Chapter 11 Biochem

Which of these consists of a long-chain alkyl amine, a saturated long-chain fatty acid, and a polar head group? sterol sphingolipid triacylglycerol glycerophospholipid

sphingolipid

A lipid bilayer has a width of 3 nm. What is the approximate length of the fatty acyl chains of the lipid molecules in the bilayer? 3 nm 6 nm 1.5 nm 0.75 nm

1.5 nm

Which answer choice correctly identifies the order of events that take place during neurotransmitter release at a synapse? 1. A fusion pore forms. 2. v-SNARE, SNAP25, and t-SNARE interact, forming a coiled bundle of four α helices. 3. The outer leaflets of both membranes come into contact. 4. Zipping causes curvature and lateral tension on bilayers. 2, 4, 3, 1 1, 2, 3, 4 2, 1, 3, 4 3, 4, 2, 1

2,4,3,1

Which statement about lipid rafts is false? Lipid rafts can occupy up to 50% of the cell surface. Certain membrane receptors and signaling proteins seem to be segregated together in membrane rafts. A single raft likely contains at least one molecule of each membrane protein. Membrane proteins can move into and out of lipid rafts in a fraction of a second.

A single raft likely contains at least one molecule of each membrane protein.

Which statement is false regarding the sarcoplasmic/endoplasmic reticulum Ca2+ ATPase (SERCA) pump? It moves Ca+ against its electrochemical gradient. ATP binding and Asp phosphorylation drive a conformational change that exposes the Ca2+-binding sites to the cytosol. The transporter moves two Ca+ across the membrane of the sarcoplasmic/endoplasmic reticulum for every molecule of ATP hydrolyzed to ADP and Pi. It pumps Ca+ from the cytosol into the lumen of the sarcoplasmic/endoplasmic reticulum.

ATP binding and Asp phosphorylation drive a conformational change that exposes the Ca2+-binding sites to the cytosol.

Which amino acid would LEAST likely be found in an α helix that spans a lipid bilayer? Arg Val Ile Leu

Arg

Which statement is true about glycophorin and the chloride-bicarbonate exchanger in the erythrocyte membrane? Glycophorin can diffuse freely within the plane of the membrane, whereas the chloride-bicarbonate exchanger is anchored in place. The chloride-bicarbonate exchanger can diffuse freely within the plane of the membrane, whereas glycophorin is anchored in place. Both glycophorin and the chloride-bicarbonate exchanger are anchored in place. Both glycophorin and the chloride-bicarbonate exchanger can diffuse freely within the plane of the membrane.

Both glycophorin and the chloride-bicarbonate exchanger are anchored in place.

Which statement is false about glucose transport in intestinal epithelial cells? GLUT2 is located on the basal surface. GLUT1 is located on the apical surface. The Na+K+ ATPase is located on the basal surface. The Na+-glucose symporter is located on the apical surface.

GLUT1 is located on the apical surface

The activity of _____ increases in response to insulin. GLUT1 GLUT2 GLUT3 GLUT4

GLUT4

What type of protein is prominent in the outer leaflet of lipid rafts? GPI-anchored proteins monotopic proteins proteins attached to one or more long-chain fatty acyl groups bitopic proteins

GPI-anchored proteins

Which statement is false regarding the liquid-ordered (Lo) state of the lipids in a bilayer? This state occurs below normal physiological temperatures. Lateral diffusion of individual lipid molecules is strongly constrained. Polar head groups are uniformly arrayed at the surface. Individual hydrocarbon chains of fatty acids constantly rotate about the carbon-carbon bonds of long acyl side chains.

Individual hydrocarbon chains of fatty acids constantly rotate about the carbon-carbon bonds of long acyl side chains.

Which statement is true about the chloride-bicarbonate exchanger of the erythrocyte membrane? It is an example of a symport system. It allows both the entry and exit of bicarbonate into the erythrocyte. Its activity increases the membrane potential. Its activity decreases the membrane potential.

It allows both the entry and exit of bicarbonate into the erythrocyte.

Which statement is false about the glucose transporter of erythrocytes (GLUT1)? It is specific for D-glucose. It allows erythrocytes to accumulate glucose at concentrations above that of blood plasma. In a living cell, it operates at close to ½Vmax. It has two conformations, one that faces outward and one that faces inward.

It allows erythrocytes to accumulate glucose at concentrations above that of blood plasma.

How does the binding of insulin to its receptor reduce blood glucose levels? It causes the removal of glucose transporters from the plasma membrane of intestinal epithelial cells by endocytosis. It causes the removal of glucose transporters from the plasma membrane of myocytes and adipocytes by endocytosis. It causes vesicles containing glucose transporters to fuse with the plasma membrane of intestinal epithelial cells. It causes vesicles containing glucose transporters to fuse with the plasma membrane of myocytes and adipocytes.

