BIO WATERPOTENTIAL

The terrestrial environment is more similar to the saltwater aquatic environment because in both environments organisms tend to lose water. True or False?

True

The value for Ψ in root tissue was found to be −0.15 MPa. If you take the root tissue and place it in a 0.1 M solution of sucrose (Ψ = −0.23 MPa), the net water flow would be from the tissue into the sucrose solution. True or False?

True

The body fluids of an osmoconformer would be __________ with its __________ environment

isoosmotic; saltwater

Most of the water taken up by a plant is ________.

lost during transpiration

Under what circumstances does membrane transport require energy?

whenever a solute is moved against its electrochemical gradient

As an undergraduate research assistant, your duties involve measuring water potential in experimental soil-plant-atmosphere systems. Assume you make a series of measurements in a system under normal daylight conditions, with stomata open and photosynthesis occurring. Which of the following correctly depicts the trend your measurement data should follow if the cohesion-tension mechanism is operating?

ψatmosphere < ψleaves < ψroots < ψsoil

If ΨP = 0.3 MPa and ΨS = −0.45 MPa, the resulting Ψ is ________.

−0.15 MPA

Which line in the graph represents the bag with the highest initial concentration of sucrose?

A

How does a flaccid cell differ from a turgid cell?

A flaccid cell has lower pressure potential.

Which of the following effects can occur because of the high surface tension of water?

A raft spider can walk across the surface of a small pond.

Which line in the graph represents the bag that contained a solution isotonic to the 0.6 M solution at the beginning of the experiment?

C

Five dialysis bags constructed of membrane, which is permeable to water and impermeable to sucrose, were filled with various concentrations of sucrose and then placed in separate beakers containing an initial concentration of 0.6 M sucrose solution. At 10-minute intervals, the bags were massed (weighed) and the percentage change in mass of each bag was graphed.The line in the graph that represents the bag that contained a solution isotonic to the 0.6 M solution at the beginning of the experiment was line D. True or False?

False

Ice floats in water because stable hydrogen bonds keep water molecules of ice closer than water molecules of liquid water. True or False?

False

If isolated plant cells with a water potential averaging −0.5 MPa are placed into a solution with a water potential of −0.3 MPa, the pressure potential of the cells would stay the same.

False

If isolated plant cells with a water potential averaging −0.5 MPa are placed into a solution with a water potential of −0.3 MPa, there would be net movement of water out of the cell. True or False?

False

In osmosis, water moves across a membrane from areas of higher solute concentration to areas of lower solute concentration. True or False?

False

One of the following characteristics of a carrier protein in a plasma membrane is that it requires the expenditure of cellular energy to function. True or False?

False

The aspect of phospholipids that is most important to the formation of bilayers is that their polar heads can interact with water. True or False?

False

The body fluids of an osmoconformer would be isoosmotic with its freshwater environment. True or False?

False

When an animal cell is placed in a hypotonic solution and water enters the cell via osmosis, the volume of the cell increases until it bursts. This does NOT happen to plant cells, because they have cell walls, which prevent the entry of water by osmosis. True or False?

False

Whenever a solute is moved against its electrochemical gradient, this does NOT require energy. True or False?

False

Which of the following is TRUE of osmosis?

In osmosis, water moves across a membrane from areas of lower solute concentration to areas of higher solute concentration.

In an experiment involving planar bilayers, a solution of table salt (sodium and chloride ions in water) is added on the left side of the membrane while pure water is added on the right side. After 30 minutes, the researchers test for the presence of ions on each side of the membrane. The right side tests negative for ions. What can you conclude?

Ions cannot cross planar bilayers.

Celery stalks that are immersed in freshwater for several hours become stiff. Similar stalks left in a 0.15 M salt solution become limp. From this we can deduce that the freshwater ________.

Is hypotonic and the salt solution is hypertonic to the cells of the celery stalks

Which of the following is a characteristic feature of a carrier protein in a plasma membrane?

