 The process of using nutrients to release energy for use by the cell is
called cellular respiration. In humans, cellular respiration is part of an
elaborate metabolic process that allows us to maintain homeostasis.
Homeostasis is the balanced internal environment of the body.
 The balanced equation for cellular respiration is:
C₆H₁₂O₆ + 6 O₂
glucose
oxygen
consumption
6 CO₂ + 6 H₂O + 36 ATP
carbon
water energy
dioxide
production
The rate of cellular respiration can be measured observing oxygen consumption or carbon
dioxide production.
2
 This experiment measures only the oxygen consumed by the mouse in
this respiration chamber.
3
 A mouse is weight and it’s mass recorded.
 Mass = 22.5 g
4
 KOH (potassium hydroxide) pellets are put in the chamber to absorb
the CO₂ produced by the mouse. Next, the cage with the mouse is
placed in it.
 This is done so CO₂ production does not interfere with measuring of
oxygen consumption.
Pipette used to measure
O₂ consumed
Mouse in cage
KOH pellets
chamber
5
 A bubble is placed at the end of the pipette, and measure the time passed for
it to move a determined distance. This process is repeated 5 times.
Bubble moving towards the mouse as it
consumes the O₂ and the CO₂ it
produces is absorbed by the KOH.
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trial Volume of O2 used
(ml)
Time
(min)
Time
(hours)
(mlO2)/h (mlO2/h)/g
1
2 ml
3
3/60= 0.05
2/0.05= 40
40/22.5= 1.77
2
2 ml
3
0.05
40
1.77
3
2 ml
4
0.066
30.3
1.346
4
2 ml
2
0.033
60.6
2.693
5
2 ml
3
0.05
40
1.77
Average= 1.87 mlO2/h/g
Organism: mouse
Weight: 22.5 grams
The number of minutes divided by 60 represents the
number of minutes converted into hours.
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 Determine the relationship between body mass and metabolic rate.
Animal (weight kg)
Metabolic rate (mlO2/g/h)
Kangaroo mouse (0.02kg)
1.8
Rat (0.10g)
0.87
Cat (10kg)
0.68
Dog (20kg)
0.33
Man (90kg)
0.21
Elephant (1,000kg)
0.07
 Look at the chart above; as body mass increases, what happens to
Decreases
oxygen consumption?
8
Metabolic rate (VO2/h/g)
Animal Size/weight (Kg)
9
 Germinating seeds are living and growing plant embryos. The seeds of
choice for this exercise are black-eyed peas. The seeds are soaked in
water for a few minutes to start the germinating process.

Experiment: Two beakers are used, each is added the strained,
germinating seeds. The contents of only one beaker will be boiled in
water for 5 minutes then drained and cooled.
Germinated seeds
Germinated–boiled seeds
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 Germinated seeds (Germ) are
placed into one bottle and
germinated-boiled seeds
(Germ-Boil) are placed into a
second bottle.
 Both bottles must contain
roughly the same amount of
seeds.
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Stoppers are placed
in the thistle tubes
to prevent losing
CO2
 The respiration apparatus is
assembled. The plastic tubing is
placed into a test tube of water
with phenol red. Phenol red is
placed in the test tubes to trap
any gas produced by the seeds.
The bottles remain undisturbed
for 40 minutes.
 Balanced equation:
H₂O
water
+
CO₂
H₂CO₃
carbon
carbonic
dioxide
acid
Phenol red is a pH indicator. It
appears red at a neutral pH, and
yellow at a low pH .
12
 After the 40 minute incubation
period, the gas in the bottle is
displaced into the test tube by
pouring tap water down the tube.
 Germinated seeds produced CO₂
lowering the pH shown by the color.
 Dead seeds did not respire,
maintaining the color of neutral pH
13
 Some eukaryotic cells will maintain their energy production by
fermenting the products of glucose breakdown rather than respiring.
One major eukaryotic fermentation produces ethanol + carbon dioxide.
 Alcoholic fermentation balanced equation:
C₂H₁₂O₆
glucose
2 CO₂ + 2 C₂H₅OH + 2 ATP
carbon
ethanol
energy
dioxide
14
 40 ml of solution (dH2O, glucose and sucrose) is
placed in each of 3 beakers.
 Yeast is added to each of the 3 beakers and let sit for 5
minutes.
15
 The mixture of yeast diluted in a solution are put in 3 different
fermentation chambers (glucose 10%, Sucrose 10% anddH2O).
Notice the markings
of volume in ml
Each chamber has a
marking informing
which solution it has.
Fermentation chamber
16
 The 3 samples are put in the incubator at 37°C and every 10 minutes
the levels of carbon dioxide formed are read. The final production of
CO₂ after 30 minutes looks like this.
The yeast has settled, there
are no bubbles here
Water
Notice the CO₂ bubbles
sucrose 10%
Notice the CO₂ bubbles overflow
glucose 10%
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Time
10% glucose
10% sucrose
Water (0% glucose)
0
0
0
0
10
4.5
3
0
20
10
8
0
30
overflow
10
0
40
 Once one of the chambers is overflown the experiment stops, usually by 20-30
minutes it is over.
 Sucrose is a disaccharide, but goes through a process that brakes it into
fructose and glucose, and yeast is able to use those to produce ethanol. Look
in the lab manual for details.
The End
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