1. Metabolism Lab In today’s lab, you will:
Determine your basal metabolic rate and compare your average daily energy intake with your average daily energy requirement.
Determine the metabolic rates of mice using indirect calorimetry and investigate the effects of temperature on the rate of metabolism.

2. Determination of Metabolic Rates
Cellular respiration: process in living organisms that extracts energy from the chemical bonds of organic molecules (food) and converts it into ATP. ATP is used to run cell activities. Organic Molecules + O2  CO2 + H2O + ATP + Heat Metabolism: the sum of all chemical reactions occurring inside an organism Calorimetry: the measurement of heat energy released from the body via metabolism calorie = amount of heat energy needed to raise 1 gram H2O by 1° C

3. Determination of Metabolic Rates
Direct calorimetry: a technique of measuring heat energy. An organism is placed in a calorimeter chamber; as the organism gives off heat it is transferred to the surrounding water jacket in the walls of the chamber. This ∆T is = energy released. Indirect calorimetry: the measurement of body heat indirectly through the dependency of heat production on oxygen consumption. Based on the principle that: Energy (heat) liberated in the body = Energy (heat) liberated out the body

4. Determination of Metabolic Rates
Average (kcal / liter O2) energy for the primary food groups:
Fats (4.7 kcal / liter O2) Proteins (4.6 kcal / liter O2) Carbohydrates (5.1 kcal / liter O2)
Combined together as “food” averages ≈ kcal / liter O2
Metabolic Rate: the total energy expenditure per unit time (kcal/hr)
Basal Metabolism: the minimum amount of energy the body needs in a resting and fasting state.

5. Determination of Metabolic Rates
Basal Metabolic Rate (BMR): the rate of energy expended for basal metabolism. BMR is measured under a set of standard conditions: Standard Conditions
1. No food ingestion 12 hours prior to test Subject mentally, physically relaxed (morning, prone, dark) 3. Room temperature must be comfortable 4. Subject must not have a fever (which elevates BMR) Conditions Affecting the BMR 1. Exercise ---> increases BMR 2. Food ingestion ---> increases BMR 3. Increased sympathetic activity ---> increases BMR 4. Release of thyroxin and growth hormone ---> increases BMR 5. Other Factors: Climate, nutrition, age, sex, body surface area

6. Determination of Metabolic Rates
Specific dynamic action (SDA): energy expended to process food
Total Energy Required = BMR + SDA + energy for physical activity
Total Energy Expenditure = Body Heat + [External Work Done + Stored Energy]
Effects of Thyroid Hormones
• Primary effect is stimulation of calorigenesis (heat production) in the body
– causes increase in metabolism
– response is reflected by an increase in oxygen consumption in most tissues
• Other systemic effects:
– increases in cardiac output, heart rate, stroke volume
– increase in respiratory rate
– increase in RBC count
– promotes normal growth
– promotes development and maturation of the nervous system

7. Environmental Influence
(cold)
Thermoreceptors
Anterior
Increased Cell Metabolism
(heat production)

8. Thyroid Conditions Hyperthyroidism Hypothyroidism
cannot tolerate warm temperatures (faster BMR/heat production)
often lose weight
highly responsive to external stimuli (often to the point of extreme nervousness)
Hypothyroidism
cannot tolerate cold temperatures (slower BMR/heat production)
often gain weight
mentally and physically sluggish

9. Grave’s Disease = Hyperthyroidism

10. Thyroid Hormone Synthesis

11. Experimental Procedure (Part 1)
Before you come to lab it is necessary for you to keep two daily diaries for a period of three days.
One will be a physical activity diary to record the energy you expend for physical activity. This is just a portion of your daily energy requirement. You also need energy for basal metabolism and specific dynamic action, which we will calculate in lab.
The other diary will be a daily record of the average energy intake as food.

12. Indirect Calorimetry
Humans and mice are endotherms, which means they generate most of their heat from inside their body by way of cell metabolism. In comparison, an ectotherm gets its heat from the environment.
During this exercise you will monitor the rate of metabolism in a mouse.
In addition, you will investigate the influence of environmental temperature on the mouse’s metabolism by comparing a mouse in a warm environment with a mouse in a cold environment.

13. Experimental Procedure (Part 2)

14. Experimental Procedure (Part 2)

15. Calculation of Metabolic Rates

16. Calculate Percent Change
Post MR – Pre MR X 100 Pre MR