Lab 1 quiz

In figure 1.5, the beaker is open to the atmosphere. What is the pressure potential of the system?

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What results would you expect if the experiment started with a glucose and IKI solution inside the bag and only starch and water outside? Why?

Based on the size of the molecules, the glucose and IKI would move out of the bag and the water would go in. The large starch molecules would be left in the beaker.

If a plant cell has a lower water potential than its surrounding environment, and if pressure is equal to zero, is the cell hypertonic or hypotonic to its environment? Will the cell gain water or lose water? Explain your response.

If the plant cell has lower water potential, that means the water will come into the cell; the cell is hypertonic to its environment. This cell will gain water because water follows its concentration gradient.

Which would have the higher water potential?

The distilled water would also have the higher water potential.

Consider what would happen to a red blood cell placed in distilled water: Which would have the higher concentration of water molecules

The distilled water would have the higher concentration of water molecules.

Why did the onion cell plasmolyze?

The environment around the cell was hypertonic to the cell so water left the cell to reach dynamic equilibrium with the NaCl solution. With all the water leaving the cell, the cell membrane separated from its cell wall.

Explain the relationship between the change in mass and the molarity of sucrose within the dialysis bags.

The molarity is directly proportional to the percent change in mass. As the mass percentage increases, so does the molarity.

Describe the appearance of the onion cells.

The onion cells appear to have great turgor pressure, spread out, thick and bright in the inside. The cell walls were very defined and it was clear where one cell ended and another began.

Remove the cover slip and flood the onion with fresh water. Observe and describe what happened.

The onion cells were again hypertonic to their environment and were restored to their original state of appearance.

Explain the results you obtained. Include the concentration differences and membrane pore size in your discussion.

The results show that the water, glucose, and IKI molecules were small enough to pass through the selectively permeable membrane. The starch didn't leave the beaker because its molecules were too large to pass through the selectively permeable membrane's pores.

In the winter, grass often dies near roads that have been salted to remove ice. What causes this to happen?

The salt causes the grass's environment to become hypertonic, and the water leaves the plant cells, causes withering and eventually death of the plant. The high concentration of salt in the soil also speeds the death of the plant.

Predict what would happen to the mass of each bag in this experiment if all the bags were placed in a 0.4-M sucrose solution instead of distilled water. Explain your response.

the higher the polite concentration the higher the rate of osmosis and the smaller or solute potential. Any bag with sucrose molarity less then .4 would lose mass and would gain mass if it was higher then .4 and soon the concentrations would meet equilibrium

Which substance(s) are entering the bag and which are leaving the bag? What experimental evidence supports your answer?

water and glucose, This is proven by the color change (starch test) and the increase in the size of the bag. Glucose left the bag and this is proven by a positive test on the surrounding water.

Calculate the water potential of the solutes within the zucchini cores. Show work.

ψ = ψ s+ ψ p ψ =0 + -8,975 , ψ = -8.975 bars

Calculate solute potential of the sucrose solution in which the mass of the zucchini cores does not change. Show work.

ψ s = -iCRT ψ s = (-1)(0.36 mole/liter)(0.0831 liter bar/mole K)(300 K) ψ s = -8.975 bars

If a potato is allowed to dehydrate by sitting in the open air, would the water potential of the potato cells decrease or increase? Why?

The water potential of the potato would decrease because water moves from a high water potential region to a low potential region, and a dehydrated potato cell is hypertonic in comparison with the environment. The concentration of solute would increase and osmotic potential would decrease.

Water will diffuse_________the bag. Why?

Water will diffuse into the bag because the inside of the bag has the highest water potential.

A dialysis bag is filled with distilled water and then placed in a sucrose solution. The bag's initial mass is 20g, and its final mass is 18g. Calculate the percent change of mass, showing your calculations in the space below.

10%

What effect does adding solute have on the solute potential component of that solution? Why?

Adding solute to a solution would increase the solute potential and decrease the water potential.

What is plasmolysis?

Plasmolysis is the separation of the plasma membrane from the cell wall in a plant cell.

Quantitative data uses numbers to measure observed changes. How could this experiment be modified so that quantitative data could be collected to show that water diffused into the dialysis bag?

The bags could be massed before and following their immersion in the solution. The volume of the solution in the beaker could be found before and after the immersion of the bag by using a graduated cylinder.

In figure 1.5, where is the greatest water potential?

The greatest water potential is within the beaker

Describe the appearance of the onion cells after the NaCl was added.

The plasma membrane shriveled from the cell wall, or in other words, plasmolysis occurred.

What would happen to the red blood cell? Why

The red blood cell would take in a lot of water and might lyse due to pressure inside. This is because animal cells lack tolerance under hypotonic situations.

Based on your observations, rank the following by relative size, beginning with the smallest: glucose molecules, water, IKI, membrane pores, and starch molecules.

The smallest substance was water, then the IKI molecules, glucose, the membrane pores, and the largest substance was the starch molecules