Question 1

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

Accepted Answer

A)  an animal connective tissue cell bathed in isotonic body fluid 
B)  a salmon moving from a river into an ocean 
C)  a red blood cell surrounded by plasma 
D)  a plant being grown hydroponically in a watery mixture of designated nutrients 
A)  an animal connective tissue cell bathed in isotonic body fluid 
B)  a salmon moving from a river into an ocean 
C)  a red blood cell surrounded by plasma 
D)  a plant being grown hydroponically in a watery mixture of designated nutrients

Question 2

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

Accepted Answer

A)  It transports equal quantities of Na+ and K+ across the membrane in opposite directions. 
B)  It is used to drive the transport of glucose against a concentration gradient. 
C)  It decreases the voltage difference across the membrane. 
D)  It generates voltage across the membrane. 
A)  It transports equal quantities of Na+ and K+ across the membrane in opposite directions. 
B)  It is used to drive the transport of glucose against a concentration gradient. 
C)  It decreases the voltage difference across the membrane. 
D)  It generates voltage across the membrane.

Question 3

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 2 M sucrose and 1 M glucose. Side B is half-filled with 1 M sucrose and 2 M 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 ________.

Accepted Answer

A)  2 M sucrose, 1 M glucose 
B)  1 M sucrose, 2 M glucose 
C)  1 M sucrose, 1 M glucose 
D)  1.5 M sucrose, 1.5 M glucose 
A)  2 M sucrose, 1 M glucose 
B)  1 M sucrose, 2 M glucose 
C)  1 M sucrose, 1 M glucose 
D)  1.5 M sucrose, 1.5 M glucose

Question 4

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?

Accepted Answer

A)  The cell will shrink because the water in the beaker is hypotonic relative to the cytoplasm of the RBC. 
B)  The cell will shrink because the water in the beaker is hypertonic relative to the cytoplasm of the RBC. 
C)  The cell will swell because the water in the beaker is hypotonic relative to the cytoplasm of the RBC. 
D)  The cell will remain the same size because the solution outside the cell is isotonic. 
A)  The cell will shrink because the water in the beaker is hypotonic relative to the cytoplasm of the RBC. 
B)  The cell will shrink because the water in the beaker is hypertonic relative to the cytoplasm of the RBC. 
C)  The cell will swell because the water in the beaker is hypotonic relative to the cytoplasm of the RBC. 
D)  The cell will remain the same size because the solution outside the cell is isotonic.

Question 5

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?

Accepted Answer

A)  Cell membranes form a border between adjacent cells in tightly packed tissues such as epithelium. 
B)  Cell membranes communicate signals between different cell types. 
C)  The two layers of a cell membrane face different environments and carry out different functions. 
D)  Proteins only function on the cytoplasmic side of the cell membrane. 
A)  Cell membranes form a border between adjacent cells in tightly packed tissues such as epithelium. 
B)  Cell membranes communicate signals between different cell types. 
C)  The two layers of a cell membrane face different environments and carry out different functions. 
D)  Proteins only function on the cytoplasmic side of the cell membrane.

Question 6

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

Accepted Answer

A)  The membrane is composed of a fluid bilayer of phospholipids between two layers of hydrophilic proteins. 
B)  The membrane is composed of a single layer of fluid phospholipids between two layers of hydrophilic proteins. 
C)  The membrane is composed of a mosaic of fluid polysaccharides and amphipathic proteins. 
D)  The membrane is composed of a fluid bilayer of phospholipids with embedded amphipathic proteins. 
A)  The membrane is composed of a fluid bilayer of phospholipids between two layers of hydrophilic proteins. 
B)  The membrane is composed of a single layer of fluid phospholipids between two layers of hydrophilic proteins. 
C)  The membrane is composed of a mosaic of fluid polysaccharides and amphipathic proteins. 
D)  The membrane is composed of a fluid bilayer of phospholipids with embedded amphipathic proteins.

Question 7

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

Accepted Answer

A)  active transport pumps 
B)  ion concentration gradients only 
C)  electrical gradients only 
D)  ion electrochemical gradients 
A)  active transport pumps 
B)  ion concentration gradients only 
C)  electrical gradients only 
D)  ion electrochemical gradients

Question 8

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?

