Question 1

Membrane fusion leading to neurotransmitter release requires the action of:

Accepted Answer

A)  cadherins. 
B)  selectins. 
C)  flipases. 
D)  tSNARE and vSNARE. 
E)  None of the answers is correct. 
A)  cadherins. 
B)  selectins. 
C)  flipases. 
D)  tSNARE and vSNARE. 
E)  None of the answers is correct.

Question 2

The following sequence is taken from an integral membrane protein.   Which part of this sequence most likely corresponds to a transmembrane helix?

Accepted Answer

The answer of The following sequence is taken from an...

Question 3

The specificity of the potassium channel for K+ over Na+ is mainly the result of the:

Accepted Answer

A)  differential interaction with the selectivity filter protein. 
B)  hydrophobicity of the channel. 
C)  phospholipid composition of the channel. 
D)  presence of carbohydrates in the channel. 
E)  presence of cholesterol in the channel. 
A)  differential interaction with the selectivity filter protein. 
B)  hydrophobicity of the channel. 
C)  phospholipid composition of the channel. 
D)  presence of carbohydrates in the channel. 
E)  presence of cholesterol in the channel.

Question 4

Reagents A and B both react covalently with primary amino groups such as those of phosphatidylethanolamine. Reagent A permeates erythrocytes, but reagent B is impermeant. Both A and B are available in radioisotopically labeled form. Describe a simple experiment by which you might determine whether the phosphatidylethanolamine of erythrocyte membranes is located in the outside face of the lipid bilayer, the inside face, or in both.

Accepted Answer

One simple experiment to determine the l

Question 5

What is the major difference between gated and nongated ion channels? Give an example of two different gating signals.

Accepted Answer

The major difference between gated and n

Question 6

(a) When relatively high concentrations of fatty acids are suspended in water, they form structures known as _____. (b) When relatively high concentrations of membrane phospholipids are dissolved in water, they form structures known as _____. (c) Why are the structures listed in your answers to (a) and (b) above energetically favored?

Accepted Answer

(a) When relatively high concentrations

Question 7

Membrane proteins:

Accepted Answer

A)  are sometimes covalently attached to lipid moieties. 
B)  are sometimes covalently attached to carbohydrate moieties. 
C)  are composed of the same 20 amino acids found in soluble proteins. 
D)  diffuse laterally in the membrane unless they are anchored 
E)  All of the answers are correct. 
A)  are sometimes covalently attached to lipid moieties. 
B)  are sometimes covalently attached to carbohydrate moieties. 
C)  are composed of the same 20 amino acids found in soluble proteins. 
D)  diffuse laterally in the membrane unless they are anchored 
E)  All of the answers are correct.

Question 8

The fluidity of the lipid side chains in the interior of a bilayer is generally increased by:

Accepted Answer

A)  a decrease in temperature. 
B)  an increase in fatty acyl chain length. 
C)  an increase in the number of double bonds in fatty acids. 
D)  an increase in the percentage of phosphatidyl ethanolamine 
E)  the binding of water to the fatty acyl side chains. 
A)  a decrease in temperature. 
B)  an increase in fatty acyl chain length. 
C)  an increase in the number of double bonds in fatty acids. 
D)  an increase in the percentage of phosphatidyl ethanolamine 
E)  the binding of water to the fatty acyl side chains.

Question 9

P-type ATPase transporters such as the SERCA pumps can be classified as enzymes. As what enzyme class would they be classified?

Accepted Answer

A)  oxidoreductases 
B)  transferases 
C)  hydrolases 
D)  lyases 
E)  ligases 
A)  oxidoreductases 
B)  transferases 
C)  hydrolases 
D)  lyases 
E)  ligases

Question 10

When a bacterium such as E. coli is shifted from a warmer growth temperature to a cooler growth temperature, it compensates by:

Accepted Answer

A)  increasing its metabolic rate to generate more heat. 
B)  putting longer-chain fatty acids into its membranes. 
C)  putting more unsaturated fatty acids into its membranes. 
D)  shifting from aerobic to anaerobic metabolism. 
E)  synthesizing thicker membranes to insulate the cell. 
A)  increasing its metabolic rate to generate more heat. 
B)  putting longer-chain fatty acids into its membranes. 
C)  putting more unsaturated fatty acids into its membranes. 
D)  shifting from aerobic to anaerobic metabolism. 
E)  synthesizing thicker membranes to insulate the cell.

