Question 1

Movement of water across membranes is facilitated by proteins called:

Accepted Answer

A) annexins. 
B) aquaporins. 
C) hydropermeases. 
D) selectins. 
E) transportins. 
A) annexins. 
B) aquaporins. 
C) hydropermeases. 
D) selectins. 
E) transportins.

Question 2

An electrogenic Na+ transporter:

Accepted Answer

A) catalyzes facilitated diffusion of Na+ from a region of high Na+ concentration to one of lower Na+ concentration. 
B) must catalyze an electron transfer (oxidation-reduction)reaction simultaneously with Na+ transport. 
C) must transport both Na+ and a counterion (Cl-,for example). 
D) transports Na+ against its concentration gradient. 
E) transports Na+ without concurrent transport of any other charged species. 
A) catalyzes facilitated diffusion of Na+ from a region of high Na+ concentration to one of lower Na+ concentration. 
B) must catalyze an electron transfer (oxidation-reduction)reaction simultaneously with Na+ transport. 
C) must transport both Na+ and a counterion (Cl-,for example). 
D) transports Na+ against its concentration gradient. 
E) transports Na+ without concurrent transport of any other charged species.

Question 3

Which of these statements about the composition of membranes is true?

Accepted Answer

A) All biological membranes contain cholesterol. 
B) Free fatty acids are major components of all membranes. 
C) The inner and outer membranes of mitochondria have different protein compositions. 
D) The lipid composition of all membranes of eukaryotic cells is essentially the same. 
E) The lipid:protein ratio varies from about 1:4 to 4:1 
A) All biological membranes contain cholesterol. 
B) Free fatty acids are major components of all membranes. 
C) The inner and outer membranes of mitochondria have different protein compositions. 
D) The lipid composition of all membranes of eukaryotic cells is essentially the same. 
E) The lipid:protein ratio varies from about 1:4 to 4:1

Question 4

You are trying to isolate an enzyme that catalyzes the conversion of A $\rightarrow$  B,and you have a sensitive assay for this enzyme.After lysing open the cells,you find that the activity is associated with the membrane fraction,not the soluble fraction (which you throw away).You then follow the procedure shown below.Explain the sudden re-occurrence of activity at the end of your protocol.

Accepted Answer

The activity of interest is membrane bou

Question 5

Which one of the following statements about membranes is true?

Accepted Answer

A) Most plasma membranes contain more than 70% proteins. 
B) Sterol lipids are common in bacterial plasma membranes. 
C) Sterol lipids are common in human cell plasma membranes. 
D) Sterol lipids are common in plant cell plasma membranes. 
E) The plasma membranes of all cell types within a particular organism have basically the same lipid and protein composition. 
A) Most plasma membranes contain more than 70% proteins. 
B) Sterol lipids are common in bacterial plasma membranes. 
C) Sterol lipids are common in human cell plasma membranes. 
D) Sterol lipids are common in plant cell plasma membranes. 
E) The plasma membranes of all cell types within a particular organism have basically the same lipid and protein composition.

Question 6

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 c

Question 7

Describe two different ways a plant can adjust the components of its cell membranes to keep them as fluid as possible on a cold winter morning.

Accepted Answer

To compensate for the solidifying effect

Question 8

Draw the structure of a biological membrane as proposed by the fluid mosaic model.Indicate the positions and orientations of phospholipids,cholesterol,integral and peripheral membrane proteins,and the carbohydrate moieties of glycoproteins and glycolipids.

Accepted Answer

Phospholipids and sterols are found in b

Question 9

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 10

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

Accepted Answer

Non-gated channels are always

Question 11

Which of the following statements is not true about the chloride-bicarbonate exchanger (AE)?

Accepted Answer

A) The AE protein increases the rate of bicarbonate transport across the membrane. 
B) The AE protein uses ATP as an energy source to drive bicarbonate transport. 
C) The AE protein transports chloride ions across the membrane. 
D) The AE protein is classified as an anti-porter. 
E) The AE protein spans the membrane at least 12 times. 
A) The AE protein increases the rate of bicarbonate transport across the membrane. 
B) The AE protein uses ATP as an energy source to drive bicarbonate transport. 
C) The AE protein transports chloride ions across the membrane. 
D) The AE protein is classified as an anti-porter. 
E) The AE protein spans the membrane at least 12 times.

