METABOLIC RATE LAB
AP BIOLOGY
Name:____________________
Period:_____
Metabolic rate is defined as the amount of energy (Calories) burned per hour per
body surface area. It is affected by : 1. gender - males have a higher rate, 2. age - rate
decreases with age, and 3. level of activity. Metabolic rate is directly related to aerobic
respiration : C6H12O6 + 6O2 -----> 6CO2 + 6H2O + 38ATP. Therefore the amount of CO2
exhaled can be a measure of the metabolic rate. In this experiment we will determine the
CO2 produced and convert this into an energy value for metabolic rate.
Part I : Basal (Resting) Metabolic Rate (BMR)
1. Place 100 mL of tap water into a clean flask.
2. Add 10 drops of phenolphthalein acid-base indicator.
3. Add dilute NaOH, one drop at a time and swirl until the solution turns pink.
4. Through a straw, bubble exhaled breath into the solution in 10 second
intervals for 1 minute. Blow slowly and evenly, and do not hyperventilate.
The solution should turn clear.
5. Slowly add NaOH from the 10 mL pipet until the solution turns back to the
original pink color. You may need more than one cylinder full.
NaOH used = _____ mL
6. Calculations : Since CO2 is a weak acid, the amount of NaOH used to
neutralize it is a measure of how much CO2 was produced, how much O2
was consumed, and how much metabolism occurred.
a. O2 consumed :
mL NaOH x
=
(calibration factor)
mL O2
b. Your body surface =
m2 (show your line on the nomogram)
c. BMR = a x .29 =
b
Calories/m2 hr
Part II : Exercise Metabolic Rate
Prepare a flask of liquid as in part I, steps 1 through 3. Repeat the above protocol
as pre-exercise and post-exercise metabolic rates. For exercise do some form of
moderate exercise (stationary bike, run in place, etc.) for a minute or two.
Pre-exercise:
ml =
Calories/m2 hr
Post-exercise:
ml =
Calories/m2 hr
1.) Calculate final results for each condition. 2.) Draw your line on the nomogram to find
body surface area. 3.) Find your estimate of BMR from the graph by showing a line going
from your age to the correct gender line and then over to your estimated BMR. Write that
value near that line.
CLEANUP