Question 11

Which factor contributes to the selectivity pore of the potassium channel from S. lividans?

Accepted Answer

A)  backbone carbonyl groups in irregular secondary structures 
B)  negatively charged amino acids near the channel opening 
C)  the N-terminal ends of 4 $\alpha$ helices 
D)  both backbone carbonyl groups in irregular secondary structures and negatively charged amino acids near the channel opening 
E)  both backbone carbonyl groups in irregular secondary structures and the N-terminal ends of 4$\alpha$helices 
A)  backbone carbonyl groups in irregular secondary structures 
B)  negatively charged amino acids near the channel opening 
C)  the N-terminal ends of 4 $\alpha$ helices 
D)  both backbone carbonyl groups in irregular secondary structures and negatively charged amino acids near the channel opening 
E)  both backbone carbonyl groups in irregular secondary structures and the N-terminal ends of 4$\alpha$helices

Question 12

What is meant by the term "positive-inside rule"?

Accepted Answer

A)  The typical transmembrane potential for plasma membranes is positive on the inside. 
B)  Integral plasma membrane proteins commonly have positively charge amino acids on the cytosolic side. 
C)  Concentrations of cations are usually higher inside than outside of cells. 
D)  All of the answers are correct. 
E)  None of the answers is correct. 
A)  The typical transmembrane potential for plasma membranes is positive on the inside. 
B)  Integral plasma membrane proteins commonly have positively charge amino acids on the cytosolic side. 
C)  Concentrations of cations are usually higher inside than outside of cells. 
D)  All of the answers are correct. 
E)  None of the answers is correct.

Question 13

Explain why nonpolar compounds are generally able to diffuse across biological membranes without the aid of a specific transport system.

Accepted Answer

Nonpolar compounds are generally able to

Question 14

Consider the transport of K+ from the blood (where its concentration is about 4 mM) into an erythrocyte that contains 150 mM K+. The transmembrane potential is about 60 mV, inside negative relative to outside. What is the free-energy change for this transport process? (These values may be of use to you: R = 8.315 J/mol . K; T = 298 K;   (Faraday constant) = 96,480 J/V; N = 6.022 × 1023/mol.)

Accepted Answer

A)  about 5 J/mol 
B)  about 15 J/mol 
C)  about 5 kJ/mol 
D)  about 15 kJ/mol 
E)  It is impossible to calculate with the information given. 
A)  about 5 J/mol 
B)  about 15 J/mol 
C)  about 5 kJ/mol 
D)  about 15 kJ/mol 
E)  It is impossible to calculate with the information given.

Question 15

What prevents proton translocation through aquaporins?

Accepted Answer

A)  Asp and Glu residues bind to protons to prevent their translocation. 
B)  Carbonyl groups in the selectivity filter interact with water molecules. 
C)  Two side chain amide groups act as hydrogen bond donors to a single water molecule. 
D)  All of the answers are correct. 
E)  None of the answers is correct. 
A)  Asp and Glu residues bind to protons to prevent their translocation. 
B)  Carbonyl groups in the selectivity filter interact with water molecules. 
C)  Two side chain amide groups act as hydrogen bond donors to a single water molecule. 
D)  All of the answers are correct. 
E)  None of the answers is correct.

Question 16

Compare and contrast symport and antiport. Which term best describes the transport system mediated by the Na+K+ ATPase?

Accepted Answer

Symport and antiport are both types of m

Question 17

What are three differences between ion channels and ion transporters?

Accepted Answer

Ion channels and ion transporters are bo

Question 18

Which transporters can be classified as active transporters?

