Cell Bio Module 2 Quiz

The glucose uniporter GLUT1 has a Km of 1.5 mM for D-glucose and 30 mM for D-galactose. At a concentration of 5 mM for each, what is the rate of glucose transport relative to galactose transport? The Vmax may be assumed to be the same for both. - 20-fold faster - 3.7-fold slower - 5.5-fold faster - equal

5.5-fold faster

Which of the following interactions contribute to the stabilization of the transmembrane domain of the integral membrane proteins? - B and C - A and B - B) Van der Waals interactions - C) Hydrophilic interactions - A) Hydrophobic interactions

A and B

What type of single-pass membrane protein would contain a hydrophobic membrane-spanning α-helix? - A peripheral protein. - A transmembrane protein. - A transmembrane protein and/or an integral membrane protein. - An integral membrane protein.

A transmembrane protein and/or an integral membrane protein.

You are studying the effects of temperature and lipid composition on membrane fluidity using artificial membranes containing only one type of phospholipid. The membrane contains only phosphatidylcholine, with various carbon-length fatty acids with different degrees of saturation, and contains no proteins. Assume that you and your lab partner have made the following artificial membranes: Membrane 1: Each of the two chains of the fatty acids is 16 carbon in length, and both are completely saturated. Membrane 2: Each of the two fatty acid chains is 14-carbon in length, and each chain contains a single double bond. Membrane 3: The same as Membrane 1, except each fatty acid chain, has a single double bond. After determining the transition temperatures of each of these artificial membranes, you discover that your lab partner failed to record which transition temperature corresponds to which artificial membrane. The values you determined were −65°C, 2°C, and 41°C. Which of the following transition temperature assignment seems most logical? A. Membrane 1: 41°C Membrane 2: −65°C, Membrane 3: 2°C B. Membrane 1: 2°C Membrane 2: −65°C, Membrane 3: 41°C C. Membrane 1: 41°C Membrane 2: 2°C, Membrane 3: −65°C D. Membrane 1: −65°C Membrane 2: 41°C, Membrane 3: 2°C

A. Membrane 1: 41°C Membrane 2: −65°C, Membrane 3: 2°C

In the plasma membrane, lipid bilayers: A. The hydrophilic ends face outside (extracellular/exoplasmic face) and inside (cytoplasmic face) of the cells, with hydrophobic ends buried in the center of the lipid bilayer. B. The hydrophobic ends face outside (extracellular/exoplasmic face) and inside (cytoplasmic face) of the cells, with hydrophilic ends buried in the center of the lipid bilayer. C. The hydrophobic ends face the outside (extracellular/exoplasmic face) of the cells, and the hydrophilic ends face inside (cytoplasmic face) of the cells. D. The hydrophilic ends face the outside (extracellular/exoplasmic face) of the cells, and the hydrophobic ends face inside (cytoplasmic face) of the cells. E. Hydrophobic and hydrophilic ends face outside (extracellular/exoplasmic face) and inside (cytoplasmic face) of the cells randomly.

A. The hydrophilic ends face outside (extracellular/exoplasmic face) and inside (cytoplasmic face) of the cells, with hydrophobic ends buried in the center of the lipid bilayer.

GLUT1 deficiency syndrome is a disorder affecting the nervous system that can have a variety of neurological signs and symptoms. Affected individuals generally have frequent seizures (epilepsy) beginning in the first months of life. As the name suggests, GLUT1 deficiency syndrome is caused by mutations in the SLC2A1 gene, which encodes GLUT1. The mutations render the transporter nonfunctional. Which of the following statement concerning these patients is probably FALSE? A. These patients are not able to carry out co-transport of glucose and Na+ ions B. Facilitated diffusion of glucose into cells is impaired in these patients C. The function of the Na+/Ca++ antiporter is likely unaffected by the mutation D. In these patients' cells, the initial rate of glucose uptake by GLUT1 is probably nonexistent or very low compared to healthy individuals without the mutation. E. In these patients' cells, the function of CFTR is probably not impaired

A. These patients are not able to carry out co-transport of glucose and Na+ ions

Which of the following statements is true? - The lipid bilayer is a stable and static structure. - The most common type of lipids in membranes is sphingolipids. - Phosphoglycerides provide most of the structure and stability to cellular membranes. - All membrane lipids are amphipathic.

All membrane lipids are amphipathic.

