Question 1

An animal cell lacking oligosaccharides on the external surface of its plasma membrane would likely be impaired in which function?

Accepted Answer

A)  transporting ions against an electrochemical gradient 
B)  cell-cell recognition 
C)  maintaining fluidity of the phospholipid bilayer 
D)  attaching to the cytoskeleton 
E)  establishing the diffusion barrier to charged molecules 
A)  transporting ions against an electrochemical gradient 
B)  cell-cell recognition 
C)  maintaining fluidity of the phospholipid bilayer 
D)  attaching to the cytoskeleton 
E)  establishing the diffusion barrier to charged molecules

Question 2

The difference between pinocytosis and receptor-mediated endocytosis is that

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 requires cellular energy, but receptor-mediated endocytosis does not. 
E)  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 requires cellular energy, but receptor-mediated endocytosis does not. 
E)  pinocytosis can concentrate substances from the extracellular fluid, but receptor-mediated endocytosis cannot.

Question 3

Which of the following factors would tend to increase membrane fluidity?

Accepted Answer

A)  a greater proportion of unsaturated phospholipids 
B)  a greater proportion of saturated phospholipids 
C)  a lower temperature 
D)  a relatively high protein content in the membrane 
E)  a greater proportion of relatively large glycolipids compared with lipids having smaller molecular masses 
A)  a greater proportion of unsaturated phospholipids 
B)  a greater proportion of saturated phospholipids 
C)  a lower temperature 
D)  a relatively high protein content in the membrane 
E)  a greater proportion of relatively large glycolipids compared with lipids having smaller molecular masses

Question 4

If HIV first enters the cell in an endocytotic vesicle, instead of directly fusing with the plasma membrane, then

Accepted Answer

A)  HIV infection should be hindered by microtubule polymerization inhibitors such as nocodazole. 
B)  HIV infection should be more efficient at lower temperatures. 
C)  intact cortical actin microfilaments should interfere with HIV infection. 
D)  cells lacking integrins should be resistant to HIV infection. 
E)  addition of ligands for other cell-surface receptors to stimulate their endocytosis should increase the efficiency of HIV infection. 
A)  HIV infection should be hindered by microtubule polymerization inhibitors such as nocodazole. 
B)  HIV infection should be more efficient at lower temperatures. 
C)  intact cortical actin microfilaments should interfere with HIV infection. 
D)  cells lacking integrins should be resistant to HIV infection. 
E)  addition of ligands for other cell-surface receptors to stimulate their endocytosis should increase the efficiency of HIV infection.

Question 5

According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly

Accepted Answer

A)  spread in a continuous layer over the inner and outer surfaces of the membrane. 
B)  confined to the hydrophobic interior of the membrane. 
C)  embedded in a lipid bilayer. 
D)  randomly oriented in the membrane, with no fixed inside-outside polarity. 
E)  free to depart from the fluid membrane and dissolve in the surrounding solution. 
A)  spread in a continuous layer over the inner and outer surfaces of the membrane. 
B)  confined to the hydrophobic interior of the membrane. 
C)  embedded in a lipid bilayer. 
D)  randomly oriented in the membrane, with no fixed inside-outside polarity. 
E)  free to depart from the fluid membrane and dissolve in the surrounding solution.

Question 6

Mammalian blood contains the equivalent of 0.15 M NaCl. Seawater contains the equivalent of 0.45 M NaCl. What will happen if red blood cells are transferred to seawater?

Accepted Answer

A)  Water will leave the cells, causing them to shrivel and collapse. 
B)  NaCl will be exported from the red blood cells by facilitated diffusion. 
C)  The blood cells will take up water, swell, and eventually burst. 
D)  NaCl will passively diffuse into the red blood cells. 
E)  The blood cells will expend ATP for active transport of NaCl into the cytoplasm. 
A)  Water will leave the cells, causing them to shrivel and collapse. 
B)  NaCl will be exported from the red blood cells by facilitated diffusion. 
C)  The blood cells will take up water, swell, and eventually burst. 
D)  NaCl will passively diffuse into the red blood cells. 
E)  The blood cells will expend ATP for active transport of NaCl into the cytoplasm.

