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AS and A Level: Molecules & Cells

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  1. Marked by a teacher

    Discuss how the structure of cell organelles is related to their functions.

    3 star(s)

    There are two main functions of the nucleus. Firstly, it segregates all the DNA molecules from the cytoplasm. Secondly, the nuclear membranes administer as a boundary where cells control the movement of substances to and from the cytoplasm. The nucleus is made up from a few constituents. The nuclear envelope is a double-membrane system that has two lipid bilayers in which many protein molecules are firmly established. This prevents water-soluble substances to move without restriction into and out of a nucleus. The second component is nucleolus, which is a highly packed cluster of RNA and proteins, which construct to make subunits of ribosomes.

    • Word count: 1023
  2. Marked by a teacher

    Beetroot Experiment.

    3 star(s)

    In the cells of a beetroot plant, a substance called anthocyanin is contained within the plasma membrane. Anthocyanin, gives the beetroot its characteristic colour. If a cell is damaged in a beetroot plant and the membrane is broken, the anthocyanin 'bleeds' from the cells. It is this characteristic that can be subjected to test which conditions influence the cell membrane. We are experimenting with the effects of temperature on the membrane, so we will place the samples of beetroot into a water baths of varying temperatures and measure the colour change in the water.

    • Word count: 1040
  3. Marked by a teacher

    Effect of temperature on the enzyme pectinase in fruit juice production.

    3 star(s)

    At this point the enzyme is saturated and the reaction remains at the saturation level. 3. TEMPERATURE: More information on this particular factor is going to be presented a little later. Pectin is a molecule which has a structure similar to starch, the only difference is that the repeating unit of pectin is galacturonic acid instead of glucose as in starch. Galacturonic acid has a similar structure to glucose apart from the fact that one of the carbons has a carboxylic acid group (-COOH)

    • Word count: 3978
  4. Marked by a teacher

    An investigation into the inhibiting effect of tomato juice on the germination of cress seeds.

    3 star(s)

    If the inhibitors of the tomato juice are to inhibit germination there are various factors they can affect. For instance, the inhibitors can affect the enzyme amylase. Amylase is used to convert starch into glucose. The glucose is then used as a respiratory substrate to produce ATP. Without respiration the seed cannot germinate (because energy/ATP is needed for metabolisms for growth). So by inhibiting the enzyme amylase the inhibitors will prevent germination. The presence of inhibitors in tomatoes can provide benefits for the tomatoes.

    • Word count: 6218
  5. Marked by a teacher

    I am going to investigate the ability of Pepsin on Gelatin. I aim to investigate the effect of temperature on the rate of action of Pepsin on Gelatin.

    3 star(s)

    The volume of the pepsin was chosen to be 20ml. Variables * The volume of pepsin that is used * The amount of filmstrip that is used * Temperature of the pepsin * The concentration of the pepsin solution that is used * The apparatus that is used. * The method that is used. * Quality of film * pH of pepsin The variable will be temperature. This will be measured with a thermometer. The following non-variable parameters will be used (determined by preliminary work) - 20ml of pepsin 2cm by 2cm of filmstrip 2% solution of pepsin Black and white film The student has elected to perform the following

    • Word count: 2080
  6. Marked by a teacher

    How long does it take for the action of the enzyme 'amylase' (a type of carbohydrate) to break down the carbohydrate 'starch'?

    3 star(s)

    Factor to be investigated: The temperature factor will be investigated. This will indicate whether by increasing the temp, or decreasing the temp, will have any effect on the speed at which the starch is broken down by the enzyme. Prediction It is expected that as the temperature increases, starch molecules will be broken down more quickly. However, the temp may reach a point the enzyme de-natures, or stops working. This can be expected to be above 37.5�C. (At this temp enzymes and other biological materials may become damaged/ destroyed). The activation site may become wobble-like, and unusable, so stopping starch molecules from being broken up (see diagram).

    • Word count: 659
  7. Marked by a teacher

    Pectinase investigation.

    3 star(s)

    I believe this due to collision theory, this theory states that substances react together when their particles (atoms/molecules) collide with sufficient energy. These are called effective collisions. At higher temperatures the particles move faster because they have more energy therefore there are more effective collisions. When the reactants are more concentrated the particles are closer together and collisions are again more frequent. When substances react the products often have less energy than the reactants. Plan of Method 1. I will start off by setting up the equipment as shown below.

    • Word count: 1005
  8. Marked by a teacher

    How Does Temperature Affect the Action of Amylase on Starch?

    3 star(s)

    When the amylase is heated too much, it will stop the amylase molecules working because they will die. The optimum temperature for enzymes is about 37�C because this is body temperature, and this will produce the best results. Variables: * Temperature - The changed will be changed during this experiment. I will be changing the temperature at 5�C intervals starting at 20�C. * Time - The time taken to break to break the starch down according to the temperature will be recorded. Method: 1) The spotting tile will have the different temperatures of the amylase written on.

    • Word count: 591
  9. Marked by a teacher

    To investigate the effect of temperature on the enzyme catalase.

