bio unit 2

Areas 1 and 3 are polar, since the membrane molecules are aligned with water molecules.

Which of the following best describes the numbered areas?

The membrane potential will be disrupted by an increase in K+ concentration inside the cell.

A cell's membrane potential is maintained by the movement of ions into and out of the cell. A model showing the influence of membrane proteins on the movement of sodium (Na+) and potassium (K+) ions across the plasma membrane is presented in Figure 1. Based on the model presented in Figure 1, which of the following outcomes will most likely result from a loss of protein X function?

Interactions of the hydrophobic and hydrophilic amino acids help to anchor the protein in the membrane.

A model of the plasma membrane showing several biological molecules, including a transmembrane protein, is shown in Figure 1. Which statement best explains why correct protein folding is critical in the transmembrane protein shown above?

Water will move out of the plant cell, causing it to shrivel. The plant cell has lower concentration of solute and a higher concentration of water than the solution it is placed in. This means that water will move out of the plant cell, causing it to shrivel.

A plant cell has a 5% salt concentration. It is placed into a solution containing a 12% salt concentration. What will happen to the plant cell?

The bacterial cell, because it has the largest surface-to-volume ratio.

A spherical bacterial cell has a radius of 3μm. The human egg cell has a radius of 100μm. Which statement correctly indicates the cell that is able to more efficiently exchange materials with the external environment and provides a correct explanation?

The drug is a small nonpolar molecule.

A team of biologists develop a new drug, and one team member hypothesizes that the drug is incapable of freely passing across the plasma membrane and requires the help of membrane proteins to enter cells. Alternatively, another biologist on the team hypothesizes that the drug can diffuse passively across the plasma membrane like O2 and CO2 can. Which of the following, if true about the drug, best supports the alternative hypothesis that the new drug will exhibit simple diffusion across plasma membranes?

Water will move into the animal cell, causing it to swell and burst. The animal cell has higher concentration of solute and a lower concentration of water than the solution it is placed in. This means that water will move into the animal cell, causing it to swell.

An animal cell has a 2% salt concentration. It is placed into a solution with a 0.05% salt concentration. What will happen to the animal cell?

Cells with mutated aquaporins exhibit moderate turgor pressure and are hypertonic.

Aquaporins are channel proteins that facilitate the transport of water across the cell membrane. One group of researchers hypothesizes that without functional aquaporins, no water will be able to enter the cell. A different group proposes an alternative hypothesis, stating that even with nonfunctional aquaporins, a small amount of water will still cross the cell membrane. An experiment is set up in which plant cells with mutated (nonfunctional) aquaporins and plant cells with normally functioning aquaporins are both placed in distilled water. Which of the following data would support the alternative hypothesis?

The animal's body cells are defective in endocytosis.

Cholesterol is an important component of animal cell membranes. Cholesterol molecules are often delivered to body cells by the blood, which transports the molecules in the form of cholesterol-protein complexes. The complexes must be moved into the body cells before the cholesterol molecules can be incorporated into the phospholipid bilayers of cell membranes. Based on the information presented, which of the following is the most likely explanation for a buildup of cholesterol molecules in the blood of an animal?

Add more of the proteins to the plasma membrane and measure the rate of the particle movement.

Figure 1 shows a model of how a channel protein influences the movement of a particle across a cell's plasma membrane. An investigator wants to understand whether a newly found membrane protein is involved in membrane transport of a certain particle. Which investigation will help determine whether the new membrane protein is a channel protein involved in membrane transport?

From higher to lower areas of concentration. During diffusion, particles will move along the concentration gradient from an area of higher concentration to an area of lower concentration in an effort to reach equilibrium (when the molecules are even throughout a space). This process does not require any energy.

In which direction do particles in a solution move during passive diffusion?

In both plant cells and fungal cells, the cell wall surrounds the outside of the cell membrane.

Plant cell walls are composed of cellulose, while fungal cell walls are composed of chitin. A group of scientists hypothesize that this difference means the cell wall has largely different functions in plant cells and fungal cells. Alternatively, another group of scientists hypothesize that despite their biochemical differences, plant and fungal cell walls serve similar functions. Which of the following observations would best support the alternative hypothesis described above?

650 micrometers

Researchers propose a model to explain variation in phytoplankton cell sizes in a marine environment. They base their model on the idea that smaller cells absorb nutrients more efficiently. The researchers predict that the mean diameter of phytoplankton cells will change by 50 micrometers for every 5-kilometer increase in distance from the shore because of a gradual decrease in nutrient availability. To test their model, the researchers determine that the phytoplankton cells found closest to shore have a mean diameter of 900 micrometers. Based on the model, what will be the mean diameter of the phytoplankton cells that are found 25 kilometers from shore?

Water will flow from side B into side A. Because the membrane is only permeable to water, the solute molecules cannot cross through. Water will move from an area of low solute concentration to an area of high solute concentration (in other words, an area of high water concentration to an area of low water concentration). Since the solute concentration in B is lower than the solute concentration in A, water will move from side B to side A to balance out the concentration gradient.

The U shaped pipe shown in the figure below is divided with a membrane that is only permeable to water. Which of the following best describes how water will flow through the membrane?

H+ ions will stop moving through the protein.

The illustration shows the active transport of hydrogen ions through a membrane protein. Which of the following best predicts the effect of not having ATP available to supply energy to this process?

The hydrophilic phosphate groups of the phospholipid molecules are attracted to the aqueous internal and external environments.

The model shows the structure of a portion of a plasma membrane in an animal cell. Which statement best explains the orientation of the phospholipid molecules in this model?

Incubate samples containing 1.0μm/mL of ATP at four temperatures other than 25°C.

The transport of a substance across a plasma membrane of a specific organelle requires energy. The rate at which the transport takes place also depends on temperature. A scientist isolated the specific organelle and then used the following treatments to determine the conditions that will result in the maximal transport. All treatments contained the extracted organelle and were maintained at 25°C. The data from this experiment indicate that maximal rate of transport of protein X at 25°C occurs at an ATP concentration of 1.0μm/mL. Which procedure should be done next to gather data needed to meet the scientist's objective?

Cell A, because it has the larger surface-area-to-volume ratio.

Two different models of a living cell are represented in the figure. Of the two cells represented in the figure, which would likely be more efficient at exchanging substances with the surrounding environment?

Passive transport is the net movement of substances down a concentration gradient that does not require metabolic energy. Active transport is the movement of substances up a concentration gradient that requires energy.

Which of the following statements best explains the processes of passive and active transport?

Water molecules will still be able to move across the cell membrane but at a slower rate.

Which statement best describes the effect on water transport across the cell membrane if the aquaporin in the figure ceases to function?