Chapter 10
The epidermal growth factor receptor has a single transmembrane helix. Find it in this partial sequence: ...RGPKIPSIATGMVGALLLLVVALGIGILFMRRRH... Enter the sequence.
MVGALLLLVVALGIGILFM
Which are present in a ganglioside but not in a fat? Select all that apply. glycerol fatty acid phosphate long-chain alcohol carbohydrate
long-chain alcohol carbohydrate
Fill in the blanks: terminal reversed same center (-) (+) 1. Make a mutant Lep that substitutes noncharged residues for the _______ charged side chains in the loop, and put _______ charged side chains in _________ positions. 2. If the inside-positive rule applies, the mutant ought to have the _________ orientation in the membrane.
(+) (+) terminal reversed
Which of the following statements is FALSE? a) Fatty acids exist in the anionic form (RCOO-) at physiological pH. B) Some unsaturated fatty acids are liquid at physiological temperatures. C) Most types of fat in many animals is used in energy production. D) The difference in melting temperature between a saturated fatty acid and an unsaturated fatty acid with the same chain length is only a few degrees C. e) The longer the chain length of a saturated fatty acid, the higher the melting temperature.
D
** model of voltage-gated potassium channel** grey red and blue stucture In eukaryotic nerve cells, K+ concentrations at rest are __________. a) equivalently low both inside and outside the cell b) equivalently high both inside and outside the cell c) higher outside the cell than inside the cell d) higher inside the cell than outside the cell ---------- Examine the molecular model of the K+ channel KcsA from Streptomyces lividans. Regions with charged amino acids can be found primarily in all of the following locations, EXCEPT in __________. a) the extracellular domain b) the transmembrane region c) the selectivity filter d) the intracellular domain ---------- Look again at the molecular model of the K+ channel KcsA from Streptomyces lividans. In what state are the K+ ions when they reside in the spacious 10-angstrom diameter cavity, prior to translocating through the selectivity pore? a) salt form (KCl) B) dehydrated (K+ alone) c) fully hydrated d) paired with another K+ ion ---------- What best explains how Na+ ions are excluded while K+ ions are allowed to pass through the selectivity channel? a) differences in electrostatic charge between the two ions b) that Na+ ions are larger than K+ ions (size exclusion) c) the higher stability of the hydrated form of Na+ compared with the dehydrated form of Na+ within the selectivity channel d) a specific interaction with K+ ions and not with Na+ ions ---------- Review the mammalian voltage-dependent K+ channel of the Shaker family. Closing of the channel in response to membrane depolarization relies primarily on essential arginine residues located where? a) in the extracellular voltage sensor domain b) on the intracellular face c) in the selectivity channel d) in the pore domain
D B C C A
Which of these is NOT a lipid? phospholipid wax RNA steroids cholesterol -------- This figure is an example of a(n) _____. **Picture** saturated fat steroid nucleic acid protein unsaturated fat ---------- Which of these is a phospholipid? **pictures**
RNA saturated fat two long yellow carbon structures
Which channel maintains the concentration gradients of ions across a neuronal membrane? a) The sodium-potassium pump moving Na+ ions in and K+ ions out. b) The potassium leak channel allowing K+ ions out. c) The sodium-potassium pump moving Na+ ions out and K+ ions in. d) The sodium leak channel allowing Na+ ions out.
c
Classify the following molecules as lipids (or lipid components), carbohydrates, or nucleic acids. glucose cholesterol (a steroid) oleic acid DNA RNA ketohexose glycerol myristate
lipids: cholesterol, oleic acid, glycerol myristate carbohydrates: glucose, ketohexose nucelic acids: DNA, RNA
Which term describes the difference in electrical charge across a membrane? Resting potential. Electrical current. Electrical potential. Membrane potential.
