The aftereffect of caffeine on center rate

In this experiment, I will determine the result of different concentration of levels of caffeine on the heartrate of Daphnia. Daphnia is assumed as the alternative of individual in this test to investigate the effect of chemicals on the heart beat of living organisms. Pulse is the frequency of heart and soul contraction in one complete cardiac cycle. The average heartrate of human being is 72 beats per minute. However, some changes that occur in the torso system such as stress, an increase in body's temperature or consumption of some chemicals may alter the heart rate. The intake of caffeine is believed to increase the heart rate as well, and so this test is carried out to check its validity.

Caffeine, 1, 3, 7-trimethylxanthine with its molecular formula of C8H10N4O2 occurs obviously as a white crystalline powder that tastes very bitter. It portrays a distinctive characteristic where it is soluble in both water and petrol. Generally, caffeine is extracted from beans, leaves and fruits of some plant life. The few commonly known sources of caffeine are coffees, tea leaves and cocoa beans. Within the perspective of technology, caffeine is grouped as one of the foods or recreational drugs. However, its results are milder than other drugs such as amphetamines, cocaine and heroin. Therefore, it is manufactured as popular beverages all over the world such as caffeine, tea, soft drinks and energy beverages. In addition to the people, we may also find caffeine in a few chocolate club and weight loss supplements. Nevertheless, level of caffeine in its 100 % pure form can be obtained in powders, caplets or tablets. Its acceptance is further proven by an estimation of global usage of levels of caffeine at 120, 000 tonnes per time. The recommended consumption for the average adult is less than 300mg of caffeine containing drinks per day.

http://upload. wikimedia. org/wikipedia/commons/thumb/d/d8/Levels of caffeine. svg/120px-Caffeine. svg. png http://upload. wikimedia. org/wikipedia/commons/thumb/2/24/Caffeine_3d_structure. png/100px-Caffeine_3d_structure. png

Figure : Structural formula of caffeine containing drinks, C8H10N4O2

How can caffeine have an effect on us? Through various beverages that contained caffeine, this chemicals can be absorbed into our body through abdomen and small intestine. It really is metabolised in the liver organ to create paraxanthine, theobromine, and theophylline which is then distributed to all tissues of the body. Although levels of caffeine is not stored in the torso, the effect of caffeine containing drinks can be noticed for up to 6 hours. Level of caffeine, as mental health or metabolic stimulant drugs can provide impact to your body system specifically to our central anxious system. Recreationally, the key function of levels of caffeine is undeniably its ability to increase alertness and wakefulness rendering it a popular source among students and employees to stay awake. Meanwhile, caffeine has an increased concentration and better general body coordination as well. Besides, caffeine containing drinks also possesses therapeutic use in planning aspirin (a pain killer). However, caffeine consumption can lead to addiction.

In this framework, caffeine can improve the heart beats of many organisms. Caffeine containing drinks binds to receptors on the top of center muscle skin cells which leads to an increase in the level of cAMP inside the skin cells which then increases the heartrate. This creates an overall effect to increase the rate of glycolysis and the amount of ATP available for muscle contraction and relaxation. In addition, one of the merchandise from the metabolism of levels of caffeine - Theophylline serves as a chronotrope and inotrope that rises heart rate and efficiency.

As to body health, caffeine containing drinks can provide positive or negative result, taking into consideration the amount of caffeine taken. Generally acknowledged, caffeine increases anxiousness, stress, insomnia and restlessness that are bad for our overall health. This is believed to be the effect of a reduction in serotonin (A neurotransmitter, synthesised from the amino acid tryptophan, that functions in the central anxious system) levels in the blood therefore of caffeine utilization. Alternatively, it can act as a diuretic in which it increases the urine development and thus decrease the blood pressure. Besides, level of caffeine can minimise the event of some diseases such as diabetes, Parkinson's disease and colon cancer. Incidentally, the level of sensitivity towards caffeine can vary greatly from individual to individual.

In this experiment, Daphnia or commonly known as water fleas is used to investigate how its heart respond to the chemicals level of caffeine. It is a tiny and almost kidney shaped crustacean, having a single compound attention, two doubly-branched antennae, and leaf-like limbs. Furthermore, their exoskeleton is translucent which attribute allows its center defeating to be clearly seen under a microscope. Thus, the keeping track of of pulse possible and can be done easier. Various aquatic conditions ranging from acidic swamps to freshwater lakes, ponds, streams and waterways are ideal habitat for Daphnia to live in. Some Daphnia are greatly found in lakes or ponds found in limestone-based areas.

