BIOL 1021 - Osmosis LAB Virtual PDF

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osmosis lab...

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BIOL 1021 OSMOSIS - Lab 1 - Virtual Required Readings: 1. Read the virtual lab report. Complete Bb Quiz.

Mark: ___ / 20

Purpose In this experiment, students will be expected to: 1. Watch the videos provided. 2. Describe a semi-permeable membrane 3. Hypothesize about what a cell will do in three solutions: hypertonic, isotonic and hypotonic. 4. Watch videos on the topic of osmosis. Introduction Right now, as you read this, there are millions of reactions occuring throughout your body. The food you recently ate is making its way through a watery slurry inside your stomach and small intestines. Your kidneys are working hard to excrete waste and extra water. The lacrimal glands near your eyes are secreting tears, which allow your eyelids to close without damaging your eyeballs. It has been estimated that an amount of water equivalent to roughly 100 times the volume of the cell diffuses across the red blood cell membrane every second; the cell doesn't lose or gain water because equal amounts go in and out. What’s one thing that all of these processes have in common? They all rely on osmosis: the diffusion of water from one place to another. Osmosis is the movement of water across a semi-permeable membrane from an area of high concentration of water to an area of low concentration of water. An egg is an excellent example of a cell that has a semi-permeable membrane. However, there is also a tough outer membrane for protection also which must be removed before exposing the inner semi-permeable membrane. Tonicity: When thinking about osmosis, we are always comparing solute concentrations between two solutions, and some standard terminology is commonly used to describe these differences: 

Isotonic: The solutions being compared have equal concentration of solutes.

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Hypertonic: The solution with the higher concentration of solutes.

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Hypotonic: The solution with the lower concentration of solutes.

Follow the links and watch the videos: https://www.youtube.com/watch?v=rMa9MzP19zI https://www.youtube.com/watch?v=FU9xE8rxnOo https://www.youtube.com/watch?v=OYoaLzobQmk

Safety o The solutions used in this experiment contain various, low concentrations of vinegar or acetic acid in water, and if spilled do not pose danger of corrosion or damage to the skin. However, damage to the eyes is possible and therefore the use of eye protection is recommended.

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Materials           

3 eggs 3 glasses (large enough to fit the egg plus liquid) 3 butter knives White vinegar (about 3 cups) Distilled water (about 2 cups) Light corn syrup (about 1 ¼ cups) Slotted spoon Measuring cup (1 cup) Measuring spoons (1 tablespoon and ½ tablespoon) Sticky notes and marker Scale (optional) or a string with a ruler

Procedure Dissolving the outer shell – note this can take 3 days so start early! 1. Place one egg in each glass. Pour in enough vinegar to cover each egg. Bubbles will start to form around the egg, and it’ll float up. To keep it submerged, put a butter knife in the glass to hold it down. 2. Put the three glasses in the refrigerator and allow to sit for 24 hours. 3. Gently holding the egg in the glass, pour out the old vinegar. Replace with fresh vinegar, and let sit in the refrigerator for another 24 hours. Repeat this process until the shells are fully dissolved and only the membrane remains. This should take about 2-3 days. 4. Gently remove the eggs using the slotted spoon and rinse with tap water in the sink. 5. WEIGH or MEASURE with a ruler each egg as precisely as your measurement tool will allow. If you are using a ruler, you may wish to use a string to wrap around the egg and then measure the string! Osmosis time! 6. 7. o o

Gently put the shell-less eggs aside for a moment on a plate. Prepare three different sugar-water solutions as follows, labeling with sticky notes: Glass 1: Label “hypertonic”. Pour in one cup of corn syrup. Glass 2: Label “isotonic”. Add 1 ½ tablespoons corn syrup to the one cup measuring cup, and fill the remainder with distilled water. Pour into glass (make sure you get all the corn syrup out!) and stir to dissolve. o Glass 3: Label “hypotonic”. Pour in one cup of distilled water. Gently put one shellless egg in each of the glasses, and let sit in the refrigerator for another 24 hours. 8. Remove the glasses from the refrigerator, and gently put the eggs on a plate. If you weighed the eggs before putting them in each solution, weigh them again. What happened to each of the eggs? 9. Now for the most dramatic change – put the egg from the hypertonic solution into the hypotonic solution and the egg from the hypotonic solution in the hypertonic solution. Wait approximately 8-24 hrs. If you weighed the eggs, weigh them again and record. What happened to each egg?

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Results If you have a scale that weighs in grams, weigh each egg before and after soaking in its respective solution. If you measured with a string and ruler, enter your measurements in cm. Solution Hypertonic Isotonic Hypotonic

Starting weight/size

Ending weight/size

FINAL SWAP N/A

Conclusions Every cell in your body needs the right amount of water inside of it to keep its shape, produce energy, get rid of wastes, and other functions that keep you healthy.

This is why medicines that are injected into patients need to be carefully designed so that the solution has the same concentration of solutes as their cells (i.e. isotonic). If you were sick and became dehydrated, for example, you would get a 0.90% saline IV drip. If it were too far off from this mark it wouldn’t be isotonic anymore, and your blood cells might shrivel and explode like in the video link in the Introduction depending on the concentration of dissolved solutes in the water.

YOUR JOB NOW:

Go onto Bb and find in Week 3 the Bb Quiz on this material. You may be required to enter data that you have collected in this report so keep it handy!

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