Membrane Structure and Function

Matching Questions

Use the following to answer questions 1-10:

Choose the correct answer from the list below. Not all of the answers will be used. a) glycolipids

b) biomolecular sheets c) lateral diffusion d) integral

e) hydrophobic effect

f) acetylsalicylic acid (aspirin) g) water h) lipid raft i) hydrophobic j) ions k) high l) peripheral m) low

106

Lipid biolayers spontaneously form ____________.

107

The driving force for the formation of membrane bilayers.

109

____________membrane proteins are embedded in the hydrocarbon chains of membrane lipids.

110

____________ This substance inhibits prostaglandin H2 synthase-1 by blocking the channel

through which the substrate, arachidonate, travels.

111

Cells maintain a __________ concentration of intracellular potassium as compared to the extracellular concentration.

112

____________ The type of amino acid found in the transmembrane helix of an integral protein.

113

____________ This is the process by which lipids and proteins move in the membrane bilayer.

114

____________ These membrane components contain carbohydrates.

115

____________ This is a complex between cholesterol and membrane phospholipids.

Fill-in-the-Blank Questions

116

is the noncovalent force that favors close packing of the tails of the lipids in a membrane.

117

are bilayer lipid vesicles with an aqueous compartment.

118

The of small molecules is correlated with their relative solubilities in water and non-polar solvents.

119

Membranes are said to be because their two faces always differ from each other.

120

inserts into lipid bilayers, disrupting interactions between fatty acids, thereby helping to

maintain membrane fluidity.

121

membrane proteins are bound primarily by electrostatic and hydrogen bond interactions with the head groups of lipids.

122

Most cell membranes are electrically polarized, the inside being relative to the outside.

123

The rate of lateral diffusion is such that a phospholipid molecule can travel from one end of a

bacterium to the other in of time.

124

The temperature at which a phospholipid membrane transitions from a rigid to a fluid state is referred to as .

125

An increase in the ratio of saturated to unsaturated fatty acid chains in a membrane the fluidity of the membrane.

Multiple-Choice Questions

126

The energy for __________ transport comes from the gradient itself. A) active

B) facilitated C) passive

D) pumped

E) ATP-mediated

127

Which of the following is true? A) Membranes are lipid bilayers.

B) Membrane lipids have both hydrophobic and hydrophilic properties. C) Many membranes are electrically polarized.

D) All of the above. E) None of the above.

128

How many molecules thick are membranes?

A) two

B) one

C) infinite

D) varying thickness, depending on structure E) None of the above.

129

Which of the following membranes would be the most fluid? A) a bilayer made of lipids with polyunsaturated 18 carbon-fatty acids B) a bilayer made of lipids with saturated 18 carbon-fatty acids C) a bilayer made of lipids with saturated 16 carbon-fatty acids D) a bilayer made of lipids with polyunsaturated 16 carbon-fatty acids E) All of the above are equivalent in fluidity.

130

Which of the following statements is consistent with the structure of biological membranes? A) All membrane proteins are integral and associate with the hydrophobic region of the membrane. B) Both proteins and lipids readily undergo transverse (“flip-flop”) diffusion from the inside to the

outside of the membrane. C) Membranes are symmetric.

D) The membrane lipids self-assemble to form the lipid bilayer.

E) A biological membrane consists of proteins sandwiched between two layers of lipids, which is referred to as a lipid bilayer.

131

Digitalis is a cardiotoinic steroid that does not act like a steroid. Instead its function is to inhibit____________.

A) the Na+-K+ pump B) fatty acid intake C) calcium channels

D) potassium and sodium pores E) dropsy channel

132

An anti-porter and a symporter are examples of _____________. A) passive diffusion

B) primary active transporters C) entropy driven pores D) an ABC transporter E) secondary transporter

133

Carbohydrate residues attached to the membrane lipids are A) always positioned on the intracellular side of the membrane. B) always positioned on the inside center of the bilayer.

C) always positioned on the extracellular side of the membrane. D) always positioned equally on both sides of the membrane. E) also covalently attached to membrane proteins.

134

What force(s) stabilize(s) the lipid bilayers? A) van der Waals interactions

B) electrostatic and hydrogen bonding between the polar heads and surrounding water C) covalent bonds between the lipid tails

D) covalent bonds between the lipids and membrane proteins E) A and B

135

The degree of membrane fluidity depends on A) the percentage of lipids that contain choline. B) the percentage of glycolipids.

C) the percentage of free fatty acids.

D) the percentage of unsaturated fatty acids. E) None of the above.

