Question 1

What is the meaning of the term "annular lipid"?

Accepted Answer

A)  lipids that tend to form micelle structures 
B)  lipids that are formed from the degradation of phospholipids 
C)  lipids that are prosthetic groups in lipid-anchored proteins 
D)  lipids that are found in close association with integral membrane proteins. 
E)  None of the answers is correct. 
A)  lipids that tend to form micelle structures 
B)  lipids that are formed from the degradation of phospholipids 
C)  lipids that are prosthetic groups in lipid-anchored proteins 
D)  lipids that are found in close association with integral membrane proteins. 
E)  None of the answers is correct.

Question 2

Bacterial cells change the fluidity of their lipid membranes to adapt to growth at lower temperatures by increasing the synthesis of:

Accepted Answer

A)  cholesterol. 
B)  long-chain fatty acids and increasing the saturation of their membrane lipids. 
C)  both long- and short-chain fatty acids. 
D)  long-chain fatty acids and decreasing the saturation of their membrane lipids. 
E)  short-chain fatty acids and decreasing the saturation of their membrane lipids. 
A)  cholesterol. 
B)  long-chain fatty acids and increasing the saturation of their membrane lipids. 
C)  both long- and short-chain fatty acids. 
D)  long-chain fatty acids and decreasing the saturation of their membrane lipids. 
E)  short-chain fatty acids and decreasing the saturation of their membrane lipids.

Question 3

Glycosphingolipids and cholesterol cluster together in membrane regions known as "_____." These microdomains are more _____ than the surrounding phospholipid-rich membrane due to a high content of _____ fatty acids. These regions are rich in proteins that are anchored to the membrane by covalently attached _____ and _____ groups and also those anchored by GPI linkage. Proteins aggregated in this fashion are often functionally related. Examples are (1) _____ proteins and (2) _____ proteins.

Accepted Answer

Glycosphingolipids and cholesterol clust

Question 4

Choline-containing lipids are enriched in the outer leaflet of erythrocyte plasma membranes. This includes:

Accepted Answer

A)  cardiolipin. 
B)  phosphatidylinositol. 
C)  sphingomyelin. 
D)  phosphatidylcholine. 
E)  both sphingomyelin and phosphatidylcholine. 
A)  cardiolipin. 
B)  phosphatidylinositol. 
C)  sphingomyelin. 
D)  phosphatidylcholine. 
E)  both sphingomyelin and phosphatidylcholine.

Question 5

Integral membrane proteins tend to be enriched for regular secondary structures in the transmembrane portions of their structures. Which statement explains this observation?

Accepted Answer

A)  Regular secondary structures allow for polar amino acids to interact with lipid head groups. 
B)  Regular secondary structures allow the polypeptide to interact with the membrane core. 
C)  Regular secondary structures are energetically favorable for polypeptides. 
D)  Regular secondary structures satisfy hydrogen-bonding potential of the backbone in a hydrophobic environment. 
A)  Regular secondary structures allow for polar amino acids to interact with lipid head groups. 
B)  Regular secondary structures allow the polypeptide to interact with the membrane core. 
C)  Regular secondary structures are energetically favorable for polypeptides. 
D)  Regular secondary structures satisfy hydrogen-bonding potential of the backbone in a hydrophobic environment.

Question 6

Which bond or functional group is NOT found in a GPI anchor?

Accepted Answer

A)  a phosphodiester bond 
B)  a glycosidic bond 
C)  a hydroxyl group 
D)  an ester bond 
E)  a thioester bond 
A)  a phosphodiester bond 
B)  a glycosidic bond 
C)  a hydroxyl group 
D)  an ester bond 
E)  a thioester bond

Question 7

GLUT1 has a Kt of 1.5 mM for glucose and a Kt of 30 mM for galactose. What concentration of galactose would be required to reach the same rate of import as 5mM glucose?

Accepted Answer

A)  3 mM 
B)  10 mM 
C)  15 mM 
D)  30 mM 
E)  100 mM 
A)  3 mM 
B)  10 mM 
C)  15 mM 
D)  30 mM 
E)  100 mM

Question 8

Which statement is TRUE regarding the SERCA pump?

