8: Metabolism of carbohydrates
- Page ID
- 234028
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- 8.2: Stage II of Carbohydrate Catabolism
- The monosaccharide glucose is broken down through a series of enzyme-catalyzed reactions known as glycolysis. For each molecule of glucose that is broken down, two molecules of pyruvate, two molecules of ATP, and two molecules of NADH are produced. In the absence of oxygen, pyruvate is converted to lactate, and NADH is reoxidized to NAD+. In the presence of oxygen, pyruvate is converted to acetyl-CoA and then enters the citric acid cycle. More ATP can be formed from the breakdown of glucose.
- 8.3: Glycolysis Regulation
- Glycolysis begins with the six carbon ring-shaped structure of a single glucose molecule and ends with two molecules of a three-carbon sugar called pyruvate. Glycolysis is regulated at different steps
- 8.4: Fermentation
- Fermentation is the process by which living organisms recycle NADH→NAD+ in the absence of oxygen. NAD+ is a required molecule necessary for the oxidation of Glyceraldehyde-3-phosphate to produce the high energy molecule 1,3-bisphosphoglycerate. Fermentation occurs in the cytosol of cells.
- 8.5: 8.5-Stage III of carbohydrate catabolism. The Krebs Cycle (Citric Acid Cycle)
- The fate of pyruvate depends on the species and the presence or absence of oxygen. If oxygen is present to drive subsequent reaction, pyruvate enters the mitochondria, where the citric acid cycle (also known as the Krebs Cycle) (Stage 2) and electron transport chain (Stage 3) break it down and oxidize it completely to CO2 and H2O . The energy released builds many more ATP molecules, though of course some is lost as heat. Let's explore the details of how mitochondria use oxygen to make more AT
- 8.6: Oxidative Phosphorylation
- You have just read about two pathways in glucose catabolism—glycolysis and the citric acid cycle—that generate ATP. Most of the ATP generated during the aerobic catabolism of glucose, however, is not generated directly from these pathways. Rather, it is derived from a process that begins with moving electrons through a series of electron transporters that undergo redox reactions. This causes hydrogen ions to accumulate within the matrix space.
- 8.8: Carbohydrate Storage and Breakdown
- Carbohydrates are important cellular energy sources. They provide energy quickly through glycolysis and passing of intermediates to pathways, such as the citric acid cycle, amino acid metabolism (indirectly), and the pentose phosphate pathway. It is important, therefore, to understand how these important molecules are made.
- 8.9: Gluconeogenesis- Reaction and regulation
- Gluconeogenesis is the metabolic process by which organisms produce sugars (namely glucose) for catabolic reactions from non-carbohydrate precursors. Glucose is the only energy source used by the brain (with the exception of ketone bodies during times of fasting), erythrocytes, and kidney medulla. In mammals this process occurs in the liver and kidneys.
- 8.10: Cori Cycle
- In a well-fed animal, most cells can store a small amount of glucose as glycogen. All cells break glycogen down as needed to retrieve nutrient energy as G-6-P. Glycogen hydrolysis, or glycogenolysis, produces G-1-P that is converted to G-6-P, as we saw at the top of Stage 1 of glycolysis. But, glycogen in most cells is quickly used up between meals. Therefore, most cells depend on a different, external source of glucose other than diet.