136

Which is the proper order of permeability of molecules across a membrane, from the most permeable to the least?

A) water, glucose, urea, sodium ion D) indole, glucose, urea, sodium ion B) water, indole, glucose, sodium ion E) indole, water, glucose, sodium ion C) water, indole, sodium ion, glucose

137

The most common motif found in membrane spanning proteins is: A)  helices of nonpolar amino acids that pass through the membrane.

B) _ helices of charged amino acids that form channels via extensive hydrogen bonding. C) triple helix of  helices.

D) a helix-turn-helix arrangement of the peptide strands. E) None of the above.

138

The fluorescence recovery after photobleaching (FRAP) technique has been used to study: A) membrane composition.

B) lateral diffusion in membranes.

C) protein structural motifs in membranes. D) All of the above.

139

The low incidence of protein or lipid flip-flop in a membrane preserves:

A) membrane fluidity. D) All of the above.

B) membrane melting temperatures. E) None of the above. C) membrane asymmetry.

140

Which of the following helps regulate membrane fluidity in animals?

A) protein D) magnesium ion

B) cholesterol E) None of the above.

C) ATP

141

Which of the following describes the role of a protein in the selective permeability of a membrane?

A) The polar heads of phospholipids in allowing polar molecule to cross membranes. B) The binding of steroids to an extracellular peripheral membrane protein.

C) The insertion of a porin with polar amino acids forming the β strands.

D) Na+_{, K}+_{-ATPase activity that sets up an electrical potential across the membrane.}

E) All of the above.

142

Would you agree that a peripheral membrane protein can act as a Na+_{, K}+_{-ATPase and why?}

A) Yes, because the Na+ _{and K}+ _{is available intracellularly and extracellularly.}

B) Yes, because the hydrophobic amino side chains of the α helices firmly anchor the protein to the membrane.

C) No, because a peripheral protein does not form a transporter across the entire membrane. D) No, because only secondary active transport proteins can act as a Na+_,K+-_ATPase.

E) No, because a P-glycoprotein must also be present for Na+_{, K}+_{-ATPase activity.}

143

What evidence exists to show that membrane asymmetry can be preserved for long periods? A) Lateral diffusion from fluorescence recovery after photo-bleaching experiments.

B) Transverse diffusion of proteins has not been observed.

C) Facilitated diffusion can take place in either direction depending on the concentration gradient. D) Tumor cells often become resistant to drugs.

E) The α helices in membrane-spanning proteins are hydrophobic and tightly packed.

144

If you wanted to study how membranes regulate their curvature and budding processes, which of the following membrane structures would you study?

A) presence of lipid rafts

B) degree of fatty acid unsaturation C) presence of active transport proteins D) presence of prostaglandin H2 synthase-1

Short-Answer Questions

145

Why are membranes impermeable to most substances?

146

How do proteins function to make membranes selectively permeable?

147

What are the key biochemical elements for transmembrane spanning proteins?

148

Flip flopping of lipids takes place once in several hours. This is evidence for what?

149

Draw a cross-section of a membrane bilayer and a liposome.

150

Describe a lipid raft and their potential role in a cell.

151

How are lipid bilayers formed? What is the driving force?

152

Why do most phospholipids preferentially form sheets instead of micelles?

153

What are liposomes? What are some of the current commercial applications?

154

Describe the effect of introducing a sodium ion pore into a membrane containing the Na+_-

glucose symporter.

156

What is the function of prostaglandin H2 synthase-1? How does its position in the membrane

facilitate its activity?

157

What is multi-drug resistance?

158

Describe the selectivity of the potassium ion channel.

Ans: There are critical amino acids on helical domains in the pore of the channel that face the center. These residues point a carboxyl group inward, which binds potassium ions, creating a selective filter for the K+ _ions

Section: 12.5

159

How do secondary transporters drive the transport of a substance up its concentration gradient? Ans: The thermodynamically uphill flow of one molecule is coupled to the downhill flow of another.

Section: 12.5

160

Why do defects in ABC transporters cause such serious health problems?

Ans: ABC transporters are transport proteins that include ATP-binding domains called ATP-binding cassettes (ABCs). ABC transporters are one of the largest protein superfamilies and are found in all forms of life. Examples include multi-drug resistance protein (MRDR) and cystic fibrosis transmembrane regulator (CFTR). Defects in ABC transporters usually involve a defect in an active transport system within an organ or cell type.

