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Nutrition and Metabolism

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Presentation on theme: "Nutrition and Metabolism"— Presentation transcript:

1 Nutrition and Metabolism

2 Objectives Definition of metabolism, anabolism and catabolism.
Ways of measurement of energy. Energy needs. Energy balance. Basal metabolic rate (BMR).

3 Metabolism Metabolism – process by which living systems acquire and use free energy to carry out vital processes Catabolism (degradation) Breakdown of nutrients and cell constituents and generation of energy (Exergonic oxidation) Anabolism (biosynthesis) Endergonic synthesis of biological molecules from simpler precursors Coupled to exergonic processes through “high-energy” compounds

4 Examples of each type of metabolism:
Anabolic Pathways Catabolic Pathways Protein Biosynthesis Glycolysis Glycogenesis TCA (Krebs cycle) Gluconeogenesis ß-oxidation Fatty Acid Synthesis Respiratory Chain ATP Generated Provides Energy FOR

5 How do we employ energy? MECHANICAL- muscle contraction ELECTRICAL- maintaining ionic gradients (e.g., Na-K ATPase; 70% of ATP used by kidney & brain used to maintain gradient) CHEMICAL- biotransformation of molecules (e.g., synthesis degradation, metabolism)

6 International Unit of Energy: Joule
: energy used when 1 Kg is moved 1 meter by a force of 1 Newton : kJ = 103 J; MJ = 106 J : 1 kcal = kJ : Protein: 17 kJ or 4 kcal/g CHO: 17 kJ or 4 kcal/g Fat: 37 kJ or 9 kcal/g

7

8 Energy needs Measurement of Energy Intake Metabolic Energy Yields

9 Average Energy Needs: European text: 100 kJ/ day x BW in kg or 24 kcal/day x BW in kg American Biochem text: kJ/ kg 31-44 kcal/kg

10 How to measure energy in food
Direct Calorimetry Direct measurement of heat produced Bomb calorimeter Calculate Calories/g: 4 (CHO), 9 (Fat) ,4 (Pro) and 7 (Alch) based: lab analysis of food composition Calorie chart or nutrient database

11 Energy needs Measurement of Energy Intake Bomb Calorimeter
Food is ignited electrically in the presence of oxygen Heat of combustion is measured from a rise in water temperature

12 Bomb Calorimeter measures heat produced when food is burned

13 Text view of bomb calorimeter

14 Energy needs Measurement of Energy Intake Bomb Calorimeter
Heat of combustion represents the gross energy of the food Energy lost during digestion and absorption Affected by illness

15 Energy needs Measurement of Energy Intake
% Energy from carbohydrates, protein and fat

16 Energy Balance: Input vs Output

17 Energy Balance Energy In = Energy Out Energy In > Energy Out
Weight Maintenance Energy In > Energy Out Weight Gain Energy In < Energy Out Weight Loss

18 Energy Balance Sources of fuel for energy
Input from diet: carbs, fat, prot, alcohol Stored energy: glycogen, fat, muscle Energy outgo from: Basal metabolism Physical activity “Dietary thermogenesis”

19 Energy In Food Complex social, environmental, physiological control
Food composition tables Bomb Calorimetry Complex social, environmental, physiological control

20 Energy Out Energy of food = Body Energy = ATP Energy out:
3 main components: Basal Metabolic Rate Thermic Effect Food Physical activity

21 BMR > Activity > Dietary Thermogenesis

22 Energy needs Measurement of Energy Output Energy Output Two methods
direct calorimetry indirect calorimetry Measurement of heat Measurement of energy used

23 Energy needs Measurement of Energy Output direct calorimetry
Measurement of heat loss

24 Energy needs Measurement of Energy Output Indirect calorimetry
Utilization of oxygen Oxygen consumption is proportional to ATP synthesis Use oxygen consumption to determine heat production

25 Energy needs Measurement of Energy Output Indirect calorimetry
Glucose oxidation Starch oxidation 6H2O + 6CO 2 C6H12O6 + 6O2 + 15.5 kJ/g of energy 5nH2O + 6nCO 2 (C6H12O5)n + 6nO2 + 17 kJ/g of energy

26 Energy needs Measurement of Energy Output Indirect calorimetry
Fat oxidation (e.g. glyceryl butro-oleostearate (main fat in butter) C3H5O3.C4H7O.C18H33O. C18H35O + 60O2 + + 43CO2 40H2O 39 kJ/g of energy

27 Energy Out: Basal Metabolism
Largest daily energy output Definition: “the sum total of minimal activity of all tissue cells of the body under steady sate conditions” Men estimate: lbs body weight X 11 Women estimate: lbs body weight X 10 affected by Muscle > Fat Male > Female Young > Old Temperature: body and environment

28 Basal Metabolic Rate BMR = number of calories would need daily simply to stay alive if were totally inactive, in bed, awake for 16 hours & slept for 8 hours Harris-Benedict Equation: Women: 661+(4.38 x weight in pounds)+(4.38 x height in inches)-(4.7 x age)=BMR Men: 67+(6.24 x weight in pounds)+(12.7 x height in inches)- (6.9 x age)=BMR

29 James & Schofield


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