Biochemistry Exam 2 Chapter 12

Front 1

Which one of the following cytoplasm membrane processes requires a membrane-bound carrier molecule but NO Energy requirement?
A. passive diffusion 
B. osmosis
C. active transport
D. facilitated diffusion
E. phase 1 oxidation

Back 1

D. facilitated diffusion

Front 2

Which of the following key features of biological membranes is TRUE
A) the two sides appear to be distinguishable in most membrane
B) lipids rotate about their long axis but do not move laterally in the membrane.
C) lipid molecules flip readily from one side of the membrane bilayer to the other.
D) the protein to lipid ratio of membranes is very close to 1 : 1 in almost all physiologically important membranes.
E) none of the above is true.

Back 2

A) the two sides appear to be distinguishable in most membrane

Front 3

Membrane fluidity:
A) decreases as the percent of unsaturated fatty acids increases.
B) increases as the percent of unsaturated fatty acids decreases.
C) increases as the length of fatty acid side chains increases.
D) is independent of the nature of fatty acids.
E) decreases as the percent of saturated fatty acids increases

Back 3

E) decreases as the percent of saturated fatty acids increases

Front 4

Please name the head group in the myristic phospholipid?
A. Ethanolamine
B. Choline
C. Serine
D. Inositol
E. Phosphatidic Acid

Back 4

A. Ethanolamine

Front 5

All of the following are correct about inophores EXCEPT
A) requires the input of metabolic energy for mediated transport of an ion
B) may diffuse back and forth across a membrane
C) may for a channel across a membrane through which an ion my diffuse
D) may catalyze electrogenic mediate transport of an ion
E) will have specificity for the ion in moves

Back 5

A) requires the input of metabolic energy for mediated transport of an ion

Front 6

Which of the following statement is TRUE about glucose transport with the GLUT transporter systems (the one discussed in class).
A) It is an antiport system
B) It requires ATP for activity
C) It utilizes alpha helical peptide strands
D) It uses the following mechanism for transport recognition, release, transport and recovery
E) Movement of glucose goes against the concentration gradient

Back 6

C) It utilizes alpha helical peptide strands

Front 7

Which of the following statements is TRUE for the heterogeneity of lipid arrangement between the outer and inner membrane leaflet?
A) Cationic lipids are enriched on the inner leaflet
B) Flippase is responsible for the high concentration of ethanolamine lipids on the inner membrane
C) Ceramide associates with lecithin via electrostatic interactions on the external leaflet
D) The small head size of the choline head group favor micelle formation and hence concentrates this lipid on the inner leaflet
E) Cholesterol is enriched on the inner leaflet via conjugation with palmatic acid

Back 7

B) Flippase is responsible for the high concentration of ethanolamine lipids on the inner membrane

Front 8

According to the fluid mosaic model of a membrane:
A) proteins are always completely embedded in the lipid bilayer.
B) transverse movement of lipids in a bilayer is faster than lateral movement in the absence of transporters.
C) the transmembrane domain on integral proteins has largely hydrophobic amino acids.
D) proteins are distributed symmetrically in the membrane
E) peripheral proteins are attached to proteins by conjugation with palmitic acid.

Back 8

C) the transmembrane domain on integral proteins has largely hydrophobic amino acids.

Front 9

Cell membranes typically
A) are 90% phospholipids
B) have both integral and peripheral proteins
C) contain cholesteryl esters
D) contain free carbohydrates such as glucose
E) contain large amounts of triacylglycerols

Back 9

B) have both integral and peripheral proteins

Front 10

The enzyme phospholipiase C can degraded bonds in which class of lipids
A) Glycerolphosphate inositol
B) Spingomylein
C) Phosphatidylethanolamine
D) Cerebrosides
E) Cardiolipipins

Back 10

A) Glycerolphosphate inositol

Front 11

A new peptide has been isolated for the internal membrane leaflet of the plasma membrane. It has the following peptide sequence. Which of the following mechanisms is the most reasonable to explain how it was attached to the membrane?
Lysine-Lysine-Serine-Glutamic Acid-Isoluecine-Aspartic Acid-Methionine

