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GCSE: Life Processes & Cells

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  • Marked by Teachers essays 82
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  1. Marked by a teacher

    Osmosis in Potatoes Lab. At which concentration of sucrose in water (% mass by sucrose) will the potato core be isotonic, meaning that there is no movement of water in or out of the potato core?

    5 star(s)

    Procedure: 1. Fill each test tube with __ mL of only one solution of water and sucrose (0%- 50% by mass). 2. Label each test tube with the solution it is holding (% of mass by sucrose in each solution). 3. Take out 6 cores of equal size from the potato given using the borer. 4. Record the mass of each potato core cut out. 5. Place each core into a separate test tube of solution. 6. Take out each core after 30 min.

    • Word count: 2498
  2. Marked by a teacher

    Testing the biochemicals present in apple and green bean using specific chemical tests.

    5 star(s)

    The positive result may be confirmed by boiling the mixture in a hot water bath for a few minutes and the blue-black colour disappears. On cooling the mixture, the colour should appear again. 3. Biuret test for proteins When protein is mixed with the dilute alkaline cooper sulphate solutions, nitrogen atoms in the peptide bonds to form a violet complex with copper(II) ions. Note. The intensity of the colour developed is an indication of the quantity of peptide bonds present in the solution tested.

    • Word count: 1530
  3. Marked by a teacher

    GCSE Bioligy Case Sudy - MRSA

    5 star(s)

    is a type of bacteria that is most abundant in hospitals all around the world. Due to its immunity to the family of beta-lactam antibiotics (which includes the common penicillin) it is difficult to prevent the reproduction and spread of this bacteria. It is a variety of Staphylococcus Aureus (often abbreviated to "staph") that is also resistant to meticillin, and some of the other antibiotics that are usually used to destroy Staphylococcus Aureus. Its has existed for thousands of years, but has become a larger problem in the past decade.

    • Word count: 2407
  4. Marked by a teacher

    Isotonic Point of Potatoes

    5 star(s)

    Such a solution is called an isotonic solution, and the concentration at which this occurs is the isotonic point of the cell. Thus when cells are placed in such a solution, there should be no change in the mass. Brief Outline Method (Provided in instructional sheet): * In this experiment the isotonic point of potato will be found. * The potato slices will be kept in salt (sodium chloride) solutions of different concentrations. * Some of the solutions would be relatively hypertonic, and some would be hypotonic, assuming constant potato concentration.

    • Word count: 3127
  5. Marked by a teacher

    Biology Coursework - Osmosis

    5 star(s)

    This is because there is a higher concentration of water molecules in the pure water than in the solution. This results in more water molecules diffusing across the concentration gradient from the water to the solution. Eventually, the level on the more concentrated side of the membrane rises, while the level on the less concentrated side falls. When the concentration is the same on both sides of the membrane, the movement of water molecules will be the same in both directions.

    • Word count: 5226
  6. Marked by a teacher

    What affects osmosis

    5 star(s)

    To keep my experiment a fair test, the only variable that I shall change is the concentration of the sucrose solution. The other factors that affect osmosis in a model potato cell and that I shall therefore control, include the amounts of solution, the length of potato, the potato width, the type of potato, the time left in the solution, the surface area, the temperature and the initial water potential of the potato. Plan Sucrose sugar solutions of different molarities (10%, 20%, 25%, 30%)

    • Word count: 1985
  7. Marked by a teacher

    To determine the water potential of a potato tuber cell using varying salt solution.

    5 star(s)

    This means that the potato cell that is left in the distilled water should gain the most weight according to the definition of osmosis. There are some things that need to be considered, water potential is affected by solute potential and pressure potential. When solute molecules are dissolved into water, the concentration of water molecules is reduced, and hence so is the water potential6. The solute potential is devised by the amount of solute in the experiment in this case it would be the salt.

    • Word count: 5471
  8. Marked by a teacher

    Osmosis in Potato Chips

    5 star(s)

    However, there must be a stage at which osmosis cannot occur because the water concentration in both the potato chip and the solution around it is balanced. I aim to investigate this. Diagram 1 - Osmosis occurring when a potato chip is placed in a solution containing 100% sucrose. Diagram 2 - Osmosis occurring when a potato chip is placed in a solution containing 0% sucrose. Plan I will set out by setting up 21 test tubes. I am going to have 3 test tubes with each different solution in them to make this a fair test.

    • Word count: 4785
  9. Marked by a teacher

    Plan: The effect of the end product, phosphate, on the enzyme phosphatase

    5 star(s)

    Supposing a metabolic pathway becomes overactive and too much end products are produced, the end products will inhibit one of the enzymes in the metabolic pathway and therefore lower the whole series of reactions. By this means, the further formation of end products is slowed down. This is called an end product inhibition. e.g enzyme a enzyme b enzyme c Substrate A Substrate B substrate C substrate D In this experiment, sodium phosphate can work as a natural inhibitor as mentioned above.