In which of the following cases is energy NOT needed for transmembrane transport? - Calcium ions (Ca2+) move out of the cell against its concentration gradient via the Ca2+/Na+ antiporter. - All of the answer choices are correct. - Lysine moves into the cell against its concentration gradient via the Na+/lysine symporter. - Potassium ions (K+) move out of the cell down the K+ concentration gradient via potassium channels. - Glucose moves into the cell down its concentration gradient via a glucose uniporter.

All of the answer choices are correct

The movement of dietary glucose and sodium from the intestine into the bloodstream relies on which transport mechanism? - sodium/potassium ATPase - Sodium-glucose symporter - All of the answer choices are correct - Transcellular transport - None of the answer choices are correct

All of the answer choices are correct

Which class of lipid is present in biomembranes? - Sterols - Sphingolipids - Phosphoglycerides - All of the answer choices are correct

All of the answer choices are correct

Parietal cells acidify the stomach contents while maintaining a neutral cytosolic pH by: - exchanging HCO3- for Cl-. - preserving electroneutrality by accompanying the movement of each Cl- ion into the stomach lumen by a K+. - exporting "excess" cytosolic OH- as HCO3-. - All of the answer choices are correct.

All of the answer choices are correct.

Proteins can be attached to the phospholipid bilayer plasma membrane by covalently linked hydrocarbon groups. Which mechanism is employed in this anchoring? - GPI (glycosylphosphatidyl-inositol) anchor - All of these answer choices are correct - Acylation with an amide linkage - Acylation with a thioester linkage Prenylation

All of these answer choices are correct

The illustration of a lipid bilayer interacting with 3 different proteins (1, 2, and 3). Which reagents will you choose most logically to remove these proteins from the membrane in their native functional form? A. Sodium Chloride 2. Sodium dodecyl sulfate (SDS) 3. Octylglucoside B. Sodium Chloride 2. Octylglucoside 3. Triton X-100 C. Triton X-100 2. Sodium Chloride 3. Octylglucoside D. Triton X-100 2. Octylglucoside 3. Sodium dodecyl sulfate (SDS) E. Both A and B are correct

B. Sodium Chloride 2. Octylglucoside 3. Triton X-100

Amino acid entry into cells can occur via uniporters or symporters. If the rate of leucine entry into the cell increases when the pH decreases, this suggests that leucine is: - Being transported by a uniporter - Crossing the membrane via simple diffusion - Being transported by a H+ symporter - Being transported by a H+ antiporter - Being actively pumped across the membrane against its concentration gradient

Being transported by a H+ symporter

Which of the following is true regarding membrane proteins? - Lipid-anchored membrane proteins are located within the phospholipid bilayer. - A protein with six hydrophobic helices is most likely a lipid-anchored membrane protein. - Beta strands can assemble into a membrane-spanning barrel structure. - All peripheral membrane proteins contact the lipid bilayer by attachments to the hydrophilic head groups on membrane lipids.

Beta strands can assemble into a membrane-spanning barrel structure.

In a laboratory activity, red-labeled glucose, blue-labeled water, and green-labeled ethanol are added to a solution placed over an artificial membrane made up of pure, and only phospholipids. Which colors will be observed on the other side of the membrane after 10 minutes? - Red - Both blue and green - Green - Blue - Both Red and Green

Both blue and green

The osmotic potential of a hypotonic solution should cause an animal cell to ___, but frog oocytes prevent this effect by ___. - Shrink; not expressing aquaporins - Burst; expressing more aquaporins - Shrink; expressing more aquaporins - Burst; not expressing aquaporins

Burst; not expressing aquaporins

Which of the following statements regarding glucose transporters (GLUT) is true? A. The Vmax for glucose import into a single cell cannot be altered without changing the type of GLUT transporter expressed by the cell. B. GLUT1 will transport glucose, mannose, and galactose with similar affinity. C. The high Km of GLUT2 leads to more drastic glucose uptake rate changes when blood glucose concentration increases after a meal. D. The high Km of GLUT3 in neuronal cells leads to high rates of glucose uptake by these cells even if blood glucose concentration is low