Accepted Answer

A)  The E1 conformation has a higher Kd value for Ca2+ than the E2 conformation. 
B)  The P domain contains a high-energy acyl phosphate structure when it is phosphorylated. 
C)  Three calcium ions are moved in each cycle of the transporter. 
D)  This protein can be classified as an antiport. 
E)  None of the statements is true. 
A)  The E1 conformation has a higher Kd value for Ca2+ than the E2 conformation. 
B)  The P domain contains a high-energy acyl phosphate structure when it is phosphorylated. 
C)  Three calcium ions are moved in each cycle of the transporter. 
D)  This protein can be classified as an antiport. 
E)  None of the statements is true.

Question 9

Glucose transport into erythrocytes is an example of:

Accepted Answer

A)  active transport. 
B)  antiport. 
C)  electrogenic uniport 
D)  facilitated diffusion. 
E)  symport. 
A)  active transport. 
B)  antiport. 
C)  electrogenic uniport 
D)  facilitated diffusion. 
E)  symport.

Question 10

Compare the structure and activity of a membrane transport protein that transports a polar substance across a membrane with a typical soluble enzyme. How are transporter and enzyme similar? How are they different?

Accepted Answer

Membrane transport proteins and soluble

Question 11

a) What is meant by the transition temperature of a membrane? List the two characteristics of the fatty acids in a biological membrane that affect the transition temperature. Using $\downarrow$ or $\downarrow$, show in which direction an increase in these characteristics would change the transition temperature.

Accepted Answer

The transition temperature of a membrane

Question 12

The fluidity of a lipid bilayer will be increased by:

Accepted Answer

A)  decreasing the number of unsaturated fatty acids. 
B)  decreasing the temperature. 
C)  increasing the length of the alkyl chains. 
D)  increasing the temperature. 
E)  substituting 18:0 (stearic acid) in place of 18:2 (linoleic acid). 
A)  decreasing the number of unsaturated fatty acids. 
B)  decreasing the temperature. 
C)  increasing the length of the alkyl chains. 
D)  increasing the temperature. 
E)  substituting 18:0 (stearic acid) in place of 18:2 (linoleic acid).

Question 13

What is the CORRECT order of steps in vesicle fusion to a cell?

Accepted Answer

A)  outer leaflet lipid mixing, content release, inner leaflet lipid mixing 
B)  outer leaflet lipid mixing, inner leaflet lipid mixing, content release 
C)  inner leaflet lipid mixing, content release, outer leaflet lipid mixing 
D)  inner-leaflet lipid mixing, outer leaflet lipid mixing, content release 
E)  content release, inner leaflet lipid mixing, outer leaflet lipid mixing 
A)  outer leaflet lipid mixing, content release, inner leaflet lipid mixing 
B)  outer leaflet lipid mixing, inner leaflet lipid mixing, content release 
C)  inner leaflet lipid mixing, content release, outer leaflet lipid mixing 
D)  inner-leaflet lipid mixing, outer leaflet lipid mixing, content release 
E)  content release, inner leaflet lipid mixing, outer leaflet lipid mixing

Question 14

Which phrase BEST describes the term "amphitropic"?

Accepted Answer

A)  cytosolic lipid-linked proteins 
B)  GPI-linked proteins 
C)  proteins that are reversibly membrane-associated or cytosolic 
D)  proteins that are either integral or lipid-linked 
A)  cytosolic lipid-linked proteins 
B)  GPI-linked proteins 
C)  proteins that are reversibly membrane-associated or cytosolic 
D)  proteins that are either integral or lipid-linked

Question 15

Which statement is TRUE regarding lipid anchors?

Accepted Answer

A)  Palmitoylations and prenylations both occur via thioester linkages. 
B)  GPI anchors and prenylations are both attached to the C-terminal end of the mature protein. 
C)  Myristoylations and palmitoylations are both reversible modifications. 
D)  Prenylations occur exclusively on the outside leaflet of the plasma membrane. 
A)  Palmitoylations and prenylations both occur via thioester linkages. 
B)  GPI anchors and prenylations are both attached to the C-terminal end of the mature protein. 
C)  Myristoylations and palmitoylations are both reversible modifications. 
D)  Prenylations occur exclusively on the outside leaflet of the plasma membrane.

Question 16

Consider the transport of glucose into an erythrocyte by facilitated diffusion. What is the free-energy change for glucose uptake into the cell when the glucose concentrations are 5 mM on the outside and 0.1 mM on the inside? (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)  less than 2 kJ/mol 
B)  about 10 kJ/mol 
C)  about 30 kJ/mol 
D)  about -30 kJoule/mol 
E)  It is 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)  It is impossible to calculate without knowledge of the membrane potential.

