9/29/17 1 Carbohydrate and Lipid MetabolismM.J. VandeHaar How does this stuff work? Protein →Lactose Starch →WorkFiber →Lactose TimemealmealInteraction of carbohydrate and lipid metabolismabsorbed CHO propionate AA glycerolglucosemilk lactose CO2and H2Ogluconeogenesislactate glycogenincomplete oxidationcomplete oxidation absorbed lipid acetate fatty acidCO2and H2Olipogenesisketones incomplete oxidationcomplete oxidation Store as triglyceridemilk fat Glucose can be converted to fatty acids but fatty acids cannot be converted to glucose!
9/29/17 2 Terminology in MetabolismTERMINOLOGY "gluco" - glucose "lysis" →dissolution, breakdown "glyco" - sugar "genesis" →creation, synthesis "lipo" - lipid"keto" - ketone "hyper" - high "hypo”- low"neo" →new "emia" →presence of a substance in blood Pattern of nutrient absorption within a dayRate of nutrient absorptionTimemealmealAs compounds are absorbed into blood, they are removed by tissues and some are stored for later release to avoid wild fluctuations in their blood concentrations. High concentrations of a metabolite like glucose result in urinary losses.
9/29/17 3 Glucose metabolism•Do these reactions all happen in same cell? •Do they all happen at the same time? Carbohydrate Metabolism: Glycolysis A.Glycolysis (Glucose breakdown) 1. Overall reaction : 1 ATP 1 ATP2 NAD2 NADH 2 NAD ↓↓glucose →glucose-6-phosphate →→→→→→→→2 pyruvate →2 lactate ↓4 ATP 2.Anaerobic glycolysis→→lactate + 2 ATP b.When and where? c.What happens to products?
9/29/17 4 Carbohydrate Metabolism: Aerobic glycolysis Aerobic glycolysis - →→pyruvate + 6 ATP a. Purpose: quick energy b. When and where? Most cells when the electron transport chain or other reactions are able to use up the NADH, so activity is directly related to activity of the cell and availablity of glucose vs. other fuels. •muscle: related to work level and rate of protein synthesis •brain: always occuring •adipose tissue: related to rate of fat synthesis Carbohydrate Metabolism: HMP pathwayPentose phosphate pathway (hexose monophosphate pathway, HMP; Fig. 7.3 of text) 1. Net reactions: G-6-P →→CO2+ H2O + 12 NADPH orG-6-P →→triose phosphates, ribose 2. Purpose: •Generates other sugars, such as ribose for RNA and DNA synthesis. •Generates NADPH (reducing equivalents) for use in reducing reactions, such as fatty acid biosynthesis. 3. When and where? •cytosol, especially in tissues in which fatty acid synthesis is active •controlled by the ratio of NADP to NADPH, so high after a meal that has plenty of starch, sugar, or glucogenic compounds