metabolism the chemical changes that occur in living organisms the chemical changes that occur in...

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).