cell bio 7.1-7.2 &11.1-11.3 & 11.5-11.6
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.
5.5-fold fasterThe plasma membrane around a eukaryotic cell is composed of:
Proteins can be attached to the phospholipid bilayer plasma membrane by covalently linked hydrocarbon groups. Which mechanism is employed in this anchoring?
Acylation- anchor through a single fatty acyl chain to the N-terminal glycinePrenylation- anchor through a prenyl group to one or two C-terminus Cys groupsGPI (glycosylphosphatidylinositol)- anchors extracellular protein to the exoplasmic surface of the plasma membrane.
Which of the following statements is true? 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. The lipid bilayer is a stable, unchanging structure.
All membrane lipids are amphipathic.
Which of the following statements is true? 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.The lipid bilayer is a stable, unchanging structure.
All membrane lipids are amphipathic.
Which statement describes the mode of action of the ABCB1 transporter (the first eukaryotic ABC transporter to be recognized)?
During transport, the ligand-binding site is alternately exposed to the exoplasmic and the cytoplasmic side of the membrane.
Which of the four classes of ATP-powered pumps share overall similarity: several subunits, the same general organization, and a similar function as H+ transporters?
F-class pumps and V-class pumps
How does inhibition of the Na+/K+ ATPase increase the force of heart muscle contraction? It increases cytosolic Na+ and therefore decreases Ca2+ export. It increases cytosolic K+ and therefore decreases Ca2+ export It decreases cytosolic Na+ and therefore decreases Ca2+ export. It decreases cytosolic K+ and therefore decreases Ca2+ export.
It increases cytosolic Na+ and therefore decreases Ca2+ export
Which of the following is NOT true of phospholipid bilayers? The chemical properties of phospholipids lead to the spontaneous formation of bilayers.The interior of phospholipid bilayers is a highly hydrophobic environment.Phospholipid bilayers separate the cell from the exterior environment as well as from compartments within the cell.Membrane budding requires transient breakages in the bilayer membrane.
Membrane budding requires transient breakages in the bilayer membrane.
Transepithelial glucose transport uses a symporter to transport glucose up a concentration gradient by coupling glucose transport to _____ movement.
Na+
Which of the following statements about ATP-powered pumps is NOT true? F-class and V-class pumps transport the same ion but in opposite directions. ABC transporters are found in organisms ranging from bacteria to humans. Only P-, F-, and V-class pumps transport ions. All ATP-powered pumps contain at least one transmembrane domain.
Only P-, F-, and V-class pumps transport ions.
Which of the following statements is NOT true? Glycoproteins are always oriented so that the carbohydrate moieties are exoplasmic. Glycoproteins are the basis for blood type compatibility between donor and receiver. 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.
The three types of lipid anchors responsible for tethering proteins to the bilayer are acylation, prenylation, and GTPase anchors.
Which of the following statements regarding membrane transport proteins is NOT true? Both transporter proteins and ATP-powered pumps represent active transport.Facilitated transport is required to move any molecule against its concentration gradient.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? Western blotting employs a nonionic detergent to denature proteins during electrophoresis. All detergents are amphipathic molecules. Triton X-100 is a useful detergent for protein extraction prior to purification. Peripheral membrane proteins can be removed from membranes without the use of a detergent.
Western blotting employs a nonionic detergent to denature proteins during electrophoresis.
The movement of dietary glucose and sodium from the intestine into the bloodstream relies on which transport mechanism? All of the answers are correct.sodium glucose symportersodium/potassium ATPasetranscellular transport
all
Parietal cells acidify the stomach contents while maintaining a neutral cytosolic pH by: exporting "excess" cytosolic OH- as HCO3-. exchanging HCO3- for Cl-. preserving electroneutrality by accompanying the movement of each Cl- ion into the stomach lumen by a K+. All of the answers are correct.
all of the answers are correct (The pH of parietal cell cytosol will maintain neutral during the acidification of the stomach lumen by combining the OH- generated while exporting protons with that of CO2 to form HCO3- (catalyzed by carbonic anhydrase). The formed HCO3- will be transported into the blood in exchange to Cl- through the basolateral membrane (anion antiporter will work here). After importation, the Cl- ion will enter the stomach lumen through the Cl-channels in the apical membrane and for every Cl- ion, one K+ ion will move outwards and like this the H+/K+ ATPase can successfully can send the excess of K+ ions to the stomach lumen. So now stomach lumen will have both H+ and Cl- accumulated and the cytosol pH will be neutral as the excess of OH- and HCO3- will be sent to the blood.
Porins
allow small hydrophilic molecules to pass through a membrane.
Cholesterol mixes with phospholipids in a biomembrane because cholesterol molecules are:
amphipathic
In a laboratory activity, red-labeled glucose, blue-labeled water, and green-labeled ethanol are added to a solution placed over an artificial, pure phospholipid membrane. Which colors will be observed on the other side of the membrane after 10 minutes?
both blue and green
The osmotic potential of a hypotonic solution should cause an animal cell to _____, but with frog oocytes prevent this effect by _____.
burst; not expressing aquaporins
Cholesterol, bile acids, ergosterol, and stigmasterol share all the following common structural features EXCEPT a:
carboxylic acid group
Lipid droplets arise from the:
endoplasmic reticulum.
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:
label the cell with a fluorescent reagent that binds specifically to the cell surface.
ABC superfamily proteins are thought to act as ATP-dependent flippases in transporting:
lipophilic drugs out of mammalian cells.
Peripheral membrane proteins:
may noncovalently interact with phospholipid heads
Which cellular organelle is enclosed by two cellular membranes?
nucleus
Which class of lipids is present in biomembranes?
phosphoglycerides, sphingolipids, sterols
The plasma membrane around a eukaryotic cell is composed of:
phospholipid bilayer
Glycolipids and glycoproteins are especially abundant in the:
plasma membrane
The major ATP-powered pump responsible for maintaining ion gradients across the plasma membrane of mammalian cells is the:
plasma-membrane Na+/K+ ATPase.
Transepithelial transport requires a _____ cell layer.
polarized and sealed
Peripheral proteins bound to the exoplasmic face of the plasma membrane can also bind to:
proteins of the ECM
All the following describe biomembranes EXCEPT: different biomembranes may contain different proportions of the same phospholipids. the two leaflets of a biomembrane may contain different phospholipids. some biomembranes have free edges. some phospholipids and cholesterol may cluster to form 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 the same rate
Sphingolipids are considered amphipathic glycolipids if:
their polar head groups are sugars that are not linked to the tails via a phosphate group.
What type of simple-pass membrane protein would contain a hydrophobic membrane-spanning α-helix?
transmembrane protein and integral membrane protein
Aquaporins are
water channels
You treat cells with the ionic detergent sodium dodecyl-sulfate (SDS) to disrupt the membrane. Will integral membrane proteins be affected by this treatment and how?
yes, integral membrane proteins will be released and denatured (because breaks disrupt all the hydrogen bond disrupt the tertiary structure of the protein)
