specification - cells and movement across membranes

    Cards (41)

    • cytoplasm: site of most cell reactions
    • nucleus: contains chromosomes which carry genetic information and controls the activities of the cell
    • mitochondrion: site of aerobic respiration
    • cell wall containing cellulose: structural support for plant cells
    • chloroplast: site of photosynthesis
    • vacuole: contains a watery sugar solution (sap), a swollen vacuole pushes the rest of the cell contents against the cell wall, making the cell firm
    • Calculation of total magnification is achieved by the multiplication of the power of the eyepiece lens by the power of the objective lenses.
    • a slide is prepared by staining
    • staining allows more detail of the cell to be seen
    • the limitations of light microscopy in studying cell structure: restriction in maximum magnification
    • a simple comparison with the electron microscope: greater magnification but can only be used to view dead tissue
    • Specialised cells are more efficient in performing specific functions than non-specialised cells.
    • tissues are groups of similar cells with a similar function and organs may comprise several tissues performing specific functions
    • organs are organised into organ systems, which work together to form organisms
    • diffusion as the movement of substances down a concentration gradient
    • the cell membrane is selectively permeable, and will allow some substances to pass through but not others
    • Visking tubing is an artificial selectively permeable membrane:
      • smaller molecules like water and glucose pass through its microscopic holes
      • larger molecules like starch and sucrose cannot pass through it
    • diffusion as a passive process, allowing only certain substances to pass through the cell membrane in this way, most importantly oxygen and carbon dioxide
    • osmosis as the diffusion of water through a selectively permeable membrane from a region of high water (low solute) concentration to a region of low water (high solute) concentration
    • active transport as an active process whereby substances can enter cells against a concentration gradient
    • Respiration provides the energy required in the form of ATP
    • enzyme control of chemical reactions in cells; enzymes are proteins made by living cells, which speed up/catalyse the rate of chemical reactions
    • Enzymes are involved in all metabolic reactions building large molecules from small ones as well breaking down large molecules into small ones.
    • different enzymes are composed of different amino acids linked to form a chain which is then folded into a specific shape
    • Carbohydrase - Carbohydrate - Simple sugar, glucose
    • Amylase - Starch - Simple sugar, glucose
    • Protease - Protein - Amino acid
    • Lipase - Fat (lipid) - Glycerol and fatty acids
    • Enzymes and substrates collide to form enzyme-substrate complexes. The substrates are broken down (or in some cases built up). The products are released. The enzyme is free to act again.
    • term optimum as a particular condition (such as temperature or pH) at which the rate of enzyme action is greatest
    • Increased temperature results in increased collisions between enzymes and substrates.
    • In a denatured enzyme the specific shape of the active site is destroyed and can no longer bind with its substrate, so no reaction occurs
    • Cheek Cells:
      1. Put a drop of methylene blue on a glass slide.
      2. Gently rub the inside of your cheek with a cotton bud.
      3. Wipe the end of the cotton bud in the drop of methylene blue on the glass slide.
      4. Place the cotton bud in the beaker of disinfectant.
      5. Use the mounted needle to gently lower a coverslip onto the glass slide.
      6. Using a light microscope, examine the slide using the 10 objective lens.
      7. Use the x40 objective lens to identify some of the cell structures.
      8. Draw a cell diagram. Identify and label: cell membrane, cytoplasm and nucleus
    • Onion Cells:
      1. Using forceps, peel a thin layer of epidermis from the inside of a freshly cut onion piece.
      2. Lay the epidermis onto a glass slide.
      3. Add a drop of iodine solution to the onion epidermis on the glass slide.
      4. Use the mounted needle to gently lower a coverslip onto the glass slide.
      5. Using a light microscope, examine the slide using the 10 objective lens.
      6. Use the x40 objective lens to identify some of the cell structures.
      7. Draw a cell diagram. Identify and label: cell wall, cell membrane, cytoplasm and nucleus.
    • Analysis of Examination of animal and plant cells using a light microscope and production of labelled scientific diagrams from observation -
      1. Calculate the total magnification of the image seen by multiplying the power of the objective lens by the power of the eyepiece.
      2. Your teacher will tell you the actual size of the cell, calculate the magnification of your diagram
    • Hazards of Examination of animal and plant cells using a light microscope and production of labelled scientific diagrams from observation
      1. Hazard - Methylene blue is harmful and/or irritant. Risk - Splashing on to hand/skin/you whilst using. Transfer from hand in to eye when placing on slide. Control measure - Wash off/ wear gloves OR Wear eye protection.
      2. Hazard - Coverslips/ mounted needles are sharp. Risk - Coverslip/mounted needle could cut skin when placing on slide. Control measure - Only use mounted needle by handle/only handle coverslip by the sides.
      1. Hazard - Cheek cells are a biohazard. Risk - Transfer of infection from cheek cell to other people when handling. Control measure - Only handle samples from your own body. After use, hygienically dispose of cotton buds and slides in a disinfectant such as Milton or Virkon.
    • Iodine is an indicator that turns blue/black when starch is present, but is otherwise brown.
    • Method of Investigation into factors affecting enzyme action
      1. Measure 10cm3 of 1% starch solution into a test tube
      2. Measure 2cm3 of 10% amylase solution into a second test tube
      3. Place both tubes into a water bath set at 20ºC for 3 minutes
      4. Place a drop of iodine in six wells of a spotting tile
      5. Remove both test tubes from the water bath, pour the amylase into the starch/iodine solution and start the stopwatch
      6. Immediately, use the dropping pipette to place one drop of the mixture onto the first drop of iodine, record the colour of the solution
      7. Repeat step 6 every minute for five minutes
      8. Repeat steps 1-7 at 30ºC, 40ºC, 50ºC, 60ºC
    • Analysis of Investigation into factors affecting enzyme action -
      1. Use your observations to reach a conclusion regarding the effect of temperature on enzyme action.
      2. Evaluate your method and suggest possible improvements