C. The high Km of GLUT2 leads to more drastic glucose uptake rate changes when blood glucose

Which of the following is true about cystic fibrosis (CF) and the CFTR transporter protein? Which of the following is FALSE? A. CFTR is a member of the ABC superfamily of transporter that requires ATP and transport chloride out of the cells B. CFTR is a member of the ABC superfamily of transporter that acts as a chloride channel to move chloride out of the cells down the concentration gradient C. CFTR is a member of the ABC superfamily of transporter that acts as a chloride channel but can't function in absence of ATP D. CFTR is a member of the ABC superfamily of transporter that acts as a chloride pump to move chloride out of the the cells against the concentration gradient

D. CFTR is a member of the ABC superfamily of transporter that acts as a chloride pump to move chloride out of the the cells against the concentration gradient

Which statement describes the mode of action of the ABCB1 transporter (the first eukaryotic ABC transporter to be recognized)? - During transport, a conserved aspartate residue is phosphorylated. - This transporter acts as a chloride channel. - During transport, the ligand-binding site is alternately exposed to the exoplasmic and the cytoplasmic side of the membrane. - This class of pumps transports only H+ ions.

During transport, the ligand-binding site is alternately exposed to the exoplasmic and the cytoplasmic side of the membrane.

One example of transepithelial transport is the system in intestinal epithelial cells that includes the ________________ in the intestine-facing membrane, the energy requiring ______________facing the blood, and the ______________ allowing facilitated diffusion out of the cell into the blood. A. Glut2, Na+/glucose cotransporter, Na+/K+ ATPase B. Na+/K+ ATPase, Na+/glucose symporter, Glut2 C. Na+/glucose antiporter, Glut2, K + channel D. H+/K+ ATPase, Glut2, Na+/K+ ATPase E. Na+/glucose symporter, Na+/K+ ATPase, Glut2

E. Na+/glucose symporter, Na+/K+ ATPase, Glut2

Which of the four classes of ATP-powered pumps share an overall similarity: several subunits, the same general organization, and a similar function as H+ transporters? - ABC superfamily and P-class pumps - F-class pumps and V-class pumps - F-class pumps and P-class pumps - ABC superfamily and V-class pumps

F-class pumps and V-class pumps

Which of the following statements regarding glucose transporters is true? - GLUT1 will transport glucose, mannose, and galactose with similar affinity - The high Km of GLUT3 in neuronal cells leads to high rates of glucose uptake by these cells even if blood glucose concentrations are low - The Vmax for glucose import into a cell cannot be altered without changing the type of GLUT transporter expressed by the cell - GLUT2 transporters have high Km but they can effectively uptake glucose after a meal when blood glucose concentration increases

GLUT2 transporters have high Km but they can effectively uptake glucose after a meal when blood glucose concentration increases

Glucose enters erythrocytes via a GLUT-1 uniporter. As the levels of glucose in the bloodstream decrease between meals, what happens to the glucose in the cells? - Glucose remains in the cell because uniporters can only transport in one direction. - Glucose leaves the cell through the GLUT-1 uniporter, traveling down the new concentration gradient. - Glucose remains in the cell because the GLUT-1 uniporters are gated and the gates close at low glucose concentrations. - Glucose remains in the cell because it has been phosphorylated and no longer has affinity for the GLUT-1 uniporter.

Glucose remains in the cell because it has been phosphorylated and no longer has affinity for the GLUT-1 uniporter.

How does inhibition of the Na+/K+ ATPase increase the force of heart muscle contraction? - It increases cytosolic K+ and therefore decreases Ca2+ export. - It decreases cytosolic K+ and therefore decreases Ca2+ export. - It increases cytosolic Na+ and therefore decreases Ca2+ export. - It decreases cytosolic Na+ and therefore decreases Ca2+ export.

It increases cytosolic Na+ and therefore decreases Ca2+ export.

An investigator wants to use FRAP to quantify the lateral movement of a specific plasma membrane protein, but to do so, this investigator must first: - Measure the intensity of the fluorescence of the cell surface - Label the cell with a fluorescent reagent that binds specifically to the cell surface protein being studied - Focus a laser on one region of the cell surface - Add detergents to make the cell surface more fluid

Label the cell with a fluorescent reagent that binds specifically to the cell surface protein being studied

Peripheral membrane proteins: - Contain membrane spanning domains - May noncovalently interact with phospholipid heads - Have covalently attached lipid or fatty acid anchors - Contain many hydrophobic amino acid residues

May noncovalently interact with phospholipid heads

Which cellular organelle is enclosed by two cellular membranes? - Mitochondria - Endoplasmic reticulum - Nucleus - Golgi - More than one answer choices are correct.

