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Agenda 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.

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Presentation on theme: "Agenda 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."— Presentation transcript:

1 Agenda 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).

2 Microworlds 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 Sizes – 40X = 5mm – 100X = 2mm – 400x = 0.5mm = 500μm – 1000x = 0.2mm = 200μm State/label what you’re estimating the size of Label at least 2 structures – More than 2 gives you a safety cushion – Animal 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.

3 Lab 3: Testing for biomolecules Testing for the presence of – Carbohydrates – Lipids – Proteins – Or all the biological molecules except for nucleic acids

4 Testing for Carbohydrates Monomers = monosaccharides – Glucose – Fructose Disaccharides – Sucrose = glucose + fructose Polysaccharides – Starch (plants) – Glycogen (animals)

5 Testing for Reducing Sugars BENEDICT’S REAGENT Tests for the presence of any monosaccharide & some disaccharides Positive results are: a change from clear blue to a cloudy or opaque green, yellow, orange or red.

6 BENEDICT’S REAGENT Tests for all monosaccharides but only some disaccharides Does not detect sucrose Tube 1 = Glucose (is a positive control) What could be our negative control (a tube that will not react)?

7 Testing 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).

8 Testing for Carbohydrates IODINE REAGENT tests for the presence of starch (what do we know about starch?

9 Testing for Carbohydrates TUBE 1 = Starch (from potato) as a positive control What 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

10 Testing for Lipids PAPER 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

11 Testing for Proteins BIURET REAGENT reacts with proteins to give a purple or pinkish color Longer polypeptides give a darker purple, shorter are pinker

12 Testing for Proteins TUBE 1 = Egg Albumen (positive control) TUBE 2 = negative control (?) Other tubes from your stock solutions Add 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).

13 Testing 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 cm 3 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.

14 Testing 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.

15 Safety: 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!

16 Wash your test tubes BEFORE you start – this lab gets cross-contaminated OFTEN Wash out all test tubes using test tube brush when you’re done, get the goo out! Put tubes away upside-down in drawer to drain Make 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!


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