Biology Chapter 7

Which of the following statements best describes a characteristic feature of diffusion?

It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration

Five dialysis bags, constructed of a type of membrane that 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 weighed, and the percent change in mass of each bag was graphed. Which line or lines in the graph represent(s) bags that contain a solution that is hypertonic to the solution in the beaker at 50 minutes?

Line that is increasing at 50 minutes

Five dialysis bags, constructed of a type of membrane that 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 weighed, and the percent change in mass of each bag was graphed. Which line in the graph represents the bag with the highest initial concentration of sucrose?

Line with the highest initial slope

Which of the following organelles plays a primary role in the digestion of bacteria engulfed by white blood cells?

Lysosomes

Which of the following statements concerning carbohydrates associated with the plasma membrane is correct?

Membrane carbohydrates function primarily in cell-cell recognition

The voltage across a membrane is called the ________

Membrane potential

All cells have voltages across their membranes. This voltage is called a(n) __________ and is often maintained by __________

Membrane potential; electrogenic pumps

Which of the following is a major difference between prokaryotic and eukaryotic cells?

Most prokaryotic cells have no internal membranes; eukaryotic cells do

Which of the following membrane activities requires energy from ATP hydrolysis?

Movement of Na+ ions from a lower concentration in a mammalian cell to a higher concentration in the extracellular fluid

Hydrophobic substances like salad oil are

Nonpolar molecules that do not have an affinity for water molecules

Which of the following molecules would likely diffuse through the lipid bilayer of a plasma membrane most rapidly?

O2

In receptor-mediated endocytosis, membrane receptors bind to molecules outside of the cell. Immediately following endocytosis where will the membrane receptors be located?

On the inside surface of the vesicle

What causes the changes in mass of sweet potatoes when exposed to varying molarities of Sucrose

Osmosis

Select the correct statement about osmosis

Osmosis is the diffusion of water molecules across a selectively permeable membrane

Which component in the figure above represents cholesterol?

Part of the lipid membrane

Which of the following cellular processes includes all of the others?

Passive transport (Transport of an ion down its electrochemical gradient, Osmosis, Facilitated diffusion)

Which of the following statements about passive transport is correct?

Passive transport permits the solute to move in either direction, but the net movement of the population of solute molecules occurs down the concentration gradient of the molecule

Which of the following types of molecules are most likely to be excluded from the hydrophobic portion of the phospholipid bilayer?

Peripheral membrane proteins

Which of the following is hydrophilic?

Periphery Membrane Proteins

An organism with a cell wall would most likely be unable to take in materials through which of the following processes?

Phagocytosis

Which of the following processes is used by white blood cells when engulfing bacteria?

Phagocytosis

Which of the following molecules are most abundant in the plasma membrane?

Phospholipids

Which of the following statements about the role of phospholipids in the structure and function of biological membranes is correct?

Phospholipids form a selectively permeable structure

Which of the following statements best describes a characteristic of biological membranes?

Phospholipids move laterally within the plane of the membrane

Which of the following statements best describes the difference between pinocytosis and receptor-mediated endocytosis?

Pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis offers more selectivity

Which of the following cell structures exhibits selective permeability between a cell and its external environment?

Plasma membrane

Which of the following results is most likely when a plant cell is submerged in a hypertonic solution?

Plasmolysis will shrink the interior of the cell

Which of the following statements is true regarding potential energy?

Potential energy is the energy possessed by matter due to its location or structure

Which of the following structural arrangements of the components in biological membranes facilitates the cell membrane's property of selective permeability?

Proteins embedded in two layers of phospholipids

How does the "fluid mosaic model" describe the structure of the plasma membrane?

Proteins in the membrane contribute to the mosaic quality of the membrane while the lateral and rotational movements of phospholipids contribute to its fluidity

Which of the following statements best explains the observation that proton pumps are used by organisms in every domain of life?

Proton gradients across a membrane were used by cells that were the common ancestor of all three domains of life

Which component in the figure above represents a microfilament of the cytoskeleton?