Question 7

Water passes quickly through cell membranes because

Accepted Answer

A)  the bilayer is hydrophilic. 
B)  it moves through hydrophobic channels. 
C)  water movement is tied to ATP hydrolysis. 
D)  it is a small, polar, charged molecule. 
E)  it moves through aquaporins in the membrane. 
A)  the bilayer is hydrophilic. 
B)  it moves through hydrophobic channels. 
C)  water movement is tied to ATP hydrolysis. 
D)  it is a small, polar, charged molecule. 
E)  it moves through aquaporins in the membrane.

Question 8

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

Accepted Answer

A)  CO₂ 
B)  an amino acid 
C)  glucose 
D)  K⁺ 
E)  starch 
A)  CO₂ 
B)  an amino acid 
C)  glucose 
D)  K⁺ 
E)  starch

Question 9

What is the voltage across a membrane called?

Accepted Answer

A)  water potential 
B)  chemical gradient 
C)  membrane potential 
D)  osmotic potential 
E)  electrochemical gradient 
A)  water potential 
B)  chemical gradient 
C)  membrane potential 
D)  osmotic potential 
E)  electrochemical gradient

Question 10

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 if the red fluorescent lipid dye-labeled HIV membrane fuses with the target cell plasma membrane?

Accepted Answer

A)  A spot of red fluorescence will remain on the infected cell's plasma membrane, marking the site of membrane fusion and HIV entry. 
B)  The red fluorescent dye-labeled lipids will diffuse in the infected cell's plasma membrane and become difficult to detect. 
C)  A spot of red fluorescence will move into the infected cell's cytoplasm. 
D)  A spot of red fluorescence will remain outside the cell after delivering the viral capsid. 
E)  Fluorescence microscopy does not have enough resolution to visualize fluorescently labeled HIV virus particles. 
A)  A spot of red fluorescence will remain on the infected cell's plasma membrane, marking the site of membrane fusion and HIV entry. 
B)  The red fluorescent dye-labeled lipids will diffuse in the infected cell's plasma membrane and become difficult to detect. 
C)  A spot of red fluorescence will move into the infected cell's cytoplasm. 
D)  A spot of red fluorescence will remain outside the cell after delivering the viral capsid. 
E)  Fluorescence microscopy does not have enough resolution to visualize fluorescently labeled HIV virus particles.

Question 11

The primary function of polysaccharides attached to the glycoproteins and glycolipids of animal cell membranes is

Accepted Answer

A)  to facilitate diffusion of molecules down their concentration gradients. 
B)  to actively transport molecules against their concentration gradients. 
C)  to maintain the integrity of a fluid mosaic membrane. 
D)  to maintain membrane fluidity at low temperatures. 
E)  to mediate cell-to-cell recognition. 
A)  to facilitate diffusion of molecules down their concentration gradients. 
B)  to actively transport molecules against their concentration gradients. 
C)  to maintain the integrity of a fluid mosaic membrane. 
D)  to maintain membrane fluidity at low temperatures. 
E)  to mediate cell-to-cell recognition.

Question 12

The sodium-potassium pump is called an electrogenic pump because it

Accepted Answer

A)  pumps equal quantities of Na⁺ and K⁺ across the membrane. 
B)  pumps hydrogen ions out of the cell. 
C)  contributes to the membrane potential. 
D)  ionizes sodium and potassium atoms. 
E)  is used to drive the transport of other molecules against a concentration gradient. 
A)  pumps equal quantities of Na⁺ and K⁺ across the membrane. 
B)  pumps hydrogen ions out of the cell. 
C)  contributes to the membrane potential. 
D)  ionizes sodium and potassium atoms. 
E)  is used to drive the transport of other molecules against a concentration gradient.