Accepted Answer

A)  Sodium and glucose compete for the same binding site in the cotransporter. 
B)  Glucose entering the cell down its concentration gradient provides energy for uptake of sodium ions against the electrochemical gradient. 
C)  Sodium ions can move down their electrochemical gradient through the cotransporter whether or not glucose is present outside the cell. 
D)  A substance that blocks sodium ions from binding to the cotransport protein will also block the transport of glucose. 
A)  Sodium and glucose compete for the same binding site in the cotransporter. 
B)  Glucose entering the cell down its concentration gradient provides energy for uptake of sodium ions against the electrochemical gradient. 
C)  Sodium ions can move down their electrochemical gradient through the cotransporter whether or not glucose is present outside the cell. 
D)  A substance that blocks sodium ions from binding to the cotransport protein will also block the transport of glucose.

Question 9

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

Accepted Answer

A)  facilitated diffusion of chloride ions across the membrane through a chloride channel 
B)  movement of Na+ ions from a lower concentration in a mammalian cell to a higher concentration in the extracellular fluid 
C)  movement of glucose molecules into a bacterial cell from a medium containing a higher concentration of glucose than inside the cell 
D)  movement of carbon dioxide out of a paramecium 
A)  facilitated diffusion of chloride ions across the membrane through a chloride channel 
B)  movement of Na+ ions from a lower concentration in a mammalian cell to a higher concentration in the extracellular fluid 
C)  movement of glucose molecules into a bacterial cell from a medium containing a higher concentration of glucose than inside the cell 
D)  movement of carbon dioxide out of a paramecium

Question 10

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

Accepted Answer

A)  an aquaporin 
B)  a proton pump 
C)  a potassium channel 
D)  a sucrose carrier protein 
A)  an aquaporin 
B)  a proton pump 
C)  a potassium channel 
D)  a sucrose carrier protein

Question 11

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

Accepted Answer

A)  pinocytosis brings only water molecules into the cell, but receptor-mediated endocytosis brings in other molecules as well 
B)  pinocytosis increases the surface area of the plasma membrane, whereas receptor-mediated endocytosis decreases the plasma membrane surface area 
C)  pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis offers more selectivity 
D)  pinocytosis can concentrate substances from the extracellular fluid, but receptor-mediated endocytosis cannot 
A)  pinocytosis brings only water molecules into the cell, but receptor-mediated endocytosis brings in other molecules as well 
B)  pinocytosis increases the surface area of the plasma membrane, whereas receptor-mediated endocytosis decreases the plasma membrane surface area 
C)  pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis offers more selectivity 
D)  pinocytosis can concentrate substances from the extracellular fluid, but receptor-mediated endocytosis cannot

Question 12

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

Accepted Answer

A)  large hydrophobic molecules 
B)  small hydrophobic molecules 
C)  large polar molecules 
D)  small ionic molecules 
A)  large hydrophobic molecules 
B)  small hydrophobic molecules 
C)  large polar molecules 
D)  small ionic molecules

Question 13

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

Accepted Answer

A)  The cell will burst. 
B)  Plasmolysis will shrink the interior of the cell. 
C)  The cell will become flaccid. 
D)  The cell will become turgid. 
A)  The cell will burst. 
B)  Plasmolysis will shrink the interior of the cell. 
C)  The cell will become flaccid. 
D)  The cell will become turgid.

Question 14

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

Accepted Answer

A)  on the outside of vesicles 
B)  on the inside surface of the cell membrane 
C)  on the inside surface of the vesicle 
D)  on the outer surface of the nucleus 
A)  on the outside of vesicles 
B)  on the inside surface of the cell membrane 
C)  on the inside surface of the vesicle 
D)  on the outer surface of the nucleus

Question 15

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

Accepted Answer

A)  transmembrane proteins 
B)  integral membrane proteins 
C)  peripheral membrane proteins 
D)  cholesterol 
A)  transmembrane proteins 
B)  integral membrane proteins 
C)  peripheral membrane proteins 
D)  cholesterol

Question 16

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

Accepted Answer

A)  The interior of the membrane is filled with liquid water. 
B)  Lipids and proteins repulse each other in the membrane. 
C)  Hydrophilic portions of the lipids are in the interior of the membrane. 
D)  There are only weak hydrophobic interactions in the interior of the membrane. 
A)  The interior of the membrane is filled with liquid water. 
B)  Lipids and proteins repulse each other in the membrane. 
C)  Hydrophilic portions of the lipids are in the interior of the membrane. 
D)  There are only weak hydrophobic interactions in the interior of the membrane.

Question 17

Which component in the accompanying figure plays a critical role in cell-cell recognition?

