Download TITLE The effect of caffeine on heart rate OBJECTIVES To

TITLE
The effect of caffeine on heart rate
OBJECTIVES
To investigate the effect on caffeine on heart rate of water fleas and to understand
the risk of high level consumption of caffeine to the health of the human circulatory
system and nervous system.
INTRODUCTION
Diagram 1: Chemical structure of caffeine
Image source: http://ismaastricht.wikispaces.com/file/list
The images above show the chemical structure of caffeine which has a
chemical formula of C8H10N4O2. Caffeine was named by the International Union of
Pure and Applied Chemistry (IUPAC) as 1,3,7-trimethyl-1H-purine-2, 6(3H, 7H)dione. Caffeine is also widely known by several other chemical names which include
1,3,7-trimethylxanthine,
trimethylxanthine,
methyltheobromine,
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methyltheophylline, theine, mateine, and guaranine. Caffeine is identified as a bitter,
odourless, white crystalline xanthine alkaloid which is a psychoactive stimulant
drug.1
Caffeine is found in the beans, leaves and fruits of some plant in various
quantities. It is most commonly found in the beans of coffee plants and leaves of tea
bush. Caffeine was originally used as natural pesticide that paralyses and kills certain
insects feeding on the plants. However, scientists have discovered that caffeine
causes an effect on the central nervous system (CNS) whereby it acts as a stimulant
in the human body.2
Diagram 2: Source of caffeine from the extraction of coffee beans
Image source: http://www.sciencedaily.com/releases/2009/01/090113203901.htm
Caffeine is considered as a drug that stimulates the body and causes an
increased amount of stimulatory neurotransmitter to be released. This temporarily
reduces the sensation of being tired throughout the day and increases alertness. At
high level of caffeine consumption, it can and has been linked to restlessness,
1
http://dictionary.reference.com/browse/caffeine
2
http://www.sciencemag.org/cgi/content/abstract/226/4671/184
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anxiety and insomnia which can cause raised stress and blood pressure and thus,
leading to hypertension. This will then lead to a more severe health problem such as
cardiovascular disease (CVD).3 The following diagram shows other common side
effects of
caffeine,
possibly
appearing at a
lower dosage
varying to
different
individuals.
Diagram 3: Side effects of caffeine
Image source:
http://crossfitoneworld.typepad.com/crossfit_one_world/2009/07/coffeeneeded.html
3
http://www.123HelpMe.com/view.asp?id=150254
3
Caffeine is now a common ingredient of soft drinks such as cola, originally
prepared from kola nuts. Research which was carried out shows that soft drinks
typically contain about 10 to 15 milligrams of caffeine per serving. Besides, chocolate
bars have a high percentage of caffeine content especially in dark chocolate.4 Those
are some examples of foods and beverages we consume almost every day which
contain high caffeine content. Hence, this experiment is conducted to determine
effect of caffeine on the human heart rate.
To determine the effect of caffeine in human heart, a suitable substitute of
human being is used to carry out this experiment. The most suitable organism to act
as the substitute to human is identified as Daphnia sp. which is a water flea.
Daphnia are small, planktonic crustacean which the size ranges between 0.2 to 5mm
in length. The habitat of Daphnia sp. ranges from acidic swamps to freshwater lakes,
ponds, streams and rivers. Daphnia sp. is a filter feeder, ingesting mainly unicellular
organism and various sort of organism, detritus including protista and bacterias.
Filter feeders refers to animals that feed by straining suspended matter and food
particles from water typically by passing the water over a specialised filtering
structure. The most prominent features of the Daphnia sp. are the compound eyes,
the second antennae, and a pair of abdominal setae. In many species, the carapace
(exoskeleton of body) is translucent and the heart is visible even under low power
lens microscope. As a result, they make excellent subjects for the microscope as one
can observe the beating heart.5
4
http://jop.sagepub.com/content/21/1/65
5
http://en.wikipedia.org/wiki/Daphnia
4
Diagram 4: Structure of water flea, Daphnia sp.
Image from: http://www.smu.ca/bioblitz/results.html
The Daphnia sp. is observed under a light microscope. The ordinary
magnification values of objectives lens are 4X, 5X, 10X, 20X, 40X, 50X, 60X and
100X. By using a low powered lens such as 4X, the heart of the Daphnia sp. can be
magnified and observed.