Under normal conditions, the common heartrate of Daphnia is approximately 180 beats per minute (bpm). Daphnia is very hypersensitive to the change of chemicals structure in its living environment. In cases like this, its heart beat is also easily affected by a wide range of chemicals such as caffeine solution found in this experiment. It will show an immediate effect after the addition of the chemicals. Daphnia is poikilothermic, whereby its body temperature and metabolic rate is highly dependent on the surrounding temperature. Averagely, Daphnia has a comparatively short lifespan where it can only just survive for under twelve months.

Problem Affirmation:

Does different attentiveness of caffeine have an effect on the heart rate of Daphnia?


To investigate the effect of caffeine on the heartrate of Daphnia(normal water fleas)

To develop the technique of utilising microscope and other effective experimental skills throughout the experiment


To determine the result of different concentrations of level of caffeine on the heartrate of Daphnia.


The higher the attentiveness of caffeine, the higher the heartrate of Daphnia.

Techniques :

Observe and calculate the heart rate of Daphnia under a light microscope

By preparing a control to the test by examining the heartrate of Daphnia under normal condition.

Record the immediate heart beats of Daphnia by by using a calculator

Materials :

Culture of Daphnia, pond water, distilled water, 0. 3 % caffeine solution, filter paper or newspaper towel, muslin cloth

Apparatus :

Microscope, cavity slides, dropper, calculating cylinder, 50ml beaker, stopwatch, calculator

Variables :


How the varying is determined

1. Manipulated

Presence and amount of level of caffeine solution

By using two different dilutions of caffeine solution, 0. 15% and 0. 30% and a control establish without level of caffeine solution

2. Responding

The pulse rate of Daphnia

By observing and determining the conquering of center of Daphnia under light microscope for 20 moments and the beliefs are multiplied by 3 to get the heart rate of Daphnia (range of beats/minute)

3. Constant

The bordering temperature

The light intensity

By conducting the entire experiment under the room temperature

By carrying out the experiment under a manipulated amount of light level of the microscope

Procedure :

0. 15 % Level of caffeine dilution is ready from the stock solution of 0. 30 percent30 % Caffeine solution using the following method :

Concentration of Caffeine

0. 30 %

1 cm3 of 0. 3% stock solution

0. 15 %

1cm3 of stock solution + 0. 1 cm3 distilled water

A microscope is set up and its brightness is adjusted to prepare for the observation of Daphnia.

A large Daphnia is moved from the culture to a cavity microscope slide utilizing a dropper.

The excess liquid is removed with a filtration system paper, in order to cause the animal toile on its glide.

Gauze or muslin material is placed within the cavity as to decelerate the activity of Daphnia.

Diagram : Keeping muslin fabric on cavity slide

The slide is placed on the stage of microscope. The Daphnia is located and analyzed using low-power target. The heart rate can be seen beating very quickly.

The glide is kept on the level for five minutes to equilibrate Daphnia such that it can adapt to the surroundings.

By working in pairs, a basic calculator is established to add one digit respectively for 20 second periods to practise keeping track of heart beats. An end watch is employed by the other university student to time.

The results of two consecutive counting periods are documented. The mean value is computed. It is indicated in beats each and every minute.

About 5 minutes is permitted to lapse.

A drop 0. 15 % caffeine containing drinks solution is put into the cavity of the slip by using a dropper. More than the answer is removed using a filter paper. Counting of the center beats is began for 20 moments.

A fresh Daphnia is utilized and the procedure 4-7 and step 11 is repeated by using 0. 30 percent30 % levels of caffeine solution.

At the finish of each test, the Daphnia is came back to the culture solution.

All the results are recorded. Each of the results is multiplied by 3 to obtain heart beat rate each and every minute. The results are tabulated and a bar chart is attracted to show the circulation.

