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A onion cell has some solute in it. So the water by itself is very hyptonic compared to the inside of the onion cell. Why don't the onion cells break open due to the water moving into the cell by osmosis? Why did the onion cells shrink when exposed to 10% NaCl?

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Bunny Greenfelder
Bunny GreenfelderLv2
29 Sep 2019

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Related questions

DNA EXTRACTION LAB

Objective

The purpose of this lab is to extract DNA from the nuclei of an onion, cup of strawberries or a banana.

Introduction

In every eukaryotic cell there are long strings of DNA. The DNA encodes for every protein needed by the organism. The DNA can be millions and millions of bases long. When the DNA is in the nucleus, it is tightly coiled around a set of proteins called the histones. When DNA is released from the nucleus by detergent, it can become long and stringy. In this lab we are going to be extracting the DNA from the nuclei of onions and wrapping the DNA around a glass rod.

Materials

Straw or Coffee Stirrer

2-plastic water bottles (single serving disposable)

Ice

Rubbing Alcohol

Liquid soap (laundry detergent) DawnR works best

Coffee filter

Water- distilled

Onion, Cup of Strawberries, or Banana

Table salt

Procedure

1. First place a bottle of rubbing alcohol on ice to chill.

2. Then make the following detergent/salt solution:

Mix together (1/8 cup) 20 mL of liquid soap, (2-tsp) 20 grams of salt, and (1 1/8 cup) 180 mL of distilled water. When you are finished making the solution, put it on ice to chill for at least 10 minutes.

3. Cut an onion in half and chop it up either in the blender, or with a knife. If using strawberries chop them up to small pieces. If using the banana smash it up in a cup.

4. Add (half) 100 mL of the detergent/salt solution to the chopped onion, strawberries, or banana. Continue crushing the onion, the onion needs to be pulverized.

5. Let the slurry sit for 5 minutes on ice.

6. Cut the top 1/3 from the water bottle and flip it over onto the lower cut portion. Use the top as a funnel and the lower portion to catch the solution as it filters through.

7. Place a coffee filter in the top funnel. Pour the slurry through and capture the filtered solution below.

8. Once all of the slurry is in the beaker slightly tilt the beaker and slowly pour down the side of the beaker an equal volume of ice cold rubbing alcohol. This will form two distinct layers. A white stringy material will form at the interface of the two layers.

* Do not mix the alcohol and the slurry.

8. Carefully insert a glass stir rod in the center of the beaker, being cautious not to touch the sides.

9. Now, twist the stir rod in a clockwise direction (like twirling spaghetti) and you should see a white stringy material collecting onto the rod.

This white stringy material is DNA. Keep twisting until you acquire the maximum amount of DNA.

* If you do not collect any DNA on the stir rod then use a piece of sandpaper to rough up the end of the stir rod and try again.

Questions

What did you observe?

Were you able to isolate DNA?

What did it look like?

1. In lecture, we described a simple osmotic pressure gradient when discussing osmosis. For question #1, describe the simple osmotic pressure gradient, in terms of osmotic pressure, that exists across the red blood cell plasma membrane when red blood cells are suspended in a severely hypotonic solution, such as a 0.2% NaCl solution. Use scientific terminology.

2. We mentioned in class that biological systems are always in a state of osmotic equilibrium due to a combination of solute diffusion in some cases and osmosis in others. In this experiment, when you add the red blood cells to a severely hypotonic solution, what substances are moving across the red blood cell plasma membrane to achieve osmotic equilibrium, Na+ and Cl- or water? Explain why based on your understanding of the permeability characteristics of biological membrane. Always use scientific language.

CAN QUESTIONS 1 AND 2 BE ANSWERED DIRECTLY AND ADEQUATLEY PLEASE.

HERE IS AN INTRO TO THE LAB EXPERIMENT

Intro:

We have known for a very long time that the mammalian red blood cell plasma membrane is very permeable to water. Even the introductory biology student understands that if you put mammalian red blood cells in water, they will rapidly swell and break open (hemolyze) due to the rapid osmosis of water into the cell. The experimental question we are asking in today's lab experiment is "Is the high water permability of mammalian red blood cell plasma membrane due solely to the lipid bilayer, or are there water channels present in the membrane?"

Experimental Design:

It has been shown by several investigators that water movement through water channels can be blocked by the known K+ channel blocker, tetraethylammonium chloride (TEAC). Brooks, Regan and Yool (2000) showed that TEAC reduces the water permeability of human water channels expressed in the plasma membranes of frog ocytes. After preincubation of the oocytes for 15 min with 100 microM TEAC, the water permeability of frog oocyte plasma membrane containing human water channels was reduced 20 to 40%. The investigators concluded that treatment of cells with TEAC can be useful in determining the presence of aquaporins in membranes.The specific objective of today's experiment is to uncover the presence of water channels in mammalian red blood cell plasma membrane by determining the effect of tetraethylammonium chloride on the water permeability of mammalian RBC plasma membrane.

We mentioned in class that biological systems are ... We mentioned in class that biological systems are always in a state of osmotic equilibrium due to a combination of solute diffusion in some cases and osmosis in others. In this experiment, what substance is moving across the red blood cell plasma membrane to achieve osmotic equilibrium, Na+ and Cl- or water? Explain why based on your understanding of the permeability characteristics of biological membrane. Always use scientific language. HERE IS AN INTRO TO THE LAB EXPERIMENT Intro: We have known for a very long time that the mammalian red blood cell plasma membrane is very permeable to water. Even the introductory biology student understands that if you put mammalian red blood cells in water, they will rapidly swell and break open (hemolyze) due to the rapid osmosis of water into the cell. The experimental question we are asking in today's lab experiment is "Is the high water permability of mammalian red blood cell plasma membrane due solely to the lipid bilayer, or are there water channels present in the membrane?" Experimental Design: It has been shown by several investigators that water movement through water channels can be blocked by the known K+ channel blocker, tetraethylammonium chloride (TEAC). Brooks, Regan and Yool (2000) showed that TEAC reduces the water permeability of human water channels expressed in the plasma membranes of frog ocytes. After preincubation of the oocytes for 15 min with 100 microM TEAC, the water permeability of frog oocyte plasma membrane containing human water channels was reduced 20 to 40%. The investigators concluded that treatment of cells with TEAC can be useful in determining the presence of aquaporins in membranes.The specific objective of today's experiment is to uncover the presence of water channels in mammalian red blood cell plasma membrane by determining the effect of tetraethylammonium chloride on the water permeability of mammalian RBC plasma membran

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