A) Carbohydrates attached to the lysine group
B) Myristic acid conjugation
C) Palmitic acid conjugation
D) Glycosyl Phosphatidylinositol linkage
E) Hydrophobic amino acid insertion

Back 11

C) Palmitic acid conjugation

Front 12

The phospholipid molecules of most membranes have
A. a hydrophobic head and a hydrophilic tail
B. a hydrophobic head and a hydrophobic tail
C. a hydrophobic head and two hydrophobic tails
D. a hydrophilic head and two hydrophobic tails

Back 12

D. a hydrophilic head and two hydrophobic tails

Front 13

What does the cell membrane do?
A. Store toxins and other waste materials
B. Sorts and modifies cell products such as hormones and digestive hormones
C. Controls the kind and amounts of substances that move in and out of a cell
D. Produce ribosomes

Back 13

C. Controls the kind and amounts of substances that move in and out of a cell

Front 14

Which statement is true of plasma membranes?
A. They have molecules on their surface that identify different substances such as proteins and hormones.
B. They are essentially impermeable and block anything from entering
C. They are basically static, non-changing structures
D. They function primarily through the activity of carbohydrates

Back 14

A. They have molecules on their surface that identify different substances such as proteins and hormones.

Front 15

Which of these is a characteristic of the cell membrane?
A. contains proteins
B. contains phospholipids
C. is a bilayer
D. A and B
E. A, B, and C

Back 15

E. A, B, and C

Front 16

Integral proteins bind specific ions or organic substrates and facilitate their movement across the cell membrane. This is known as:
A. osmosis
B. carrier-mediated transport
C. diffusion
D. filtration
E. tonicity

Back 16

B. carrier-mediated transport

Front 17

Which statement is not true of membrane phospholipids?
A. They flop readily from one side on the membrane to the other.
B. They give the membrane fluidity.
C. They have hydrophilic "heads."
D. They have hydrophobic "tails."
E. They associate to form bilayers.

Back 17

A. They flop readily from one side on the membrane to the other.

Front 18

Which of the following factors would tend to increase membrane fluidity?
A. a lower temperature.
B. a lower cholesterol concentration in the membrane.
C. a greater proportion of unsaturated phospholipids.
D. a greater proportion of relatively large glycolipids compared to lipids having smaller molecular weights.
E. B and C

Back 18

E. B and C

Front 19

Which statement is not true of membrane proteins?
A. They all extend from one side of the membrane to the other.
B. Some serve as channels for ions to cross the membrane.
C. Many are free to migrate laterally within the membrane.
D. Their position in the membrane is determined by their tertiary structure.
E. Some participate in certain enzymatic reactions.

Back 19

A. They all extend from one side of the membrane to the other.

Front 20

The glycerophospholipids and sphingolipids of membranes
A) all contain phosphorus
B) all are amphipathic
C) all have individual charges but are zwitterions (no net charge)
D) are present in membranes in equal quantities
E) all contain one or more monosaccharides

Back 20

B) all are amphipathic

Front 21

Which of the following statements concerning plasma membranes is correct?
A) Lipid composition of the two layers of the membrane equilibrate
B) Microdomains, called rafts, are fixed in position in the membrane
C) The flippase lipid transporter catalyzes unidirectional movement of specific lipids
D) An increase in the cholesterol content of a plasma membrane increases membrane fluidity
E) As demonstrated with liposomes, the membrane is the most fluid at the surface.

Back 21

C) The flippase lipid transporter catalyzes unidirectional movement of specific lipids

Front 22

Which of the following does not serve as a lipid anchor to a peripheral membrane protein?
A. palmitic acid
B. myristic acid
C. phosphotidylinositol
D. cholesterol
E. geranyl isoprenoid

Back 22

D. cholesterol

Front 23

Naturally-occuring unsaturated fatty acids normally have which geometry about the double bond, cis or trans? _________. Does the presence of a double bond increase or decrease the fluidity? ______________

Back 23

Cis
increase

Front 24

A membrane protein can be dissociated from a membrane by changing the pH of the solution. Is this protein peripheral or integral? _______________

Back 24

peripheral

Front 25

What is the major structure difference between sphingosine and ceramides?

