IB 1108 L07 Osmosis - BIO 110 Lab assignments PDF

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BIO 110 Lab assignments...

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Osmosis PRE-LAB QUESTIONS 1. What is the water potential of an open beaker containing pure water? Zero because there is no solute and the pressure in the container is zero. 2. Why don’t red blood cells swell or shrink in blood? Because blood is an isotonic solution compared to the cytoplasm in the reed blood cells 3. How do osmotic power plants work? Converts the pressure differential between water with high salinity and water with lower or no salinity into hydraulic pressure. This hydraulic pressure can be used to drive a turbine that produces electrical energy. 4. Research the structures that protect plant and animal cells from damage resulting from osmotic pressure. Write a few paragraphs explaining what they are, how they work, and where they are located. Plants have a rigid cell wall. The entering water is placed inside a large vesicle. The wall protects against expansion, and the resulting pressure makes the plant rigid, a phenomena called tugor pressure. Animal cells lack a wall, and use active transport systems to move ions outside the cell, reducing the osmotic pressure.

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Osmosis EXPERIMENT 1: TONICITY AND THE ANIMAL CELL Hypothesis

Data

Data Tables Table 1: Osmosis Results Solution Type

Volume (mL) Before Osmosis

Volume (mL) After Osmosis

100% Distilled Water

50 mL

30 mL

100% Corn Syrup

50 mL

65 mL

10% Corn Syrup/90% Distilled Water

50 mL

60 mL

Control

0 mL

10 mL

Table 2: Observations of Eggs After Osmosis 100% Distilled Water

100% Corn Syrup

10% Corn Syrup/ 90% Distilled Water

Control

Very soft

Sticky egg

Slightly soft, sticky to the touch

Some liquid

Post-Lab Questions 1. Record your hypothesis from Step 15 here. Be sure to include scientific reasoning to support your predictions. I believe that water will absorb into the egg more than any other solution, due to the fact that water has a thinner molecular structure than corn syrup. 2. How do each of the three eggs placed in solution compare to the control egg?

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Osmosis The size of each of the three eggs changed after being placed in the solution. It seems that the eggs that were placed in the 100% corn syrup and 10% corn syrup/90% distilled water decreased in size, but the volume of the solution increased. 3. For each beaker, identify whether the solution inside was hypotonic, hypertonic, or isotonic in comparison to the control beaker. 100% distilled- isotonic solution, 100% corn syrup- hypertonic solution, 10% corn syrup/90% distilled water- hypertonic solution 4. What was the direction of osmosis in the beaker labeled “100% distilled water”? Did the egg in this beaker burst? The direction of osmosis in the beaker moved into the egg. Although, the egg did increase in size, the egg did not burst. 5. Was there any liquid in the “control” beaker after 24-48 hours? If so, why do you think this is? If not, why do you think this is? Yes, there was volume in the control beaker after 24 hours. I am insisting that volume is in the beaker because the egg is in hypotonic solution. 6. Which solution contained a dehydrated cell? Think about someone with a high sugar diet. Hypothesize how their cells might be affected by osmosis. The egg placed in hypertonic solution, 100% corn syrup, contained the dehydrated egg. The cells of an individual with a high sugar diet would be impacted by osmosis. The cells would become dehydrated due to the high sugar solute concentration meaning that osmosis would move from outside the cell into the outside solution.

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Osmosis EXPERIMENT 2: TONICITY AND THE PLANT CELL Data Tables Table 3: Water Displacement per Potato Sample Potato Type

Potato Observations

Sweet

Lumpy around

Sweet

Smooth around

B-(20%NaCl)

Russet

Lumpy around

A-Water

Russet

Smooth around

B-(20%NaCl)

Sample A- Water

Initial Displacement (mL) 6 mL

Final Displacement (mL) 7 mL

Net Displacement (mL) 1 mL

7 mL

7 mL

0 mL

5 mL

7 mL

2 mL

5 mL

4 mL

-1 mL

Post-Lab Questions 1. How did the physical characteristics of the potato vary before and after the experiment? Did it vary by potato type?

The russets were somewhat soft before the experiment but seemed o stiffen. Whereas the sweet potatoes were stiff and hard beforehand and afterwards they were soft

2. What does the net change in the potato sample indicate?

More water entered the potatoes compared to the strips that were in the 20% salt mix.

3. Different types of potatoes have varying natural sugar concentrations. Explain how this may influence the water potential of each type of potato.

A higher natural sugar concentration might allow more water to enter the cell rather than something with a low natural sugar concentration.

4. Based on the data from this experiment, hypothesize which potato has the highest natural sugar concentration. Explain your reasoning.

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Osmosis I believe that the russet potato has a higher natural sugar concentration. I believe this to be because it consistently had the most size change compared to a sweet potato.

5. Did water flow into or out of the plant cells (potato cells) in each of the samples examined? How do you know this?

In the first type, the water moved out as the net displacement is positive which is +1mL. In the second type, there is no displacement of water. This means the movement of water from inside to outside and vice-versa is the same. In the third type, the water moved out as the net displacement is positive which is +2mL. In the fourth type, the water has moved from inside to outside as the net displacement of water is negative which is -1mL.

6. Would this experiment work with other plant cells? What about with animal cells? Why or why not?

The experiment is about tonicity. If you place an animal or a plant cell in a hypertonic solution, the cell shrinks because it loses water.

7. From what you know of tonicity, what can you say about the plant cells and the solutions in the test tubes?

The hypertonic solution has a lower water concentration than the hypotonic solution, so a concentration gradient of water now exists across the membrane. Water molecules will move from the side of higher water concentration to the side of lower concentration until both solutions are isotonic.

8. What do your results show about the concentration of the cytoplasm in the potato cells at the start of the experiment?

At the start of the experiment, the potato cell was hypotonic.

9. If the potato is allowed to dehydrate by sitting in open air, would the potato cells be more likely to absorb more or less water? Explain.

If it dehydrates then it loses water then probably it would absorb more water © eScience Labs, 2018...