LAB REPORT - CELLULAR RESPIRATION
PURPOSE:
This experiment was conducted in order to prove that living things do respiration while non-living things
do not. The rate of cellular respiration in living peas, dead peas and non-living things were calculated
and the effects of temperature to the rate of cell respiration were observed. There are various ways of
measuring cellular respiration. It can be measured by calculating the amount of glucose consumed or by
measuring the amount of oxygen consumed or measuring the amount of carbon dioxide produced (how
fast the byproduct appears). In this experiment respiration was measured by measuring the amount of
oxygen consumed. Every cell is responsible for energy exchanges as it is necessary to sustain its ordered
structure. To do this cells break down nutrient molecules to generate ATP, which is called cellular
respiration. Basically in respiration the chemical energy stored in organic molecules are turned into a
type that can be used by organisms. It’s a catabolic activity as it breaks down complex molecules (which
have a lot of stored energy) to simpler molecules (with less energy) by releasing energy, which is stored
in the form of ATP.
C₆ H₁₂ O₆ + 6O₂ -> 6CO₂ + 6H₂ O + Energy
In respiration glucose is oxidized and releases energy and oxygen is reduced to form water and the
carbon atoms of sugar molecule are released as carbon dioxide.
HYPOTHESIS:
It is hypothesized that the living peas will respire because the cells in living peas are alive. Every living
thing needs energy and therefore the living peas have to respire, or else it can be classified as dead peas
because eventually it’ll die without energy to drive the numerous things cells do. Neither of the dead
peas nor the paper balls will respire. Again it comes to cells and how living cells do respiration because
they need energy. As for paper balls, it’s simply non-living and it doesn’t have “cells” in the first place.
Dead peas however have cells but dead ones. Talking about dead peas and respiring is like talking about
dead people and respiration because neither of them respires. The cells are already dead that it doesn’t
need any energy to survive since they are already dead.
In this experiment three different temperatures are used in which each sample of peas are kept: cold,
warm and room temperature. It’s predicted that the condition in which the peas are kept in affects the
rate of respiration. The hypothesis is that the warm living peas will do more respiration than either of
the peas left in cold or room temperature and it’s predicted it’s got something to do with the enzymes
used in respiration. Enzymes in higher temperature work fast because there the heat energy is
converted into kinetic energy and there’ll be more substrate-enzyme collisions and therefore there’s a
higher chance of respiration, increasing the rate of it. The peas in room temperature is mostly likely to
have the next highest rate of oxygen consumption out of the 3 temperatures and the rate of respiration
in peas that were frozen will be the slowest since coldness slows things down. Similar to what’s learnt
about how atoms in particles vibrate more when heat is added and how cooling down turns gases into
solids (because atoms become more still). In respiration the cold temperature will reduce the collisions
between the enzyme and the substrate and might even end up denaturing the
EQUIPMENT LIST:
-Peas
-Boiling tubes (6)
-Boiling tubes Stand
-Rubber stoppers (5)
-Plastic tubes
-Cotton Balls (10)
-Microwave
-Petri Dish
-Potassium hydroxide
-Ink
-Tweezers
-Graduated Cylinder
-Ruler
-Taps and sinks
-Dropper
-Paper balls
-Temperature probe
-Beakers
-Rubber bands
-Lid of the fish tank
-Stopwatch
-Tap Water
The Set Up of the Respirometer
PROCEDURE:
1. The peas were taken out from the pods
2. The volume of the peas was measured by submerging them into a graduated cylinder filled with
20mls of water to get them to 25mls for 4 groups. (Take 5 ml volume of peas)
3. The peas which were divided into 4 groups were put in 4 differently labeled tubes.
4. Paper was torn to pieces to make small paper balls
5. The last tube labeled as- paper with paper balls was filled with paper balls, approximately matching
the volumes with the peas in other tubes
6. One group of peas was put in the microwave for 3 minutes to kill them.
7. Those peas were put in the tube that is labeled as “dead”
8. One group of peas was put into the freezer just before it freezes, and those peas were put in the tube
that is labeled as “frozen”
9. Another group of peas were kept submerged in hot water, not boiling and not killing the peas, and
those peas were put in the tube that is labeled- warm
10. A dry piece of cotton wool was placed on top of the peas using tweezers.
11. Another piece of cotton wool was soaked in potassium hydroxide and put on top of the dry cotton
wools using tweezers, and left horizontal.