Question 13

Ions diffuse across membranes through specific ion channels

Accepted Answer

A)  down their chemical gradients. 
B)  down their concentration gradients. 
C)  down the electrical gradients. 
D)  down their electrochemical gradients. 
E)  down the osmotic potential gradients. 
A)  down their chemical gradients. 
B)  down their concentration gradients. 
C)  down the electrical gradients. 
D)  down their electrochemical gradients. 
E)  down the osmotic potential gradients.

Question 14

In most cells, there are electrochemical gradients of many ions across the plasma membrane even though there are usually only one or two electrogenic pumps present in the membrane. The gradients of the other ions are most likely accounted for by

Accepted Answer

A)  cotransport proteins. 
B)  ion channels. 
C)  carrier proteins. 
D)  passive diffusion across the plasma membrane. 
E)  cellular metabolic reactions that create or destroy ions. 
A)  cotransport proteins. 
B)  ion channels. 
C)  carrier proteins. 
D)  passive diffusion across the plasma membrane. 
E)  cellular metabolic reactions that create or destroy ions.

Question 15

In a paramecium, cell surface integral membrane proteins are synthesized

Accepted Answer

A)  in the cytoplasm by free ribosomes. 
B)  by ribosomes in the nucleus. 
C)  by ribosomes bound to the rough endoplasmic reticulum. 
D)  by ribosomes in the Golgi vesicles. 
E)  by ribosomes bound to the inner surface of the plasma membrane. 
A)  in the cytoplasm by free ribosomes. 
B)  by ribosomes in the nucleus. 
C)  by ribosomes bound to the rough endoplasmic reticulum. 
D)  by ribosomes in the Golgi vesicles. 
E)  by ribosomes bound to the inner surface of the plasma membrane.

Question 16

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

Accepted Answer

A)  phospholipids and cellulose 
B)  nucleic acids and proteins 
C)  phospholipids and proteins 
D)  proteins and cellulose 
E)  glycoproteins and cholesterol 
A)  phospholipids and cellulose 
B)  nucleic acids and proteins 
C)  phospholipids and proteins 
D)  proteins and cellulose 
E)  glycoproteins and cholesterol

Question 17

Familial hypercholesterolemia is characterized by which of the following?

Accepted Answer

A)  defective LDL receptors on the cell membranes 
B)  poor attachment of the cholesterol to the extracellular matrix of cells 
C)  a poorly formed lipid bilayer that cannot incorporate cholesterol into cell membranes 
D)  inhibition of the cholesterol active transport system in red blood cells 
E)  a general lack of glycolipids in the blood cell membranes 
A)  defective LDL receptors on the cell membranes 
B)  poor attachment of the cholesterol to the extracellular matrix of cells 
C)  a poorly formed lipid bilayer that cannot incorporate cholesterol into cell membranes 
D)  inhibition of the cholesterol active transport system in red blood cells 
E)  a general lack of glycolipids in the blood cell membranes

Question 18

The movement of potassium into an animal cell requires

Accepted Answer

A)  low cellular concentrations of sodium. 
B)  high cellular concentrations of potassium. 
C)  an energy source such as ATP. 
D)  a cotransport protein. 
E)  a potassium channel protein. 
A)  low cellular concentrations of sodium. 
B)  high cellular concentrations of potassium. 
C)  an energy source such as ATP. 
D)  a cotransport protein. 
E)  a potassium channel protein.

Question 19

When a membrane is freeze-fractured, the bilayer splits down the middle between the two layers of phospholipids. In an electron micrograph of a freeze-fractured membrane, the bumps seen on the fractured surface of the membrane are

Accepted Answer

A)  peripheral proteins. 
B)  phospholipids. 
C)  carbohydrates. 
D)  integral proteins. 
E)  cholesterol molecules. 
A)  peripheral proteins. 
B)  phospholipids. 
C)  carbohydrates. 
D)  integral proteins. 
E)  cholesterol molecules.