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Diagram 5: Light microscope
6
http://en.wikipedia.org/wiki/Optical_microscope
5
Image source:
http://en.wikipedia.org/wiki/File:Optical_microscope_nikon_alphaphot_%2B.jpg
PROBLEM STATEMENT
What is the effect of caffeine on heart rate?
HYPOTHESIS
Caffeine increases the rate of heart beat.
VARIABLES
Manipulated variable: Treatment of caffeine
Responding variable: Rate of heart beat of Daphnia sp.
Fixed variable: Type of water flea, concentration of caffeine, temperature of solution
APPARATUS
Light microscope, beakers, measuring cylinders, stopwatch, and dropping pipette
MATERIALS
Culture of Daphnia (water fleas), cavity slides, pond water, 0.3% caffeine solution,
cotton wool, and filter paper.
PROCEDURE
1. A few strands of cotton wool are placed on the glass slide to help in
restricting the movement of the water flea.
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2. Using a pipette, the water flea, Daphnia sp, is the transferred from the beaker
to the glass slide. Excess water surrounding the water flea is removed using a
filter paper.
3. The glass slide is then carefully place on the stage of the light microscope.
4. Using a low powered lens, the heart of the Daphnia sp. is magnified and
observed.
5. The number of heart beat per minute of Daphnia sp. is counted with the aid
of a stop watch. The number of heart beat per minute is recorded and
tabulated in the result table.
6. Step 5 is repeated to obtain three sets of result of the number of heart beat
of Daphnia sp, in natural condition.
7. All the distilled water is absorbed using a dry filter paper and a drop of 0.3%
caffeine solution is added to the Daphnia sp. on the glass slides.
8. The number of heart beat per minute of Daphnia sp. is counted again with
the aid of stop watch. The number of heart beat per minute is recorded and
tabulated in the result table.
9. Step 8 is repeated to obtain another three sets of result of the number of
heart beat of Daphnia sp. with the presence of caffeine.
RESULTS
TREATMENT
HEART RATE/ BEATS MIN-1
MEAN FOR
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INDIVIDUAL/
BEATS MIN-1
TRIAL 1
TRIAL 2
TRIAL 3
CONTROL
21.0
22.0
20.0
21.0
CAFFEINE
25.0
26.0
25.0
25.3
DISCUSSION
To determine the effects of caffeine in human life, it is very risky and harmful
to conduct this experiment on a human itself. Hence, a substitute to human being is
used in this experiment. The most suitable substitute is water flea, Daphnia sp. By
using Daphnia sp, we can infer that any result obtained from this experiment will be
the same as what will happen in the human body. Hence, the effect of caffeine on
the heart rate of Daphnia sp. will be similar to the effect of heart rate on a human
heart,
In this experiment to investigate the effect of caffeine on heart rate, I have
made some predictions and assumptions. As caffeine is a proven as a central
nervous system (CNS) stimulant, it is safe to assume that caffeine will act on the
brain which will result in the increase of heart rate. I predicted that since caffeine
temporarily ward of drowsiness and restore alertness, the heart is definitely affected
by caffeine to provide sufficient oxygen and energy to the brain cells and to the rest
of the body cells. In order to provide sufficient oxygen and nutrients and at the
same time, removing waste products especially carbon dioxide, I predicted caffeine
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would increase the heart rate of the organism. The result of the experiment shows
my predictions and assumptions to be correct.
Table 1 shows the result of this experiment of the effect of caffeine on the
heart rate of Daphnia. At the natural condition without the presence of caffeine
solution, the heart rate of Daphnia is counted as 21 beats per minute. This result is
from the control experiment to indicate the average heart beat of Daphnia without
any caffeine solution. By having the control experiment or control result of the heart
rate of Daphnia, we can easily compare the result of the heart rate of Daphnia with
the caffeine treatment. After adding 0.3% caffeine solution to the Daphnia sp, the
heart rate of the Daphnia has increased to 25.3 beats per minute. The increase of
heart rate by 4.3 beats per minute shows clearly the effect of caffeine on heart rate.
