glucose catabolism pathways.
  • Triglycerides can be both made and broken down through parts of the glucose catabolism pathways.
  • 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.

• Connecting Other Sugars to Glucose Metabolism

  • Sugars, such as galactose, fructose, and glycogen, are catabolized into new products in order to enter the glycolytic pathway.
  • You have learned about the catabolism of glucose, which provides energy to living cells.
  • Like sugars and amino acids, the catabolic pathways of lipids are also connected to the glucose catabolism pathways.
  • The catabolism of both fructose and galactose produces the same number of ATP molecules as glucose.
  • The catabolism of sucrose breaks it down to monomers of glucose and fructose.

• Connecting Proteins to Glucose Metabolism

  • Excess amino acids are converted into molecules that can enter the pathways of glucose catabolism.
  • They can be broken down into their constituent amino acids and used at various steps of the pathway of glucose catabolism.
  • However, if there are excess amino acids, or if the body is in a state of starvation, some amino acids will be shunted into the pathways of glucose catabolism.
  • For example, deaminated asparagine and aspartate are converted into oxaloacetate and enter glucose catabolism in the citric acid cycle.
  • Several amino acids can enter glucose catabolism at multiple locations.

• ATP Yield

  • The amount of energy (as ATP) gained from glucose catabolism varies across species and depends on other related cellular processes.
  • The number of ATP molecules generated via the catabolism of glucose can vary substantially.
  • Glucose catabolism connects with the pathways that build or break down all other biochemical compounds in cells, but the result is not always ideal.
  • Overall, in living systems, these pathways of glucose catabolism extract about 34 percent of the energy contained in glucose.

• Control of Catabolic Pathways

  • Catabolic pathways are controlled by enzymes, proteins, electron carriers, and pumps that ensure that the remaining reactions can proceed.
  • The pyruvate produced can proceed to be catabolized or converted into the amino acid alanine.

• Outcomes of Glycolysis

  • If the cell cannot catabolize the pyruvate molecules further (via the citric acid cycle or Krebs cycle), it will harvest only two ATP molecules from one molecule of glucose.
  • Glycolysis, or the aerobic catabolic breakdown of glucose, produces energy in the form of ATP, NADH, and pyruvate, which itself enters the citric acid cycle to produce more energy.

• Control of Metabolism Through Enzyme Regulation

  • Metabolic reactions, such as anabolic and catabolic processes, must proceed according to the demands of the cell.
  • It is the product of the catabolic metabolism of sugar (cellular respiration), but it also acts as an allosteric regulator for the same enzymes that produced it.
  • When levels of ADP are high compared to ATP levels, ADP triggers the catabolism of sugar to produce more ATP.

• ATP in Metabolism

  • ATP, produced by glucose catabolized during cellular respiration, serves as the universal energy currency for all living organisms.
  • In this way, ATP is a direct link between the limited set of exergonic pathways of glucose catabolism and the multitude of endergonic pathways that power living cells.

• Food Energy and ATP

  • The digestible carbohydrates in an animal's diet are converted to glucose molecules and into energy through a series of catabolic chemical reactions.