Back 25

Sphingosine has a single acyl chain whereas ceramides have two acyl chains. The second acyl chain is attached via an amide bond.

Front 26

Give an example of a liposome drug product and describe an advantage of this liposome produce over administering the drug not encapsulated in a liposome.

Back 26

Amphotericin-An antifungal drug. This drug is nephrotoxic. Formulated in a liposome and administered systemically prevents nephrotoxicity by preventing the drug from collecting in the nephritic venules and precipitating out of solution. Secondly, liposome formulation increases the circulation half life.

Doxorubicin-This is a chemotherapy that can cause cardiac toxicity by binding to cardiolipin in the heart myocytes. Formulation in liposomes prevents drug deposition in the cardiac myocytes, thus preventing binding of drug to cardiolipin. Secondly, liposome formulation increases circulation half life of the drug. Increased circulation half life results in deposition of the liposomal doxorubicin in the fenestrated endothelium of the tumor. The drug is slowly released from the liposome and taken up by the tumor cells resulting in tumor killing.

Depocyt-Formulated as a liposomal foam and admistered intrathecally. Serves as a slow release drug depot for treatment of cancerous lesions in the spinal cord.

Front 27

What amino acid is involved in covalent attachment of the farnesyl isoprenoid lipid?

Back 27

glutamine, methionine, serine

Front 28

The sodium-potassium exchange pump:
A. requires ATP
B. is used for active transport
C. moves substances against their concentration gradients
D. A and B
E. A, B, and C

Back 28

E. A, B, and C

Front 29

Aquaphorins (APQ)
A) permit translocation of water and small solutes
B) reduce the pH gradient because they transport H3O+
C) are peripheral proteins of the membrane
D) form channels through which water flows
E) have no specific controls to open the channel

Back 29

D) form channels through which water flows

Front 30

Which of the following statements is true for mammalian fatty acids?
A) The double bond in unsaturated fatty acids often occurs at C-9 resulting in a bend in the hydrophobic tail increasing the interactions between molecules
B) Increasing the fatty acyl chain results in a higher melting point
C)Fatty acids chains of 15 carbons is the most common
D) Polyunsaturated lipids are always conjugated
E) Are all water miscible

Back 30

B) Increasing the fatty acyl chain results in a higher melting point

Front 31

Which of the phospholipid head groups contains a carboxylic acid?
A) choline
B) ethanolamine
C) serine
D) glycerol
E) inositol

Back 31

C) serine

Front 32

Which of the phospholipid heads often functions as a second messenger?
A) choline
B) ethanolamine
C) serine
D) glycerol
E) inositol

Back 32

E) inositol

Front 33

The Bartlett assay is a biochemical method of measuring inorganic phosphate. In biochemistry often a molecule is degraded producing phosphate which then can be quantified. Which of the following compounds would the Bartlett assay NOT be able to detect?
A) Ceramides
B) Sphingomyelins
C) Cardiolipins
D) Plasmalogens
E) Glycerophospholipid

Back 33

A) Ceramides

Front 34

Which of the following compounds contains sialic acid?
A) Cardiolipins
B) Plasmalogens
C) Sphingomyelins
D) Gangliosides
E) Dihydrosphingosine

Back 34

D) Gangliosides

Front 35

A new membrane protein “Sullivan Protein” has been isolated from membranes by treatment with phospholipase C. Which of the following statements is true for “Sullivan Protein”
A) It is associated with the external membrane leaflet
B) It is an extrinsic proteins
C) It likely contains the amino acid serine
D) It would NOT be associated with lipid rafts
E) It spans the membrane 12 times

Back 35

A) It is associated with the external membrane leaflet

Front 36

There is a cellular event know as “Apoptosis”, during this process phosphatidylserine if transported from the inner to outer membrane leaflet. Which of the following transporters is likely involved in this process.
A) Scramblase
B) Lipase
C) Glut 1
D) Na /K ATPase
E) Sodium/glucose contransporter