membrane potential
Axons insulated by a(n) _____ are able to conduct impulses faster that those not so insulated. node of Ranvier synaptic terminal myelin sheath layer of asbestos astrocytes
myelin sheath
Suggest a saturated fatty acid that should melt below 30 ∘C benzoic acid n-octadecanoic acid n-octanoic acid iso-dodecanoic acid
n-octanoic acid
An impulse relayed along a myelinated axon "jumps" from _____ to _____. oligodendrocyte ... Schwann cell node of Ranvier ... Schwann cell node of Ranvier ... node of Ranvier Schwann cell ... Schwann cell Schwann cell ... node of Ranvier
node of Ranvier....node of Ranvier
Which of these is rich in unsaturated fats? butter beef fat olive oil lard a fat that is solid at room temperature
olive oil
A semipermeable membrane is placed between the following solutions. Which solution will decrease in volume? Solution A: 1.4% (m/v) starch Solution B: 7.62% (m/v) starch ------ A semipermeable membrane is placed between the following solutions. Which solution will increase in volume? Solution C: 9% (m/v) NaCl Solution D: 12.4% (m/v) NaCl --------- Solution A: 3.21% (m/v) NaCl Solution B: 1.65% (m/v) glucose Solution C: distilled H2O Solution D: 6.97% (m/v) glucose Solution E: 5.0% (m/v) glucose and 0.9%(m/v) NaCl Sort the solutions into the following bins: crenation, hemolysis, or neither
solution A solution D crenation: A D E hemolysis: B C neither: none
Rank from highest melting point to lowest melting point. To rank items as equivalent, overlap them. lauric acid oleic acid linolenic acid stearic acid linoleic acid myristic acid
stearic acid myristic lauric oleic linoleic linolenic
Fill in the blanks: unsoluble hydrophilic steroid nonmediated peptide would pore-mediated soluble hydrophobic would not __________ hormones are generally ___________ and can cross the outer membrane bilayer by ___________ diffusion. ___________ hormones are generally water ___________ proteins/oligopeptides that ___________ easily cross the outer membrane of a cell.
steroid hydrophobic nonmediated peptide soluble would not
Which class of lipids does the following molecule belong to? **picture with 6-mem rings and 5-mem ring and Na+ ** fatty acids waxes triacylglycerols glycerophospholipids sphingolipids glycosphingolipids steroids
steroids
What part of a neuron relays signals from one neuron to another neuron or to an effector? dendrite axon hillock synaptic terminal axon node of Ranvier
synaptic terminal
Determine whether each number is never always only before equilibrium is reached only at equilibrium 1. Orange dye moves independently of purple dye. 2. Concentration gradients exist that drive diffusion of both dyes. 3. There is a net movement of orange dye from side A to side B. 4. Purple dye moves only from side B to side A. 5. There is no net movement of purple dye.
1. always 2. only before eq 3. only before eq 4. never 5. only at eq
Show that these data can be accounted for only if the erythrocyte membrane is a bilayer. The ratio of monolayer area to cell surface = ________
1.89
Linolenic acid has cis double bonds with the formula CH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7COOH. Write out the abbreviated systematic numbering for this fatty acid. Enter the abbreviation for the fatty acid using systematic numbering. Type Delta if the Greek symbol is required.
18:3delta9,12,15
How many H2 molecules are needed to completely hydrogenate the following triacylglycerol molecule? (Figure 2)
4
Drag the labels onto the flowchart to show the sequence of events that occurs once the membrane potential reaches threshold. You may use a label once or not at all. membrane potential reaches threshold ---> a) ________ -----> b) _________ ------> c) __________ 1) Many voltage-gated Na+ channels open 2) membrane potential rises (depolarizes) rapidly 3) Na+ ions rush into the cell 4) Na+ ions rush out of the cell
A - 1 B- 3 C - 2
Which statements about the makeup of biological membranes are true? 1) They are composed of bilayers in which the polar head group of the lipid is oriented toward solvent and the lipophilic tails are pointed inward toward the interior of the membrane. 2) All fatty acids can form micelles. 3) The major classes of lipids that make up membranes are glycerophospholipids, sphingolipids, glycosphingolipids, and glycoglycerolipids. 4) The hydrophobic interior is typically twice as thick as the polar, hydrophilic head groups.
ALL
A function of cholesterol that does not harm health is its role _____. a) All of cholesterol's effects cause the body harm. b) as a component of animal cell membranes c) as the primary female sex hormone d) the most abundant male sex hormone e) in calcium and phosphate metabolism
B
Saturated fatty acids are different than unsaturated fatty acids because they: a) mostly have cis double bonds. b) have no C=C double bonds. c) have an even number of carbon atoms. d) exhibit free rotation about the carbon carbon bonds in the hydrocarbon tail. e) have short hydrophobic tails.
B
Hydrogenation of a monounsaturated fatty acid yields a saturated fatty acid. Oleic acid, CH3(CH2)7CH=CH(CH2)7CO2H, is a monounsaturated fatty acid. Predict the product of its hydrogenation Express your answer as a condensed structural formula.
CH3 (CH2)16 CO2H
Resting neurons are most permeable to which of the following ions? O--. K+. Na+. Cl--.