Since caffeine increases the heart rate of Daphnia, we can infer from this result that
caffeine would also increase the human heart rate. Hence, caffeine has an effect on
the heart by increasing the heart rate varying in each individual which may lead to
other health issues.
EVALUATION
Before conducting this experiment, I have identified the dependent and
independent variables. The dependent variable is the rate of heart beat of Daphnia
sp. and the presence of caffeine as the independent variable. After indentifying the
two variables, I found out that there are a few other variables that needed to be
controlled as it may affect the outcome of the experiment. One of the variables that
are needed to be controlled throughout the experiment is the type of water flea
used. Different species of water flea would certainly have a different average of
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heart rate. Since Daphnia sp is the most common water flea, it is most suitable to be
used in the experiment.
On top of that, the same water flea, Daphnia sp. is used throughout the
experiment. This is because Daphnia sp. varies in different sizes ranging from 0.2 to
5 millimetres. Different size of Daphnia sp. would definitely have different heart rate
because larger organisms has higher rate of metabolism which will lead to a higher
rate of heart beat and vice versa. Since it is impossible to obtain two Daphnia sp. st
the same length with the same rate of metabolism, it is important to use the same
Daphnia sp. in the control experiment and during the treatment of 0.3% caffeine
solution.
As shown in the Practical Biology website by the Nuffield Foundation and
Society of Biology, the temperature of solution surrounding the Daphnia would have
an effect on the outcome of this experiment.7 The heart rate of Daphnia is easily
affected by the difference of temperature of solution. This is because with the
increase of temperature of solution surrounding the Daphnia would cause an
increase in the heart rate. This would affect the result as the presence of caffeine is
the independent variable and not the temperature of solution. Therefore, it is
important to make sure the temperature of solution is always constant at room
temperature.
7
http://www.practicalbiology.org/areas/advanced/control-and-communication/control-of-heartrate/investigating-factors-affecting-the-heart-rate-of-daphnia,92,EXP.html
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While carrying out this experiment, there are also other possible errors that
may affect the final result of the experiment. One of it is too much water around the
Daphnia sp is removed while preparing the slide. During the process of placing the
Daphnia sp. on the glass slide, excess water was also added on the slide. To remove
the excess water, a filter paper was used and during that process of absorbing
excess water, too much water was absorbed instead. With low volume of pond
water surrounding the Daphnia which supplies oxygen to the Daphnia, the heart rate
of Daphnia decreases tremendously. As the duration of experiment is quite long, the
Daphnia was lacking of oxygen and has a very low heart rate. This contributes to
random error as all the values of heart beat lies below the true value of heart beat
with or without the treatment of caffeine. Hence, to improve the accuracy of the
result, more pond water should be supplied to the Daphnia sp to obtain sufficient
oxygen.
Before adding the 0.3% caffeine solution, the pond water surrounding the
Daphnia sp was first absorbed using a filter paper. During this process, it is
impossible to absorb the pond water surrounding the Daphnia sp completely.
Therefore, the final concentration of caffeine added to the Daphnia is not accurately
to 0.3%. This will also lead to random error in the result of treatment with caffeine.
The actual value should be higher than the result obtained in the experiment.
In order to improve the degree of accuracy of the result, replication of at
least three trials of Daphnia heart beat is highly needed for each treatment. By
having replication of results, the average heart beat per minute can be calculated
and obtain. Replication and average readings helps in reducing random errors and
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thus, increasing accuracy of final result. For example, we may have missed a count
of heart beat of Daphnia in a minute. This error can be reduced by having two other
sets of results and averaging it.
To observe the heart of Daphnia, a light microscope was used in this
experiment. The light microscope is very suitable because the small heart of Daphnia
is easily visible under transmitted light under a low power microscope. By using a
light microscope, the heart of Daphnia can be magnified and the heart beat can be
counted.
In this experiment, pond water was used instead of distilled water. Pond
water is more suitable because it is the natural habitat to Daphnia. On the other
hand, distilled water is purified and has a neutral pH. By using pond water, Daphnia
sp is able to adapt to the surrounding and less likely to die during the experiment.
