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How light intensity affects the rate of photosynthesis
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How light intensity affects the rate of photosynthesis The aim of my experiment was to determine whether intensity of light would affect the rate of photosynthesis in a plant. To do this, I placed a piece of Canadian pondweed in varying light intensities, and observed the amount of oxygen being given off. I used Canadian pondweed because of its unusual quality of giving off bubbles of gas from a cut end, when placed in water. Introduction Photosynthesis occurs only in the presence of light, and takes place in the chloroplasts...
repeat readings and find

an average. To extend my enquiries into the rate of photosynthesis, I

could perhaps try to link in some of the other limiting factors to the

same experiment, as well as investigating them in their own right. It

could also be interesting to explore the effects of coloured lights on the

rate of photosynthesis, which could lead to the question of whether or not

other types of light, such as fluorescent lights or halogen lights, would

have a different effect on the rate of photosynthesis.

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Aim: I am going... Aim: I am going to investigate how different surface areas, and therefore enzyme concentration, of the same volume of potato affects rate of reaction, when placed in 10ml hydrogen peroxide. Prediction: As the surface area increases, so do the amount of enzymes, which are biological catalysts that are on show, free for the hydrogen peroxide to collide with. Because the catalase and hydrogen peroxide are a complimentary pair, and the enzymes are the ones that break down the substrate, then the more enzymes there are, the more hydrogen peroxide will be reacting at once, and once that has been broken down, then another hydrogen peroxide molecule will 'lock' into the catalase's active site, and the process will start again. Therefore the more enzymes or catalysts available, the faster the rate of reaction will be. As the reaction is taking place, oxygen and water are made from the hydrogen peroxide. The oxygen is given off as a gas, this is what I will be measuring, but the water will be left in the test tube along with the hydrogen peroxide. As the reaction goes on, there will be less hydrogen peroxide, because it has reacted, so there is less chance of collision between substrate and enzyme because the concentration of hydrogen peroxide has decreased. Making the chance of collision even lower is the water that has been broken down from the hydrogen peroxide, which is now in the way of the substrate still left trying to collide and react, which is now colliding into the water molecules, and taking longer to collide with an enzyme, making the reaction slow down. Results Volume Pieces Size of sides cm Surface Potato no. of potato cm of potato h:w:d area cm 1 2 3 Average Average 3sf 1 1 1 1 1 6 Oxygen 1.4 1.1 1.3 1.266666667 1.27 1 2 1 1 0.5 8 produced 1.8 2.1 1.8 1.9 1.90 1 4 1 0.5 0.5 10 ml 2.7 2.7 2.4 2.6 2.60 1 8 0.5 0.5 0.5 12 3.3 3.1 3.2 3.2 3.20 1 16 0.5 0.5 0.25 16 4.4 3.9 4.2 4.166666667 4.17 Skill A: Analysis My results show that, as surface area increased, the rate of reaction also increased, with 6cm² producing the least amount of oxygen in 4 minutes, and 16cm² surface area producing the most oxygen in 4 minutes. The relationship between the two surface area and oxygen produced is that, they are almost directly proportional, but with rate decreasing just a little at each recorded surface area, at around 0.1ml from 6cm² until 12cm². When it reaches 16cm², the oxygen produced is about 0.5ml less than if oxygen produced was directly proportional to surface area in that, from 6cm², oxygen produced goes up 0.3ml every 1cm². If I investigated further, with higher surface areas, I would expect to start seeing the graph level off gradually, as it had started to at 16cm², and eventually, the rate at which it would level off, would increase rapidly, until almost completely level. My results support my prediction up to just below 16cm² surface area. Below this point, the results were both directly proportional and oxygen production doubling, as surface area doubled, with a few points slightly out, which is to be expected. At and therefore I would expect, after 16cm², the results started to become lower than the line of direct proportionality, and I expect that the doubling would also. This is due to the breakdown of hydrogen peroxide, which leaves less substrate for collision, and also producing water, making the solution more dilute, so collisions become less frequent, after the more hydrogen peroxide that has reacted. If you double the surface area of enzymes then the rate of reaction doubles as well. When the surface area is doubled form 8cm² to 16cm², the rate goes up from 1.9ml "“ 4.17ml of oxygen produced in 4 minutes, which is an increase of 2.19 times. I would expect the rate to keep increasing but a bit less rapid than as previously from 16cm² onwards. The 0.19 more than two times rate can be put down to experimental error, and could be due to anomalous results. All the active sites can never all be being used at the same time, because they all may vary slightly in the time it takes to break down their individual substrate, and some may not be being used, or some finishing as some are starting, plus it takes time for the substrate to fit in and leave the active site, so you could never really reach the theoretical maximum value of oxygen that could be produced for a specific volume to surface area ratio because of this. As the surface area increases, so do the amount of enzymes, which are biological catalysts that are on show, free for the hydrogen peroxide to collide with. Because the catalase and hydrogen peroxide are a complimentary pair, and the enzymes are the ones that break down the substrate, then the more enzymes there are, the more hydrogen peroxide will be reacting at once, and once that has been broken down, then another hydrogen peroxide molecule will 'lock' into the catalase's active site, and the process will start again. Therefore the more enzymes or catalysts available, the faster the rate of reaction will be. As the reaction is taking place, oxygen and water are made from the hydrogen peroxide. The oxygen is given off as a gas, this is what I will be measuring, but the water will be left in the test tube along with the hydrogen peroxide. As the reaction goes on, there will be less hydrogen peroxide, because it has reacted, so there is less chance of collision between substrate and enzyme because the concentration of hydrogen peroxide has decreased. Making the chance of collision even lower is the water that has been broken down from the hydrogen peroxide, which is now in the way of the substrate still left trying to collide and react, which is now colliding into the water molecules, and taking longer to collide with an enzyme, making the reaction slow down. This is why I expect a slow down in the increase of oxygen production as surface area becomes greater than 16cm². I kept the conditions for each experiment the same, with the exception of surface area, which I was measuring. If I had altered any of the other variables, then it would not have been a fair test, as the enzymes work at different rates in different conditions, with an optimum level for each variable, and also a point in each variable where the enzymes start to denature. I kept the temperature throughout the experiment at a constant of 24ºC. If I had increased the temperature then the hydrogen peroxide would have had more kinetic movement energy, and therefore would have moved faster, and as collision theory is basically how the rate of reaction depends on how often and how hard particles collide with each other. So in order to react they need to collide hard enough. So with the increase in temperature, the hydrogen peroxide will have more energy to move faster, so they have more collisions, and also hit harder. Faster collisions only come with increasing temperature. If the temperature is too low, then the particles do not have enough kinetic energy to hit hard enough to react with each other. Enzymes also work better in warmer temperatures; so unless in their optimum temperature environment, temperature is a limiting factor, and the enzymes will not work at their optimum rate. However, if the temperature goes too high, or too low, the enzymes will become denatured, and therefore start to stop working, and may start to die off, which decreases rate of reaction. Concentration is another variable that changes the rate of reaction. If there are many particles of substrate between water molecules, then there is bound to be more collisions of enzymes and substrate, whereas, if there are few particles of substrate between the water molecules, then there is less chance of reaction of the complimentary pairs. If there are more packed in together, then they are closer and are more likely to collide with their reactant. Enzymes also work best in an optimum pH value, and if not at that, like temperature, pH is a limiting factor. But as the enzymes were left in their tissues/optimum environment, then it was not a factor in this experiment. Hydrogen peroxide breaks down on its own without catalase. Catalase is just a catalyst, which just speeds up a reaction, by reducing the initial amount of energy needed for a reaction; it breaks down the substrate faster, in this case the hydrogen peroxide. An enzyme is like a lock, for which it only has one specific substrate, that being the 'key'. As the substrate fits into this 'lock', it goes into what is called the active site, the part of the enzyme that actually does the breaking down of the molecules. But after the reaction, the catalase is not used up, or does not differ after the reaction; it can be used again and again after countless reactions. It also does not cause the reaction, but simply speeds the reaction up. I also kept the same potato, for each set of results I took three, as using lots of different ones could have produced unreliable results, as different potatoes' enzymes' reaction times may differ slightly. I did 5 different experiments each on 3 different potatoes 5 experiments on each, to obtain accurate results incase one potatoes enzymes were very different from most.   

