Lab3_Chemical Composition of Cells & Cell Membranes

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Rowan University *

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Chemistry

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Feb 20, 2024

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Lab 3: Chemistry of Life Lab3_Chemical Composition of Cells & Cell Membranes Presentation Objectives: • Become familiar with the structure and function of the 4 biomolecules of life (Activity 2a) • Test for the presence of sugars (Activity 2b) • Explore how substances move in and out of cells via diffusion (Activity 2c) The Structure and Function of Biomolecules Introduction: Your body contains about 37 trillion cells. The cells of all living organisms are made up of four main groups of large biomolecules. These 4 biomolecules are: (1)Proteins (2)Nucleic Acids (which includeDNA and RNA) (3)Lipids (4)Carbohydrates You will use the information in the Lab Presentation to answer most of the questions below. Proteins: List the 6 major functions of proteins. 1-Metabolism 2- Structural Support 3- Transport Molecules 4- Immune Defense 5- Regulation 6-Motion

What are the building blocks of proteins called? Amino acids What is a polypeptide? Long chain of amino acids Lipids: Using the informationfrom the Lab PowerPoint, list the 3 major functions of lipids. 1-Long-term energy storage & insulation (fats and oils) 2-Major components of cell membranes (phospholipids, cholesterol) 3-Steroid hormones (estrogen, testosterone) What is one property shared by ALL lipids? Large nonpolar molecules (insoluble in water) Why are lipids not considered polymers? Because their structure varies and they are not composed of repeated units The basic building blocks for carbohydrates are called__(1) __. The most common polysaccharide in our diet is_(2) ___, which is simply just a chain of _(3) ___molecules. (1)Monosaccharide (2)Starch (3)Glucose When we eat foods containing starch like breads and crackers,what happens to the starch after it enters our body? (4)Digestion

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Read the paragraph above, then answer the following question. 1. Briefly describe and define the purpose of a positive control and negative control? Positive Control– It contains the substance being tested Negative Control- It does not contain the substance being tested Experiment 1: Testing for Starch (a polysaccharide) You will use an Iodine Solution (Lugolś; IKI) to test for the presence of starch. Iodine solutions are usually a yellowish-brown color , but when the iodine reacts with starch, it will turn a blue-black color. Basedon the information above, answer the following questions. 1. Which solution will you use to test for starch? Iodine Solution 2. Based on this test, how will you know if starch is present? It will turn blue/black Procedure: 1. Obtain 4 clean test tubes and a test tube rack for your table. 2. Label the test tubes # 1-4. 3. Using a clean pipet for each solution, add 1 mL of the experimental solutions listed in the data table to the test tubes according to their numbers. Make sure you mix up the stock solutions before you pipet your sample.

4. Add 5 drops of iodine solution to test tubes 1 and 2. 5. Note the final color changes and observations in the table. 6. Add 5 drops of Benedictś reagent to test tubes 3 and 4. Swirl to mix. 7. Place both test tubes into the hot water bath at the same time. 8. After 5 minutes (or a color change occurs) remove your test tubes from the hot water bath using tongs. 9. Note the final color changes and record your observations below. 10.When you are finished, clean your test tubes with the test tube cleaners and place them upside down on your test tube rack. TUBE CONTENTS Results: Final Color Conclusions: #1 Distilled Water ( Negative Control for Starch) Orange There was no starch or glucose #2 Glucose/Starch Solution Black (opaque) Its lumpy (has starch and glucose) #3 Distilled Water ( Negative Control for Glucose) Clear Light Blue No glucose or starch #4 Glucose/Starch Solution Mustard yellow (cloudy) Has starch and glucose Basedon the information above, answer the following questions. 1. Which solution will you use to test for glucose? A starch solution (2 and 4) 2. Based on this test, how will you know if glucose is present? When it changes color and gets cloudy or opaque.

