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UMUC Biology 102/103 Lab 3: Cell Structure and Function




Question;Your Full Name;UMUC Biology 102/103;Lab3:Cell Structure and Function;INSTRUCTIONS;?;On your own and without assistance, complete thisLab3AnswerSheet electronically;and submit it via theAssignments Folder by the date;listedintheCourse Schedule (underSyllabus).;?;To conduct your laboratory exercises, use the;Laboratory Manuallocated under Course Content. Read the;introduction and the directions for each exercise/experiment carefully before;completing the exercises/experiments and answering the questions.;?;Save your Lab3AnswerSheet in the following format: LastName_Lab3 (e.g.;Smith_Lab3).;?;You should;submit your documentas a Word;(.doc or.docx) or Rich Text Format (.rtf) file for best compatibility.;Pre-Lab;Questions;Identify;three major similarities and differences between prokaryotic and;eukaryotic cells.;Where;is the DNA housed in a prokaryotic cell? Where is it housed in a;eukaryotic cell?;Identify three structures which provide;support and protection in a eukaryotic cell.;Experiment;1: Cell Structure and Function;The structure of;a cell dictates the majority of its function. You will view a selection of;slides that exhibit unique structures that contribute to tissues function.;Materials;Onion (allium) Root Digital Slide Images;Procedure;Examine the onion root tip digital;slide images on the following pages. Then, respond to the Post-Lab;Questions.;Onion Root Tip: 100X;Onion Root Tip: 1000X;Onion Root Tip: 1000X;Onion Root Tip: 100X. Each dark circle indicates a different nucleus.;Onion Root Tip: 1000X;Post-Lab Questions;1. Label each of;the arrows in the following slide image: A=Chromosomes;B=Nucleus, C=Cytoplasm, D=Cell Wall;2.;What;is the difference between the rough and smooth endoplasmic reticulum?;3.;Would;an animal cell be able to survive without a mitochondria? Why or why not?;4.;What;could you determine about a specimen if you observed a slide image showing the;specimen with a cell wall, but no nucleus or mitochondria?;5.;Hypothesize;why parts of a plant, such as the leaves, are green, but other parts, such as;the roots, are not. Use scientific reasoning to support your hypothesis.;Experiment;2: Osmosis - Direction and Concentration Gradients;In this;experiment, we will investigate the effect of solute concentration on osmosis.;A semi-permeable membrane (dialysis tubing) and sucrose will create an osmotic;environment similar to that of a cell. This selective permeability allows us to;examine the net movement of water across the membrane. You will begin the;experiment with a 30% sucrose solution, and perform a set of serial dilutions;to create lower concentration solutions. Some of the sucrose concentrations;will be membrane permeable, while others will not be permeable (can you determine;why this is?).;Materials;(3) 250 mL;Beakers;(1) 10 mL Graduated Cylinder;(1) 100 mL Graduated Cylinder;Permanent Marker;*8 Rubber Bands (2 blue, 2 green, 2 red;and 2 yellow);60 g Sucrose (Sugar) Powder, C12H22O11;4 Waste Beakers (any volume);*Paper Towels;*Scissors;*Stopwatch;*Water;*(4) 15 cm. Pieces of Dialysis Tubing;*Contains latex. Please handle wearing safety;gloves if you have a latex allergy.;*You Must Provide;*Be sure to measure and cut only the length;you need for this experiment. Reserve the remainder for later experiments.;Procedure;Use the permanent marker to label the;three 250 mL beakers as 1, 2, and 3.;Cut four strips of dialysis tubing;each 15.0 cm long. Fill Beaker 3 with 100 mL of water and submerge the;four pieces of dialysis tubing in the water for at least 10 minutes.;After 10 minutes, remove one piece of;tubing from the beaker. Use your thumb and pointer finger to rub the;tubing between your fingers, this will open the tubing. Close one end of;the tubing by folding over 3.0 cm of one end (this will become the;bottom). Fold it again and secure with a yellow rubber band (use;Tie a knot in the remaining dialysis;tubing just above or just below the rubber band. This will create a seal;and ensures that solution will not leak out of the tube later in the;experiment.;To test