METABOLISM The chemical changes that occur in living organisms The chemical changes that occur in living organisms The Principal Organs: Digestive Organs Digestive Organs Liver Liver Pancreas Pancreas Heart and Blood Vessels Heart and Blood Vessels Kidneys Kidneys

Energy Metabolism Centers on 4 Basic Units: From Carbohydrate – glucose From Carbohydrate – glucose From Lipids – glycerol and fatty acids From Lipids – glycerol and fatty acids From Protein – amino acids From Protein – amino acids

Metabolic pathways break down compounds (CATABOLIC) or build more complex compounds (ANABOLIC) Metabolic pathways break down compounds (CATABOLIC) or build more complex compounds (ANABOLIC) Metabolic pathways are never completely inactive Metabolic pathways are never completely inactive

IMPORTANT METABOLIC COMPOUNDS ATP – adenosine triphosphate ATP – adenosine triphosphate A high energy compound that is the main direct fuel for cells A high energy compound that is the main direct fuel for cells Production of ATP is the fundamental goal of metabolism’s energy producing pathway Production of ATP is the fundamental goal of metabolism’s energy producing pathway

BREAKDOWN and RELEASE of ENERGY - CARBOHYDRATE 1. Glycolysis: the anaerobic metabolic pathway that breaks down glucose into two molecules of pyruvate 1. Glycolysis: the anaerobic metabolic pathway that breaks down glucose into two molecules of pyruvate

BREAKDOWN and RELEASE of ENERGY - CARBOHYDRATE 2. Pyruvate to Acetyl CoA: an aerobic reaction 2. Pyruvate to Acetyl CoA: an aerobic reaction If oxygen is unavailable, this reaction cannot occur and lactate is formed If oxygen is unavailable, this reaction cannot occur and lactate is formed Lactate is an alternative fuel that muscle cells can use, or liver cells can convert to glucose Lactate is an alternative fuel that muscle cells can use, or liver cells can convert to glucose

BREAKDOWN and RELEASE of ENERGY - CARBOHYDRATE 3. Citric acid cycle/Kreb’s Cycle/Tricarboxylic Acid Cycle: a circular metabolic pathway 3. Citric acid cycle/Kreb’s Cycle/Tricarboxylic Acid Cycle: a circular metabolic pathway

BREAKDOWN and RELEASE of ENERGY - CARBOHYDRATE 4. Electron Transport Chain: This pathway produces most of the ATP available from glucose 4. Electron Transport Chain: This pathway produces most of the ATP available from glucose

END PRODUCTS When completely broken down, each glucose molecule yields carbon dioxide, water, and ATP When completely broken down, each glucose molecule yields carbon dioxide, water, and ATP ATP are formed by the complete break down of glucose ATP are formed by the complete break down of glucose

BREAKDOWN and RELEASE of ENERGY - FATS To begin breaking down fat, the body breaks triglycerides into glycerol and fatty acids To begin breaking down fat, the body breaks triglycerides into glycerol and fatty acids Most of the energy is stored in the fatty acids (glycerol can be converted to glucose or pyruvate) Most of the energy is stored in the fatty acids (glycerol can be converted to glucose or pyruvate) Fatty acids usually produce substantially more ATP than glucose (16 carbon fatty acid = 129 ATP) Fatty acids usually produce substantially more ATP than glucose (16 carbon fatty acid = 129 ATP)

BREAKDOWN and RELEASE of ENERGY - PROTEIN Protein is only used for energy in the absence of carbohydrate or fat Protein is only used for energy in the absence of carbohydrate or fat Carbon skeletons: are formed by the deamination of amino acids and can enter the metabolic pathways at several points depending on their structure (# carbons) Carbon skeletons: are formed by the deamination of amino acids and can enter the metabolic pathways at several points depending on their structure (# carbons)

BREAKDOWN and RELEASE of ENERGY - PROTEIN Glucogenic Amino Acids: become pyruvate or a citric acid cycle intermediate Glucogenic Amino Acids: become pyruvate or a citric acid cycle intermediate Ketogenic Amino Acids: become acetyl CoA Ketogenic Amino Acids: become acetyl CoA The carbon skeleton’s point of entry determines the amount of ATP produced The carbon skeleton’s point of entry determines the amount of ATP produced

FEASTING

FASTING

FASTING Figure 6-5 (continued fasting).