The caffeine solution used to test on the Daphnia is also at the suitable
concentration. If the caffeine solution is too concentrated, the Daphnia would die
easily. Hence, 0.3% caffeine solution is a diluted caffeine solution which would not
cause death in Daphnia and it is safe to use it on Daphnia.
To investigate the effect of caffeine on heart rate, Daphnia sp was used in
this experiment. Ethical issues may arise from using and harming live invertebrates.
Ethical issues may arise due to the amount of Daphnia that has been used or will be
used in the future if every student or scientists conduct this experiment. By then, the
amount of Daphnia left in the ecosystem will be small and little. This will then cause
a major disruption in the food chain as Daphnia consume unicellular organisms and
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other organism such as small fishes consume Daphnia as food. If the Daphnia is out
of the food chain, there would be an increase of unicellular organisms which includes
protista and bacteria in the aquatic environment which may cause hazardous alert to
human as the water may no longer be safe to drink. Apart from that, if Daphnia is
out of the food chain, small fishes or other organisms which rely on Daphnia as a
source of food will die due to insufficient of food. This will then cause other
organisms to die. Therefore, if too much Daphnia is used, it would bring harm to the
entire ecosystem. To overcome this problem, I would suggest that after using the
Daphnia, we could either put it back to its natural habitat or to be reused by other
students.
Apart from that, ethical issues will be brought up when a higher concentration
of caffeine solution is used and tested on the Daphnia. A high concentration of
caffeine would cause harm and kill the Daphnia sp. Therefore, while conducting the
experiment, one must make sure to dilute the caffeine solution first. To cause harm
and kill Daphnia by just using too concentrated caffeine solution is cruel and should
be avoided by everyone. After judging and weighing the consequences of using
Daphnia as a subject of experiment, in my opinion, it is considered to be alright to
use the water fleas for the sake of science as it helps us to understand the effect of
caffeine in human and this understanding will help us in our future but efforts should
be taken to maintain the amount of Daphnia sp in the ecosystem.
SAFETY PRECAUTIONS
While conducting this experiment, we have used several glasswares which include
beakers and glass slides. This beakers and glass slides are very fragile and easily
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broken. Student should take safety precaution while handling those items to prevent
from breaking it as a breaking glass can easily cut and cause bleeding injuries.
Correct method and technique of using a light microscope should also be a practice
to all students to prevent from damaging or spoiling an expensive equipment. Other
basic rules such as wearing a laboratory coats and covered shoes when entering the
laboratory should be followed to prevent any hazard from happening in case of
spillage of chemicals or harmful substances.
CONCLUSION
Caffeine increases the rate of heart beat of Daphnia. This shows that caffeine would
also increase the rate of heart beat of a human. The hypothesis is accepted.
REFERENCES
1. Dictionary.com 2010, viewed 21 August 2010,
<http://dictionary.reference.com/browse/caffeine>
2. Nanthanson, J A 1984, Caffeine and related methylxanthines: possible natural
occurring pesticides, volume 226, issue 4671, page 184-187, viewed on 21
August 2010,
<http://www.sciencemag.org/cgi/content/abstract/226/4671/184>
3. The Effect of Caffeine on Heart Rate, viewed on 21 August 2010,
<http://www.123helpme.com/view.asp?id=150254>
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4. Haskell, C F, Kennedy, D O, Wesnes, K A, Milne, A L, Scholey, A B 2007, A
double-blind, placebo-controlled, multi-dose evaluation of the acute
behavioural effects of guaraná in humans, Journal of Psycopharmacology,
viewed on 21 August 2010, < http://jop.sagepub.com/content/21/1/65>
5. Anonymous (n.d), Daphnia, viewed on 21 August 2010,
<http://en.wikipedia.org/wiki/Daphnia>
6. Anonymous (n.d), Optical microscope, viewed on 21 August 2010,
<http://en.wikipedia.org/wiki/Optical_microscope>
7. Nuffield Foundation and Society of Biology 2010, Investigating the factors
affecting the heart rate of Daphnia, viewed on 22 August 2010,
<http://www.practicalbiology.org/areas/advanced/control-andcommunication/control-of-heart-rate/investigating-factors-affecting-the-heartrate-of-daphnia,92,EXP.html>
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