Question 20

You are working on a team that is designing a new drug. In order for this drug to work, it must enter the cytoplasm of specific target cells. Which of the following would be a factor that determines whether the molecule selectively enters the target cells?

Accepted Answer

A)  blood or tissue type of the patient 
B)  hydrophobicity of the drug molecule 
C)  lack of charge on the drug molecule 
D)  similarity of the drug molecule to other molecules transported by the target cells 
E)  lipid composition of the target cells' plasma membrane 
A)  blood or tissue type of the patient 
B)  hydrophobicity of the drug molecule 
C)  lack of charge on the drug molecule 
D)  similarity of the drug molecule to other molecules transported by the target cells 
E)  lipid composition of the target cells' plasma membrane

Exam 7: Membrane Structure and Function

An animal cell lacking oligosaccharides on the external surface of its plasma membrane would likely be impaired in which function?

The difference between pinocytosis and receptor-mediated endocytosis is that

Which of the following factors would tend to increase membrane fluidity?

If HIV first enters the cell in an endocytotic vesicle, instead of directly fusing with the plasma membrane, then

According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly

Mammalian blood contains the equivalent of 0.15 M NaCl. Seawater contains the equivalent of 0.45 M NaCl. What will happen if red blood cells are transferred to seawater?

Water passes quickly through cell membranes because

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

What is the voltage across a membrane called?

The primary function of polysaccharides attached to the glycoproteins and glycolipids of animal cell membranes is

The sodium-potassium pump is called an electrogenic pump because it

Ions diffuse across membranes through specific ion channels

In most cells, there are electrochemical gradients of many ions across the plasma membrane even though there are usually only one or two electrogenic pumps present in the membrane. The gradients of the other ions are most likely accounted for by

In a paramecium, cell surface integral membrane proteins are synthesized

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

Familial hypercholesterolemia is characterized by which of the following?

The movement of potassium into an animal cell requires

When a membrane is freeze-fractured, the bilayer splits down the middle between the two layers of phospholipids. In an electron micrograph of a freeze-fractured membrane, the bumps seen on the fractured surface of the membrane are

You are working on a team that is designing a new drug. In order for this drug to work, it must enter the cytoplasm of specific target cells. Which of the following would be a factor that determines whether the molecule selectively enters the target cells?

Introduction: Themes in the Study of Life

The Chemical Context of Life

Water and Life

Carbon and the Molecular Diversity of Life

The Structure and Function of Large Biological Molecules

A Tour of the Cell

An Introduction to Metabolism

Cellular Respiration and Fermentation

Photosynthesis

Cell Communication

The Cell Cycle

Meiosis and Sexual Life Cycles

Mendel and the Gene Idea

The Chromosomal Basis of Inheritance

The Molecular Basis of Inheritance

From Gene to Protein

Regulation of Gene Expression

Viruses

Biotechnology

Genomes and Their Evolution

Descent with Modification: A Darwinian View of Life

The Evolution of Populations

The Origin of Species

The History of Life on Earth

Phylogeny and the Tree of Life

Bacteria and Archaea

Protists

Plant Diversity I: How Plants Colonized Land

Plant Diversity II: The Evolution of Seed Plants

Fungi

An Overview of Animal Diversity

An Introduction to Invertebrates

The Origin and Evolution of Vertebrates

Plant Structure, Growth, and Development

Resource Acquisition and Transport in Vascular Plants

Soil and Plant Nutrition

Angiosperm Reproduction and Biotechnology

Plant Responses to Internal and External Signals

Basic Principles of Animal Form and Function

Animal Nutrition

Circulation and Gas Exchange

The Immune System

Osmoregulation and Excretion

Hormones and the Endocrine System

Animal Reproduction

Animal Development

Neurons, Synapses, and Signaling

Nervous Systems

Sensory and Motor Mechanisms

Animal Behavior

An Introduction to Ecology and the Biosphere

Population Ecology

Community Ecology

Ecosystems and Restoration Ecology

Conservation Biology and Global Change

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