Rope-like structures

The solutions in the two arms of a U-tube are separated by a membrane that is permeable to water and glucose but not to sucrose. Side A is half-filled with a solution of 2M sucrose and 1M glucose. Side B is half-filled with 1M sucrose and 2M glucose. Initially, the liquid levels on both sides are equal. Which of the following statements best describes the relationship between the solutions on both sides of the U-tube?

Side A is isotonic to side B

Which of the following statements most accurately compares primary factors responsible for simple diffusion versus active transport?

Simple diffusion is driven by a concentration gradient, while active transport is driven by ATP hydrolysis

Which of the following types of molecules will diffuse through a cell membrane most readily?

Small hydrophobic molecules

Which of the following types of molecules are least likely to diffuse through the phospholipid bilayer of a cell membrane?

Small ions

Sweet potato cubes lose mass when soaked in _________

Sucrose

Which of the following statements best describes the normal tonicity conditions for typical plant and animal cells in their native environments?

The animal cell is in an isotonic solution, and the plant cell is in a hypotonic solution

Which of the following results is most likely result if a portion of an animal's blood is replaced with distilled water?

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

Red blood cells contain approximately a 2% concentration of solutes. A red blood cell is placed into a solution that contains a 4% concentration of solutes to which the cell is not permeable. What will happen to the red blood cell?

The cell will decrease in size as water flows out of it

What will happen to a red blood cell (RBC), which has an internal ion content of about 0.9%, if it is placed into a beaker of pure water?

The cell will swell because the water in the beaker is hypotonic relative to the cytoplasm of the RBC

Which statement is correct?

The contents of a red blood cell are hyperosmotic to distilled water

Which of the following statements best describes how unsaturated fatty acids increase membrane fluidity at lower temperatures?

The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly.

Celery stalks that are immersed in fresh water for several hours become stiff. Which of the following statements best explains the observation that similar stalks left in a 0.15 M salt solution become limp?

The fresh water is hypotonic and the salt solution is hypertonic to the cells of the celery stalks

Which of the following statements best describes the structure of a membrane based on the fluid mosaic model?

The membrane is composed of a fluid bilayer of phospholipids with embedded amphipathic proteins

Which of the following statements best explains how the membranes in winter wheat are able to remain fluid in extremely cold temperatures?

The membranes contain an increased proportion of unsaturated phospholipids

The plasma membrane exhibits selective permeability. This means that __________

The plasma membrane allows some substances to flow through it more easily than others

How do membrane phospholipids interact with water?

The polar heads interact with water; the nonpolar tails do not

Which of the following statements about osmosis is correct?

The presence of aquaporins (proteins that form water channels in the membrane) speeds up the process of osmosis

Which of the following statements best describes characteristic activities of a sodium-potassium pump?

The pump moves three sodium ions out of a cell and two potassium ions into a cell using energy from ATP hydrolysis

Which factors affect the rate of osmotic movement of water?

The rate of osmosis increases with increasing differences in solute concentrations between two solutions separated by a selectively permeable membrane

Human immunodeficiency virus (HIV) infects cells that have both CD4 and CCR5 cell surface molecules. The viral nucleic acid molecules are enclosed in a protein capsid, and the protein capsid is itself contained inside an envelope consisting of a lipid bilayer membrane and viral glycoproteins. One hypothesis for viral entry into cells is that binding of HIV membrane glycoproteins to CD4 and CCR5 initiates fusion of the HIV membrane with the plasma membrane, releasing the viral capsid into the cytoplasm. An alternative hypothesis is that HIV gains entry into the cell via receptor-mediated endocytosis, and membrane fusion occurs in the endocytotic vesicle. To test these alternative hypotheses for HIV entry, researchers labeled the lipids on the HIV membrane with a red fluorescent dye. What would be observed by live-cell fluorescence microscopy immediately after HIV entry if HIV enters the cell by endocytosis first, and then later fuses with the endocytotic vesicle membrane?

The red fluorescent dye-labeled lipids will appear in the infected cell's interior

A new drug designed for the treatment of lung cancer must specifically enter the cytoplasm of lung cells while not entering the cells of other tissues. Which of the following characteristics would likely enhance the specificity of this drug?