Accepted Answer

A)  A 
B)  B 
C)  C 
D)  E 
A)  A 
B)  B 
C)  C 
D)  E

Question 18

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

Accepted Answer

A)  Phospholipids are found only in certain membranes. 
B)  Certain proteins are unique to each membrane. 
C)  Only certain membranes of the cell are selectively permeable. 
D)  Some membranes have hydrophobic surfaces exposed to the cytoplasm while others have hydrophilic surfaces facing the cytoplasm. 
A)  Phospholipids are found only in certain membranes. 
B)  Certain proteins are unique to each membrane. 
C)  Only certain membranes of the cell are selectively permeable. 
D)  Some membranes have hydrophobic surfaces exposed to the cytoplasm while others have hydrophilic surfaces facing the cytoplasm.

Question 19

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?

Accepted Answer

A)  antiviral medications that are efficient and work well with most viruses 
B)  intravenous feeding techniques 
C)  medications to slow blood loss 
D)  hydrating drinks with high concentrations of salt and glucose 
A)  antiviral medications that are efficient and work well with most viruses 
B)  intravenous feeding techniques 
C)  medications to slow blood loss 
D)  hydrating drinks with high concentrations of salt and glucose

Question 20

Three lab groups carried out an experiment to identify the concentration of sucrose in six solutions. Each unknown solution (1-6) contained one of the following sucrose concentrations: 0.0 M, 0.2 M, 0.4 M, 0.6 M, 0.8 M, and -1.0 M. Cubes of sweet potato (1 cm3) were soaked for 24 hours in each solution and weighed to determine the change in mass. Each data entry represents the average of three sample replicates expressed as percent change in mass following a 24-hour soak in the unknown solutions. From the data given, which statement below most accurately describes something that has occurred in response to a particular unknown solution?

Accepted Answer

A)  Unknown solution 5 contains the highest concentration of sucrose, and the change in mass is due to the active transport of sucrose out of the cell. 
B)  Osmosis of water molecules from unknown solution 2 likely caused the increase in mass observed. 
C)  Passive transport of sucrose out of the potato cells explains the change in mass observed for unknown solution 6. 
D)  Unknown solution 3 represents a sucrose concentration slightly higher than the molarity of sweet potato cells, thus water is transported out of the cells. 
A)  Unknown solution 5 contains the highest concentration of sucrose, and the change in mass is due to the active transport of sucrose out of the cell. 
B)  Osmosis of water molecules from unknown solution 2 likely caused the increase in mass observed. 
C)  Passive transport of sucrose out of the potato cells explains the change in mass observed for unknown solution 6. 
D)  Unknown solution 3 represents a sucrose concentration slightly higher than the molarity of sweet potato cells, thus water is transported out of the cells.

Exam 8: Cell Membranes

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

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

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?

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?

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

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

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?

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

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

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

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

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

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

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

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

Which component in the accompanying figure plays a critical role in cell-cell recognition?

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

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?

Biology and Its Themes

Atoms and Molecules

The Chemistry of Water

Carbon: the Basis of Molecular Diversity

Biological Macromolecules and Lipids

Energy and Life

Cell Structure and Function

Cellular Signaling

Cell Respiration

Photosynthetic Processes

Mitosis

Sexual Life Cycles and Meiosis

Mendelian Genetics

Linkage and Chromosomes

Nucleic Acids and Inheritance

Expression of Genes

Control of Gene Expression

Dna Technology

The Evolution of Genomes

How Evolution Works

Phylogenetic Reconstruction

Microevolution

Species and Speciation

Macroevolution

Introduction to Viruses

Prokaryotes

The Origin and Evolution of Eukaryotes

Nonvascular and Seedless Vascular Plants

Seed Plants

Introduction to Fungi

An Introduction to Animal Diversity

Invertebrates

Vertebrates

Plant Structure and Growth

Transport in Vascular Plants

Plant Nutrition

Reproduction of Flowering Plants

Plant Signals and Behavior

The Animal Body

Chemical Signals in Animals

Animal Digestive Systems

Animal Transport Systems

Animal Excretory Systems

Animal Reproductive Systems

Development in Animals

Animal Defenses Against Infection

Electrical Signals in Animals

Neural Regulation in Animals

Sensation and Movement in Animals

An Overview of Ecology

Behavioral Ecology

Populations and Life History Traits

Biodiversity and Communities

Energy Flow and Chemical Cycling in Ecosystems

Conservation and Global Ecology

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