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AS and A Level: Energy, Respiration & the Environment

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Things to remember when planning an A level experiment

  1. 1 Write your procedure/method as a series of numbered steps. This helps the reader to follow your procedure easily. Describe precisely how you plan to control all control variables. Explain why it is necessary to control these variables in terms of how they could impact on the results.
  2. 2 Include all volumes, weights, concentrations, times, temperatures etc ensuring that you specify SI units. The method needs to provide all relevant details, so that another A-level student could complete the experiment to obtain data.
  3. 3 Use the results of a trial experiment to explain your reasons for selecting specific equipment, volumes, times, independent variable ranges, concentrations, pH, etc.
  4. 4 Clearly state the statistics test you plan to use to analyse your data. To look for:
    a) Statistically significant relationships between the independent and dependent variables use Spearman’s rank.
    b) Statistically significant differences between two categories use t-tests for normally distributed data or a Mann Witney U for non-normally distributed data.
  5. 5 Ensure that you state the range you plan to investigate and the number of times you will repeat the experiment clearly. Make sure that you include an independent variable range of at least 7 if you plan to use Spearman’s rank (eg. 7 different temperatures or concentrations) or at least 6 repeats if you plan to use the Mann Witney U test for difference.

Helpful hints for ecological sampling

  1. 1 Systematic sampling along a transect is used to investigate species distribution along an environmental gradient. For example if you are investigating the effect of water depth on seaweed growth as you move further up a rocky shore, you would use a transect and sample systematically at specified intervals (eg 2 Metres).
  2. 2 Random sampling is used to investigate the abundance of species in two distinct areas. For example the growth of daisies in mowed and un-mowed areas of a park.
  3. 3 Quadrats are used for both systematic and random sampling to ensure that species are counted within a defined and controlled area.
  4. 4 Random coordinates are generated and used to sample un-biased areas of each plot during random sampling.
  5. 5 The data from systematic sampling is analysed for correlation using Spearman’s rank. The data from random sampling is analysed for significant difference using a t-test (if the data is normally distributed) or Manny Whitney U.

Respiration and ATP facts

  1. 1 Energy cannot be produced, it is transferred. Conversely ATP is produced when energy is transferred from glucose during respiration.
  2. 2 The energy stored in ATP is released after ATP is hydrolysed to ADP and Pi. Some energy is required for ATP hydrolysis, but when bonds form between Pi and water more energy is released than is required for the initial hydrolysis of ATP, i.e. the reaction is exergonic.
  3. 3 Glycolysis is the first step in both aerobic and anaerobic respiration. Glycolysis occurs in the cell cytoplasm and yields 2 ATP molecules by substrate level phosphorylation. Glycolysis is the only source of ATP in anaerobic respiration.
  4. 4 The link reaction, Kreb’s cycle and electron transfer stages of respiration occur in the mitochondria and depend on oxygen as a terminal electron acceptor. In the absence of oxygen these aerobic stages cannot take place.
  5. 5 In aerobic respiration the majority of ATP is produced as a consequence of electron transfer. Each reduced NAD molecule donates electrons to the electron transfer chain, and 3 ATP molecules are generated as a consequence. Each reduced FAD molecule that donates electrons leads to the generation of 2 ATP molecules. During glycolysis, the link reaction and the Kreb’s cycle a total of 10 reduced NAD and 2 reduced FAD are produced, leading to the generation of approximately 34 ATP molecules following electron transfer.

  • Marked by Teachers essays 42
  • Peer Reviewed essays 15
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  1. Marked by a teacher

    The Development of Antiseptics.

    4 star(s)

    Semmelweiss' ideas on cleanliness Ignaz Semmelweiss had noticed that there was an unusually high death rate amongst women after childbirth and realised that mothers whose children were delivered by a mid-wife usually survived unlike those who had there offspring delivered by medical students. Semmelweiss thought that if only the students washed their hands before entering the maternity wards they may save many lives, he made them do this and it worked. Unfortunately Semmelweiss was ignored, he called those who did not wash their hands 'murderers' and so many called him a crank and a fanatic.

