Microscope Lab Worksheet PDF

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Microscope Lab Worksheet. Virtual Yogurt lab...

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Introduction to the Microscope and Laboratory Reporting Preparation Instructions: Complete the worksheet for up to 20 points possible. Step 1: Learn about variation in the size of samples viewed with a microscope. Gain an understanding of the measurement scale utilized. Go to Learn Genetics: Cell Size and Scale. Move the slider from left to right to see the various sizes of the samples. Write down the size of each of the samples below. (1 point each) a. Human Egg ____130µm______ b. Sperm ____60 x 5µm______ c. Skin Cell ______30µm____ d. Blood Cell ____8µm______ e. Chromosome _____7µm_____ f. Mitochondria _____4 x 0.8µm_____ g. Antibody _____12nm_____ h. tRNA ____7nm______ i. Glucose _____900pm_____ j. HIV _____130nm_____ k. E. coli ____3 x 0.6µm______ l. Lysosome ____1 µm______

Step 2: Complete a virtual lab activity to learn about the different parts of the microscope and how to operate it. If the links do not open directly, copy and paste into your web browser. Suggested browser for this activity is Firefox or Safari. This virtual lab requires Flash Player. Go to Click to: Go to: Click to:

Prepare virtual slides for analysis View the slide using a microscope

Step 3: Outline what you would include if writing a formal lab report describing the experiment completed in Step 2. Include the following sections in your outline: • Introduction • Hypothesis • Methods • Results • Discussion • Conclusion .

Fill in the outline below: You may add or subtract from the specific number of items in each section of the outline. I. Introduction – What was the purpose of the experiment? (1 pt) a. To determine if yogurt samples are contaminated b. To determine what kind of bacteria contaminated the yogurt c. To determine the source of the contamination II. Hypothesis – Indicate what you anticipate will be the result of the experiment. (1 pt) a. The yogurt is contaminated due to having a suspicious appearance with bubbles at the bottom of the jar it is stored in. This can mean undesirable bacteria is present in the yogurt. Further investigation is needed to confirm contamination and where the yogurt became contaminated. III. Methods – Describe the materials and methods that were used to complete the experiment. (2 pts) a. The area is wiped down with 70% ethanol solution to sanitize the work area. b. The bunsen burner is then lit with a striker, to sanitize inoculating loops and help maintain a sterile working environment. c. Diluent (Phosphate Buffered Saline) is placed in a test tube (1mL) to dilute the yogurt so it can be better seen on a slide. d. The inoculation loop is used after being sterilized by the bunsen burner (placed in flame until “red hot” then cooled) e. The inoculation loop is inserted deep into the yogurt jar to obtain a small sample of the yogurt that is suspected to be contaminated. Then the loop is placed in the test tube with the diluent, then is shaken for 5-10 seconds. f. The inoculation loop is then sterilized again, and is used to obtain the sample from the test tube. (2 loops full) Then is placed on the slide.

g. The slide is tilted to spread the sample to about the size of a penny, then the slide is passed over the bunsen burner to dry out the bacteria to prevent them from being washed away. h. The sample is then covered in crystal violet solution to stain gram positive bacteria (sits for 60 seconds) then is rinsed. i. The sample is covered in Gram’s iodine (sits for 60 seconds), this fixes the dye to the cell walls of the bacteria, then it is rinsed. j. 95% alcohol solution is applied to the slide to wash off excess dye. (Only sits for no more than 30 seconds) k. Safranin is applied to the slide to stain gram negative bacteria (sits for 60 seconds) then is rinsed. l. Slide is dried using highly absorbent bibulous paper by dabbing. m. Microscope is used on the 10x objective first then increased to the 40x objective. n. 100x objective is then used with oil applied to the slide to see the bacteria’s shape and color to decipher whether undesirable bacteria is present. IV. Results – Indicate the observations made and results of the experiment. (1 pt) a. Bacteria is seen in the color of pink and purple on the sample slide at 1000x magnification with oil immersion lens. b. Purple stained bacteria are normally found in yogurt and are safe to consume. c. Pink stained bacteria indicate that the yogurt sampled from is contaminated with undesirable bacteria. V. Discussion – Was your hypothesis correct? Why or why not? How do the results of the experiment relate to concepts being discussed in class? (2 pts) a. Hypothesis was correct. The bubbles in the bottom of the jar were indicative of bacterial growth. b. These results can be compared to the material we are learning in class about molecules and their reactions. c. The undesirable bacteria causes a chemical reaction which the bacteria generate gasses in the bottom of the jar, that in turn, create the bubbles seen.

d. The whey and water are seen separating in the contaminated yogurt, which can be compared to a chemical reaction that causes one of the elements to become hydrophobic. Vi. Conclusion – Summarize what was learned. Are there questions you still have? (1 pt) In conclusion, we learned that gram staining is used to find and identify bacteria. This is beneficial in the world of food processing to make sure that contamination is prevented, and if it can’t be prevented that the contaminated food can be recalled to prevent food-borne illnesses.

Step 4: DO NOT WRITE AN ACTUAL LAB REPORT FOR THIS ACTIVITY. Save this file with your answers and outline completed. Submit via IvyLearn Module....