Question 17

(a) List three different major components of eukaryotic membranes. (b) When a preparation of mitochondrial membranes was treated with high salt (0.5 M NaCl), it was observed that 40% of the total protein in this preparation was solubilized. What kind of membrane proteins are in this soluble extract, and what forces normally hold them to the membrane? (c) What kind of proteins constitute the insoluble 60%, and what forces hold these proteins in the membrane?

Accepted Answer

(a) Three different major components of

Question 18

Calculate the free-energy change associated with pumping protons out of a cell if the pH inside is 7 while the pH outside is 6. Assume 37°C (310K) and a 50 mV membrane potential (inside negative). (R = 8.315 J mol-1 K-1; Faraday constant = 96,480 J V-1.)

Accepted Answer

To calculate the free-energy change (ΔG)

Question 19

In a chloride channel, an $\alpha$-helix is found to be part of the specificity filter. Which end of the helix do you expect to be interacting with the chloride anions and why?

Accepted Answer

In a chloride channel, the specificity f

Question 20

You have discovered a protein that transports Ca2+ up a concentration gradient, from the cytoplasm into the endoplasmic reticulum. No other ions move during this transport. What type of transport protein does this appear to be?

Accepted Answer

A)  a Ca2+ channel 
B)  a Ca2+ ion porin 
C)  a primary active uniporter 
D)  a secondary active uniporter 
E)  an ionophore 
A)  a Ca2+ channel 
B)  a Ca2+ ion porin 
C)  a primary active uniporter 
D)  a secondary active uniporter 
E)  an ionophore

Exam 11: Biological Membranes and Transport

What is the meaning of the term "annular lipid"?

Bacterial cells change the fluidity of their lipid membranes to adapt to growth at lower temperatures by increasing the synthesis of:

Choline-containing lipids are enriched in the outer leaflet of erythrocyte plasma membranes. This includes:

Integral membrane proteins tend to be enriched for regular secondary structures in the transmembrane portions of their structures. Which statement explains this observation?

Which bond or functional group is NOT found in a GPI anchor?

GLUT1 has a Kt of 1.5 mM for glucose and a Kt of 30 mM for galactose. What concentration of galactose would be required to reach the same rate of import as 5mM glucose?

Which statement is TRUE regarding the SERCA pump?

Glucose transport into erythrocytes is an example of:

Compare the structure and activity of a membrane transport protein that transports a polar substance across a membrane with a typical soluble enzyme. How are transporter and enzyme similar? How are they different?

The fluidity of a lipid bilayer will be increased by:

What is the CORRECT order of steps in vesicle fusion to a cell?

Which phrase BEST describes the term "amphitropic"?

Which statement is TRUE regarding lipid anchors?

Calculate the free-energy change associated with pumping protons out of a cell if the pH inside is 7 while the pH outside is 6. Assume 37°C (310K) and a 50 mV membrane potential (inside negative). (R = 8.315 J mol-1 K-1; Faraday constant = 96,480 J V-1.)

In a chloride channel, an α\alphaα -helix is found to be part of the specificity filter. Which end of the helix do you expect to be interacting with the chloride anions and why?

You have discovered a protein that transports Ca2+ up a concentration gradient, from the cytoplasm into the endoplasmic reticulum. No other ions move during this transport. What type of transport protein does this appear to be?

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

GLUT1 has a K_t of 1.5 mM for glucose and a K_t of 30 mM for galactose. What concentration of galactose would be required to reach the same rate of import as 5mM glucose?

Calculate the free-energy change associated with pumping protons out of a cell if the pH inside is 7 while the pH outside is 6. Assume 37°C (310K) and a 50 mV membrane potential (inside negative). (R = 8.315 J mol^-¹ K^-¹; Faraday constant = 96,480 J V^-¹.)

In a chloride channel, an $\alpha$ -helix is found to be part of the specificity filter. Which end of the helix do you expect to be interacting with the chloride anions and why?

You have discovered a protein that transports Ca²⁺ up a concentration gradient, from the cytoplasm into the endoplasmic reticulum. No other ions move during this transport. What type of transport protein does this appear to be?