required practicals

• what is the test for glucose?

  benedicts reagent and heat in a water bath for 2 mins
• what colour does Benedicts reagent change to and from?

  blue to brick red
• what is the test for starch?

  iodine solution
• what colour does iodine solution change to and from?

  orange to blue/black
• what is the test for proteins?

  biuret reagent
• what colour does buret reagent change to and from?

  Colorless to purple
• method for effect of pH on rate of reaction of amylase:

  1. put a test tube with starch solution and a test tube with amylase into a water batch at 37 degrees
  2. after 5 mins add the amylase solution to the starch
  3. every 30s take a drop of the mixture and test it for starch using iodine solution
  4. record how long it takes for the starch to be completely digested
  5. repeat the experiment at different pH values using different buffer solutions
• method for finding the effect of diff concs of sugar solution on plant tissue:

  1. cut some cylinders of potato tissue & measure their mass on a top pan balance making sure they're equal
  2. place the cylinders in different concs of sugar solution
  3. after abt 30 mins, remove the cylinders and measure their mass again
  4. if the cylinders change in mass, they have gained or lost water by osmosis
• method for finding the effect of light intensity on the rate of photosynthesis:

  1. place a piece of pondweed in a beaker and shine a light at it using a lamp a specific distance away
  2. record the number of bubbles of gas coming out of the pondweed in 1 min
  3. repeat this with the lamp at different distances from the pondweed
• method for finding the effect of different antibiotics on bacterial growth:

  1. inoculate a Petri dish with a culture of bacteria
  2. soak small disks of filter paper in different antibiotics
  3. using sterilised forceps, place the antibiotic discs on the surface of the agar
  4. incubate the sealed disc upside down at 25 degrees for several days