biology practicals paper 1

• how do you prepare a slide for microscope?

  Specimens must be prepared on a microscope slide to be observed under a light microscope. This must be done carefully to avoid damaging any biological specimen

  The most common specimens to observe under a light microscope are cheek cells (animal cells) and onion cells (plant cells) Stains are used to highlight structures within cells - iodine for onion cells
• Microscope practical - light microscope meathod.

  1. clip the slide onto the stage

  2. ensure the lowest powered objective lens is over the slide

  3. use the coarse adjustment knob to bring the stage up just below the lens.

  4.look down the eyepiece and gradually move the stage downwards using the knob.stop when the image is roughly in focus.
• what does the benedicts test test for


  sugars
• what does the iodine test test for


  starch
• what does the biurets test, test for

  proteins
• what does the sudan 3 test for?


  lipids
• how do your prepare the food samples?


  1. crush the food into small pieces using a petal and mortar

  2. put the food into a beaker with some distilled water.

  3. with glass rod until some of the food disolves.

  4.pour the mixture into a funnel that has been filled with filter paper.

  5. filter the mixture and what is the product left in the funnel is what you use as the food sample
• what are all carbohydrate made up of ?

  sugars
• what are the two types of sugars

  Reducing and non-reducing
• what type of sugars does benedicts test search for?

  reducing sugars
• how to test for sugar using benedicts test?

  1. prepare food sample and transfer 5cm cubed of the sample into a test tube

  2. prepare a water bath and set it to 75 degrees Celsius.

  3. once the water bath is ready add 10 drops of benedicts solution into the sample.

  4. place the sample into the water bath using a test tube holder for safety reasons and then leave the sample for 5 mintues.

  5. if no reducing sugars are present after 5 minutes the solution will stay blue. whereas if there are reducing sugars present the solution will turn into green, yellow or brick red depending on the concentration of the sugar.
• how to test for starch


  1.prepare a 5cm cubed food sample

  2. add a few drops of iodine soloution wich will turn the solution a brown orange colour.

  3. gently shake the test tube.

  if the soloution changes into a blue black colour starch is present.
• how to test for proteins


  1. add a 2cm food sample into a test tube.

  2. the add 2cm of the biuerts soloution into the test tube. this turn it blue.

  3.gently shake the test tube.

  4.if the solution contains proteins it will turn pink or purple.
• how to test for lipids?


  1. add 5cm of the sample into a test tube which is not filtered.

  2.add 3 drops of the Sudan 3 solution into the sample.

  4 gently shake the solution.

  5. if lipids are present it should get stained and after separation from water as not soluble it may turn red.
• what is thr tool useed that cuts pieces of vegitable with the same diameter

  Cork Baurer