Diffusion Procedures: 1. Obtain a piece of dialysis tubing (approx. 12 cm long). 2. Soak the tubing in water for about a minute so that it is soft and pliable. 3. Close one end of the tubing by tying a tight knot near the end of the tube. 4. Using a pipet, add 8-10 mL of the Glucose/Starch solution to your tubing. This mixture represents the intracellular fluid. 5. Add 1-2 mL of the Glucose/Starch solution to Test Tube #1. 6. Add 200 mL of distilled wàter to a 250 mL beaker. Then add a few drops of the iodine (IKI) solution to the beaker and stir. Continue until your beaker has an amber (tea-like) appearance. The solution in the beaker represents the extracellular fluid.

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7. Remove 1 mL of the solution from the beaker and add it to test tube #2 and place it in your test tube rack. 8. Record the starting color and contents of the solution in the bag and beaker in the table below. 9. Now add your bag to the beaker with the iodine solution. 10.After 10-15 minutes you should begin to see a color change. Record the final color of the solution in the bag and beaker in the table. 11. Starch Results: You should be able to tell if the starch moved out of the bag or the iodine moved into the bag because when iodine and starch come in contact they create a blue-black color. 12.Use a clean pipet to remove 1 mL of the solution from the bottom of the beaker and add it to Test Tube #3. 13.Cut the tubing and use a clean pipet to remove 1 mL of the content and add it to Test Tube #4. 14. Add 5 drops of Benedictś reagent to test tube 3 & 4. 15. Place both test tubes into the hot water bath at the same time. 16. Glucose Results: After 5 minutes remove your test tubes from the hot water bath and note any color changes. 17. When you are finished, rinse your test tubes in the sink, empty them, and then dispose of them in the broken glass box at the front of the lab. 18. Complete the table below.

Observations at the Start Observations after Soaking Color? Content? Highlight Color? Content? Highlight Solution in the Bag “Cell” Cloudy white Starch Yes or No Glucose Yes or No Iodine Yes or No Cloudy white with some dark blue Starch Yes or No Glucose Yes or No Iodine Yes or No Solution in the Beaker Amber light yellow Starch Yes or No Glucose Yes or No Iodine Yes or No There were spots turning dark blue but still mostly amber Starch Yes or No Glucose Yes or No Iodine Yes or No Data Interpretation: Use the information and your results to answer the questions. 1. How is dialysis tubing similar to a cell membrane? It’s similar because it controls the movement of materials in and out of the cell. Its semipermeable just like the dialysis tubing. 2. Was glucose able to move out of the bag? How could you tell? Yes because the glucose because when we tested it, it changed colors 3. Was starch able to move out of the bag? How could you tell? No because the beaker didn’t turn black. 4. Was iodine able to move into the bag? How could you tell?

Yes because the color inside the bag turned blue. 5. What factor prevented some molecules from moving through the dialysis tubing? Starch molecules are too large to fit through the pores of the dialysis tubing. Activity 4: Cell Membrane Model • Create a model of a Cell Membrane and examine characteristics that make it essential to life (Activity

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Cell Membrane Bubble Lab - Student Analysis In this lab, soap bubbles were used to model several properties that are characteristic of cellular membranes. Below is a chart listing each of the “Cell Concepts” investigated in the Cell Membrane Bubble Lab. Complete the following steps for each cell concept from the lab. 1. Describe the cell concept, as you understand it, in your own words. 2. Describe how the soap bubble was used to model the cell concept. Cell Concept 1 – Membranes are Fluid and Flexible 1-A cell membrane is flexible and bendy, it controls the materials going in and out 2-The bubble was flexible and able to move. Cell Concept 2 – Membranes Can Self-Repair 1-A cell membrane can repair small breaks or tears in the bilayer. 2-When a finger covered in solution is taken out of the bubble, the bubble doesn’t break. Cell Concept 3 – Membrane Bound Organelles 1- Eukaryotic cells have membrane bound organelles that create smaller compartments in a single cell 2- We were able to make a smaller bubble inside the bigger bubble, representing the compartment and the whole cell.

Cell Concept 4 – Membrane Proteins 1- The cell membrane has a lipid bilayer that allows molecules to pass through it. 2- The loop in the bubble allows us to put things through it. Cell Concept 5 – Gap Junctions 1- Gap junctions allow material to pass through cells through a small opening. 2- Theres a small tunnel with the straw in the bubble, allowing air to enter.