Aim: I am going to investigate how different surface areas, and therefore enzyme concentration, of the same volume of potato affects rate of reaction, when placed in 10ml hydrogen peroxide. Prediction: As the surface area increases, so do the amount of enzymes, which are biological catalysts that...

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Global Warming!! Some of you... Global Warming!! Some of you might be wondering what Global is Warming. Some might be wondering is it even real? Or is it just some environmentalist scam trying to get people to care about the environment?? Global Warming is not a fiction or a hoax. It is real and if people don't take action now, then when the time comes, it will be TOO LATE. One might ask what is global warming any way. Global warming, according to Dictionary.com, is an increase in the earth"s average atmospheric temperature that causes corresponding changes in the climate and that may result from the greenhouse effect. As mentioned on epa.gov website the greenhouse effect is the rise in temperature that the Earth experiences because certain gases in the atmosphere water vapor, carbon dioxide, nitrous oxide, and methane, for example trap energy from the sun. Without these gases, heat would escape back into space and Earth's average temperature would be about 60ºF colder. Because of how they warm our world, these gases are referred to as greenhouse gases. The greenhouse effect is caused by increased levels of greenhouse gases, which are usually due to effects of human industry and agriculture. Scientists have proved that there was a dramatic increase in the Carbon Dioxide and methane concentration which are usually produced by burning of fossil fuels, such as gasoline in an automobile or coal in power plant generating electricity. What if the concentrations increase, who cares! Well, the atmospheric levels of carbon dioxide have increased by 34% according to Carbon Dioxide Information Analysis Center. As mentioned in an article on Global Warming in San Jose Mercury News Paper, the Intergovernmental Panel on Climate Change said the likelihood was 90-99% that emissions of heat-trapping greenhouse gases like carbon dioxide were the dominant cause of the observed warming over the past 50 years. In a recent article, William K.Stevens stated that if greenhouse gas emissions continue unabated, they most likely will warm the Earth by about 3-7 degrees Fahrenheit by the end of this century, with a wider range of about 2-12 degrees possible. Furthermore, 11 out of the 12 past years were among the 12 warmest years on record worldwide. In regards to weather, the frequency of cold days, cold nights and frosts has diminished, while the frequency of hot days, hot nights and heat waves has increased. Droughts in other parts of the world have become more frequent and more intense. Precipitation has decreased in the tropics and subtropics and has increased in the Northern and Southern hemispheres. This means that in many places, it rains and snows less often but harder "“ a characteristic of a warming atmosphere. In addition, hurricanes have become more frequent due to the warming of the seas. Like our recent catastrophic hurricane Katrina, there will be more hurricanes or other catastrophic events because of global warming. President Bush in his 2007 Union State of Address emphasized, technological breakthroughs will help us be better stewards of the environment, and they will help us to confront the serious challenge of global climate change. One can conspicuously conclude from the above mentioned evidences that Global Warming is indeed a FACT, which President Bush In his Union State of Address emphasized.   

Global Warming!! Some of you might be wondering what Global is Warming. Some might be wondering is it even real? Or is it just some environmentalist scam trying to get people to care about the environment?? Global Warming is not a fiction or a hoax. It is real and...

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