Section: 12.5

Chapter 12 Membrane Structure and Function

Matching Questions

Use the following to answer questions 1-10:

Choose the correct answer from the list below. Not all of the answers will be used. a) glycolipids

b) biomolecular sheets c) lateral diffusion d) integral

e) hydrophobic effect

f) acetylsalicylic acid (aspirin) g) water h) lipid raft i) hydrophobic j) ions k) high l) peripheral m) low

161

Lipid biolayers spontaneously form ____________.

162

The driving force for the formation of membrane bilayers.

163

________ has a higher permeability through lipid bilayers than ions and most polar molecules.

164

____________membrane proteins are embedded in the hydrocarbon chains of membrane lipids.

165

____________ This substance inhibits prostaglandin H2 synthase-1 by blocking the channel

through which the substrate, arachidonate, travels.

166

Cells maintain a __________ concentration of intracellular potassium as compared to the extracellular concentration.

167

____________ The type of amino acid found in the transmembrane helix of an integral protein.

168

____________ This is the process by which lipids and proteins move in the membrane bilayer.

170

____________ This is a complex between cholesterol and membrane phospholipids.

Fill-in-the-Blank Questions

171

is the noncovalent force that favors close packing of the tails of the lipids in a membrane.

172

are bilayer lipid vesicles with an aqueous compartment.

173

The of small molecules is correlated with their relative solubilities in water and non-polar solvents.

174

Membranes are said to be because their two faces always differ from each other.

175

inserts into lipid bilayers, disrupting interactions between fatty acids, thereby helping to

maintain membrane fluidity.

176

membrane proteins are bound primarily by electrostatic and hydrogen bond interactions with the head groups of lipids.

177

Most cell membranes are electrically polarized, the inside being relative to the outside.

178

The rate of lateral diffusion is such that a phospholipid molecule can travel from one end of a

bacterium to the other in of time.

179

The temperature at which a phospholipid membrane transitions from a rigid to a fluid state is referred to as .

180

An increase in the ratio of saturated to unsaturated fatty acid chains in a membrane the fluidity of the membrane.

181

The energy for __________ transport comes from the gradient itself. A) active B) facilitated C) passive D) pumped E) ATP-mediated

182

Which of the following is true? A) Membranes are lipid bilayers.

B) Membrane lipids have both hydrophobic and hydrophilic properties. C) Many membranes are electrically polarized.

D) All of the above. E) None of the above.

183

How many molecules thick are membranes?

A) two

B) one

C) infinite

D) varying thickness, depending on structure E) None of the above.

184

Which of the following membranes would be the most fluid? A) a bilayer made of lipids with polyunsaturated 18 carbon-fatty acids B) a bilayer made of lipids with saturated 18 carbon-fatty acids C) a bilayer made of lipids with saturated 16 carbon-fatty acids D) a bilayer made of lipids with polyunsaturated 16 carbon-fatty acids E) All of the above are equivalent in fluidity.

185

Which of the following statements is consistent with the structure of biological membranes? A) All membrane proteins are integral and associate with the hydrophobic region of the membrane. B) Both proteins and lipids readily undergo transverse (“flip-flop”) diffusion from the inside to the

outside of the membrane. C) Membranes are symmetric.

D) The membrane lipids self-assemble to form the lipid bilayer.

E) A biological membrane consists of proteins sandwiched between two layers of lipids, which is referred to as a lipid bilayer.

186

Digitalis is a cardiotoinic steroid that does not act like a steroid. Instead its function is to inhibit____________.

A) the Na+-K+ pump B) fatty acid intake C) calcium channels

D) potassium and sodium pores E) dropsy channel

187

An anti-porter and a symporter are examples of _____________. A) passive diffusion

B) primary active transporters C) entropy driven pores D) an ABC transporter E) secondary transporter

188

Carbohydrate residues attached to the membrane lipids are A) always positioned on the intracellular side of the membrane. B) always positioned on the inside center of the bilayer.

C) always positioned on the extracellular side of the membrane. D) always positioned equally on both sides of the membrane. E) also covalently attached to membrane proteins.

189

What force(s) stabilize(s) the lipid bilayers? A) van der Waals interactions

B) electrostatic and hydrogen bonding between the polar heads and surrounding water C) covalent bonds between the lipid tails

D) covalent bonds between the lipids and membrane proteins E) A and B

190

The degree of membrane fluidity depends on A) the percentage of lipids that contain choline. B) the percentage of glycolipids.

C) the percentage of free fatty acids.

D) the percentage of unsaturated fatty acids. E) None of the above.

