How temperature will affect the respiration of an organism.
How temperature will affect the respiration of an organism.
Kathryn Hinchcliffe.
Aim:
The respiratory rate of an organism is usually the same as the rate of aerobic respiration, which takes place within the body tissue. The chemical equation for this is can be shown as, C6H12O6 + 602 6CO2 + 6H2O. I will be estimating the respiratory rates of the organisms using a respirometer and express me results by the amount of oxygen used up in a given time by 1 gram of the tissue held at a constant temperature.
Hypothesis:
I expect the rate of respiration of the organisms to increase as temperature increases.
Prediction:
Respiration, is a process by which an organism exchanges gases with its environment. The term now refers to the overall process by which oxygen is abstracted from air and is transported to the cells for the oxidation of organic molecules while carbon dioxide and water, the products of oxidation, are returned to the environment. In single-celled organisms, gas exchange occurs directly between cell and environment, i.e., at the cell membrane. In plants, gas exchange with the environment occurs in special organs, the stomata's, found mostly in the leaves.
Organisms that utilise respiration to obtain energy are aerobic, or oxygen-dependent. Some organisms can live in the absence of oxygen and obtain energy from fuel molecules solely by fermentation or glycolysis. These anaerobic processes are much less efficient, since the fuel molecules are merely converted to end products such as lactic acid and ethanol, with relatively little energy-rich ATP produced during these conversions.
When our body temperature increases or we do exercise our muscles use more oxygen and produce more carbon dioxide. This leads to both an increase n tidal volume and frequency of breathing due to demand for oxygen within the respiratory system.
The most vital part of the respiratory system in humans starts in the inspiratory center located in the medulla of the brain, which consists of nerve cells. Nerve impulses pass down the phrenic and intercostal nerves causing contractions within the diaphram and external muscles, which then brings about inspiration. Expiration can be assisted by nerve impulses from the expiratory center, which causes contractions of the internal intercostal muscle. The inspatory and expiatory nerve cells inhabit each other so the cannot be active simultaneously.
The remaining elements of the control system act to modify the basic pattern of nerve impulses produced by these centers. In this way the respiratory system can respond to stimuli, received by sense organs such as stretch receptors, carotid and aortic bodies and from chemorecepters.
. During inspiration stretch receptors that line the walls of the lungs send signals, which help to terminate the bursts of impulses from the inspiratory center and so prevent over expansion of the lungs.
2. The carotid bodies are locked on the external carotid artery whilst the aortic bodies are locked between the aorta in the subctavian artery. Within each of these bodies there are chemorecepter cells, which respond in two stimuli. Firstly they are sensitive to pO2, which is the partial pressure of oxygen dissolved in the blood plasma. If these levels are to low, they stimulate the receptor cells and lead via the medulla to increase ventilation of the lung.
3. The second more important stimuli for the chemorecepter cells is pCO2, the partial pressure of carbon dioxide dissolved in the blood plasma. When carbon dioxide is dissolved in the plasma, carbonic acid is produced which, is show in the equation, CO2 + H2O H2CO3 HCO3 + H
So whenever pCO2 is changed, hydrogen ions (H ) change in a corresponding way, and is the H that the carotid chemorecepters actually respond to. So, it is the concentration of the carbon dioxide in the blood that is the main factor controlling the gas exchange.
The ...
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3. The second more important stimuli for the chemorecepter cells is pCO2, the partial pressure of carbon dioxide dissolved in the blood plasma. When carbon dioxide is dissolved in the plasma, carbonic acid is produced which, is show in the equation, CO2 + H2O H2CO3 HCO3 + H
So whenever pCO2 is changed, hydrogen ions (H ) change in a corresponding way, and is the H that the carotid chemorecepters actually respond to. So, it is the concentration of the carbon dioxide in the blood that is the main factor controlling the gas exchange.
The system above is only a small part of the human bodies' process for regulating the supply of oxygen and removal of carbon dioxide from the tissue. There are a whole series of parallel changes, which take place in the circulatory system such as when the heart rate and blood pressure increase during exercise or increased temperatures.
In insects respiration differs from the above system, as they don't have lungs. In insects, the body is pinched in and divided into three main sections. The head, which holds the eyes (usually compound), antennae and mouthparts. The thorax, which is in three segments with three pairs of legs, and is where some spiracles are located on the second and third thoracic. And the abdomen which containing parts of the digestive and other systems, and also holds the remaining spiracles on the first eight abdominal segments. The insect body plan is incapable of being scaled up to be larger than a few centimetres, but insects can make up for this by producing larger numbers of individuals, and reproducing rapidly in suitable conditions. The main problem caused by the exoskeleton is growth. This necessitates periodic moulting of the outer layer or cuticle, and relatively large increases in size whilst the soft and vulnerable body beneath is capable of expansion.