Question 12

Peripheral membrane proteins:

Accepted Answer

A) are generally noncovalently bound to membrane lipids. 
B) are usually denatured when released from membranes. 
C) can be released from membranes only by treatment with detergent(s). 
D) may have functional units on both sides of the membrane. 
E) penetrate deeply into the lipid bilayer. 
A) are generally noncovalently bound to membrane lipids. 
B) are usually denatured when released from membranes. 
C) can be released from membranes only by treatment with detergent(s). 
D) may have functional units on both sides of the membrane. 
E) penetrate deeply into the lipid bilayer.

Question 13

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

Question 14

Consider the transport of glucose into an erythrocyte by facilitated diffusion.When the glucose concentrations are 5 mM on the outside and 0.1 mM on the inside,the free-energy change for glucose uptake into the cell is: (These values may be of use to you: R = 8.315 J/mol·K;T = 298 K;9 (Faraday constant)= 96,480 J/V;N = 6.022 *1023/mol. )

Accepted Answer

A) less than 2 kJ/mol. 
B) about 10 kJ/mol. 
C) about 30 kJ/mol. 
D) about -30 kJoule/mol. 
E) impossible to calculate without knowledge of the membrane potential. 
A) less than 2 kJ/mol. 
B) about 10 kJ/mol. 
C) about 30 kJ/mol. 
D) about -30 kJoule/mol. 
E) impossible to calculate without knowledge of the membrane potential.

Question 15

Explain the differences between integral and peripheral membrane proteins.

Accepted Answer

Integral membrane proteins are very firm

Question 16

Integrins are:

Accepted Answer

A) membrane proteins that are involved in ion transport. 
B) membrane proteins that are involved in sugar transport. 
C) membrane proteins that mediate cell adhesion. 
D) proteins of the extracellular matrix that bind to cell surface proteins. 
E) proteins that are found at the membrane-cytoplasm interface. 
A) membrane proteins that are involved in ion transport. 
B) membrane proteins that are involved in sugar transport. 
C) membrane proteins that mediate cell adhesion. 
D) proteins of the extracellular matrix that bind to cell surface proteins. 
E) proteins that are found at the membrane-cytoplasm interface.

Question 17

A process not involving the fusion of two membranes or two regions of the same membrane is:

Accepted Answer

A) endocytosis. 
B) entry of enveloped viruses into cells. 
C) entry of glucose into cells. 
D) exocytosis. 
E) reproductive budding in yeast. 
A) endocytosis. 
B) entry of enveloped viruses into cells. 
C) entry of glucose into cells. 
D) exocytosis. 
E) reproductive budding in yeast.

Question 18

The shortest $\alpha$ helix segment in a protein that will span a membrane bilayer has about _____ amino acid residues.

Accepted Answer

A) 5 
B) 20 
C) 50 
D) 100 
E) 200 
A) 5 
B) 20 
C) 50 
D) 100 
E) 200

Question 19

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

Reagent A will label phosphatidylethanol

Question 20

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.

Exam 11: Biological Membranes and Transport

Movement of water across membranes is facilitated by proteins called:

An electrogenic Na+ transporter:

Which of these statements about the composition of membranes is true?

Which one of the following statements about membranes is true?

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

Describe two different ways a plant can adjust the components of its cell membranes to keep them as fluid as possible on a cold winter morning.

Draw the structure of a biological membrane as proposed by the fluid mosaic model.Indicate the positions and orientations of phospholipids,cholesterol,integral and peripheral membrane proteins,and the carbohydrate moieties of glycoproteins and glycolipids.

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

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

Which of the following statements is not true about the chloride-bicarbonate exchanger (AE)?

Peripheral membrane proteins:

Membrane fusion leading to neurotransmitter release requires the action of:

Explain the differences between integral and peripheral membrane proteins.

Integrins are:

A process not involving the fusion of two membranes or two regions of the same membrane is:

The shortest α\alphaα helix segment in a protein that will span a membrane bilayer has about _____ amino acid residues.

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

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

Recombinant Dna Technology

Lipids

Biosignaling

Principles of Bioenergetics

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

Integration and Hormonal Regulation of Mammalian Metabolism

Genes and Chromosomes

Dna Metabolism

Rna Metabolism

Protein Metabolism

Regulation of Gene Expression

Filters

An electrogenic Na⁺ transporter:

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

The shortest $\alpha$ helix segment in a protein that will span a membrane bilayer has about _____ amino acid residues.

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