Lecture 13 - Basal Metabolic Rate and Thyroid Hormone

Lecture 13 - Basal Metabolic Rate and Thyroid Hormone -...

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1 Basal Metabolic Rate and Thyroid Hormone Biology 1F25 for Biology Non-Majors Lecture 13 Background Reading Textbook, Chapter 8, pages 156-160 and Chapter 15, especially pages 300- 304. The People Who Prepared This Lecture Harry Peery Jeff Stuart Energy – a User’s Guide 1. The energy in food 2. Metabolism 3. The basal metabolic rate (BMR) 4. Energy homeostasis 5. The biology of fat 6. An obesity epidemic in Canada! 7. Obesity and diabetes 8. Energy and reproduction 9. Energy and aging
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2 1. The energy in food Food is composed of large, complex molecules held together by chemical bonds Chemical bonds contain energy Measured in calories (= kilocalories) or kjoules Different amounts of energy in different kinds of food molecules: carbohydrate, fat, protein – which is most energy dense? 1. The energy in food Food is composed of large, complex molecules held together by chemical bonds Chemical bonds contain energy Measured in Calories (=kilocalories) or kjoules Different amounts of energy in different kinds of food molecules: carbohydrate, fat , protein – which is most energy dense? Fat = 9 Calories / gram Carbohydrate = 4 Cal / gram Protein = 4 Cal / gram 1. The energy in food Food is composed of large, complex molecules held together by chemical bonds Chemical bonds contain energy Measured in Calories (=kilocalories) or kjoules Different amounts of energy in different kinds of food molecules: carbohydrate, fat , protein – which is most energy dense? Fat = 8 ATPs per carbon Carbohydrate = 6 ATPs per carbon Protein = variable, but < 8 ATPs per carbon 1. The energy in food To liberate the energy in food, it first must be digested and absorbed. Requires initial expenditure of energy. Sometimes called ‘ Thermic Effect of Food ’. Differs for different types of molecules: Fat: very low – readily absorbed Carbohydrate: moderate – requires some initial processing Protein: very high – requires much processing
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3 1. The energy in food Summary: – Fat has most Cal/g – Fat has most ATP/carbon – Fat requires little energy to assimilate – Fat can thus be dangerous! ***Fat in your body can be produced from dietary fat, carbohydrate or protein whenever the energy available exceeds needs Measuring metabolic rate in people -Usually measured as oxygen consumption / min Comparing between people -Must account for size differences. Why? How? Oxygen consumption / unit mass Or Oxygen consumption / unit body surface area Measurement of metabolic rate: why size matters (1) More weight = more living tissue to keep alive = more energy use (2) Relationship between size and surface area – heat dissipation Partitioning metabolism Typical Contributions to Total Daily Energy Expenditure Physical activity 15-30% Resting metabolic rate 60-75% Thermic effect of feeding 10%
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4 Your Basal Metabolic Rate Is: Your metabolic rate when you are: - Not following a meal (at least 12 h since last ate) - Laying down (and not moving) - Not stressed or sick or tired - Not too cold or too hot (thermoneutral)
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Lecture 13 - Basal Metabolic Rate and Thyroid Hormone -...

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