Instead of inhaling, insects respire by gases entering and leaving their bodies hard exoskeleton through pores called spiracles, which are located on the second and third thoracic and first eight abdominal segments as I have already stated. Each spiracle is surrounded by tiny hairs, which help retain water vapour and can be opened and closed due to a system of valves operated by muscles. Respiring cells within the body release carbon dioxide and as it accumulates it is detected by chemoreceptors and so the spiracle opens.
The spiracles open into a complex series
of tubes called tracheae, which run throughout
the body. Rings of chitin found in the body's
exoskeleton support them, which prevent them
from collapsing when the pressure inside falls.
These tracheae divide into tracheoles, which
extend right into the body's tissue. The respiratory
gases are not carried within the insect's blood
but are instead carried through the tracheal system
between the environment and the respiring cells. This system carries oxygen straight to the insect's cells and so allows them to develop a high metabolic rate. The ends of the fine tracheoles are fluid filled, and so whilst the insect is at rest the tissues are hypotonic to the fluid in the tracheoles. As activity increases the muscles anerobically respire, causing an accumulation of lactic acid. This raises the osmotic pressure of the cells so that they are hypertonic to the fluid in the tracheoles and water therefore moves out of them. As fluid is lost, air is drawn further into to the tracheoles, making more oxygen available for cellular respiration. When activity ceases the metabolites are oxidised, the osmotic pressure is lowered and the fluid re-enters the tracheoles. This system is ventilated due to the insect flattening its body and so contraction abdominal muscles. This reduces the volume of tracheal system, but can increase again when the elastic nature of the body returns the tracheal system and the insect's body to its original shape.
After the oxygen has entered the cells, biochemical respiration occurs. Carbohydrates, amino acids, and fatty acids, which are the organic fuel molecules of the cell, can be converted to acetyl CoA, a derivative of acetic acid and coenzyme A. Acetyl CoA then enters a series of reactions in the mitochondria, in the cell's cytoplasm, known as the Krebs cycle. These reactions convert the acetic acid portion of acetyl CoA to carbon dioxide protons, and hydride ions. This molecule is oxidised back to NAD when it donates the hydride ion to the series of enzymes known as the electron transport chain. In a process called oxidative phosphorylation, each electron transport enzyme is in turn reduced (receives the hydride ion), then oxidised (donates a hydride ion to the next enzyme in the series), and the chemical energy liberated in this series of reactions is coupled to the synthesis of adenosine triphosphate (ATP) from adenosine diphosphate (ADP) and phosphoric acid.
ATP, the cell's form of energy storage and supply, furnishes the chemical energy needed for muscle contraction, protein synthesis, and active transport of substances across membranes, and electrical impulses. At the end of the electron transport chain, a hydride ion is donated to an atom of oxygen; this pair, together with a proton from the surrounding solution, forms a molecule of water. Thus, in the overall process of cellular respiration, the fuel molecules are convert to carbon dioxide and water while the chemical energy gained is trapped in a useful form as ATP.
For this experiment I have decided to study the respiration of insects rather than humans as insects do not respire in such large quantities as humans do and so it will be easier to measure the oxygen intake over a longer period of time.
Particle theory dictates that increasing the temperature provides kinetic energy to all molecules so causing them to move more quickly so react more often, so enzyme activity increases and the Q10 theory states that increasing the temperature by 10ºC should double enzyme activity. Considering that enzyme activity is directly linked to the rate of respiration it can be assured that increasing the temperature by 10ºC should lead to the doubling of the respiration rate if the Q10 theory is to be observed.
Plan:
. 10 grams of soda lime granules needs to be poured into a boiling tube.
2. A wire cage must be inserted just above the granules with five live mealworm beetles.
3. A bung needs to be placed on top with two glass manometer tubes coming out of it. One tube must be placed into a small beaker of manometer fluid and the other must have a clip on it, which can be tightened at the beginning of the experiment and loosened at the end.
4. The boiling tube must then be then placed within a water bath with a controlled temperature of 5 C.
5. The boiling tube needs to be left for about 3 minutes to equilibrate, then close the clip on the respirometer.
6. A record of how far the manometer fluid rises up the manometer tube also needs to be measured at intervals of 20 seconds.
7. The experiment but be repeated at 10 C, 15 C, 20 C, 25 C, and 30 C.
8. When the experiment is completed the living material then must be measured.
The readings I will take shall be measured at every 20 seconds as in my pilot study I found that the manometer fluid rose quite quickly. Yet anything less than this would be hard to take the reading to the precise second as I may still be writing down the last results. The amount of oxygen taken up shall be measured to 1 gram as this makes comparing the results easier as some organisms weighed more than others.
Apparatus:
A large beaker Manometer fluid
Hot water Spring clip
Ice Soda lime granules/ (15%potassium hydroxide solution)
Thermometer Measuring cylinder
Boiling tubes Insects
Rubber bung Clamp stand
Manometer tube
I feel that using a big beaker rather than a water bath is the better as it allows me to work where I want and not next to a power supply where it is quite cramped. Using the beaker also means that I can pick it up and pour away any unwanted water if I wish. Manometer tube and fluid was used as it is the most accurate was to measure how much oxygen is taken up. All I had to do extra to the tube was to put a scale on it, which I did using a permanent marker and a ruler, putting on millimetres for accuracy. Soda lime and potassium hydroxide are both good substances for removing carbon dioxide, however as I found out, when using soda lime do not compress the cotton wool (which separates the organisms and the granules) in too much, as this wont allow the carbon dioxide to get across.
