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METABOLISMMETABOLISM
The chemical changes that occur in living The chemical changes that occur in living organismsorganisms
The Principal Organs:The Principal Organs: Digestive OrgansDigestive Organs LiverLiver PancreasPancreas Heart and Blood VesselsHeart and Blood Vessels KidneysKidneys
Energy Metabolism Centers on 4 Basic Units:Energy Metabolism Centers on 4 Basic Units: From Carbohydrate – glucoseFrom Carbohydrate – glucose From Lipids – glycerol and fatty acidsFrom Lipids – glycerol and fatty acids From Protein – amino acidsFrom Protein – amino acids
Metabolic pathways break down Metabolic pathways break down compounds (CATABOLIC) or build more compounds (CATABOLIC) or build more complex compounds (ANABOLIC)complex compounds (ANABOLIC)
Metabolic pathways are never completely Metabolic pathways are never completely inactiveinactive
IMPORTANT METABOLIC IMPORTANT METABOLIC COMPOUNDSCOMPOUNDS
ATP – adenosine triphosphateATP – adenosine triphosphate A high energy compound that is the main A high energy compound that is the main
direct fuel for cells direct fuel for cells Production of ATP is the fundamental goal Production of ATP is the fundamental goal
of metabolism’s energy producing pathwayof metabolism’s energy producing pathway
BREAKDOWN and RELEASE of BREAKDOWN and RELEASE of ENERGY - CARBOHYDRATEENERGY - CARBOHYDRATE
1. Glycolysis: the anaerobic metabolic 1. Glycolysis: the anaerobic metabolic pathway that breaks down glucose into two pathway that breaks down glucose into two molecules of pyruvatemolecules of pyruvate
BREAKDOWN and RELEASE of BREAKDOWN and RELEASE of ENERGY - CARBOHYDRATEENERGY - CARBOHYDRATE
2. Pyruvate to Acetyl CoA: an aerobic reaction 2. Pyruvate to Acetyl CoA: an aerobic reaction If oxygen is unavailable, this reaction cannot If oxygen is unavailable, this reaction cannot
occur and lactate is formedoccur and lactate is formed Lactate is an alternative fuel that muscle cells can Lactate is an alternative fuel that muscle cells can
use, or liver cells can convert to glucoseuse, or liver cells can convert to glucose
BREAKDOWN and RELEASE of BREAKDOWN and RELEASE of ENERGY - CARBOHYDRATEENERGY - CARBOHYDRATE
3. Citric acid cycle/Kreb’s Cycle/Tricarboxylic 3. Citric acid cycle/Kreb’s Cycle/Tricarboxylic Acid Cycle: a circular metabolic pathwayAcid Cycle: a circular metabolic pathway
BREAKDOWN and RELEASE of BREAKDOWN and RELEASE of ENERGY - CARBOHYDRATEENERGY - CARBOHYDRATE
4. Electron Transport Chain: This pathway produces 4. Electron Transport Chain: This pathway produces most of the ATP available from glucosemost of the ATP available from glucose
END PRODUCTSEND PRODUCTS
When completely broken down, each When completely broken down, each glucose molecule yields carbon dioxide, glucose molecule yields carbon dioxide, water, and ATP water, and ATP
30-32 ATP are formed by the complete 30-32 ATP are formed by the complete break down of glucose break down of glucose
BREAKDOWN and RELEASE of BREAKDOWN and RELEASE of ENERGY - FATSENERGY - FATS
To begin breaking down fat, the body To begin breaking down fat, the body breaks triglycerides into glycerol and fatty breaks triglycerides into glycerol and fatty acidsacids
Most of the energy is stored in the fatty Most of the energy is stored in the fatty acids (glycerol can be converted to glucose acids (glycerol can be converted to glucose or pyruvate)or pyruvate)
Fatty acids usually produce substantially Fatty acids usually produce substantially more ATP than glucose (16 carbon fatty more ATP than glucose (16 carbon fatty acid = 129 ATP)acid = 129 ATP)
BREAKDOWN and RELEASE of BREAKDOWN and RELEASE of ENERGY - PROTEINENERGY - PROTEIN
Protein is only used for energy in the Protein is only used for energy in the absence of carbohydrate or fatabsence of carbohydrate or fat
Carbon skeletons: are formed by the Carbon skeletons: are formed by the deamination of amino acids and can enter deamination of amino acids and can enter the metabolic pathways at several points the metabolic pathways at several points depending on their structure (# carbons)depending on their structure (# carbons)
BREAKDOWN and RELEASE of BREAKDOWN and RELEASE of ENERGY - PROTEINENERGY - PROTEIN
Glucogenic Amino Acids: become pyruvate Glucogenic Amino Acids: become pyruvate or a citric acid cycle intermediateor a citric acid cycle intermediate
Ketogenic Amino Acids: become acetyl Ketogenic Amino Acids: become acetyl CoA CoA
The carbon skeleton’s point of entry The carbon skeleton’s point of entry determines the amount of ATP produceddetermines the amount of ATP produced
FEASTINGFEASTING
FASTINGFASTING
FASTINGFASTING
Figure 6-5 (continued fasting).