    3 star(s)

    7.Take the first conical flask containing the celery extract; arrange the apparatus as above and empty the syringe into the flask closing the 3-way tap start the stopwatch. 8.Measure the volume of oxygen released every 30 seconds for 2 minutes or until it is constant. 9.Repeat the experiment at 15, 35, 45 and 55�C. 10.Record the results in a suitable results table. Gas syringe (collect O2) Boss & Clamp 3-way tap Syringe (Contain catalase) Bung Clamp & boss Conical flask (Contain hydrogen peroxide)

    • Word count: 1317
  10. Marked by a teacher

    The Effect Of pH On Invertase Activity.

    3 star(s)

    Furthermore, there is a most favorable pH for enzyme - the point where the enzyme is most active. This point is known as the optimal pH. The aim of this experiment is to find out the range of pH which invertase is effective. Method This experiment was based on the premise that activity of invertase will be affected by different pH. Benedict solution was used as an indicator to determine whether the invertase had been denatured or not. If invertase was not denatured, glucose and fructose were produced. Benedict solution then would react with glucose and change its colour from blue to red.

    • Word count: 852
  11. Marked by a teacher

    To determine the effect of Detergent on the Permeability of Cell Membranes.

    3 star(s)

    They can be cationic or anionic. They exist in solution as the hydrophobic regions on the inside and hydrophilic regions on the outside make then soluble. They are able to penetrate lipids and make them soluble in water. The phospholipids in the cell membrane, as explained earlier also have long hydrophobic (non-polar) side chains and a polar (hydrophilic) head but they are arranged in a bilayer with the polar heads on the outside and the hydrophobic tails directed inwards. If a detergent comes into contact with the cell membrane, the non-polar, hydrophobic side chain of the detergent molecule penetrates and is taken up by the bi-layer of the cell membrane, and the polar head repels the individual phospholipids.

    • Word count: 3933
  12. Marked by a teacher

    To investigate the effect of Diastase on Starch

    3 star(s)

    Research in to Enzymes Enzymes are biological catalysts made up from protein that control vital biological processes. As we know catalysts are substances that speed up a rate of a reaction without itself being used up. An enzyme has an active site, which has a unique shape into which only a substrate of the exact same unique shape can fit. When this substrate fits into the active site it forms an enzyme-substrate complex. Enzymes can be denatured at certain conditions. These conditions are high temperatures and extreme levels of pH. The bonds that hold enzymes together are quite weak and so are easily broken by the above conditions.

    • Word count: 1325
  13. Marked by a teacher

    The effect of amylase concentration on the breakdown of starch

    3 star(s)

    Because the thing I am trying to test in the effect of the concentration of the enzyme, the only thing that I should be changing in each experiment is the concentration of the enzyme and nothing else. This will make all of the tests identical (apart from the enzymes concentration) which means the experiment should be accurate and fair. Because of this any differences in the results of my experiment I will be able to put down to the concentration of the enzyme.

    • Word count: 2298
  14. Marked by a teacher

    The Effect Of Temperature On Trypsin Enzymes

    3 star(s)

    The active site is an area on the surface of an enzyme where the substrate binds to and then the enzyme helps break up the substrate. An active site is for a specific substrate only and the shape of the active site is complimentary to the shape of the substrate. The diagram below should help explain this. Safety - Wear safety goggles because it could be dangerous if any substances were to make contact with your eyes. - Have something ready to wipe up any spillage's.

    • Word count: 1535
  15. Marked by a teacher

    Enzyme Investigation

    3 star(s)

    At first the rates increase, but when the enzymes begin to approach the maximum rate at which it can work (make the products), the effects of increasing substrate concentration goes away, because the enzymes are working at full pace and more substrate is useless. Biology Coursework Enzyme Concentration: Prediction: Reason - I predict that an increase in the concentration of urease will lead to a corresponding increase in the rate of reaction up to a point. For when there is enough enzymes to hold every molecule of substrate, an increase in enzyme concentration will have no effect.

    • Word count: 1319
  16. Marked by a teacher

    The Effect of pH on Pectinase

    3 star(s)

    Commercial pectinase may contain cellulase and other cell wall degraders. Pectin, which is found inside the apple puree I will be testing the pectinase on, can form gels that will bind up liquids. They do this by binding water. However they can only do this when the pectin molecules are very large, for example in fruits such as apples. In fruits pectin naturally functions as a type of 'glue' to help hold the cell wall together. The middle lamella in plant cells, which is between two cells, is densely packed with pectin, indicating that pectin helps hold cells together.

    • Word count: 3495
  17. Peer reviewed

    The effect of drugs on the nervous system

    5 star(s)

    The PNS receives thousands of sensory inputs and transmits them to the brain via the spinal cord. The brain will then process this information, discarding around 99% of it as unimportant. After this sensory information has been processed, areas of the nervous system generate nerve impulses to organs or tissue and form a suitable response. As influences from chemicals are able to affect how the nervous system functions, it can be assumed that chemicals such as drugs are potentially able to change the way an organism functions. Whilst our knowledge of different regions of brain function and neurotransmitters within the brain is limited, explanations involving the mechanisms of drugs may be vague.