    • Word count: 922
  2. Marked by a teacher

    How caffeine affects daphnia heartrate

    3 star(s)

    Then, we got rid of the excess water, by squeezing the pipette to get rid of the extra water onto a paper towel. 3. Then, one of the daphnia was placed onto the small bit of wool which was on the cavity slide. 4. After that, we placed a small amount of cooled distilled water onto the second cavity slide before putting that underneath the first cavity slide directly under the daphnia. 5. Then we put both cavity slides under the microscope.

    • Word count: 997
  3. Free essay

    Biological Importance of Water

    3 star(s)

    For example an ionic salt such as potassium chloride would dissolve because the charged particles (ions) will dissociate within the water. The positive ions attract to the negative oxygen atom and the negative ions to the positive hydrogen. Substances that are non polar however, for example lipids, do not mix with water and consequently can be easily separated from aqueous solutions. For example, when droplets of oil merge in water they do not mix (they are said to be immiscible) and can easily be drained from the top surface of the water. Water as a lubricant: Water's properties, especially its viscosity, make it a useful lubricant.

    • Word count: 941
  4. Marked by a teacher

    An Experiment to Show the Rate of Respiration In a Locust.

    3 star(s)

    * I left screw clips A and B open at these times to allow air to escape as it expands. * I closed both screw clips after 5 minutes, allowing the experiment to start. * The carbon dioxide given off by the respiration of the locust was absorbed by the soda lime, hence a reduction in the volume of air in chamber B. * As chamber B was airtight, this lead to a reduction in pressure within, thus the pressure of chamber A (control)

    • Word count: 987
  5. Marked by a teacher

    To investigate the energy content of different foods.

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    The amount of energy foods can produce is measured in units called calories. A food calorie, or kilocalorie, is the amount of heat required to raise the temperature of 1 kilogram (2.2 pounds) of water 1 degree Celsius (1.8 degrees Fahrenheit). The body changes the calories in food into energy, which is necessary for every act from blinking an eye to running a race. Energy is also used for the growing process, for rebuilding damaged cells, and for regulating body systems. The number of calories needed each day depends upon how much energy an individual's body uses.

    • Word count: 729
  6. Marked by a teacher

    Renewable and non-renewable energy sources.

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    * It is good to use for heating water (Solar thermal electric generating plants) * Solar power does not store or travel well. It looses a lot of energy when done so. * At the moment, solar power is more expensive than using fossil fuelled power stations. * Solar power would only be effective in some places in the world. It would not be effective in e.g. London, UK. But it would be effective in somewhere e.g. Australia. Wind energy: Moving air turns the blades of large windmills or generators to make electricity, or to pump water out of the ground.

    • Word count: 907
  7. Marked by a teacher

    Why is pyramid of biomass important in illustration than pyramid of numbers?

    It is not essential, however, to use dry biomass. There are some circumstances where it is far more sensible and convenient to consider fresh or live biomass. Pyramids of biomass may be expressed in terms of biomass at each trophic level. Information from: http://www.tutorvista.com/content/biology/biology-iv/ecosystem/biomass-pyramid.php "Pyramid of biomass is the graphic representation of biomass present per unit area of different trophic levels, with producers at the base and top carnivores at the tip". The total amount of living or organic matter in an ecosystem at any time is called 'Biomass'.

    • Word count: 653
  8. Peer reviewed

    Purpose: To investigate the effect of caffeine on the heart rate of Daphnia (water fleas).

    4 star(s)

    This can lead to heart and circulatory problems. Safety: 1. Handle glassware with care. 2. Wear a lab coat to prevent spill on fabrics. 3. The microscope is fragile and the light bulbs can get hot so handle with care. Apparatus: 1. Culture of Daphnia (water fleas) 2. Cavity slides 3. Dropping pipettes 4. Distilled water 5. Cotton wool 6. Standard glassware (beakers, measuring cylinders, etc.) 7. Stopwatch 8. Filter paper 9. Microscope Hypotheses: I believe that the Daphnia subjected to caffeine solution will show a rise in heart rate, this rise in heart rate will depend on the concentration of caffeine in the solution.

    • Word count: 838
  9. Peer reviewed

    Core PracticalDoes caffeine affect heart rate?)

    4 star(s)

    Method:- * We took a cavity slide and placed some cotton wool on it and then placed a water flea on to the cotton wool two drops of water were added with the help of a pipette. * The cavity slide was placed under a microscope.