K+
What type of cell makes up the myelin sheath of a motor neuron? astrocytes microglial cells Ranvier cells ependymal cells Schwann cells
Schwann cells
Suppose, however, that an action potential is artificially triggered at the point indicated by the red arrow. In what sequence would the action potential pass through points (a), (b), and (c)? Enter the sequence in which the action potential would pass through the points. Enter the letters in the correct order separated by commas. For example if the order is point (c), then (b), then (a), enter c, b, a. If the action potential would not pass though a point, do not include that point in your answer.
b,a,c
The Na+/glucose symport transports glucose from the lumen of the small intestine into cells lining the lumen. Transport of 1 glucose molecule is directly coupled to the transport of 1 Na+ ion into the cell. 1Na+out+1glucoseout→1Na+in+1glucosein Assume the following conditions at 37 ∘C: [Na+]in = 12.0 mM,[Na+]out = 145 mM, [glucose]out = 28.0 μM, and Δψ= -72 mV (inside negative). What is ΔG for transport of Na+ from outside to inside under these conditions? --------- What is the upper limit for [glucose]in under these conditions? --------- Which of the two hypothetical symports shown below (A or B) would achieve the highest concentration of [glucose]in under the conditions described above? Briefly explain your choice. A: 1Na+out+2glucoseout→1Na+in+2glucosein B: 2Na+out+1glucoseout→2Na+in+1glucosein A) Symport B would achieve higher [glucose]in because it provides a higher driving force per glucose than does symport A. B) Symport A would achieve higher [glucose]in because it provides a greater concentration of glucose than does symport B.
-13.4 kJ/mol 5.0 mM A
H+ transport from the outside of the IMM into the matrix drives this process. The inside the matrix is 8.2, and the outside is more acidic by 0.8 units. Assuming the IMM membrane potential is 168 (inside negative), calculate for the transport of 1 of across the IMM into the matrix at 37C : H+ (out) ----> H+ (in). --------- Write the overall reaction for ATP synthesis coupled to H+ transport. ---------- Assume three mol be translocated to synthesize one mol ATP as described in part B above. Given the following steady-state concentrations: = 2.70 and = 5.20 , the membrane potential = -168 (inside negative), and the values in part A, calculate the steady-state concentration of at 37 when = -11.7
-21.0 kJ/mol 3H+ (out) ----> 2H+ (in) 5.30 mM
Suppose calcium ion is maintained within an organelle at a concentration 1000 times greater than outside the organelle (T=37∘C). What is the contribution of Ca2+ to the membrane potential? --------- Which side of the organelle membrane is positive, and which is negative? The inside of the organelle is negative with respect to the outside. The outside of the organelle is negative with respect to the inside.
-92.2 mV the inside of the organelle is negative with respect to the outside
Decide whether each type of molecule or ion is a) hydrophobic or hydrophilic b) able to cross lipid bilayer c) transport protein required 1. nonpolar molecules (hydrocarbons, O2, CO2) 2. polar molecules (H2O, sugars) 3. Ions (Na+, K+, Ca+, Cl-)
1. hydrophobic, can cross easily, no transport protein required 2. hydrophilic, have difficulty crossing the hydrophobic part, transport protein required to cross efficiently 3. hydrophilic, have diff crossing the hydrophobic part, transport protein required to cross eff
Fill in the blanks: the concentration of ions won't be in equilibrium the concentration of ions will equalize yes no 1. For (a) - ______., because __________________. 2. For (b) - ______., because _________________ 3. For (c) - ______., because ________________.
1. no. the con of ions WON'T be 2. no. the con of ions WON'T 3. yes. the con of ions WILL
1. In what direction will the K+ ions move through the artificial channel? 2. Does the K+ concentration gradient promote or impede the movement of K+ ions through the artificial channel? 3. Does the membrane potential promote or impede the movement of K+ ions through the artificial channel? 4. How does the movement of K+ ions through the artificial channel affect the membrane potential?
