1. Nutrition and Metabolism

2. 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

3. 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

4. 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)

5. 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. Energy needs
Measurement of Energy Intake
Metabolic Energy Yields

8. 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

9. 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

10. 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

11. Bomb Calorimeter measures heat produced when food is burned

12. Text view of bomb calorimeter

13. 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

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

15. Energy Balance: Input vs Output

16. Energy Balance Energy In = Energy Out Energy In > Energy Out
Weight Maintenance
Energy In > Energy Out
Weight Gain
Energy In < Energy Out
Weight Loss

17. 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”

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

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

20. BMR > Activity > Dietary Thermogenesis

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

22. Energy needs Measurement of Energy Output direct calorimetry
Measurement of heat loss

23. 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

24. 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

25. 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

26. 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

27. 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

28. James & Schofield