12. All the tubes were closed or covered using rubber stoppers which had a rubber tube attached to it.
13. Rubber bands were placed on the rubber tubes.
14. The sink was filled with water.
15. A drop of ink was added on to the end of the rubber tubes using a dropper
16. The rubber bands were moved to the end of where the ink is. That was the starting point.
17. The end of the rubber tube was closed and submerged inside the water for 30 seconds, which was
timed with a timer.
18. The amount of inked moved was observed, and the rubber bands were rolled down to where the ink
had moved to. This is the new starting point after all the water pressure had effect on the ink.
19. Something heavy was used to keep the tubes submerged inside the water and those tubes were kept
in that state for 20 minutes
20. Keeping the tubes inside the water, and the amount of distance the ink moved from the point
indicated by the rubber band is measured.
21. The results were recorded per tube.
22. The results were graphed.
RESULTS:
ITEM IN BOILING TUBE
TIME
(seconds)(s)
DISTANCE INK MOVED
(cm)
RATE
(cm/s)
1. Paper balls
1200
1.5
0.001
2. Dead Peas
1200
2.3
0.002
1200
3
0.003
4. Living Peas
(Frozen - 18.8⁰C)
1200
0.5
0.0004
5. Living Peas
(Warm - 29.5⁰C)
1200
0.2
0.0002
3. Living Peas (Normal 27.1⁰C)
Explanation of the experiment:
The structure of the respirometer is, the peas/ paper balls at very bottom, a piece of cotton on top of it,
another piece of cotton which is soaked in KOH on the dry cotton, the rubber stopper at the mouth of
the boiling tube and a plastic tube stuck to the rubber stopper.
KOH is a chemical that absorbs carbon dioxide. In respiration cells take in oxygen and give out carbon
dioxide. The only way air comes inside the boiling tube is through the narrow plastic tube. Every time
carbon dioxide enters the boiling tube; it’s absorbed by the KOH cotton. The oxygen inside the boiling
tube, or the ones that enter through the plastic tube is taken in by the peas and respiration takes place.
And as it takes in all the oxygen and gives out carbon dioxide, the carbon dioxide is absorbed by the KOH
cotton. If this happens for quite some time, this will create a pressure difference between the outside
and the inside, as kind of a vacuum is created inside (all oxygen taken in by peas, all carbon dioxide
taken in by KOH). When the boiling tube is first submerged in the water, the water doesn’t enter the
plastic tube stuck to the end of the rubber stopper because there is air inside the boiling tube and air
takes space too, so water can’t just flow inside. But as all the oxygen and carbon dioxide are absorbed
either by KOH or the peas, in an attempt to take in oxygen and due to the pressure difference between
the inside of the boiling tube and the outside water, the ink, along with some water, is sucked inside,
resulting in the movement of the ink. At the rate oxygen is used up, ink is sucked in towards the boiling
tube through the plastic tube. To measure the rate of respiration, the distance the ink moved is divided
by the time it took.
The controls in respiration of this experiment were the paper balls and the dead peas. Other controls
include the concentration of the KOH solution, the volume of the peas, and the time the respirometers
were submerged in the sink.
ANALYSIS:
Uncertainties Table:
EQUIPMENTS
UNCERTAINTIES
1. Ruler
± 0.05cm
2. Graduated Cylinder
± 0.5 ml
3. Time
4. Temperature probe
±1s
± 0.1 ⁰C
According to the results collected from this experiment, it’s clear that the experiment wasn’t done very
accurate or carefully. It suggests problems with the technique or the procedure. Most flaws that were
seen in the procedure were due to the lack of planning and organization among the members of the
group. The mistakes that were done during the experiment reflected on our results table which
contained some unexpected results. Dead peas and paper balls seem to have a surprisingly high rate of
respiration while the Warm living peas seem to have a surprisingly low rate of respiration than
expected. We were told to consider 1.5 cm (the distance ink moved in the boiling tube with paper balls)
as the amount of distance the ink moved due to the pressure and temperature differences between the
inside of the boiling tube and the outside water. If that’s considered it would suggest that in frozen and
warm peas, the ink moved backwards which wouldn’t make sense.
There is a possibility that “dead peas” weren’t actually dead, but were just warm, which resulted in such
a high rate of respiration compared to others and according to what’s expected. It’s a possibility that we
ended up killing the cells or completely denaturing the enzymes in the peas that were labeled as “Warm
peas”. As the temperature of the dead peas wasn’t measured, it’s impossible to come to a conclusion on
this. Another that explains the situation is that, the two respirometers might have gotten switched in
the process due to some problems that were faced. A major problem was, that nobody was quite sure
which respirometer was which and in the end it was down to people guessing which one was which. All
the boiling tubes or respirometers were labeled using stickers, which were made out of paper and the
fact that paper would no longer stick to the glass underwater didn’t come into account. Once they were
submerged, the paper stickers came off and in the end there was no evidence left that each was the
respirometer that was thought to be.