The similarity of the drug molecule to other molecules normally transported lung cells

A cell is placed into a solution and the cell shrinks. Which of the following is true regarding the solution?

The solution is hypertonic

Cell membranes have distinct inside and outside faces. Which of the following statements is the most plausible explanation for the asymmetrical nature of the two layers of the membrane?

The two layers of a cell membrane face different environments and carry out different functions

Which of the following statements about a typical plasma membrane is correct?

The two sides of the plasma membrane have different lipid and protein composition

The solutions in the two arms of a U-tube are separated by a membrane that is permeable to water and glucose but not to sucrose. Side A is half-filled with a solution of 2M sucrose and 1M glucose. Side B is half-filled with 1M sucrose and 2M glucose. Initially, the liquid levels on both sides are equal. Which of the following is the most likely result when the system has reached equilibrium?

The water level will be higher in side A than in side B

Which of the following statements best explains the reason that lipids and proteins are free to move laterally in membranes?

There are only weak hydrophobic interactions in the interior of the membrane

When the interior of a cell is in equilibrium with its environment, which of the following statements best describes the relative movement of molecules that can diffuse through the plasma membrane?

There is random movement of molecules into and out of the cell

Which of the following is correct regarding peripheral proteins?

These proteins are found only on the surface of the plasma membrane

Which of the following is correct regarding integral proteins?

These proteins exhibit both hydrophilic and hydrophobic properties

Which of the following statements best describes a characteristic feature of integral membrane proteins?

They are amphipathic, with at least one hydrophobic region

Which of the following statements describes the role of the transport protein in facilitated diffusion?

Transport proteins allow solutes to move passively down their concentration gradients across the membrane

The sodium-potassium pump __________

Transports sodium ions out of the cell and transports potassium ions into the cell

Which of the following best describes the structure of a biological membrane?

Two layers of phospholipids, with proteins either crossing the layers or on the surface of the layers

What happens when two solutions separated by a selectively permeable membrane reach osmotic equilibrium?

Water molecules move between the two solutions, but there is no net movement of water across the membrane

Which of the following molecular movements is due to diffusion or osmosis?

When a plant cell is placed in concentrated salt water, water moves out of the cell

Which of the following is least likely to be important in holding the components of a biological membrane together?

covalent interactions between the phospholipid and protein components of the membrane

The permeability of a biological membrane to a specific polar solute may depend on which of the following?

the types of transport proteins in the membrane

The internal solute concentration of a plant cell is about 0.8M. To demonstrate plasmolysis, it would be necessary to suspend the cell in what solution?

1.0M

The solutions in the two arms of a U-tube are separated by a membrane that is permeable to water and glucose but not to sucrose. Side A is half-filled with a solution of 2M sucrose and 1M glucose. Side B is half-filled with 1M sucrose and 2M glucose. Initially, the liquid levels on both sides are equal. When the system illustrated above reaches equilibrium, the sugar concentrations on both sides of the U-tube will be ________

1.5M glucose, 1.5M glucose

Which of the following plant cells would exhibit the most turgor pressure?

A cell placed in a hypotonic solution

The force driving simple diffusion is ________, while the energy source for active transport is ________

A concentration gradient; ATP hydrolysis

Which of the following would be least likely to diffuse through a plasma membrane without the help of a transport protein?

A large polar molecule

Which of the following substances would be most likely to pass through the plasma membrane without the help of a transport protein?

A nonpolar molecule, such as a hydrocarbon

Which of the following molecules would decrease the electrochemical gradient across a membrane?

A potassium channel

In which of the following circumstances would the cell or organism have the greatest need for osmoregulation?

A salmon moving from a river into an ocean

Which of the following statements best describes some aspect of the function of a protein that cotransports glucose and sodium ions into the intestinal cells of an animal?

A substance that blocks sodium ions from binding to the cotransport protein will also block the transport of glucose

If the concentration of phosphate in the cytosol is 2.0 mM, and the concentration of phosphate in the surrounding fluid is 0.1 mM, how could the cell increase the concentration of phosphate in the cytosol?

