• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

An experiment to see if caffeine affects heart rate

Extracts from this document...


An experiment to see if caffeine affects heart rate Hypothesis To test if caffeine affects the heart of daphnia Prediction I think that the higher the concentration of the caffeine solution the faster the heart rate will be. Caffeine is also known as trimerhylaxanthine and the chemical formula is C8H10N4O2. The caffeine will be absorbed into the blood where it travels into the brain. The caffeine molecule is the same size as the adenosine. Adenosine is a chemical in the blood that attaches to the nerve cells and slows it down therefore making a person tired. As caffeine is the same shape as adenosine the caffeine molecules attach to the nerve cell instead meaning, the adenosine molecule cannot get into the nerve cell. As the caffeine is a stimulant it then stimulates the nerve cell and this makes a person feel more awake and speeding up the heart rate. Caffeine also stimulates the pituitary gland to release cortiocostreiods, which then travel to the adrenal gland triggering the release of adrenaline. Adrenaline is a hormone, which helps to stimulate the body therefore making the heart beat faster. Variables The independent variable is the variable that we change. In this experiment the thing we are measuring in the concentration of caffeine that the daphnia is put into. The dependent variable is the variable in the experiment that we measure. In this experiment it is the heart rate of the daphnia. ...read more.


Once the daphnia have been used in the experiment it needs to be considered what will happen to them after this. It is best to place the, back into their natural environment, so they adjust back to this, but this may again cause them more stress as they are being moved from one place to another. Concentration The 0.5% of caffeine must be made up to do this the following equation is used: Volume of stock solution to be diluted = Final volume of diluted solution x concentration of diluted solution Concentration of stock solution 10cm3 = 10cm3 x 0.5 molar 0.5% 8cm3 = 10cm3 x 0.4 molar 0.5% 6cm3 = 10cm3 x 0.3 molar 0.5% 4cm3 = 10cm3 x 0.2 molar 0.5% 2cm3 = 10cm3 x 0.1 molar 0.5% 0cm3 = 10cm3 x 0.0 molar 0.5 Apparatus: * Culture of daphnia * Cavity slides * Dropping pipettes * Distilled water * 05% solution of caffeine * Cotton wool * Measuring cylinder * 7 beakers * Stopclock * Filter paper * Microscope * Pen * Paper Method: * Make up the caffeine solutions and place in beakers. Label each beaker * Get a daphnia out of the pond culture with a pipette * Place daphnia on a cavity slide and place under a microscope. This is a control * If the daphnia move to much use cotton wool to restrict their movement * Start stop clock * Record heart beat every 2 minutes for 15 seconds * Do this for 6 minutes * To ...read more.


The daphnia were also moving around in the cavity slide this also meant that the heart rate was difficult to record; we had to restrict the daphnia's movement so we could see them under the microscope, by using cotton wool, but this soaked up all the solution out of the cavity slide and may have caused discomfort for the daphnia raising ethical issues. All the daphnia had very different heart rates even when in the control solution, if I were to do this experiment again I would use daphnia which had similar heart rates when in the control, so the results when added to caffeine could have been seem a lot easier. The experiment also needed to be repeated more three times, because if there were a problem with one the daphnia's heart, for example it was stressed and this increased the heart rate it would be impossible to tell which daphnia had a unreliable heart rate if we were to do only two experiments. Doing three or more experiments means that if one of the sets of results were invalid it means we can easily see this and analyse the results on the other two sets of results. Evaluation If I were to repeat this experiment I would use daphnia with the same speed heart beat for each test as there are many varying degrees of heart beat even when in the control. Looking at the results the daphnia with the fastest heart rate in the control all seemed to be placed in the lower concentration of caffeine. This meant our results look as though caffeine slows down the heart rate. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Humans as Organisms section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Humans as Organisms essays

  1. Marked by a teacher

    Does Caffeine Affect Heart Rate?

    4 star(s)

    This is known because caffeine is a stimulant, which has the effect, among other things, of increasing the heart rate of any living organism, which consumes or absorbs it. Caffeine causes increased amounts of stimulatory neurotransmitters to be released. At high levels of consumption, caffeine has been linked to raise blood pressure and raised heart rate.

  2. Stem Cell Research

    Therefore the chances of rejection are much higher if embryonic stem cells are used in treatments. This is because the embryonic stem cells are going to have a different genome and will be covered in foreign antigens; thus the body will recognise them as foreign, increasing the chances of rejection from the body and complications after transplantation.

  1. The effect of caffeine concentration on the heart rate of Daphnia.

    This served two purposes. One, the Daphnia did not succumb to any effects that the heat from the light may have caused and it that it did not suffer any effects of being taken out of the liquid for too long. Secondly, replicates were taken to increase reliability, the more replicates taken, the more reliable the experiment was.

  2. The heart rate of a Daphnia (water flea)

    If enzyme activity falls, the metabolic rate falls, and less food is being processed. This means that fewer nutrients are needed to be pumped around the body for bodily functions. When enzyme activity rises, the metabolic rate increases because more food is being processed so more nutrients can be distributed

  1. Does caffeine affect heart rate

    Results table Heart beats per minute Concentration (%) 1 2 3 average Water 180 230 61 134 20 - - 105 105 40 240 - 151 196 60 228 207 - 218 80 247 300 - 274 100 260 347 280 296 Analysis of results By looking at the average

  2. Effect of Caffeine on Heart Rate in Daphnia

    there was a sudden decrease in the heart rate There were 2 anomalous results for the 10.0 mg dm concentration and this may have caused the heart rate to drop, as the results (252 and 246)

  1. Effect of Ethanol on the Daphnia heart rate

    that it is practically immobile (by making sure that you squirted the least amount of water possible) and put it under the microscope. Turn the microscope on. 6. Get the paper and marker ready. Look into the microscope and make sure you can count the heart beat.

  2. Investigating the effects of temperature on the heart rate of Daphnia.

    off but a small amount of heat could have permeated the daphnia, and thus causing a slight increase in metabolism. Also another explanation could be due to the daphnia itself. In the life cycle of daphnia they have both sexual and asexual phases; some of the daphnia used in this

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work