Due to the fact that the whole experiment was quite unorganized, some important rules or instructions
were forgotten. For example, it’s always advised to keep the respirometers totally submerged once it’s
put inside the sink. During the experiment, the water stopper of the sink didn’t seemed to fit the sink
hole or due to some other problem it kept on unblocking the sink, draining all the water that was
collected to do the experiment. So, the respirometers were exposed to air after keeping it submerged in
water for a few minutes. Due to all the chaos going on, it was forgotten to keep the respirometer
horizontal at all times, after the ink was added and after having the respirometer submerged in water
for a few minutes. Taking the respirometer in and out of water might have moved the ink dramatically
after the rubber band was placed indicating the starting point. In the first place marking the starting
point underwater was challenging as it was hard to distinguish the blue ink on the plastic tube in a sink
with a black surface.
CONCLUSION:
The first section of conclusions can be made about the respiration rates of dead peas, living peas and
paper balls. According to the results, living peas in room temperature do more respiration than both
dead peas and paper balls (non-living things).
A conclusion can be drawn from the results we have for the rate of respiration done in living peas and
dead peas. Living peas have a respiration rate of 0.003 cm/s, while dead peas have a respiration rate of
0.002 cm/s. From this it concludes that living peas do more respiration than dead peas. Dead peas do
respire, and they respire less than living peas do. It actually does respiration close to the rate of
respiration done by living peas. In one sense the hypothesis is wrong and in the other sense it’s correct.
The hypothesis suggests that living peas do respiration, which is proven correct by this experiment. The
hypothesis also states that dead peas will not be doing respiration and here the hypothesis is proven
wrong as the results are able to show that dead peas do respire at a rate of 0.002 cm/s, which is very
close to the respiration rate of living peas. This suggests, living cells as well as dead cells respire and
therefore do catabolism to get energy.
The second conclusion can be made about paper balls and living peas. The results suggest that both the
paper balls and the living peas respire as paper balls respire at a rate of 0.001 cm/s while living peas
respire at a rate of 0.003 cm/s. From the results it suggests that living peas do more respiration than
paper balls. In this experiment paper balls represent non-living things and the living peas represent the
living cells. So according to the results it basically says that non-livings things are capable of respiring,
along with living cells and that both the living and the non-living needs energy. But it’s a fact that nonliving things don’t do respiration as they aren’t alive, they don’t need energy and they don’t have
biological cells with organelles. Due to this fact we use the 1.5 cm, which is the distance the ink moved
in the respirometer with paper balls, as the movement that was caused due to the pressure and
temperature differences between the inside of the respirometer and the outside water. If that’s done it
still suggests that living peas respire more than non-living peas, but that non-living peas don’t respire at
all, which is exactly what was hypothesized.
The third conclusion is on how temperature affects the rate of respiration in living cells. According to the
results table, the highest rate of respiration occurred in room temperature, compared to peas that were
kept in cold or warm temperatures. It shows that the peas did more respiration when the temperature
was cold and did the least amount of respiration at a high temperature (warm). It can be concluded that
peas are able to do more respiration in room temperature and therefore the optimum temperature of
enzymes in peas that are responsible for respiration is around 27⁰C. From observing the graph it can be
concluded that extreme temperatures lead to denaturing of enzymes which leads to slower rates of
respiration. The hypothesis isn’t that similar to the conclusion that is drawn from this part of the
experiment. It was hypothesized that warm peas would do more respiration than peas in room
temperature and peas in cold temperature. The order from least to highest rate of respiration as
suggested in the hypothesis was: Warm peas, room temperature peas and cold peas. The results as
suggested from this experiment: room temperature peas, cold peas and warm peas.
Explaining the graph:
At a cold temperature enzymes in peas aren’t able to do a lot of respiration, most likely they are
denatured. As temperature increases, the enzymes start re-nature. As temperature increase, it gives out
a lot of energy in the form of heat, which then turns to kinetic energy. The energy makes substrates
interact with the enzymes faster and quicker and increase the number of collisions, therefore increasing
the rate. That is until a point where the enzymes work at its best and gives the highest rate of
respiration. But as temperature starts to increase more, the enzymes starts to denature again as the
temperature is too much. The kinetic energy caused by heat energy damages the bonds with in the
enzyme and breaks them, changing the active site. The rate of respiration drops suddenly.