Active transport

Active and passive transport of solutes across a membrane typically differ in which of the following ways?

Active transport always involves the utilization of cellular energy, whereas passive transport does not require cellular energy

Which of the following is a correct difference between active transport and facilitated diffusion?

Active transport requires energy from ATP, and facilitated diffusion does not

A defect in which of the following molecules would dramatically reduce the rate of diffusion of water across cell membranes?

Aquaporins

How does cholesterol affect membrane fluidity?

At body temperature, it makes the membrane less fluid

Cells A and B are the same size, shape, and temperature, but cell A is metabolically less active than cell B; cell B is actively converting oxygen to water in cellular respiration. Oxygen will diffuse more rapidly into cell __________ because __________

B; the diffusion gradient in cell B is steeper

Why is energy required for active transport?

Because it moves solutes against their concentration gradient

If a red blood cell and a plant cell were placed in seawater, what would happen to the two types of cells?

Both cells would lose water; the red blood cell would shrivel, and the plant plasma membrane would pull away from the cell wall

Which component plays a critical role in cell-cell recognition?

Carbohydrates on the exterior of the phospholipid bilayer

Which of the following molecules is most likely to passively diffuse across the plasma membrane?

Carbon dioxide

An animal cell that lacks carbohydrates on the external surface of its plasma membrane would likely be impaired in which of the following functions?

Cell-cell recognition

What function do carbohydrates fulfill in the plasma membrane?

Cell-to-cell recognition

In which of the following ways do the membranes of a eukaryotic cell vary?

Certain proteins are unique to each membrane

In facilitated diffusion, __________ proteins provide openings in the plasma membrane for substances to flow through without changing structure, and __________ proteins allow passage of substances through the plasma membrane after undergoing a subtle change in shape

Channel; carrier

The phosphate transport system in bacteria imports phosphate into the cell even when the concentration of phosphate outside the cell is much lower than the cytoplasmic phosphate concentration. Because phosphate import depends on a pH gradient across the membrane, phosphate transport is most likely an example of which of the following transport processes?

Cotransport

The movement of glucose into a cell against its concentration gradient is most likely to be accomplished by which of the following?

Cotransport of the glucose with a proton or sodium ion that was pumped across the membrane using the energy of ATP hydrolysis

In some cells, there are many different ion electrochemical gradients across the plasma membrane even though there are usually only one or two types of proton pumps present in the membrane. The gradients of the other ions are most likely established by which of the following?

Cotransport proteins

Which of the following factors is a primary contributor underlying cause of familial hypercholesterolemia?

Defective LDL receptors on the cell membranes

A nursing infant is able to obtain disease-fighting antibodies, which are large protein molecules, from its mother's milk. These molecules probably enter the cells lining the baby's digestive tract via which process?

Endocytosis

Which of the following statements correctly describes some aspect of exocytosis or endocytosis?

Exocytosis and endocytosis change the surface area of the plasma membrane

Which of the following processes and organelle(s) accounts for the replacement of lipids and proteins lost from the plasma membrane?

Exocytosis and smooth and rough ER

Which of these statements describes some aspect of facilitated diffusion?

Facilitated diffusion of solutes may occur through channel or transport proteins in the membrane

Five dialysis bags, constructed of a type of membrane that 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 weighed, and the percent change in mass of each bag was graphed. 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?

Flat Line

Several epidemic microbial diseases of earlier centuries incurred high death rates because they resulted in severe dehydration due to diarrhea. Today these diseases are usually not fatal because of the development of which of the following types of treatments?

Hydrating drinks with high concentrations of salt and glucose

Which of the following statements best describes a characteristic feature of osmosis?

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

Diffusion of ions across membranes through specific ion channels is driven by ________

Ion electrochemical gradients

Which of the following statements best describes a characteristic feature of a carrier protein in a plasma membrane?

It exhibits specificity for a particular type of molecule

Which of the following statements best explains why the sodium-potassium pump is an electrogenic pump?

It generates voltage across the membrane

Which of the following statements about diffusion is true?

It is a passive process