More than one answer choices are correct.

Which of the following statements is NOT true? - Glycoproteins are the basis for blood type compatibility between donor and receiver - Glycoproteins are always oriented so that carbohydrate moieties are exoplasmic - Movement of proteins from the cytoplasmic to the exoplasmic face of the lipid bilayer requires specialized transport proteins, often flippases - The three types of lipid anchors responsible for tethering proteins to the bilayer are acylation, prenylation and GTPase anchors

Movement of proteins from the cytoplasmic to the exoplasmic face of the lipid bilayer requires specialized transport proteins, often flippases

Transepithelial glucose transport uses a symporter to transport glucose up a concentration gradient by coupling glucose transport to __________ movement. - Ca2+ - Cl- - H+ - Na+ - proton

Na+

The plasma membrane around a eukaryotic cell is composed of: - hydrophobic phospholipids - a phosphoprotein bilayer. - None of the answer choice is correct. - hydrophilic fatty acyl side chains

None of the answer choice is correct.

Which property contributes more to the fluidity/transition temperature of membranes? - Length of the fatty acid chains - Number of fatty acid bond saturation - Degree of protein saturation - All of the other choices are correct.

Number of fatty acid bond saturation

Which of the following statements about ATP-powered pumps is NOT true? - Only P-, F- and V- class pumps transport ions - F-class and V-class pumps transport the same ion but in opposite directions - All ATP powered pumps contain at least one transmembrane domain - ABC transporters are found in organisms ranging from bacteria to humans

Only P-, F- and V- class pumps transport ions

Which statement is TRUE about cystic fibrosis? - CFTR mutations result in a mutated protein, which pumps too many chloride ions out of the cell. - The normal CFTR channel protein is a chloride uniporter, but CF patients have a mutation that makes it require ATP. - Patients with the most common mutation make a CFTR protein that is non-functional or not present in the membrane. - There are no treatments for patients with CF that are specifically targeted to the CFTR membrane receptor.

Patients with the most common mutation make a CFTR protein that is non-functional or not present in the membrane.

Which of the following lipid is involved in signal transduction - Phosphatidyl-choline - Phosphatidyl- inositol - Phosphatidyl ethanolamine - Phosphatidyl-serine

Phosphatidyl- inositol

Transepithelial transport requires a ___ cell layer - Polarized and sealed - Permeable - Polarized - Sealed

Polarized and sealed

Classes of membrane transport proteins include all of the following EXCEPT: - Ion channels - ATP-powered pumps - Proteases - Transporters

Proteases

Movement of phospholipids from one leaflet to the other: - Requires flippases - Occurs routinely - Is impossible - Requires cholesterol

Requires flippases

All of the following describe biomembranes EXCEPT: - Different biomembranes may contain different proportions of the same phospholipids - Some biomembranes have free edges - The two leaflets of a biomembrane may contain different phospholipids - Some specific phospholipids, cholesterol, and sometimes GPI anchored proteins clusters to form microdomains on the membranes known as lipid rafts

Some biomembranes have free edges

The partition coefficient K, the equilibrium constant for partitioning between oil and water, for butyric acid is about 10-2, and for 1,4-butanediol it is about 10-4. You add liposomes containing only water to a solution with an initial concentration of 1 mM butyric acid and 100 mM 1,4-butanediol outside the liposomes. What is the relative rate of diffusion of the two substances into the liposome interior? - The two diffuse into the liposome at equal rates. - Not enough information is provided to permit an answer. - Butanediol diffuses into the liposome 100-fold faster than butanediol. - Butyric acid diffuses into the liposome 100-fold faster than butanediol.

The two diffuse into the liposome at equal rates.

Sphingolipids are considered amphipathic glycolipids if: - They are phospholipids with a one-chain hydrophobic tail - None of the answer choices are correct - They have one fatty acyl chain attached to carbon 2 of glycerol - Their polar head groups are sugars that are not linked to the tails via a phosphate group

Their polar head groups are sugars that are not linked to the tails via a phosphate group

Which statement is TRUE regarding lipid-anchored membrane proteins? - They can be present on either the cytosolic or exoplasmic leaflet of the cell. - They are only present on the cytosolic leaflet of the cell. - They are only present on the exoplasmic leaflet of the cell. - They are only present on the endoplasmic leaflet of the cell.