Accepted Answer

A)  flippases 
B)  floppases 
C)  scramblases 
D)  both flippases and floppases 
E)  both flippases and scramblases 
A)  flippases 
B)  floppases 
C)  scramblases 
D)  both flippases and floppases 
E)  both flippases and scramblases

Question 19

Which statement describes a general feature of the lipid bilayer in all biological membranes?

Accepted Answer

A)  Individual lipid molecules are free to diffuse laterally in the surface of the bilayer. 
B)  Individual lipid molecules in one face (monolayer) of the bilayer readily diffuse (flip-flop) to the other monolayer. 
C)  Polar, but uncharged, compounds readily diffuse across the bilayer. 
D)  The bilayer is stabilized by covalent bonds between neighboring phospholipid molecules. 
E)  The polar head groups face inward toward the inside of the bilayer. 
A)  Individual lipid molecules are free to diffuse laterally in the surface of the bilayer. 
B)  Individual lipid molecules in one face (monolayer) of the bilayer readily diffuse (flip-flop) to the other monolayer. 
C)  Polar, but uncharged, compounds readily diffuse across the bilayer. 
D)  The bilayer is stabilized by covalent bonds between neighboring phospholipid molecules. 
E)  The polar head groups face inward toward the inside of the bilayer.

Question 20

What symmetry types (e.g., cyclic, dihedral, icosahedral) would you expect transport proteins to exhibit? Why?

Accepted Answer

Transport proteins are likely to exhibit

Exam 11: Biological Membranes and Transport

Membrane fusion leading to neurotransmitter release requires the action of:

The following sequence is taken from an integral membrane protein. Which part of this sequence most likely corresponds to a transmembrane helix?

The specificity of the potassium channel for K+ over Na+ is mainly the result of the:

What is the major difference between gated and nongated ion channels? Give an example of two different gating signals.

Membrane proteins:

The fluidity of the lipid side chains in the interior of a bilayer is generally increased by:

P-type ATPase transporters such as the SERCA pumps can be classified as enzymes. As what enzyme class would they be classified?

When a bacterium such as E. coli is shifted from a warmer growth temperature to a cooler growth temperature, it compensates by:

Which factor contributes to the selectivity pore of the potassium channel from S. lividans?

What is meant by the term "positive-inside rule"?

Explain why nonpolar compounds are generally able to diffuse across biological membranes without the aid of a specific transport system.

What prevents proton translocation through aquaporins?

Compare and contrast symport and antiport. Which term best describes the transport system mediated by the Na+K+ ATPase?

What are three differences between ion channels and ion transporters?

Which transporters can be classified as active transporters?

Which statement describes a general feature of the lipid bilayer in all biological membranes?

What symmetry types (e.g., cyclic, dihedral, icosahedral) would you expect transport proteins to exhibit? Why?

The Foundations of Biochemistry

Water

Amino Acids, Peptides, and Proteins

The Three-Dimensional Structure of Proteins

Protein Function

Enzymes

Carbohydrates and Glycobiology

Nucleotides and Nucleic Acids

DNA-Based Information Technologies

Lipids

Biosignaling

Bioenergetics and Biochemical Reaction Types

Glycolysis, Gluconeogenesis, and the Pentose Phosphate Pathway

Principles of Metabolic Regulation

The Citric Acid Cycle

Fatty Acid Catabolism

Amino Acid Oxidation and the Production of Urea

Oxidative Phosphorylation and Photophosphorylation

Carbohydrate Biosynthesis in Plants and Bacteria

Lipid Biosynthesis

Biosynthesis of Amino Acids, Nucleotides, and Related Molecules

Hormonal Regulation and Integration of Mammalian Metabolism

Genes and Chromosomes

DNA Metabolism

RNA Metabolism

Protein Metabolism

Regulation of Gene Expression

Filters

The specificity of the potassium channel for K⁺ over Na⁺ is mainly the result of the:

Compare and contrast symport and antiport. Which term best describes the transport system mediated by the Na⁺K⁺ ATPase?