It causes vesicles containing glucose transporters to fuse with the plasma membrane of myocytes and adipocytes.

Which statement about cardiolipin is false? It consists of a head group and two fatty acyl chains. It is highly localized at the two poles of rod-shaped bacteria. It can create or reorganize membrane curvature. It is present primarily in mitochondrial membranes of eukaryotes.

It consists of a head group and two fatty acyl chains.

Which statement is false about caveolin? It associates with cholesterol-rich regions in the plasma membrane. It forms dimers. It is unique in its ability to induce curvature in membranes. It has two globular domains connected by a hairpin-shaped hydrophobic domain.

It is unique in its ability to induce curvature in membranes.

Which statement is true regarding the structure shown? It is a hollow structure enclosing an aqueous cavity. This structure forms when a two-dimensional lipid bilayer folds on itself. Its formation is favored when the cross-sectional area of the head group is greater than that of the acyl side chain(s). Its formation is favored when the cross-sectional areas of the head group and acyl side chain(s) are similar.

Its formation is favored when the cross-sectional area of the head group is greater than that of the acyl side chain(s).

Gliflozins treat diabetes by acting as specific inhibitors of: quaporins. GLUT2 glucose transporters. GLUT4 glucose transporters. Na+-glucose symporters.

Na+-glucose symporters.

All of these can be used to release a peripheral protein from a membrane EXCEPT for: carbonate. urea. a chelating agent. phospholipase C.

Phospholipase C

Which statement is true about simple diffusion of ions across a membrane? Removal of the hydration shell and rehydration of the ion are both endergonic. Removal of the hydration shell is exergonic, whereas rehydration of the ion is endergonic. Removal of the hydration shell and rehydration of the ion are both exergonic. Removal of the hydration shell is endergonic, whereas rehydration of the ion is exergonic.

Removal of the hydration shell is endergonic, whereas rehydration of the ion is exergonic.

Which of these does NOT describe biological membranes? Selectively permeable Self-repairing Flexible Symmetric

Symmetric

Which statement about the three general classes of transport systems is false? Symporters and antiporters are both examples of cotransport systems. Cotransport systems carry more than one type of solute. The Na+K+ ATPase of animal cells is an antiporter for Na+ and K+ ions. These classification systems distinguish between active and passive transport processes.

These classification systems distinguish between active and passive transport processes.

Which statement is true about the state of membrane lipids in biological membranes? They generally fluctuate between the liquid-ordered (Lo) state and the liquid-disordered (Ld) state. They are generally maintained in the liquid-disordered (Ld) state. They are generally maintained in the liquid-ordered (Lo) state. They are generally maintained somewhere between the liquid-ordered (Lo) state and the liquid-disordered (Ld) state.

They are generally maintained somewhere between the liquid-ordered (Lo) state and the liquid-disordered (Ld) state.

Which statement is false about integrins? They mediate a cell's interaction with the extracellular matrix and with other cells. They bind to proteins with the RGD integrin-binding sequence. They are homodimeric proteins with subunits anchored to the plasma membrane by a single transmembrane helix. They carry signals in both directions across the plasma membrane.

They are homodimeric proteins with subunits anchored to the plasma membrane by a single transmembrane helix.

Which statement is false about proteins that mediate the fusion of two membranes? They ensure that two membranes recognize each other. They include a family of proteins called SNAREs. They facilitate receptor-mediated endocytosis and regulated secretion. They are the products encoded by two fused genes.

They are the products encoded by two fused genes.

How do transporter proteins facilitate the movement of solutes across biological membranes? They provide a hydrophobic transmembrane pathway. They increase the ΔG‡ for transmembrane diffusion of the solute. They form noncovalent interactions with the dehydrated solute that replace its hydrogen bonds to water. They hydrolyze ATP and use the released energy to pump the solute across the membrane.

They form noncovalent interactions with the dehydrated solute that replace its hydrogen bonds to water.

Which is true of lipid bilayers? Their formation is favored when the cross-sectional area of the head group is greater than that of the acyl side chain(s). A two-dimensional bilayer sheet is relatively stable in an aqueous environment. They spontaneously form vesicles or liposomes. Individual lipid units are wedge-shaped.

They spontaneously form vesicles or liposomes.

Which statement is false regarding transporters and ion channels? Transporters have two gates that are never open at the same time. Transporters allow ions to flow down the electrochemical gradient, whereas channels can move ions against a concentration gradient. Channels can allow transmembrane movement of ions at rates that are much greater than those typical of transporters. Ions move through channels at a rate limited only by the maximum rate of diffusion.

Transporters allow ions to flow down the electrochemical gradient, whereas channels can move ions against a concentration gradient.