1. out of the cell 2. promote 3. impede 4. causes a hyperpolarization
**Model with pink strands of Aquaporin-1*** Aquaporin-1 exists in the cell membrane as a tetramer. Each monomer is a water channel that can hold 4 molecules of water at a time. How many water molecules would be present in a complete aquaporin complex in the membrane of a red blood cell at one time? 4 8 12 16 ------- View the side groups in the model, with attention to the water channel. What do the numerous aromatic rings on the surface of the channel suggest about the chemical properties of the channel? a) The channel will have significant hydrophilic properties. b) The channel will have a net negative charge. c) The channel will have a net positive charge. d) The channel will have significant hydrophobic properties. --------- Conserved histidine, asparagine (blue), and cysteine (yellow) residues are present on the surface of the water channel. Which of the following is LEAST likely to hydrogen-bond with a water molecule? a) the R group (side chain) of the cysteine b) the backbone carbonyl groups of amino acids on the surface of the channel c) the R group (side chain) of a histidine d) the R groups (side chains) of the two asparagines --------- What prevents glycerol from passing through the water channel? a) the backbone carbonyl groups of amino acids in the channel B) the chemical properties of the cysteine in the channel c) the narrow diameter (~2.8 Å) of the selectivity channel d) the chemical properties of the two conserved asparagines in the channel -------- Aquaporins allow water to pass through the channel but prevent other solutes and ions from also crossing the membrane. Protons can move with water using the same hydrogen bonding facillitated movement. What PREVENTS protons from passing through the water channel? a) the backbone carbonyl oxygen groups of amino acids in the channel b) the chemical properties of the amine groups of the two conserved asparagines in the channel c) the narrow diameter (~2.8 Å) of the selectivity channel d) the chemical properties of the sulfur within the R group of the conserved cysteine in the channel
16 D A C B
Match each lipid with its correct components or description. 1) glycerophospholipids 2) cerebrosides 3) gangliosides 4) sphingolipids A) built on sphingosine B) anionic phospholipids contianing one or more sialic acid residues C) lipids with phosphate-containing head groups D) fatty acid linked through an amide bond to the sphingosine C(2)-amine
1C, 2D, 3B, 4A
The lipid portion of a typical bilayer is about 30Å thick. Calculate the minimum number of residues in an α-helix required to span this distance. -------- Calculate the minimum number of residues in a β-strand required to span this distance. --------
20 9
In the situations described below, what is the free energy change if 1 of is transported across a membrane from a region where the concentration is 1 to a region where it is 100 ? (Assume .) In the absence of a membrane potential. ---------- When the transport is opposed by a membrane potential of 70 . ---------- In each case, will hydrolysis of 1 mole of suffice to drive the transport of 1 of ion, assuming = 7.4 and the following cytoplamic concentrations: = 4.6 , Pi = 5.10 , = 310 ? a) Only when a membrane potential is 70 mV. b) Only is case of the absence of a membrane potential. c) No, for both cases. d) Yes, for both cases.
29.7 kJ/mol 36.4 kJ/mol yes, for both cases
Which of the following are sources of cholesterol for the body? Check all that apply. 1) Eating vegetables 2) Synthesis in the pancreas from proteins 3) Eating meats and eggs 4) Synthesis in the liver from lipids 5) Drinking milk 6) Synthesis in the liver from carbohydrates 7) Synthesis in the pancreas from nucleic acids 8) Synthesis in the liver from fats
3, 5, 6, 8
Calculate the equilibrium membrane potentials to be expected across a membrane at 37 , with a concentration of 0.10 on the right and 0.01 on the left, given the following conditions. Consider the process is spontaneous. Membrane permeable only to Na+. ---------- State which side is positive (+) A) The right side of the bilayer is (+). B) Charge is equalized on both sides of the bilayer. C) The left side of the bilayer is (+). --------- Membrane permeable only to Cl-. ---------- State which side is positive (+) a) The left side of the bilayer is (+). b) Charge is equalized on both sides of the bilayer. c) The right side of the bilayer is (+). ----------- Membrane equally permeable to both ions. ----------- State which side is positive (+) a) Charge is equalized on both sides of the bilayer. b) The right side of the bilayer is (+). c) The left side of the bilayer is (+).
6.15 x 10^-2 V C - left side -6.15 x 10^-2 V C - right side 0 V A - equalized
There are two properties that affect the conduction speed of an action potential along an axon: the axon's diameter and whether or not the axon is myelinated. Rank the axons from slowest to fastest conduction speed. If two axons have the same conduction speed, place one on top of the other. A) non-myelinated invertebrate axon - 20microm diameter B) non-myelinated invertebrate axon - 40 microm dia C) myelinated vertebrate axon - 30 microm dia D) non-myelinated invertebrate axon - 30 microm dia
A < D < B < C
Which of the following statements correctly describe(s) the driving forces for diffusion of Na+ and K+ ions through their respective channels? Select all that apply. a) The diffusion of Na+ ions into the cell is facilitated by the Na+ concentration gradient across the plasma membrane. b) The diffusion of Na+ ions into the cell is impeded by the electrical gradient across the plasma membrane. c) The diffusion of K+ ions out of the cell is impeded by the K+ concentration gradient across the plasma membrane. d) The diffusion of K+ ions out of the cell is impeded by the electrical gradient across the plasma membrane. e) The electrochemical gradient is larger for Na+ than for K+.