191

Which is the proper order of permeability of molecules across a membrane, from the most permeable to the least?

A) water, glucose, urea, sodium ion D) indole, glucose, urea, sodium ion B) water, indole, glucose, sodium ion E) indole, water, glucose, sodium ion C) water, indole, sodium ion, glucose

192

The most common motif found in membrane spanning proteins is: A) _ helices of nonpolar amino acids that pass through the membrane.

B)  helices of charged amino acids that form channels via extensive hydrogen bonding. C) triple helix of  helices.

D) a helix-turn-helix arrangement of the peptide strands. E) None of the above.

193

The fluorescence recovery after photobleaching (FRAP) technique has been used to study: A) membrane composition.

B) lateral diffusion in membranes.

C) protein structural motifs in membranes. D) All of the above.

E) None of the above.

194

The low incidence of protein or lipid flip-flop in a membrane preserves:

A) membrane fluidity. D) All of the above.

B) membrane melting temperatures. E) None of the above. C) membrane asymmetry.

195

Which of the following helps regulate membrane fluidity in animals?

A) protein D) magnesium ion

B) cholesterol E) None of the above.

C) ATP

196

Which of the following describes the role of a protein in the selective permeability of a membrane?

A) The polar heads of phospholipids in allowing polar molecule to cross membranes. B) The binding of steroids to an extracellular peripheral membrane protein.

C) The insertion of a porin with polar amino acids forming the β strands.

D) Na+_{, K}+_{-ATPase activity that sets up an electrical potential across the membrane.}

E) All of the above.

197

Would you agree that a peripheral membrane protein can act as a Na+_{, K}+_{-ATPase and why?}

A) Yes, because the Na+ _{and K}+ _{is available intracellularly and extracellularly.}

B) Yes, because the hydrophobic amino side chains of the α helices firmly anchor the protein to the membrane.

C) No, because a peripheral protein does not form a transporter across the entire membrane. D) No, because only secondary active transport proteins can act as a Na+_,K+-_ATPase.

198

What evidence exists to show that membrane asymmetry can be preserved for long periods? A) Lateral diffusion from fluorescence recovery after photo-bleaching experiments.

B) Transverse diffusion of proteins has not been observed.

C) Facilitated diffusion can take place in either direction depending on the concentration gradient. D) Tumor cells often become resistant to drugs.

E) The α helices in membrane-spanning proteins are hydrophobic and tightly packed.

199

If you wanted to study how membranes regulate their curvature and budding processes, which of the following membrane structures would you study?

A) presence of lipid rafts

B) degree of fatty acid unsaturation C) presence of active transport proteins D) presence of prostaglandin H2 synthase-1

E) None of the above.

Short-Answer Questions

200

Why are membranes impermeable to most substances?

201

How do proteins function to make membranes selectively permeable?

202

What are the key biochemical elements for transmembrane spanning proteins?

203

Flip flopping of lipids takes place once in several hours. This is evidence for what?

204

Draw a cross-section of a membrane bilayer and a liposome.

205

Describe a lipid raft and their potential role in a cell.

207

Why do most phospholipids preferentially form sheets instead of micelles?

208

What are liposomes? What are some of the current commercial applications?

209

Describe the effect of introducing a sodium ion pore into a membrane containing the Na+_-

glucose symporter.

210

Draw a bilayer membrane that has both an integral and peripheral protein present.

211

What is the function of prostaglandin H2 synthase-1? How does its position in the membrane

facilitate its activity?

212

What is multi-drug resistance?

213

Describe the selectivity of the potassium ion channel.

Ans: There are critical amino acids on helical domains in the pore of the channel that face the center. These residues point a carboxyl group inward, which binds potassium ions, creating a selective filter for the K+ _ions

Section: 12.5

214

How do secondary transporters drive the transport of a substance up its concentration gradient? Ans: The thermodynamically uphill flow of one molecule is coupled to the downhill flow of another.

Section: 12.5

215

Why do defects in ABC transporters cause such serious health problems?

Ans: ABC transporters are transport proteins that include ATP-binding domains called ATP-binding cassettes (ABCs). ABC transporters are one of the largest protein superfamilies and are found in all forms of life. Examples include multi-drug resistance protein (MRDR) and cystic fibrosis transmembrane regulator (CFTR). Defects in ABC transporters usually involve a defect in an active transport system within an organ or cell type.

In document Test Bank of Tymoczko's Biochemistry a Short Course 3Rd EDITION (Six Month Access) John L. Tymoc (Page 89-104)