Water Potential and Cell Transport Review

These flashcards cover key concepts about water potential, cell transport, osmosis, and solutions to help review for the exam.

What is the effect of a hypertonic solution on a cell?

Water moves out of the cell, causing it to shrink.

What is a hypotonic solution?

A solution that has fewer nonpenetrating solutes than the cell, leading to water moving into the cell.

Define osmosis.

The diffusion of water through a selectively permeable membrane from high water concentration to low water concentration.

What equation is used to calculate water potential?

"
\psi = \psip + \psis
", where "\psi" is water potential, "\psip" is pressure potential, and "\psis" is solute potential.

What does an isotonic solution mean for a cell?

There is no net movement of water, and the concentrations of solutes are equal on both sides of the membrane.

What happens to the water potential if a solute is added to distilled water?

The water potential becomes negative because the concentration of water molecules decreases.

What is the concept of dialysis in relation to cell membranes?

The separation of small molecules from large molecules using a selectively permeable membrane.

What is the significance of pressure potential in water potential?

It affects the water potential by pushing against the cell walls, which can make the value positive.

In what condition do animal cells lyse?

When placed in a hypotonic solution, as they lack a protective cell wall.

Why do plant cells not lyse in hypotonic solutions?

The rigid cell wall creates turgor pressure which prevents bursting despite water entering the cell.

How does water potential predict the direction of water flow?

Water tends to move from areas of higher water potential to areas of lower water potential.

Why is drinking seawater detrimental for survival?

Seawater is hypertonic to body cells, causing water to leave cells and leading to dehydration.

What is the primary factor affecting water movement across membranes?

The relative concentrations of solutes and water in the solutions on either side of the membrane.

What effect do salts in soil have on plant health?

High salt concentrations lower the soil water potential, causing dehydration in plants.

What is turgor pressure?

The pressure exerted by water inside the cell against the cell wall.

What happens when potato cores are placed in a sucrose solution of high concentration?

They lose mass as water moves out by osmosis.

How do you determine the osmolarity of potato tissue using a graph?

Identify the molarity where the graph intersects the zero change line.

What is the relationship between osmolarity and water potential?

Higher osmolarity indicates lower water potential.

What does a low water potential indicate about solute concentration?

It indicates a high concentration of solutes.

What is the term used to describe a solution with a high concentration of solutes compared to another solution?

Hypertonic.

Which type of transport requires energy (ATP)?

Active transport.

What is the meaning of 'selectively permeable'?

A membrane that allows certain substances to pass while blocking others.

Calculate the solute potential (\psi_s) of a 0.2 \text{ M} sucrose solution at 25\text{°C}. (Given: Ionization constant (i) for sucrose is 1, pressure constant (R) is 0.0831 \text{ liter bars/mole K}).

First, convert temperature to Kelvin: T = 25\text{°C} + 273 = 298\text{ K}.Using the formula: \psis = -iCRT\psis = -(1)(0.2 \text{ M})(0.0831 \text{ liter bars/mole K})(298 \text{ K})\psi_s = -4.95 \text{ bars}Therefore, the solute potential is -4.95 \text{ bars}.

If the solute potential (\psi_s) of a NaCl solution is -6.0 \text{ bars} at 20\text{°C}, what is the molar concentration (C) of the solution? (Given: Ionization constant (i) for NaCl is 2, pressure constant (R) is 0.0831 \text{ liter bars/mole K}).

First, convert temperature to Kelvin: T = 20\text{°C} + 273 = 293\text{ K}.Rearrange the formula to solve for C: \psis = -iCRT \implies C = -\frac{\psis}{iRT}C = -\frac{(-6.0 \text{ bars})}{(2)(0.0831 \text{ liter bars/mole K})(293 \text{ K})}C = \frac{6.0}{(2)(24.3633)}C = \frac{6.0}{48.7266} \approx 0.123 \text{ M}Therefore, the molar concentration is approximately 0.123 \text{ M}.

In an experiment, potato cores were placed in various sucrose solutions. After 24 hours, the cores in a 0.3 \text{ M} sucrose solution showed no change in mass. What can be inferred about the osmolarity of the potato tissue?

The potato tissue has an osmolarity approximately equal to 0.3 \text{ M}. This is because at this concentration, the solution is isotonic to the potato cells, meaning there is no net movement of water into