Results :

Condition of the solution

No. of Center beats of Daphnia in 20 s / Times

Trial 1

Trial 2






Concentration of Caffeine containing drinks Solution

0. 15




0. 30




Table 1: The heartrate per minute of Daphnia under different conditions of solution


Formula 1 : The mean value of the date obtained


Formula 2 : Heart rate per minute of Daphnia / times


Analysis of Data - Pub Chart :


Based on the aforementioned experiment, the effect of different concentrations of caffeine containing drinks is successfully motivated. A bar graph is drawn based on the results obtained in the experiment to show the data in a clearer way and a much better mean for analysing. The results show the heartrate of Daphnia is positively affected by the occurrence of caffeine, and it is increased when the attention of caffeine solution is elevated. The average heart rate of Daphnia under normal condition which functions as a control test is 114 center beats each and every minute. When 0. 15% levels of caffeine solution is added, its heart rate increases to 138 center beats each and every minute. The heart is better than surge to 153 in solution containing 0. 30% caffeine solution. However, theoretically, the increase of the heart rate should reach a maximum point in which a further increase in the attentiveness of caffeine does not have any further influence on the heart rate of Daphnia. With this test, the saturated or maximum amount of levels of caffeine that impacts the heart rate of Daphnia can't be obtained due to the lower awareness of caffeine used in the test.

In this experiment which includes the utilization of Daphnia as a living organism, some honest issues arise. Despite the fact that Daphnia is so small to be seen unless by by using a microscope, it remains a fact that each every Daphnia is a life and we have no to harm or wipe out them even though by the name of knowledge. In this case, we have to be very careful when carrying out any experiment involving the use of organisms in order not to harm them. Therefore, after completed every test, the Daphnia which continues to be alive should be went back to its culture means to fix sustain its survival. The light intensity of microscope should be controlled so that it will not eliminate the Daphnia engaged. Furthermore, the test is carried out as quickly as possible because the Daphnia may well not endure for long in a fresh environment. The attentiveness of levels of caffeine should be less than 1% to prevent the dying of Daphnia. Furthermore, the process to remove unnecessary water utilizing a filter newspaper is completed cautiously concerning prevent the absorption of Daphnia unintentionally which will kill it.

However, throughout the test some errors might occur in which the real values might not exactly be obtained. Firstly, as this experiment is done predicated on the observation on the specimen, some counting of heart and soul beats might be missed due to individuals limited abilities. That is probably because of the immediate and inconsistent conquering of Daphnia's center. In cases like this, a calculator is set up to ensure a more appropriate reading. Parallax problem might occur as well when the dilution of level of caffeine is measured utilizing a measuring cylinder. To minimise the problems, the test is repeated twice and the mean reading is obtained. To help expand increase the exactness of the results, a camera may be used to record the entire process and is then played regularly. A 'blind' review is preferable where the observer is unfamiliar of the health of solution being put into Daphnia as to avoid bias. Addititionally there is assumption manufactured in this experiment. In the experiment, the heart rate of each Daphnia is assumed to be the same whenever a fresh Daphnia can be used for different attention of level of caffeine.

Consequently, there are a few precautions that ought to be taken to raise the reliability of the results obtained. Before a new drop of caffeine solution is added to the Daphnia, about five minutes is allowed to equilibrate the Daphnia. This is done to change it to the surroundings so that other factors would not interfere with the manipulated adjustable. Next, as the swift motion of Daphnia can affect the results taken, it is better to place muslin towel or cotton wool to keep it in spot to make the keeping track of process easier. Besides, during the test, the light level of microscope should be tweaked to a spot where it could not be too smart to influence the vision of the observer. Through the transition of every test, the light intensity should be handled as well to prevent dying of Daphnia. Additionally, we ought to not spill any normal water used onto the microscope specially the electrical area as this will damage the microscope. The Daphnia should be handled carefully to prevent accidental injuries as this will modify its heart and soul beats.

Along the procedure of the test carried out, some problems arise. For example, the Daphnia is difficult to be captivated using a pipette as it is too dynamic. Besides, the test of normal water provided contain other microorganisms such as tadpole, euglena and amoeba that are being thought as Daphnia to be tested in the experiment. Throughout the experiment, some safety measures should be abided by. A laboratory coat should be put on. The wine glass wares and the microscope used should be completed carefully as they are fragile.


The hypothesis is accepted. The existence of caffeine escalates the heart rate of Daphnia. Once the amount of caffeine solution used rises, the heart rate of Daphnia also increases.


The years of the Daphnia

An old Daphnia may have a lower heart rate when compared with a young and energetic Daphnia

The size of Daphnia

A bigger Daphnia may have a lesser heart rate when compared to a smaller one

The species of Daphnia

Different kinds of Daphnia may show different heart rate and may vary in the way it respond to the different amount of caffeine

Further Work:

The effect of heat on the heart rate of Daphnia

The aftereffect of different light intensity of microscope on the heart rate of Daphnia

The effect of different chemicals such as ethanol or aspirin on the heart rate of Daphnia

The aftereffect of different concentrations of caffeine containing drinks on other microorganism beside Daphnia such as paramecium

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