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Unit 6 - Investigative Project learning aim A
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Unit 6 - Investigative Project learning aim A
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Unit 6A: Scientificinvestigation
Effects of caffeine on the heart rate of daphnia
Abstract
Caffeine is a compound that occurs naturally and is soluble in both oil and water. It is generally
extracted from leaves beans and fruits of plants (mostly coffee beans, cocoa beans, and tea leaves).
Scientifically caffeine is classified as a recreational drug even though its effects are milder than other
recreational drugs like cocaine amphetamines and heroin. So, it is used all around the world to make
different kinds of foods and drinks like tea, coffee, and energy drinks. I researched and tested the
effect of caffeine on the heart rate of daphnia. When daphnia is exposed to caffeine their heart rate
increases as with the concentration this is because caffeine can block receptors on the surface of the
heart muscle cells.
Keywords: caffeine, heart, neurotransmitter, central nervous system (CNS)
Introduction
Caffeine which is known as 1,3,7-trimethyl xanthine in chemistry binds to the receptors on the
surface of the heart muscles and increases the level of cAMP inside the cells, causing an increase in
the heart rate. This result in an overall increase in the rate of glycolysis and the amount of ATP
available for muscle relaxation and contraction. Caffeine also inhibits a class of enzymes called cyclic
nucleotide phosphodiesterase. Part of these enzymes’ responsibility is to degrade a stimulatory
signal produced when excitatory neurotransmitters activate neurons in the CNS. So, if caffeine
inhibits them, the stimulatory signal remains active for a longer time, resulting in a greater sense of
alertness and higher blood pressure, higher respiratory rate, and higher heart rate. Caffeine also
causes an increase in stimulatory neurotransmitters to be released. Neurotransmitters are the key
mediators of communication between nerve cells. In my research and experiment, daphnia is used
to investigate how its heart responds to caffeine and its chemicals. The type of daphnia used is
daphnia magma as they have hearts that are comparable to human hearts. Daphnia has a myogenic
heart meaning their heart rhythm is controlled or generated by a specialized muscle in the heart
rate. Daphnia also has a transparent body which can easily allow us to see its heart with a
microscope while it is alive. There is no threat to daphnias’ existence or reproduction as they
reproduce asexually as clones. Their central nervous systems are not as developed as
humans/vertebrates therefore they are not self-aware. The rationale behind this research was that
caffeine is known to affect/alter the nervous system functions.
Aim
To investigate the effect of caffeine on the heart rate of daphnia
Hypothesis
The concentration of caffeine will affect the heart rate of daphnia accordingly which means if the
caffeine concentration increases the heart rate of daphnia will increase same goes for the opposite.
Objective & technique
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