that no solution can leak out;add a few drops of water to the tubing and look for water leakage. If any;water leaks, tighten the rubber band and/or the knot in the tubing. Make;sure you pour the water out of the tubing before continuing to the next;step.;Repeat Steps 4 - 5 with the three;remaining dialysis tubes, using each of the three remaining rubber band;colors.;Reconstitute the sucrose powder;according to the instructions provided on the bottle?s label (your kit;contains 60 g of sucrose in a chemical bottle). This will create 200 mL;of a 30% stock sucrose solution.;Use Table 2 to create additional;sucrose solutions that are 30%, 15% and 3% concentrated, respectively. Use;the graduated cylinder and waste beakers to create these solutions. Set;these solutions aside.;Table 2: Serial Dilution Instructions;Sucrose Solution;mL of Stock Sucrose Solution;Needed;mL of Water Needed;30%;10;0;15%;5;5;3%;1;9;3%;1;9;Pour 150 mL of the remaining stock;sucrose solution into Beaker 1.;Use some of the remaining stock;sucrose solution to create an additional 200 mL of a 3% sucrose solution;into Beaker 2.;Hint: Use your;knowledge of serial dilutions to create this final, 3% sucrose solution.;Measure and pour 10 mL of the;remaining 30% sucrose solution into the dialysis bag with the yellow;rubber band. Seal the top of this tubing with the remaining yellow rubber;band.;Measure and pour 10 mL of the 15%;sucrose solution in the bag with the red rubber band, and seal the top of;the dialysis tubing with the remaining red rubber band. 10 mL of the 3%;sucrose solution in the bag with the blue rubber band, and seal the;dialysis tubing with the remaining blue rubber band. The final 10 mL of 3%;sucrose solution in the bag with the green rubber band. Seal the dialysis;tubing with the remaining green rubber band.;Verify and record the initial volume;of solution from each bag in Table 3.;Figure 8: The dialysis bags;are filled with varying concentrations of sucrose solution and placed in one;of two beakers.;Place the yellow, red, and blue banded;tubing in Beaker 2. Place the green banded tubing in Beaker 1 (Figure 8).;Hypothesize whether water will flow in;or out of each dialysis bag. Include your hypotheses, along with;supporting scientific reasoning in the Hypotheses section at the end of;this procedure.;Allow the bags to sit for one hour.;While waiting, pour out the water in the 250 mL beaker that was used to;soak the dialysis tubing in Step 1. You will use the beaker in Step 19.;After allowing the tubing to sit for;one hour, remove them from the beakers.;Carefully open the tubing. The top of;the tubing may need to be cut off/removed as they tend to dry out over the;course of an hour. Measure the solution volumes of each dialysis bag using;the 100 mL graduated cylinder. Make sure to empty and dry the cylinder;completely between each sample.;Record your data in Table 3.;Table 3: Sucrose Concentration vs. Tubing Permeability;Band Color;Sucrose %;Initial Volume (mL);Final Volume (mL);Net Displacement (mL);Yellow;Red;Blue;Green;Hypothesis;Post-Lab Questions;1. For each of the tubing pieces, identify whether the;solution inside was hypotonic, hypertonic, or isotonic in comparison to the;beaker solution in which it was placed.;2. Which tubing increased the most in volume? Explain;why this happened.;3. What do the results of this experiment this tell;you about the relative tonicity between the contents of the tubing and the solution;in the beaker?;4. What would happen if the tubing with the yellow;band was placed in a beaker of distilled water?;5. How are excess salts that accumulate in cells;transferred to the blood stream so they can be removed from the body? Be sure;to explain how this process works in terms of tonicity.;6. If you wanted water to flow out of a tubing piece;filled with a 50% solution, what would the minimum concentration of the beaker;solution need to be? Explain your answer using scientific evidence.;7. How is this experiment similar to the way a cell;membrane works in the body? How is it different? Be specific with your;response.


Paper#62722 | Written in 18-Jul-2015

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