A D E
**Purple structures** What is the function of Structure E? a) structural support of the cell B) stabilization of the phospholipids c) transport across the plasma membrane d) detection of environmental change e) cell-cell communication -------- Identify Structure D. A) cholesterol b) phospholipid bilayer of membrane c) glycoprotein d) extracellular matrix e) protein -------- Identify Structure A. a) glycoprotein b) cholesterol c) extracellular matrix d) protein e) phospholipid
B B A
Explain why α-helices are most commonly observed in transmembrane protein sequences when the distance from one side of a membrane to the other can be spanned by significantly fewer amino acids in a β-strand conformation. A) The helical conformation spanning the bilayer is much more stable and can form covalent bonds with proteins, whereas the strand would be unstable and can be cleaved. B) The helical conformation spanning the bilayer satisfies all the main-chain H-bond donors and acceptors within the helix, whereas the strand would be unable to form intramolecular H-bonds to satisfy it. C) The helical conformation spanning the bilayer completely fills all the free space so the entropy of the system is low, whereas the strand would left some free space between amino acids that can be filled with other molecules.
B
Many transmembrane proteins are oligomeric, with several identical sub-units. The oligomers are usually found to have some form of Cn symmetry, rather than Dn or any higher order. Suggest a reason for this observation. a) Symmetrical oligomers are favored because of stability and finite control of assembly. Several functions limit symmetry, such as interaction with DNA or membranes, and directional motion. b) The subunits traversing the membrane usually need to present different domains to the two sides. No symmetry involving twofold axes parallel to the membrane surfaces should be expected. c) Symmetrical oligomeric complexes consist of two or more identical subunits, which explains specific transport functions and provide additional stability for the molecule.
B
What behavior is observed if the voltage across a neuronal membrane is set to -20 mV? a) The voltage-gated sodium and potassium channels both remain closed. b) The sodium channel opens, and Na+ ions flow in. c) The potassium channel opens, and K+ ions flow in. d) The sodium channel opens, and Na+ ions flow out.
B
1. At location _____ , the membrane potential changes sign (from a positive value to a negative value) and the voltage-gated K+ channels are open. 2. At location _____ , the axon membrane reaches threshold and the voltage-gated Na+ channels open. 3. At location ____, the voltage-gated Na+ channels reactivate. 4. At location _____, the voltage-gated Na+ channels are inactivating and the voltage-gated K+ channels are opening. 5. At location _____, the axon membrane is at resting potential. 6. At location ______, the voltage-gated K+ channels are closing. 7. At location _____, the membrane potential changes sign (from a negative value to a positive value) and the voltage-gated Na+ channels are open.
C F A D G B E
Membrane proteins often have unique characteristics relative to globular proteins that function in largely aqueous environments. Which of the following does NOT describe a trait of a membrane protein? a) They often have high hydrophobic content. b) They can often contain common motifs, such as seven transmembrane α-helical proteins or β-barrels. c) They can form membrane receptors, such as integrins (or LDL receptor), located on the surface of cells. d) Membrane proteins typically have hydrophilic residues situated on the surface in contact with membrane lipids and hydrophobic residues buried in the interior of the protein core.
D
In contrast to phospholipids, the transport of fatty acids across membranes is much more rapid (less than a second). Propose an explanation for this observation. A) The process of crossing the membrane bilayer is more favorable for an uncharged fatty acid. Phospholipids are charged and require a protein transporter to facilitate their crossing of the bilayer. B) The steric factor has a great influence on the process of crossing the membrane bilayaer. The molecule of the fatty acid is much smaller, which provides much more rapid transport. C) The pKas of phospholipids in biomoleucles are generally in the range of 1-3, whereas the pKas of fatty acids are typically near 4.5 in an aqueous solution. pKas of fatty acids are much closer the the at physiological pH, that allows faster protonation of fatty acids and faster crossing the membrane.
a
Which of the following is NOT used by the aquaporins to achieve rapid transport of water across membranes? a) the presence of a very large pore that allows many molecules of water to pass quickly across the membrane b) The narrow channel precludes the passage of any molecules larger than water. c) Main-chain carbonyl groups, as well as those in conserved side chains, form H-bonds with the individual water molecules. d) A conserved, positively charged Arg residue repels any other positively charged ions via electrostatic repulsion.