    • Word count: 462
  10. Peer reviewed

    Ethics behind selective breeding of animals

    4 star(s)

    This has given rise to a reliable cheap food source throughout the year. It could considerably raise the standard of living in developing countries where starvation is a prevalent problem. However some believe the development of new varieties should be allowed to take place naturally. We should accept a lower standard of living in return for natural breeding. When looking at this problem we should look at how useful the varieties will be in terms of helping humans. Perhaps one way forward would be to allow selective breeding only in countries where it is most needed.

    • Word count: 548
  11. Peer reviewed

    Use of a Redox Indicator to show Dehydrogenase Activity

    4 star(s)

    This mixture should be allowed to stand for 24 hours before the experiment takes place. * Tiphenyl tetrazolium chloride is used as a redox indicator to investigate the activity of dehydrogenase enzymes when yeast suspension is exposed to different temperatures. * Distilled water for the preparation of the yeast suspension. * Test tubes to place the mixture of yeast and T.T.C. * Test tube rack to allow the test tubes to stand upright in the water baths. * Incubator to allow enzyme activity to occur at different temperatures * Syringes to accurately measure the right amount of yeast and T.T.C needed for each solution.

    • Word count: 825
  12. Peer reviewed

    Mitochondria & Chloroplast

    3 star(s)

    Have ATP-synthatases appearing as stalked particles (on the thylakoid membrane of chloroplast, on the cristae of mitochondria) Have electron transport chains (on the thylakoid membrane of chloroplast, on the cristae of mitochondria) Self-replicate. Differences found in both plants and animals. found in plants only Help in respiration help in photosynthesis. No pigment contains thylakoid membranes and pigment molecules Matrix Stroma Releases energy from sugar Requires energy (light)

    • Word count: 396
  13. Peer reviewed

    Global Warming

    3 star(s)

    Greenhouse Gases include carbon dioxide, water vapour, methane, nitrous oxide and ozone. > The Green house gases are also play a huge role in global warming as these gases trap the heat that would otherwise escape to into space. This is called the greenhouse effect > Deforestation is also another cause of global warming because when the excess amount of trees are cut down and not replanted, there becomes an increase in Carbon Dioxide concentration in the atmosphere as there are no trees to use it for respiration.

    • Word count: 574
  14. Peer reviewed

    The Role of ATP

    3 star(s)

    ATP * One molecule can contain large amounts of energy which can be used very easily. * ATP is not a storage molecule. * Every cell makes its on ATP, depending on how active it is and its job. * ATP is constantly made and used. 40 kg is made in a 24hr period. Structure Organic base - adenine Pentose sugar - ribose 3 Phosphate groups - inorganic phosphates which are joined by high energy bonds. ATP is a nucleotide and because of its structure, is water soluble and is easily transported around the cell.

    • Word count: 621
  15. Peer reviewed

    Respiration including Glycolysis and Link Reaction

    3 star(s)

    proteins AA, steroids cholesterol, cellulose from B-glucose. Replication of DNA & synthesis of organelles before a cell divides Movement e.g. flagella, cilia and muscle contraction Activation of chemicals- glucose is phosphorylated at start of respiration so more unstable and can be broken down to release energy b) The hydrolysis of ATP is coupled with synthesis reactions e.g. DNA replication or protein synthesis as these require energy. The energy released from ATP hydrolysis is the immediate source of energy for these biological processes. c) Adenosine= 0 phosphate groups Adenosine Monophosphate (AMP) = 1 PG Adenosine Diphosphate (ADP)

    • Word count: 581
  16. Peer reviewed

    Investigating effect of changing glucose concentration on respiration in yeast

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    2. 20cm3 of this is added to a conical flask 3. Now, add 10cm3 of water and the appropriate amount of glucose 4. Keep the contents of the conical flask at a constant temperature (40c) using a water bath. 5. Use a glass gas syringe to measure the amount of CO2 produced in two minutes. 6. Repeat each reaction three times to get an average of carbon dioxide produced.

