Onion & Cheek Cell Lab - Weebly



AP BIOLOGY 2016-17September 16, 2016Today’s Agenda (Day 20)Housekeeping:Homework Check Ch 2 & 3 Reading Guides Virtual Labs Write-Ups (Solutions and Cells)Class Activity Lab Safety Quiz Lab: Onion and Cheek CellsHOMEWORK:Read Chapter 7 and 8 of Biology (2009) – see emailed resourceRead Chapter 4 – Carbon and Molecular Diversity of LifeChapter 4 Reading GuideStudy for Lab Safety Quiz Complete Virtual Labs (Cells in Different Solution Concentrations AND Onion and Cheek Cells)REMINDERS:Lab Safety Quiz Friday, Sept. 16Ch 4 Reading Guide Monday, Sept. 19AP BIOLOGY 2016-17Lab ActivityOnion & Cheek Cell LabIntroduction: Many things that are viewed using a microscope, particularly cells, can appear quite transparent under the microscope. The internal parts of the cells, the organelles, are so transparent that they are often difficult to see. Biologists have developed a number of stains that help them see the cells and their organelles by adding color to their transparent parts. Today we will be using methylene blue.Purpose: In this lab, you will prepare and observe cells from both a plant (onion) and an animal (your own cheek!!).Materials: You will need the following materials: ? glass slide ?coverslip ?toothpick ?iodine (or methylene blue) stain ?paper towel?onion tissue ?your own cheek.Assignment: Your assignment is to prepare and observe as many samplings of both types of cells as possible and sketch them in the spaces provided on the back of this sheet. You are also required, on your sketch, to label any visible parts or organelles, as well as list what magnification you used. Lastly, you need to write down any other interesting observations (difference between cells, cool things you saw, etc.) on this sheet or another piece of paper.Procedure:For the onion cell:Get a glass slide and place a small amount of onion tissue in the center.Add a small drop of iodine/methylene blue stain directly to the tissue. Careful, iodine is not toxic, but it will stain both your skin and your clothes.Place a coverslip over the newly stained tissue.Put the slide on the microscope, making sure the microscope is onLOW POWER!Go through the three powers (Be careful when changing to higher objective lenses as it may touch glass slide and crack it!), focusing each time, making sketches, and writing down observations. Be sure to write what magnification you used for each sketch.Be sure to label any parts you see. You may be able to see: cell wall, nucleus, and cytoplasm.For the cheek cell:Clean off your slide from above or get a clean slide (in case you want to compare them later.Add a drop of iodine/methylene blue to the empty slide.Using the blunt (not sharp) end of a toothpick, gently scrape the inside of your cheek.Swirl the toothpick end, now with cheek cells, in the iodine/methylene blue drop on the slide.Place a coverslip on the stained cheek cells.Observe under the microscope like you did for the onion cell above.Don’t forget to clean up!!Analysis:The light microscope used in this lab is not powerful enough to view other organelles in the cheek cell. Fill out the table below to show what we could and could not see through our microscope.Cheek CellsWhat organelles COULD be seen?What organelles COULD NOT be seen?Onion CellsWhat organelles COULD be seen?What organelles COULD NOT be seen?Data:In the circles, on the next page, draw what you see through the microscope. On the High magnification, label the nucleus, cytoplasm, and cell membrane for EACH of the cheek and onion cells. Draw you cells to scale and include the magnification (scanning, low, high).Conclusion:In complete sentences, answer the following questions.What type of cell did the cheek cell represent? What about the onion cell?What were the shapes of the two different type of cells?Why did we have to stain the cells?AP BIOLOGY 2016-17Reading GuideChapter 4: Carbon and the Molecular Diversity of Life Concept 4.1 Organic chemistry is the study of carbon compounds 388620077877 Study this figure of Stanley Miller’s experiment to simulate conditions thought to have existed on the early Earth. Explain the elements of this experiment, using arrows to indicate what occurs in various parts of the apparatus. What was collected in the sample for chemical analysis? What was concluded from the results of this experiment? Concept 4.2 Carbon atoms can form diverse molecules by bonding to four other atoms Make an electron distribution diagram of carbon. It is essential that you know the answers to these questions: How many valence electrons does carbon have? How many bonds can carbon form? b. What type of bonds does it form with other elements? Carbon chains form skeletons. List here the types of skeletons that can be formed. What is a hydrocarbon? Name two. Are hydrocarbons hydrophobic or hydrophilic? In Chapter 2 you learned what an isotope is. Since students often confuse this word with isomer, please define each term here and give an example. Definition Example isotope isomer 3962400-52424Use this figure to identify the three types of isomers. For each type, give a key character and an example. Give one example of enantiomers that vary in their pharmacological effect. Concept 4.3 A small number of chemical groups are key to the functioning of biological molecules Here is an idea that will recur throughout your study of the function of molecules: Change the structure, change the function. You see this in enantiomers, you will see it in proteins and enzymes, and now we are going to look at testosterone and estradiol. Notice how similar these two molecules are, and yet you know what a vastly different effect each has. Label each molecule in the sketch below, and circle the differences. Define functional group. There are seven functional groups. Complete the following chart. Hydroxyl Carbonyl Carboxyl Amino Sulfhydryl Phosphate Methyl Structure Example Functional Properties You will need to master the chart and the information in it. Using the functional groups above, see if you can answer the following prompts: –NH2 41910007010 Can form cross-links that stabilize protein structure Key component of ATP Can affect gene expression CH3 Is always polar Determines the two groups of sugars Has acidic properties –COOH Acts as a base Circle and identify three functional groups in the molecule shown above. Testing Your Knowledge: Self-Quiz Answers Now you should be ready to test your knowledge. Place your answers here: 1._______ 2._______ 3._______ 4._______ 5._______ ................
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