It exhibits a specificity for a particular type of molecule.

What is the most important factor in explaining why osmosis occurs spontaneously?

It leads to an increase in entropy.

Why does ice float in liquid water?

Stable hydrogen bonds keep water molecules of ice farther apart than water molecules of liquid water.

In an experiment involving planar bilayers, a solution of table salt (sodium and chloride ions in water) is added on the left side of the membrane while pure water is added on the right side. After 30 minutes, the researchers test for the presence of ions on each side of the membrane. The right side tests negative for ions. From this, one could conclude that ions cannot cross planar bilayers.True or False?

TRUE

A patient was involved in a serious accident and lost a large quantity of blood. In an attempt to replenish body fluids, distilled water—equal to the volume of blood lost—is added to the blood directly via one of his veins. What will be the most probable result of this transfusion?

The patient's red blood cells will swell and possibly burst because the blood has become hypotonic compared to the cells.

Celery stalks that are immersed in freshwater for several hours become stiff. Similar stalks left in a 0.15 M salt solution become limp. From this we can deduce that the freshwater is hypotonic and the salt solution is hypertonic to the cells of the celery stalks. True or False?

True

A patient was involved in a serious accident and lost a large quantity of blood. In an attempt to replenish body fluids, distilled water—equal to the volume of blood lost—is added to the blood directly via one of his veins. The result of this transfusion will likely cause the patient's red blood cells to swell and possibly burst because the blood has become hypotonic compared to the cells. True or false?

True

A raft spider can walk across the surface of a small pond because of the high surface tension of water?

True

Negative pressure on the surrounding solution would enhance water uptake by a plant cell. True or False?

True

For a protein to be an integral membrane protein, it would have to be ________.

amphipathic, with at least one hydrophobic region

The value for Ψ in root tissue was found to be −0.15 MPa. If you take the root tissue and place it in a 0.1 M solution of sucrose (Ψ = −0.23 MPa), the net water flow would ________.

be from the tissue into the sucrose solution

Glucose diffuses slowly through artificial phospholipid bilayers. The cells lining the small intestine, however, rapidly move large quantities of glucose from the glucose-rich food into their glucose-poor cytoplasm. Using this information, which transport mechanism is most probably functioning in the intestinal cells?

facilitated diffusion

Water potential (ψ) can be thought of as the tendency for water to move from one place to another. In plants, it is made up mainly of solute potential and pressure potential. Hypothetical plant cells A and B are adjacent to each other. The solute potential (ψS) of cell A is −0.35 MPa, and its pressure potential (ψP) is +0.15 MPa. The solute potential (ψS) of cell B is −0.30 MPa, and its pressure potential (ψP) is +0.05 MPa. In which direction will net water movement occur?

from cell A to cell B

Compared to plants from other environments, the cells of many desert plants contain high concentrations of solutes. This helps them survive in their arid surroundings because the high solute concentrations create relatively ________, which help reduce water loss.

low solute potentials

Compared to plants from other environments, the cells of many desert plants contain high concentrations of solutes. This helps them survive in their arid surroundings because the high solute concentrations create relatively __________, which leads to lower water potential inside the cells and helps reduce water loss.

low solute potentials

If isolated plant cells with a water potential averaging −0.5 MPa are placed into a solution with a water potential of −0.3 MPa, which of the following would be the most likely outcome?

net movement of water into the cell

Which of the following types of molecules are the major structural components of the cell membrane?

phospholipids and proteins

What would enhance water uptake by a plant cell?

positive pressure on the surrounding solution

Water potential in plants consists mainly of ________.

pressure potential and solute potential

When an animal cell is placed in a hypotonic solution and water enters the cell via osmosis, the volume of the cell increases until it bursts. This does NOT happen to plant cells, because ________.

they have cell walls, which provide pressure to counteract the pressure of the incoming water