    • Word count: 4551
  10. Marked by a teacher

    How does the concentration of a sucrose solution affect the rate of Osmosis in Potato Cells?

    5 star(s)

    This diagram shows what happens during osmosis: The solution on the left side is hypotonic, and the one on the right is hypertonic. The water particles will move through the cell membrane from the left side to the right side, as there are more water particles on the left than on the right. If the left side was the solution in the beaker, and the right was the solution in the vacuole, then water would be moving into the cell and the potato cylinder would increase in mass.

    • Word count: 5574
  11. Marked by a teacher

    Investigating the effect of Sucrose Concentration on the Rate of Osmosis in Potato Chips.

    5 star(s)

    to obtain a given amount of liquid that exceeds the capacity of the measuring cylinder used e.g. 60ml. The constant refilling of a small measuring cylinder to gain a larger amount increases the chance of error, as spillage is more probable. There is no need to use a 200ml to measure either the distilled water or the sucrose concentration as the maximum amount of each that I plan to use is only 100ml, a measuring cylinder of the same amount is sufficient.

    • Word count: 7619
  12. Marked by a teacher

    Effects of Surface Area on Catalase Activity in Potato.

    5 star(s)

    Catalysts are molecules which increase the rate of chemical reactions and remain unchanged at the end of the reaction. Enzymes are made up of a chain of amino acids which are constructed into a precise three-dimensional shape. The three-dimensional shape of the enzyme is very important as it determines which substrate (the molecule which is broken down by enzyme) the enzyme is compatible with; usually each particular enzyme will only act as a catalyst for one reaction. The 3D shape provides the enzyme with an active site, this is the only place where the substrate can attach itself onto the enzyme and this is also the place where the substrate is broken down to give its product(s).

    • Word count: 1479
  13. Marked by a teacher

    Potato / Osmosis Experiment.

    5 star(s)

    As the concentration of the sucrose solution becomes hypertonic to the potato sample, more and more water molecules have to leave the potato sample to dilute it - which gives the potato sample a greater loss in mass. Similarly, as the sucrose solution becomes hypotonic to the potato sample, more and more water molecules will have to leave the sucrose solution to dilute the potato sample- giving the potato sample a greater gain in mass. This means that as the concentration of the sucrose solution increases, the mass gain of the potato sample decreases - so they are in direct inverse proportion.

    • Word count: 2857
  14. Marked by a teacher

    Investigation into the effects of osmosis on Potato cells

    5 star(s)

    However if the potato cell was unturgid, we will find it will actually grows in length as again the movement from a region of high water concentration to a region of low water concentration will make the potato cell turgid. Apparatus * Cork borer Vernier calliper * 6 specimen bottles 1 large potato * Labels Approx. 80ml of glucose solution (0.5M) * One-sided blade Approx. 100ml of distilled water * Filter paper Measuring cylinders - 10ml & 25ml Method * Label the specimen bottles: 0M through to 0.5M * Pour the glucose solution into their respective bottles (20ml). See table.

    • Word count: 1409
  15. Marked by a teacher

    Investigating Enzymes and the effects of different variables such as temperature on how they work

    4 star(s)

    The results also contained lots of variation, and two outliers. Temperature Rate of Reaction (Vol. Produced � Time) 0�C 0.67 1.53 0.65 20�C 1.7 1.75 1.72 80�C 0 2 0.2 The variable we change here is the temperature, but the ones we kept the same were potato size (although not accurately) and the concentration of hydrogen peroxide. Unfortunately we have no control over room temperature, and exact potato size. Conclusion and evaluation of preliminary experiment We decided that the best step to take was to use yeast instead of potatoes because they contain a consistent amount of catalase, and all come from the same source, unlike potatoes and they also do not have different varieties.

    • Word count: 1896
  16. Marked by a teacher

    Research into Brewing and Fermentation

    4 star(s)

    http://chemistry.about.com/od/lecturenoteslab1/f/What-Is-Fermentation.htm What types (varieties) of yeast is used in brewing? Active Dry Yeast: dry yeast requires that it is initially dissolved in warm water before adding a recipe. Active dry yeast should not be exposed to and liquid that are higher than 110 degrees Fahrenheit in temperature. Baker?s Yeast: bakers yeast is the term, which is given to forms of Saccharomyces cerevisiae utilized to make bread products. There are several forms of bakers yeast and these include liquid, fresh (cake), active dry and instant. Brewer?s yeast: this yeast is used in order to make beer.

    • Word count: 966
  17. Marked by a teacher

    Investigating the breakdown of hydrogen peroxide by the enzyme catalyse in potatoes.