a
Which of the following is unlikely to be a characteristic of a membrane protein? a) Symmetric orientation across the membrane b) Covalently attached lipid moities c) Largely hydrophobic transmembrane segments d) β-sheet membrane-spanning motifs e) α-helical membrane-spanning motifs.
a
Which term describes an electrical signal generated by neurons? Action potential. Resting potential. Membrane potential. Equilibrium potential.
action potential
Which of the following mechanisms is responsible for the selectivity of aquaporins for water? Prevention of ion gradient formation Electrostatic repulsion Dynamic hydrogen bonding Size exclusion All of the above
all of the above
Sphingomyelin contains a fatty acid linked by an ________ bond and phosphocholine linked via the C-3 hydroxyl group of sphingosine.
amide
A nerve impulse moves away from a neuron's cell body along _____. dendrites Nissl bodies synapses axons glia
axons
Which of the following is NOT relevant to facilitated transport across biological membranes? a) Some permeases can transport their substrates in both directions. b) ATP hydrolysis is required. c) A symport will transport two molecules in the same direction across a membrane. d) An antiport will move substrates in opposite directions across a membrane. e) An ionophore is a carrier protein that increases the permeability of a membrane to ions.
b
Which of the following statements is NOT true with respect to potassium ion channels? a) The hinge region of the proteins that move as a result of external influences has Gly residues, which facilitates protein movement, given its small size. b) The binding of the first potassium ion induces a conformational change in the channel protein that allows it to selectively bind only additional potassium ions. c) External influences, such as a change in pH or the binding of an appropriate ligand, alter the conformation of the channel protein, opening or closing it as appropriate. d) The channels have closed and open conformations.
b
The abbreviated name below is short for which of the following biologically important fatty acids? 18:3cΔ9,12,15 a) all-cis-9,12,15-Eicosatetraenoic acid b) cis,cis,trans-9,12,15-Octadecatrienoic acid c) all-cis-9,12,15-Octadecatrienoic acid d) cis,cis,trans-9,12,15-Eicosatetraenoic acid
c
The standard free energy that is required for the sodium-potassium ATPase to pump two K+ ions into the cell and three Na+ ions is +43.8 kJ/mol but the standard free energy change of hydrolysis of ATP is only -32 kJ/mol. This apparent imbalance of free energy can be accounted for because: a) the membrane potential favours the flow of ions. b) the movement of K+ ions is down the concentration gradient. c) the free energy provided from the hydrolysis of one ATP is sufficient under physiological conditions. d) the movement of Na+ ions is down the concentration gradient. e) more than one ATP is hydrolyzed.
c
Which of the following statements about biological membranes is FALSE? a) Phospholipids often require a specialized enzyme to facilitate movement across (flipping) the membrane. b) They are composed of a mixture of lipids and proteins in which lateral diffusion of components is possible. c) Lipids and proteins move laterally at approximately the same rate within the membrane. d) They are often organized into smaller regions of specific function. e) The faces of biological membranes are distinct and usually different in both composition and structure.
c
Drag the labels to their respective positions to identify the different components of the cell membrane. Drag the appropriate labels to their respective targets. Starting with top and moving in a clockwise circle. carbohydrate cholesterol hydrophilic polar head hydrophobic nonpolar tail intergral membrane protein peripheral membrane protein phospholipid bilayer
carbohydrate integral mem pro peripheral mem pro cholesterol hyrophilic po head hydrophobic nopo phospholipid bilay
A neuron's nucleus is located in its _____. cell body axon myelin sheath dendrite synaptic terminals
cell body
What is the key factor of an experiment that would distinguish pore-mediated diffusion (e.g., by gramicidin) from carrier-mediated diffusion (e.g., by valinomycin). a) The key factor is to allow the concentration of membrane lipids to be higher than ionophores under conditions where the bilayer is fluid, and then drop the temperature below the Tm of the bilayer. b) The key factor is to allow the concentration of membrane lipids to be lower than ionophores under conditions where the bilayer is fluid, and then increase the temperature below the Tm of the bilayer. c) The key factor is to allow the membrane lipids and ionophores to equilibrate under conditions where the bilayer is fluid, and then increase the temperature above the Tm of the bilayer. d) The key factor is to allow the membrane lipids and ionophores to equilibrate under conditions where the bilayer is fluid, and then drop the temperature below the Tm of the bilayer.