    • Word count: 283
  17. Peer reviewed

    The effect of light on plant activities

    3 star(s)

    and phytochrome far-red (Pfr), with phytochrome red absorbing red light and phytochrome far-red absorbing far-red light. Sunlight contains a lot more red light than far-red light. Therefore, during the day, phytochrome exists in the form Pfr. At night it gradually changes back into the Pr form. Phytochrome is involved in a range of plant responses to light, including the germination of seeds, elongation of seedlings, the size, shape and number of leaves, the synthesis of chlorophyll, and the straightening of the epicotyl or hypocotyl hook of dicot seedlings. In particular, many flowering plants use phytochrome to regulate the time of flowering based on the length of day and night (the photoperiod), and depending on which type of plant - short day plant (SDP)

    • Word count: 722
  18. Peer reviewed

    The effect of caffeine on the heart rate

    3 star(s)

    In addition, it has medicinal uses in aspirin preparations, and is found in weight-loss drugs and as a stimulant in students' exam-time favourites like Pro-plus and Red Bull. In humans, caffeine acts as a stimulant drug, causing increased amount of stimulatory neurotransmitters to be released. At high levels of consumption caffeine has been linked to restlessness, insomnia and anxiety, causing raised stress and blood pressure.

    • Word count: 395
  19. Peer reviewed

    The part played by micro-organisms in the nutrient cycles

    3 star(s)

    Carbon too is a main part of life. Carbon is the fourth most abundant chemical element in the universe by mass after hydrogen, helium, and oxygen. It is present in the oceans, the atmosphere, the biosphere, both the biotic and abiotic, in glucose and water and so in extention the earth can only exist with carbon present. The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere (the sum of all ecosystems), pedosphere (the soil), geosphere (rock and regolith), hydrosphere (the sum of all water), and atmosphere (the layer of gases surrounding the earth), of the Earth.

    • Word count: 918
  20. Catalase Investigation - Core practical

    Variables Variables are factors in an experiment which can be altered or varied. An independent variable is a factor which is changed to show the purpose of the investigation. The independent variable for this experiment was the amount of potato discs in each solution. This meant altering the amount of potato would affect the dependant variable. The dependant variable in the investigation was the volume of oxygen gas produced. This meant I could observe this dependant variable and record the results to make a conclusion. In the experiment I also had controlled variables.

    • Word count: 845
  21. Investigating Population; Random sampling; what is transects? How does it work?

    Random sampling can be carried out by dividing the study into a grid of numbered lines, e.g. by setting two long calibrated rulers at right angles to each other. Then random coordinates can be obtained by either using log chart or random number generator in a calculator. Finally, we take samples from the intersection of each pair of coordinates. This process prevents sampling bias by eliminating human involvement of choosing the sample. {Figure 1 shows a diagram that briefly describes the method of random sampling}. There are two types of quadrats that can be used in random sampling: 1.

    • Word count: 558
  22. Malnutrition occurs when the body does not get enough vitamins, minerals, and other nutrients it needs to maintain healthy tissues and organ function. Both undernourished and over-nourished people can suffer from malnutrition.

    Both undernourished and over-nourished people can suffer from malnutrition. Under nutrition is a consequence of consuming too few essential nutrients or using or excreting them more rapidly than they can be replaced. Insufficient food intake is the most common cause of malnutrition worldwide. In some areas, cultural and religious food customs may play a role. Inadequate sanitation further endangers children by increasing the risk of infectious diseases that increase nutritional losses and alters metabolic demands. People who are chronically malnourished lack the nutrients needed for proper health and development.

    • Word count: 688
  23. Sheltered Rocky Shore

    This level was to high to detect organisms which live far away from the coastal area. * Zonation 1. Splash zone > As temperature is high and the humidity is low in this zone, the organisms inhabited in this zone must withstand the extreme climate > e.g. periwinkle Characteristic: 1. Have radula to scrape algae on the rock 2. Also feed on small invertebrates 2. Littoral Zone > This zone is subjected to strong wave, varying environment and great temperature range, only organisms that can withstand strong wave action can inhabit in this zone > e.g.

    • Word count: 535
  24. Investigate the effect of on exercise on the heart rate.

    Again, the partner will be timing this. Lastly, after recording the heart rate the person should wait for its heart rate to return back to its resting heart rate and again the partner should time it and record the results in the table. In order for my experiment to be fair and gain accurate results I carried out two or three more times so that to see if there have been any changes to the results. I also consider the following points as I thought they would also make a huge difference.

    • Word count: 879

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