Energetic Metabolism
Observing the Effects of
Respiration and Photosynthesis
Interconnections:
Photosynthesis & Respiration
Chemical Equations
• Aerobic Respiration
C6H12O6 + 6O2  6CO2 + 6H2O + energy
Measure O2 use
• Photosynthesis
6CO2 + 6H2O + light energy  C6H12O6 + 6O2
Measure O2 production
Metabolic Rate
• Speed of aerobic respiration in an
organism (use of O2)
• Measured in Calories
– unit of energy
– amount of heat required to increase
temperature of 1 kg of H2O by 1oC
– 1 liter of O2 consumption = 4.825 Calories
• Our experiment measures metabolic rate as
mL O2/gram/day, which can be converted to
calories
Factors Affecting Metabolic Rate
• Body Temperature
Mealworms
are
ectothermic
animals
Hypotheses: Do plants or animals have a higher metabolic rate?
How do environmental temperatures influence metabolic rates?
Experimental Set Up
Pipettes for
peas:
1-mL at 15oC
5-mL at 30oC
mealworms
peas
cheesecloth
soda lime
Pipettes for
mealworms:
5-mL at both
15 and 30oC
Reading the Respirometer Pipettes
For 1-mL pipette
0.1 mL between
numbers
0.01 mL between
smallest lines
For 5-mL pipette
1 mL between
numbers
0.1 mL between
smallest lines
1 mL
0.1 mL
Calculations
•Suppose the total amount of O2 consumed in 30
minutes by 15.6 grams of mealworms was 3.5 mL.
•Calculation of mL O2/gram/day
3.5 mL
30 min
3.5 mL
30 min
1
x 60 min
1 hour
2
x 60 min
1 hour
x 24 hours x _____1______
1 day
weight in grams
x 24 hours
1 day
x1
=
15.6 grams
= 10.8 ml O2/gram/day
Graphing: Histogram
4.5
4
3.5
3
Metabolic 2.5
Rate (mL
O2/gram/day) 2
Peas
Mealworms
1.5
1
0.5
0
15
30
Temperature (degrees C)
Plot the class averages for pea and mealworm
metabolic rates at both temperatures.
More Calculations (see page 62)
•Suppose the metabolic rate of your peas was
2.1 mL O2/ gram/day
•Calculation of the calorie intake of a 150 pound
student whose metabolic rate matches the peas
2.1 mL x 4.825 calories x 68040 grams
gram day 1000 mL
150 x 453.6 =
68040 grams
2.1 mL x 4.825 calories x 68040 grams
gram day 1000 mL
= 689.4 calories/day
Photosynthesis Experiment
Hypothesis
Will the rate of photosynthesis be
increased by increased light energy?
Experimental Set Up
Syringe
1-mL pipette
For 1-mL pipette
0.1 mL between
numbers
0.01 mL between
smallest lines
bicarbonate
solution
Elodea
Graphing Photosynthesis Data
Photosynthetic Rate (mL O2 produced)
0.045
0.04
0.035
0.03
0.025
25 cm
0.02
50 cm
0.015
0.01
0.005
0
0
5
10
15
20
25
Time (minutes)
Plot the oxygen produced for light at 50 cm
and 25 cm for each timed reading.
Graphing Photosynthesis Data
Photosynthetic Rate (mL O2 produced)
0.045
0.04
0.035
0.03
25 cm
0.025
50 cm
Linear (50 cm)
0.02
Linear (25 cm)
0.015
0.01
0.005
0
0
5
10
15
20
25
Time (minutes)
Use separate lines to connect the sets of points.
CLEAN UP!
• Return your mealworms, peas, and
elodea to the appropriate containers
• Put used soda lime in discard bottle
• Clean and dry your respirometers.
• Discard cheesecloth into the trash
• Make sure the sinks stay clean
Worksheet
• Complete pages 59-62 from lab
manual
• Be sure your instructor checks your
completed worksheet before you
leave the lab