Method:
This was carried out in the same way that I planed it to, but instead of soda lime granules being used, 10 cm of potassium hydroxide (15%) solution was used with a piece of folded filter paper acting as a wick to remove any carbon dioxide. I did this because I felt that with the cotton wool being so tightly compacted separating the insects and the granules, that the carbon dioxide could not travel through it, so pushing some of the manometer fluid back down the manometer tube. Care needs to be taken into consideration when pouring this down the tube as it is a corrosive and may harm the insects if the touched it.
Safety:
. Before I carried out my actual experiment, I did a pilot study to check the variables I was using and to ensure that the temperatures didn't go to either extremes.
2. Whilst carrying out the experiment I was aware that precaution should be taken when handling the potassium hydroxide, so I used goggles to protect my eyes from spillage's.
3. Also for the insects safety I made sure that none of the potassium hydroxide splashed up on either side of the boiling tubes as it is a corrosive and so could of harmed them.
4. Even though the temperatures I was using only varied from 5 C to 30 C, I still used a kettle for hot water. To ensure that the kettle was not knocked over I put it far back on the workbench and made sure that the lead did not hang over the edge.
The organisms I was using were live and so I had to ensure that they were not harmed and survived the whole week. I kept them in a ventilated box with what plenty of food, bedding and space. After the experiment was over I released them.
Results:
Experiment 1.
Time (secs)
Temperature( C)
20
40
60
80
00
5
0
0
0
0
0.78
0
0.78
.56
2.34
2.34
2.34
5
0.78
2.35
3.13
4.7
6.27
20
.57
3.39
6.29
8.65
0.22
25
.57
3.39
6.29
9.43
2.57
30
3.14
5.5
8.64
1.78
3.7
Experiment 2.
Time (secs)
Temperature( C)
20
40
60
80
00
5
0
0
0
0
0
0
0
0.78
.36
.56
2.34
5
0.78
2.35
3.92
4.7
3.48
20
.57
3.14
4.71
7.07
9.43
25
2.36
4.72
7.86
0.22
2.85
30
2.36
5.5
8.64
1.78
4.92
Experiment 3.
Time (secs)
Temperature( C)
20
40
60
80
00
5
0
0
0
0.78
0.78
0
0.78
.56
.56
2.34
3.12
5
0.78
.56
3.13
4.7
5.48
20
.57
3.09
3.45
7.02
8.59
25
2.36
4.72
7.08
9.44
1.8
30
3.14
6.28
9.42
3.34
6.02
Experiment 4.
Time (secs)
Temperature( C)
20
40
60
80
00
5
0
0
0.78
0.78
0.78
0
0
0
0.78
.57
2.34
5
0.78
.56
2.24
3.91
4.69
20
.57
3.14
5.5
7.86
9.43
25
2.36
5.5
8.64
1.0
3.36
30
3.14
6.28
0.2
3.34
6.48
Average.
Time (secs)
Temperature( C)
20
40
60
80
00
5
0
0
0.2
0.39
0.59
0
0.39
0.98
.78
2.34
2.53
5
0.78
.96
3.13
4.5
5.48
20
.57
3.19
5.49
7.36
9.41
25
2.16
4.17
7.65
0.01
2.58
30
2.95
5.89
9.14
2.56
5.39
When collecting these results, I measured the up take of oxygen on the manometer tubes to the millimetre, and then when calculating it out by the equation: V= ?r h
W
I did so to two decimal places.
I carried out the experiment four times before taking the average. This was to expel any anomalous results, which could have been obtained due to a mistake in the apparatus being put up wrongly, or because of error in reading the result. With the averages I then drew up a graph which allowed me to compare my averaged results easily.
Analysis:
The basic overall conclusion that can be drawn is that there is a positive correlation between the increase in temperature and the rate of respiration and that this increase is proportional as the graph of average respiration rates is roughly follows a straight line. This increase was hypothesised as a rise in temperature provides enzymes kinetic energy to metabolise at a faster rate so use oxygen up more quickly.
However there are a few slight anomalous results. For both 20 C and 40 C all results I obtained over the different temperatures were bellow the line of best fit. The reason for this could be because each time I started the experiment I didn't leave the boiling tube in the water long enough to equilibrate. I left it for about 3 minutes, though I didn't time this, so it may have been for a longer or for a shorter time. At the end of the experiment, both 5 C, 10 C, 15 C, and 30 C all ended above their line of best fit. This could be because
The Q10 theory was not upheld by the results as increases in temperature by 10ºC did not lead to doubling the respiration rate, instead it seemed to triple.