They can be present on either the cytosolic or exoplasmic leaflet of the cell.

The glucose transporter GLUT2 is localized in the basolateral membrane of epithelial cells of the small intestine. How do these cells achieve this polarized distribution of GLUT2? - With the apical brush border cilia - Lipid rafts - Tight junctions - GPI anchors

Tight junctions

How does uniport transport compare with simple diffusion? - Simple diffusion is reversible but uniport transport is not. - Uniport transport is slower but more specific than simple diffusion. - Uniport transport is much faster and more specific than simple diffusion. - Similar to simple diffusion, uniport transport is nonspecific.

Uniport transport is much faster and more specific than simple diffusion.

Which of the following statements regarding membrane transport proteins is NOT true? - Facilitated diffusion move specific molecules down its concentration gradient. - Both ABC transporter proteins and ATP-powered pumps represent active transport. - Uniporters move ions faster through membranes than do ion channels. - Uniporter transport is fast, reversible, and highly specific.

Uniporters move ions faster through membranes than do ion channels.

Which of the following statements is NOT true regarding detergents? - Peripheral membrane proteins can be removed from membranes without the use of detergent - Triton X-100 is a useful detergent for protein extraction prior to purification - Western blotting employs a nonionic detergent to denature proteins during gel electrophoresis - All detergents are amphipathic molecules

Western blotting employs a nonionic detergent to denature proteins during gel electrophoresis

You have isolated some fibroblasts cells from cell culture, and treated cells with the ionic detergent sodium dodecyl-sulfate (SDS) to disrupt their membranes. Will integral membrane proteins be affected by this treatment and how? - No; integral membrane proteins are not released from membranes by SDS. - Yes; integral membrane proteins will be released by the SDS treatment and will now function in soluble form. - Yes; integral membrane proteins will be released and denatured by this treatment. - Yes; integral membrane proteins will be released from the membrane but now form micelles within the cytoplasm.

Yes; integral membrane proteins will be released and denatured by this treatment.

Porins: - have many hydrophobic α-helical regions. - are peripheral membrane proteins. - contain no hydrophobic amino acid residues. - allow small hydrophilic molecules to pass through a membrane.

allow small hydrophilic molecules to pass through a membrane.

Cholesterol mixes with phospholipids in a biomembrane because cholesterol molecules are: - phospholipid derivatives - amphipathic - entirely hydrophobic - steroid derivatives

amphipathic

Phospholipids with short or unsaturated fatty acyl chains: - allow hydrophilic molecules to diffuse across the lipid bilayer. - cause biomembranes to become thicker. - decrease membrane fluidity. - increase membrane fluidity.

increase membrane fluidity.

The _____________________ proteins are transmembrane proteins - lipid-anchored membrane - peripheral membrane - integral membrane - extracellular matrix

integral membrane

Following the production of membrane extracts using the non-ionic detergent Triton X-100, you analyze the membrane lysates via mass spectrometry and note a high content of cholesterol and sphingolipids. Furthermore, biochemical analysis of the lysates reveals potential kinase activity. Which of the following membrane component is likely to be present in a high amount in your extract? - porins - micelles - lipid droplets - lipid rafts

lipid rafts

ABC superfamily proteins are thought to act as ATP-dependent flippases in transporting: - H+ out of mammalian cells. - Ca2+ out of mammalian cells. - Na+ out of mammalian cells, K+ into mammalian cells. - lipophilic drugs out of mammalian cells.

lipophilic drugs out of mammalian cells.

The major ATP-powered pump responsible for maintaining ion gradients across the plasma membrane of mammalian cells is the: - calmodulin-activated plasma membrane Ca2+ ATPase - vacuolar F-class proton pump. - sarcoplasmic reticulum Ca2+ ATPase - plasma-membrane Na+/K+ ATPase.

plasma-membrane Na+/K+ ATPase.

Acidification of the stomach uses all of the following types of transport EXCEPT: - symporters - pumps - All of the answer choices are correct. - channels - antiporters

symporters

Aquaporins are: - membrane spanning ABC proteins - symporters - β-barrel proteins that transport ions in an aqueous environment. - transmembrane water channels

transmembrane water channels

Which of the following events requires active transport in an intestinal epithelial cell? - None of the answer choice is correct. - All of the answer choices are correct - uptake of glucose - uptake of Na+ - export of glucose

uptake of glucose