d
Which of the following circumstances allow(s) membranes to bypass transport equilibrium? a) the presence of an electrical potential that is maintained across the membrane b) transport that is coupled to a thermodynamically favored process, in which the free energy released from the favorable process drives the thermodynamic transport of another reagent c) chemical modification of a compound after it crosses to the other side d) All of these circumstances allow membrane transport processes to avoid reaching equilibrium.
d
Which of the following represent(s) facilitated diffusion across a membrane? a) transport through protein pores b) permeases, such as GLUT1, a glucose transporter found on erythrocytes c) carriers, such as ionophores d) All of the listed choices represent facilitated diffusion.
d
Which of the following statements about the thermodynamics of transport is NOT true? a) The concentration of reagents on one side of the membrane must equal the concentration on the other side so that Keq = 1. b) In terms of kinetics, when at equilibrium, the number of substances entering on one side of the membrane will be proportional to the number entering from the other side. c) Flow from one side of the membrane to the other will continue until the concentrations of reagents on both sides of the membrane are equal. d) At equilibrium, there is no movement across the membrane.
d
Which statement correctly describes what causes the second voltage-gated Na+ channel to open? a) As Na+ ions enter the cell through the first channel, they spread out from the channel. When these Na+ ions reach the second channel, it opens. b) As Na+ ions enter the cell through the first channel, Na+ ions outside the cell move toward the open Na+ channel. When the concentration of Na+ ions near the second channel becomes low enough, the second channel opens. c) After the first channel opens, the movement of Na+ ions (both inside and outside the cell) alters the Na+ ion distribution across the membrane near the second channel, causing it to open. d) After the first channel opens, the movement of many types of ions (both inside and outside the cell) alters the distribution of charges near the second channel, causing it to open.
d
A nerve impulse moves toward a neuron's cell body along _____. dendrites synaptic terminals oligodendrocytes axons nodes of Ranvier
dendrites
**blue pic with green dots** What name is given to the process shown in this animation? To view the animation, click here. Then click on the image to start the animation. active transport diffusion turgor sodium-potassium pump osmosis
diffusion
Which of the following characteristics determines when the refractory period ends? a) how long it takes for the voltage-gated K+ channels to close during the undershoot phase b) how low the membrane potential drops below resting potential during the undershoot phase c) how long it takes for the membrane potential to return to resting potential after the undershoot phase d )how long it takes for the voltage-gated Na+ channels to close at the end of an action potential e) how long it takes for the voltage-gated Na+ channels to reactivate at the end of an action potential
e
The amino alcohol is a polar part of a glycerophospholipid and, thus, a hydrophilic (water-loving) section of the molecule. What is the common name for the amino alcohol present in the glycerophospholipid shown in Part A? Enter the common name of the amino alcohol.
ethanolamine
**red triangles, purple mouth** animation The process shown in this animation is referred to as _____. To view the animation, click here. Then click on the image to start the animation. phagocytosis facilitated diffusion active transport pinocytosis osmosis ---------- The red triangles are: solvent phospholipid solute water molecule transport protein --------- The purple mouth is: solvent phospholipid solute water molecule transport protein
facilitated diffusion solute transport protein
The sodium-glucose cotransport system is an example of: an antiport transporter. an ATP-dependent transporter. facilitated transport. passive transport. none of the above.
facilitated transport
One of the curves below describes nonmediated diffusion, and the other describes facilitated transport. Which curve is which? Drag the appropriate labels to their respective targets. (top to bottom) facilitated transport nonmediated diffusion
facilitated transport nonmediated diffusion
Lipid rafts are small long-lived structures that respond to stimuli to transiently associate with each other to form larger raft platforms. True False
false
Mediated transport or diffusion will ultimately result in the concentration of diffusing substance being the same on both sides of the membrane. True False
false
True or false? The potential energy of a membrane potential comes solely from the difference in electrical charge across the membrane. True False
false
Which two are present in both waxes and sphingomyelin? Select all that apply. glycerol fatty acid phosphate long-chain alcohol carbohydrate
fatty acid long-chain alcohol
Some of the lipid groups appear similar, but changing a few components significantly alters their biological properties. Identify the similarities and differences between glycerophospholipid and sphingolipid structures. Drag the appropriate items to their respective bins. Classify the following as glycerophospholipid, sphingolipid, or both lipids. sphingosine amino alcohol fatty acid phosphate group glycerol
glyc: glycerol sphing: sphingosine both: amino alcohol, fatty acid, phosphate group
Which two are present in both fats and phosphatidylcholine? Select all that apply. glycerol fatty acid phosphate long-chain alcohol carbohydrate
glycerol fatty acid
Sort the phrases into the appropriate bins depending on whether they are true only for channels, true only for carrier proteins, or true for both channels and carriers. 1) allow water molecules and small ions to flow quickly across the membrane 2) transport primarily small polar organic molecules 3) provide a continuous path across the membrane 4) provide a hydrophilic path across the membrane 5) transport solutes down a concentration or electrochemical gradient 6) undergo a change in shape to transport solutes across the membrane 7) are integral membrane proteins
only channels: 1, 3 only carriers: 2, 6 both: 4, 5, 7
Which of the following are characteristics of cholesterol? 1) It is a weakly amphipathic, rigid substance. 2) It is the precursor for all steroidal hormones. 3) It packs neatly with the fatty acid tails of membrane bilayers. 4) It is part of the lipid family of biomolecules.