Back 36

A) Scramblase

Front 37

Which of the following statements are true in terms of liposomes?
A) Requires ATP for the lipids to assemble into bilayers
B) Often reduces the toxicity of encapsulated drugs
C) Are only useful for transporting hydrophophilic drugs
D) Are composted of proteins and phospholipids
E) Taste like chocolate

Back 37

B) Often reduces the toxicity of encapsulated drugs

Front 38

A mediated transport system would be expected to:
A) establish a concentration gradient across the membrane
B) be slower than that of simple diffusion system
C) show a continuously increasing initial rate of transport with increasing substrate concentration
D) exhibit structural and/or sterospecificity for the substance transported
E) exist only in plasma membranes

Back 38

D) exhibit structural and/or sterospecificity for the substance transported

Front 39

Which membrane would most likely be in the liquid crystalline state at 37 C.
A) A liposome composed entirely of phospholipids with a Tm of 45 C
B) A liposome composed entirely of phospholipids with a Tm of 40oC
C) A liposome composed of a 10% cholesterol and a 90% of a phospholipids with a Tm of 40 C
D) A liposome composed of a 20% cholesterol and a 80% of a phospholipids with a Tm of 40 C
E) A liposome composed of a phospholipids with a Tm of 25 C

Back 39

E) A liposome composed of a phospholipids with a Tm of 25 C

Front 40

An experiment was conducted addressing the transport of compound X. Two different systems were used. The first system looked at the transport of X in a variety of liposome systems and a second approach addressed transport in living cells.
The permeability of X in the liposome system was 4 x10^-5 cm/s
The permeability of X in the cell system was 4 X 10^-3 cm/s.

Which of the following explains the results of this experiment
A) There is an efflux pump (P-glycoprotein) in the cell system
B) The compound has a greater diffusion coefficient in the cell system as compared to the liposomes
C) There is either an active transport system or carrier system for compound X
D) The data can only be explained by an energy dependent transport system
E) An ABC transporter is used for the movement of compound X

Back 40

C) There is either an active transport system or carrier system for compound X

Front 41

Gramicidin A is an example of a/an
A) ATP-binding cassette transport protein
B) Ionophore
C) Na/K ATPase dependent system
D) F-type transporter
E) Antiport transport system

Back 41

B) Ionophore

Front 42

Small lipid-soluble molecules move in and out of cells by:
a. active transport
b. facillitated diffusion
c. simple diffusion
d. an energy-requiring pump
e. both a and b

Back 42

c. simple diffusion

Front 43

1.As individual molecules, saturated fatty acids are more ___ [(1) flexible; or (2) rigid] than the unsaturated fatty acids in their conformation of the aliphatic chains.

Back 43

(2) rigid

Front 44

1.For membranes, the higher the content of unsaturated acids in lipids, the ________ the membranes will be; and the higher the content of shorter chain fatty acids in lipids, the ____ the membranes will be. [(1) more fluid; (2) less fluid]

Back 44

(1) more fluid
(1) more fluid

Front 45

1.Proteins in biological membranes ____ [(1) can efficiently; (2) cannot efficiently] undergo transverse diffusion.

Back 45

(2) cannot efficiently

Front 46

List three proteins that can facilitate the transverse movements of lipids ____________________________.

Back 46

flippase, floppase, scramblase

Front 47

ATP-binding cassette (ABC) transporters:
A) all have both a membrane-spanning domain that recognizes the substrate and an ATP-binding domain.
B) All effect translocation by forming channels
C) Are found only in eukaryotes
D) All have two functions-forming a channel and conductance regulation
E) Are all P-glycoproteins

Back 47

A) all have both a membrane-spanning domain that recognizes the substrate and an ATP-binding domain.

