Presentation on theme: "Agenda Turn in Pre-lab #4: biomolecules Lab Quiz #3 (pH)"— Presentation transcript:
1Agenda Turn in Pre-lab #4: biomolecules Lab Quiz #3 (pH) 2nd two Microworlds due at the end of the lab today.Samples for Microwords today include thin & squished slices of banana and potato (peanut does not work as it is baked).
2Microworlds Each Microword is worth 5 pts totaling 60 points. Turn in the graded and ungraded Microworlds totaling 12 at the end of the term, due date is the last lab.Field Sizes40X = 5mm100X = 2mm400x = 0.5mm = 500μm1000x = 0.2mm = 200μmState/label what you’re estimating the size ofLabel at least 2 structuresMore than 2 gives you a safety cushionAnimal cells don’t have a cell wall!Bacteria don’t have a nucleus!You normally can’t see the cell membrane of a plant cell.
3Lab 3: Testing for biomolecules Testing for the presence ofCarbohydratesLipidsProteinsOr all the biological molecules except for nucleic acids
5Testing for Reducing Sugars BENEDICT’S REAGENTTests for the presence of any monosaccharide & some disaccharidesPositive results are: a change from clear blue to a cloudy or opaque green, yellow, orange or red.
6BENEDICT’S REAGENTTests for all monosaccharides but only some disaccharidesDoes not detect sucroseTube 1 = Glucose (is a positive control)What could be our negative control (a tube that will not react)?
7Testing for Carbohydrates Add 2 mls of your stock solution to 2 mls of Benedicts reagent.Benedicts Test uses a boiling water bath, Heat tubes for 5 minutes and observe.Must wear goggles f/ this test! (Boiling Benedicts is an eye hazard!)Dispose of Benedict’s waste in appropriate container (heavy metals harm the environment).
8Testing for Carbohydrates IODINE REAGENT tests for the presence of starch (what do we know about starch?
9Testing for Carbohydrates TUBE 1 = Starch (from potato) as a positive controlWhat can we use as a negative control?In Ex4. change from adding 5 drops to 3 drops of iodine and observe immediately. (5 drops is rather dark even in water.)NOTE: Iodine stains badly
10Testing for LipidsPAPER TEST – paper will look translucent and greasy in the presence of lipids (KFC napkins)Do early if you want it to dry (takes ~15 min)You can usually tell immediately just by holding it up to the light
11Testing for ProteinsBIURET REAGENT reacts with proteins to give a purple or pinkish colorLonger polypeptides give a darker purple, shorter are pinker
12Testing for Proteins TUBE 1 = Egg Albumen (positive control) TUBE 2 = negative control (?)Other tubes from your stock solutionsAdd 1mL (about two droppers FULL) of Biuret to the tube. Let stand for ~ 2 min and then record your results.Dispose of Biuret’s waste in appropriate container (contains the heavy metal Cu).
13Testing for biomolecules in food This lab was re-written and is not very clear.In Ex. 1 you set up your stock cultures of food.If the food is a liquid, just add the proper amount (about 6 ml) to each tube.If the food is a solid, mince 1-2 cm3 very finely, add it to a tube & mix with ~9 mL distilled water.Use these stock cultures to set up Ex. 2, 4-5. Note, for the lipid test, Ex. 3, crush solid food & add undiluted liquid foods directly to the paper.
14Testing for biomolecules in food For Ex. 2,& 5, add 2 ml of your stock solutions to the tubes for that Exercise. For Ex. 4, use 1 ml of your stock solutions. (For example, if you want to test banana for the presence of reducing sugars in Ex. 2, add 2 mls of your stock solution to the banana tube of Ex. 2.)You can greatly speed up this lab by dividing and conquering! When you are waiting for a test, start setting up for the next test or start cleaning.
15Safety:Wear GOGGLES at all times when people are working with hazardous chemicals (Benedict’s Solutions)Debriefing:This lab has a debriefing study guide.After completing the lab, check it out to see how well you understood the lab!
16CLEAN UP REALLY WELLWash your test tubes BEFORE you start – this lab gets cross-contaminated OFTENWash out all test tubes using test tube brush when you’re done, get the goo out! Put tubes away upside-down in drawer to drainMake sure your tray is returned to its original position & looks neat and clean up the food table! No food scraps lying around.Attendance points today, but a penalty if you leave a mess!