Glycophorin is _____ integral protein. not an a monotopic a bitopic a polytopic

a bitopic

What is the "clamp" in patch-clamping? a micropipette a tiny region of plasma membrane an electronic circuit one or a few ion channels

an electronic circuit

What does a cadherin bind on the surface of an adjacent cell? a specific polysaccharide an identical cadherin a selectin a protein with the sequence Arg-Gly-Asp

an identical cadherin

Antidiuretic hormone (vasopressin) regulates the activity of a(n): ion channel. glucose transporter. ion pump. aquaporin.

aquaporin

All of these hallmarks of passive transport EXCEPT: high rates of diffusion down a concentration gradient. saturability. stereospecificity. being coupled to an exergonic process.

being coupled to an exergonic process

The amino acid sequence Leu-Ile-Ile-Phe-Gly-Val-Met-Ala-Gly-Val is found in the erythrocyte protein glycophorin A. This portion of the sequence is MOST likely: on the intracellular surface. at the carboxy terminus. on the extracellular surface. buried in the lipid bilayer. attached to sugars.

buried in the lipid bilayer

Plasma membranes are enriched in _____ but lack _____. cholesterol; cardiolipin cholesterol; sphingolipids cardiolipin; cholesterol sphingolipids; cholesterol

cholesterol; cardiolipin

In lipid rafts, which would NOT be expected to be found in high levels? GPI-anchored proteins glycosphingolipids cholesterol glycerophospholipids

glycerophospholipids

Caveolin is BEST defined as a(n): surface adhesion protein that mediates a cell's interaction with the extracellular matrix and with other cells. integral membrane protein that associates with the inner leaflet of the plasma membrane. GPI-anchored protein that forms stable associations with cholesterol and long acyl groups. protein that allows certain polar solutes to cross the outer membrane of gram-negative bacteria.

integral membrane protein that associates with the inner leaflet of the plasma membrane.

Membrane proteins that speed the passage of solutes across membranes by providing an aqueous path across the membrane are called: ion channels. transporters .ionophores. diffusers.

ion channel

Which type of membrane protein mediates electrical signaling between cells? receptors transporters ion channels adhesion molecules

ion channels

FRAP is a technique that is used to measure: total lipid content in a membrane. transport of molecules across a bilayer. membrane curvature. lateral diffusion in a membrane. transbilayer diffusion in a membrane.

lateral diffusion in a membrane

Which membranes has the lowest content of cholesterol and sphingolipid? plasma mitochondrial lysosomal Golgi

mitochondrial

All of these affect membrane fluidity except: fatty acid composition molarity of the cytosol sterol content temperature

molarity of the cytosol

Which is the principal phospholipid in the lumenal leaflet of the Golgi membrane? phosphatidylserine phosphatidylethanolamine phosphatidylinositol phosphatidylcholine

phosphatidylcholine

Ionophores kill bacteria, fungi, and parasites by disrupting _____ and energy-conserving reactions. passive transport processes secondary active transport processes primary active transport processes membrane integrity

secondary active transport

Which type of membrane transport uses ion gradients across the plasma membrane as the source of energy? facilitated diffusion passive diffusion secondary active transport primary active transport

secondary active transport

All of these proteins mediate surface adhesion EXCEPT for: integrins cadherins septins selectins

septins

For many cells, movement of phosphatidylserine from the inner to the outer leaflet of the plasma membrane: has not been observed in biological systems. occurs very quickly by uncatalyzed transbilayer diffusion. signals a cell for apoptosis. enables the lipid to be evenly distributed on both sides of the membrane.

signals a cell for apoptosis

All of these processes can drive active transport EXCEPT for: ATP hydrolysis. an oxidation reaction. the flow of another substrate against its electrochemical gradient. the absorption of sunlight.

the flow of another substrate against its electrochemical gradient.

What is "flip-flop" diffusion? the movement of lipids from one membrane leaflet to the other the movement of proteins within the plane of the membrane the movement of lipids within the plane of the membrane the movement of proteins from one membrane leaflet to the other

the movement of lipids from one membrane leaflet to the other

Fatty acids in aqueous solution form micelles and not vesicles because: they are too hydrophobic to form vesicles. they are not amphipathic. their overall surface is cone-shaped rather than cylindrical. they are too small to form vesicles. they do form vesicles if there are no bile salts available.

their overall surface is cone-shaped rather than cylindrical.

Which event is likely to occur very quickly, at the rate of approximately 1 μm/s? a)uncatalyzed transbilayer diffusion of a single phospholipid b) uncatalyzed lateral diffusion of a single phospholipid c)both uncatalyzed transbilayer diffusion and uncatalyzed lateral diffusion of a single phospholipid d) neither uncatalyzed transbilayer diffusion nor uncatalyzed lateral diffusion of a single phospholipid

uncatalyzed lateral diffusion of a single phospholipid