only statements 1, 2, and 4 are characteristics of cholestoerol
Some solutes are able to pass directly through the lipid bilayer of a plasma membrane, whereas other solutes require a transport protein or other mechanism to cross between the inside and the outside of a cell. The fact that the plasma membrane is permeable to some solutes but not others is what is referred to as selective permeability. Which of the following molecules can cross the lipid bilayer of a membrane directly, without a transport protein or other mechanism? Select all that apply. ions oxygen water sucrose proteins carbon dioxide lipids
oxygen water CO2 lipids
Fill in the blanks: choline group fatty acid glycerol hydrophilic hydrophobic phosphate group 1. A phospholipid has a "head" made up of a glycerol molecule attached to a single ____________, which is attached to another small molecule. 2. Phospholipids vary in the small molecules attached to the phosphate group. The phospholipid shown in the figure has a ___________ attached to phosphate. 3. Because the phosphate group and its attachments are either charged or polar, the phospholipid head is __________, which means it has an affinity for water. 4. A phospholipid also has two "tails" made up of two ___________ molecules, which consist of a carboxyl group with a long hydrocarbon chain attached. 5. Because the C-H bonds in the fatty acid tails are relatively nonpolar, the phospholipid tails are __________, which means they are excluded from water. --------- Label letters on the structure with the purple membrane with either hydrophobic or hydrophilic. A B C D E F G
phosphate group choline group hydrophilic fatty acid hydrophobic ------- a. hydrophilic b. hydrophilic c. d. e. hydrophilic f. hydrophobic g. hydrophilic
Which of following lipids can be a major component of biological membranes? Phosphatidylinositol Phosphatidylcholine Phosphatidic acid Cholesterol Phosphatidylcholine and cholesterol
phosphatidylcholine and cholesterol
Which channel is mainly responsible for the resting potential of a neuron? Voltage-gated potassium channel. Chloride leak channel. Voltage-gated sodium channel. Potassium leak channel.
potassium leak channel
Fill in the blanks: cis trans longer fatty acids shorter fatty acids The membranes of cells grown at 25 °C would have (i) ____________ with (ii) a greater number of ______ - double bonds compared to the membranes of cells grown at 37 °C.
shorter fatty acids cis
The process of phosphorylating the glucose after it has been transported into the cell is considered a form of active transport-called "transport by modification"-even though is not bound by the transporter protein, nor is hydrolysis directly involved in the movement of glucose across the membrane. Which part of this process effectively stimulates glucose transporting inside the cell? (Hint: Consider Le Chatelier's principle). the phosphorylation reaction the transport reaction --------- Given = 4.7 ; = 0.15 ; = 6.1 , calculate the theoretical maximum concentration of inside a liver cell at 37 , = 7.2 when the glucose concentration outside the cell (i.e., is 5.0 : Express your answer to three significant figures and include the appropriate units.
the phosphorylation rxn 313 M
Selective permeability of membranes **blue, gray, white, yellow animation** Structure A in this animation is a(n) _____. To view the animation, click here. Then click on structure A in the image to start the animation. antibody structural protein receptor molecule enzyme transport protein -------- Which of these cannot rapidly pass directly through the phospholipids of the plasma membrane? D only B only C only A only B, C, and D
transport protein B, C, and D
Action potentials are propagated along a nerve axon by sequentially opening and closing a series of voltage-gated potassium and sodium channels. True False
true
Digitoxin can act as a short term cardiac stimulant by inhibiting the Na+-K+ pump. True False
true
Integral membrane proteins can be inserted into the membrane and folded into the normal 3D structure during translation. True False
true
Passive facilitated cotransport can move some substrate across a membrane against its concentration gradient. True False
true