    4 star(s)

    A reaction like this, where a molecule is broken down into smaller pieces, is known as an anabolic reaction. Variables To ensure that our experiment was fair we identified the key different factors, which could affect the results. We then went on to explore the dependant and independent variables. What we change is the independent variable and the result of this determines our dependant variable. Independent Variable The independent variable we chose to do for this experiment was the number of 1cm3 potato cubes placed in the test tube which was to find out how fast the breakdown of hydrogen peroxide by the enzyme catalyse takes place by changing the concentration of the enzyme.

    • Word count: 4770
  18. Marked by a teacher

    What factors affect osmosis?

    4 star(s)

    me to show a higher level of scientific knowledge and I chose it as opposed to other factors as I believe that the other acts would have changed the investigation too greatly. Changing the temperature would have given the water particles greater energy, which would mean they would have greater energy to move around. If I were to change the type of plant material this could have affected the semi-permeable membrane, which without it is near impossible for osmosis to take place.

    • Word count: 2366
  19. Marked by a teacher

    Investigating the effect of sucrose concentration on osmosis in potato cells

    4 star(s)

    I will take the mass of the disks before and after the experiment and use the percentage change in the mass of potato tissue to see how concentration affects osmosis. I have done some preliminary experiments to aid my investigation. I have used potato tissue and sucrose solutions in a similar way to investigate concentration and osmosis, however, in my previous experiment I only experimented using 2M sucrose solution and distilled water (0M solution). I based my results on length and appearance rather than mass, but it was still possible to come to a conclusion.

    • Word count: 5138
  20. Marked by a teacher

    Biology Coursework: Osmosis

    4 star(s)

    As the water enters the cell membrane, the cytoplasm will boost, though not burst because plant cells do not burst in pure water because its cell wall is very strong. Though the cytoplasm will push outwards against the cell wall, the cell wall is firm enough to resist the pressure. When this occurs, a plant cell is said to be turgid, like a well-blown-up tyre. Preliminary Experiment Aim I will be investigating the effect of osmosis using different concentrations of glucose solution on plant cells.

    • Word count: 3258
  21. Marked by a teacher

    Investigation Osmosis in Potato Tissue

    4 star(s)

    In the dark, guard cells lose water by osmosis and become flaccid, this closes the pore. The presence of solutes dissolved in the water lowers the water potential. Water then moves from an area where the solute concentration is lower to an area where the solute concentration is higher. Distilled water is the purest water and water with dissolved salts has lower water potential. Key Variables There are three different variables that will affect my experiments; Independent variable, Dependent variable and Controlled Variable. The Independent Variable is the variable that I have control over; the one that I change.

    • Word count: 3775
  22. Marked by a teacher

    Biology Coursework Enzymes

    4 star(s)

    The active site breaks down the substrates by affecting the substrates bond of electrons. Once the enzyme has broken down the substrate into products the enzyme can then act on the next substrate as enzymes can be reused. The collision theory is also another theory that states how chemical reactions occur and the reason why the rate of reaction differs. In order for a reaction to take place particles must collide. When successful collisions take place they cause some chemical changes because of the impact caused by the collision causing the bonds of some substrates to break resulting in a "successful collision".

    • Word count: 3548
  23. Marked by a teacher

    Effect of Temperature on Enzyme Activity

    4 star(s)

    The break down of substances is done by the lock-and-key model of an enzyme. This theory suggests that certain enzymes break down only certain substances. For example the enzyme lipase (lock) can only break down the substance lipid (key) because lipids only fit into the lipase. Another substance such as protein would not, however, fit into the lipase and therefore doesn't break it down. There is another reason why enzymes may not break down a substance. This is because the enzyme could get denatured for various reasons. A common reason is the enzyme may not be in the correct PH value of 7.

    • Word count: 1316
  24. Marked by a teacher

    effects of substrate concentration on the activity of the enzyme catalase.

    4 star(s)

    Susceptibility of PH changes: - Enzymes can be denatured by changes in PH. This happens because the ionisation of the Amino acids changes, the Ionic bonds with stabilise the enzyme, that shape is broken so they are no longer stable. So you need the right PH for the ionic bonds to stay stable for the reaction to occur. Enzyme concentration: - The rate of reaction increases when the collision rate increases. You can increase the successful collision rate by increasing the enzyme concentration, this gives substrate particles an easier chance to collide with particles as the surface area has been increased, because simply there are more particles to hit.

    • Word count: 2067
  25. Marked by a teacher

    Science Coursework: Investigating Osmosis in potato tissue

    4 star(s)

    We will not need the equal mass of the potatoes as this will be very hard to measure to two decimal points of a gram. We will be measuring the change of mass in the potato and so equal mass is not a major factor, equal surface area however, is. We will measure the change in mass of the potato (and therefore the amount of osmosis that has occurred) by the percentage change in the mass of the potato. This is the DEPENDANT VARIABLE.

    • Word count: 3514

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