    • Word count: 923
  18. Peer reviewed

    The Function and Structure of Lipids in Living Organisms

    4 star(s)

    Fatty acids can be saturated or unsaturated depending on their carbon bonding and can be told apart easily because of their state at room temperature, ether solid or liquid. Saturated fatty acids are made up of hydrogen, oxygen and carbon, the carbon in the saturated fatty acid has single bonds and it is bonded to the maximum number of atoms that it can bond with. Because of this it is a strait chain which means that it can be closely packed with other chains which means that it is a solid at room temperature.

    • Word count: 977
  19. Peer reviewed

    Effect of enzyme concentration on rate of reaction

    4 star(s)

    The shape of the active site is determined by the 3D structure of the enzyme as aforementioned. The 3D structure is dependant the bonds in the protein molecule that are affected by the enzyme's primary structure. Enzyme work by lowering the activation energy required for a certain reaction to take place. Activation energy is the minimum energy that must be supplied (usually in the form of heat) to chemicals before a reaction can take place. Image 1: Enzyme lowers the activation energy needed for a reaction to take place3 The basic mechanism of an enzyme is that the substrate molecules bind to the enzyme to form an enzyme-substrate complex.

    • Word count: 4053
  20. Peer reviewed

    Determination of Vitamin C in food

    4 star(s)

    The titration method takes advantage of the ability of Iodine to oxidise Vitamin C. Iodine is relatively insoluble, but this can be improved by binding to iodide to form triiodide: I2 + I- <--> I3- Triiodide oxidizes vitamin C to form dehydroascorbic acid: C6H8O6 + I3- + H2O --> C6H6O6 + 3I- + 2H+ As long as vitamin C is present in the solution, the triiodide ion is converted to the iodide ion very quickly. However, when the all the vitamin C is oxidized, iodine and triiodide will be present.

    • Word count: 1478
  21. Peer reviewed

    Compare the structures of a cell to those of a city. Although vast differences in size, organization and infrastructures seem alike, the cell and the city may share a lot in common.

    4 star(s)

    A denser region inside the nucleus is called the nucleolus which is the site of RNA and ribosomal synthesis. Surrounding the nucleus is a nuclear envelope which contains many pores allowing it to communicate with the cytosol by permitting the passage of large molecules. (5) Analytically, in a city the control centre is the city hall, where a Mayor works and along with the elected party runs the whole city, creating rules and legislation, administering public policies and regulating industries.

    • Word count: 2191
  22. Peer reviewed

    Skeletal System. What is the difference between the axial and appendicular skeleton? What is the difference between ligaments and tendons? How are bones important in maintaining homeostasis?

    4 star(s)

    The human endoskeleton skeleton is a combination of cartilage and 206 bones that make up the skeletal system. It is organized into two basic units: the axial skeleton and the appendicular skeleton. The axial skeleton supports the axis or trunk of the body and includes the skull, enclosing and protecting the brain, vertebrae of the spinal column, enclosing the spinal cord and the rib cage, around the heart and lungs. It includes 80 bones.

    • Word count: 428
  23. Peer reviewed

    Cell Structure

    4 star(s)

    * Contains molecules for the light dependant stage of photosynthesis * Synthesis of ATP * Enzymes required for conversion of CO2 and water to carbohydrate * Temporary storage of carbohydrate Sacs called thylakoids formed by membranes Stroma contains enzymes plants, protists (rare kleptoplastic organisms)

    • Word count: 536
  24. Peer reviewed

    Features of Lungs & Tissues

    4 star(s)

    * Macrophages that destroy foreign material, such as bacteria. Where they are located? Type II cell is located in the alveolar epithelium. Macrophage cell is found in the pulmonary alveolus, near the pneumocytes, but separated from the wall and type I cell is located beneath the plasmalemma . Main organelles within the cell? Organelles found within the cells are as follows: Nucleus, Mitochondria, Lysosomes, Vacuole, Ribosomes and Cell membrane. Their function? Nucleus controls the cell's activity. Mitochondrion produces energy. Lysosomes is capable of breaking down all types of biological polymers-proteins, nucleic acids. Vacuole is the storage.

    • Word count: 1109
  25. Peer reviewed

    Explain how the structure of collagen and haemoglobin are related to their function.

    4 star(s)

    Furthermore, the triple helix is held together by an extensive network of hydrogen bonds. Covalent cross-links are also present within tropocollagen molecules to impart the collagen fibre with strength and rigidity. Proline with its ring structure also helps in stabilizing the rigid three-stranded collagen helix. Beside, the tropocollagen molecules are arranged in a staggered manner with each other. This confers collagen greater strength. Secondly, it is insoluble in water. This is due to the large molecular size of the tropocollagen molecule and the nature of the amino acid residues. Each of the three polypeptide chains in a collagen molecule is about 1000 amino acid residues long and they coil up into a collagen helix.

    • Word count: 612

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