Front 48

The difference between a cerebroside and a ganglioside is that
A) one is a sphingolipid, the other a phosphatidyl lipid
B) one contains a fatty acid amide, the other a fatty ester
C) one contains a sugar head group, the other an oligosaccharide
D) one has sugar phosphate, the other a simply a sugar
E) cerebrosides contain cholesterol while gangliosides do not

Back 48

C) one contains a sugar head group, the other an oligosaccharide

Front 49

According to the fluid mosaic model of cell membranes, which type of molecule spans the membrane, from its inner to the outer surface?
A) carbohydrate
B) cholesterol
C) hydrocarbon tails
D) phospholipid
E) protein

Back 49

E) protein

Front 50

All of the following are found in membranes except:
A) nucleic acids
B) phospholipids
C) glycoproteins
D) glycolipids
E) steroids (i.e. cholesterol)

Back 50

A) nucleic acids

Front 51

A new protein has been isolated from the cell membrane by treatment with neuraminidase. Neuroaminidase is an enzyme that specifically cleaves glycosyl phosphatidylinositol bonds. Where was this protein within the cell?
A) The inner membrane leaflet
B) The outer membrane leaflet
C) It is an integral protein
D) Within the cytoplasm of the cell
E) Within the lysosomes of the cell

Back 51

B) The outer membrane leaflet

Front 52

In a separate experiment a protein was isolated from a cell. This protein had myristic acid attached. Which of the following statements describes this new protein.
A) has myristic acid attached through the protein via an ester bond
B) this protein is associated with the outer membrane leaflet
C) myristic acid is conjugated to a glycine amino acid
D) has myristic acid attached through the protein via a thioester bond
E) is an integral protein

Back 52

C) myristic acid is conjugated to a glycine amino acid

Front 53

1.Which of the following statements is/are true in regards to microdomains (lipid rafts)
A) are highly enriched in phosphatidyl choline
B) contain high concentrations of cardiolipin
C) contain high concentrations of sphingolipids
D) are maintained in the plasma membrane via the action of P-glycoprotein
E) has a high concentration of ankyrin

Back 53

C) contain high concentrations of sphingolipids

Front 54

All of the following are ways in which peripheral proteins bind to membranes except:
A. Binding to an integral protein
B. Electrostatic binding between phospholipids and positive groups on the protein
C. By a short hydrophobic group at one end of the protein
D. Attached by the charged carboxyl group at the carboxyl terminus of the protein.
E. Binding noncovalently to membrane phosphatidylinositol.

Back 54

D. Attached by the charged carboxyl group at the carboxyl terminus of the protein.

Front 55

Characteristics of a mediated transport system include:
A. Non-specific binding of solute to transporter.
B. Release of the transporter from the membrane following transport.
C. A rate of transport directly proportional to the concentration of solute.
D. Release of the solute only if the concentration on the new side is lower than that on the original side.
E. A mechanism for translocating the solute from one side of the membrane to the other.

Back 55

E. A mechanism for translocating the solute from one side of the membrane to the other.

Front 56

Cells control the distribution of water across membranes by aquaporins and aquaglyceroporins because nonfacilitated diffusion is too slow. Aquaporins (AQP):
a. Permit translocation of water and small solutes
b. Reduce pH gradient because they transport H3O+.
c. Are peripheral proteins of the membrane.
d. Form channels through which water flows.
e. Have no specific controls to open the channel.

Back 56

d. Form channels through which water flows.

Front 57

Which of the following statements is correct about membranes?
a. Microdomains, called lipid rafts, are fixed in position in membranes.
b. Lipid composition of the two layers of the membrane equilibrate.
c. As demonstrated with liposomes, the membrane is most fluid at the surfaces.
d. An increase in cholesterol content of a membrane increases membrane fluidity.
e. Lipid transporters catalyze unidirectional movement of specific lipids from one layer to another.

Back 57

e. Lipid transporters catalyze unidirectional movement of specific lipids from one layer to another.

Front 58

Membrane channels:
A. Have a large aqueous area in the protein structure so are not very selective.
B. Commonly contain amphipathic alpha-helices.
C. Are opened or closed only as a result of a change in the transmembrane potential.
D. Are the same as gap junctions
E. Allow substrates to flow only from outside to inside of the cell.

Back 58

B. Commonly contain amphipathic alpha-helices.

Front 59

One type of transport system that maintains the Na+ and K+ gradients across the plasma membrane of cells:
a. Involves an enzyme that is ATPase
b. Is a symport system
c. Moves Na+ either into or out of the cell
d. Is an electrically neutral system
e. In the membrane, hydrolyzes ATP independently of the movement of Na+ and K+

Back 59

a. Involves an enzyme that is ATPase