Category - Definitions

Query - What definition best describes the term below?

Reversal

Category - Term Recognition

Query - What term does the description below refer to?

(Terms are shown on left, definitions in middle, relevant figures from 2nd edition on right).

Actin | A peripheral membrane protein of erythrocytes, it helps to link spectrin to the membrane at its ends and is also complexed with an erythrocyte-specific tropomyosin. | Figure 10.18 | Action Potential | A wave of transient depolarization that travels along the membrane of a nerve cell (or any other kind of excitable cell, such as a muscle cell) as a result of fluxes of ions across the membrane. A nerve impulse. | Figure 10.31 | Active Transport | A mechanism for transporting materials across a membrane irrespective of the concentration gradient. Generally materials are transported against a concentration gradient at the expense of free energy. |  | Adipocytes | Animal cells specialized for fat storage. |  | Amphipathic | For a molecule, the property of having both hydrophobic and hydrophilic portions. Usually one end or side of the molecule is hydrophilic and the other end or side is hydrophobic. |  | Anion Channel Protein (Band 3 protein) | An integral protein of the erythrocyte membrane. It is attached to spectrin by the protein called adducin. The function of this protein is to allow the passage of bicarbonate and chloride ions through the membrane and thereby facilitate carbon dioxide transport by the hemoglobin. It may associate with glyceraldehyde-3-phosphate dehydrogenase. The N-terminal domain of this protein is associated with the peripheral protein, ankyrin | Figure 10.18 | Ankyrin | A peripheral protein that is part of the erythrocyte membrane skeleton. It serves to link the skeleton to the band 3 (anion channel) integral protein. | Figure 10.18 | Antiport | A transport system in which two substances are transported in opposite directions. |  | Axon | A threadlike process extending from a nerve cell by which impulses are transmitted to other nerve cells or to effector cells such as muscle or gland cells. Most nerve cells have one. Shorter processes that function in receiving impulses from other neurons are called dendrites. | Figure 10.29 | Band 4.1 Protein | A peripheral membrane protein of erythrocytes found at junctions of spectrin. | Figure 10.18 | Carrier Facilitated Transport | A mechanism of facilitated transport in which a molecule binds another molecule to be transported and rapidly moves it across a membrane, depositing it on the other side. An example is valinomycin, which selectively transports potassium ions across the membrane. | Figure 10.20 | Cotransport systems | Active transport system that indirectly uses energy from ATP hydrolysis to drive transport of molecules across a cell membrane against a concentration gradient. |  | Dendrites | Short threadlike process extending from a nerve cell that receive impulses from other neurons. | Figure 10.29 | Electrogenic | A transport system which, as a result of moving materials across a membrane, causes a net movement of ionic charge to occur. |  | Electroneutral | A transport system which, as a result of moving materials across a membrane, causes no net movement of ionic charge to occur. |  | Erythrocyte Ghost | The remnants of an erythrocyte created by gentle lysing of such a cell to release its diffusible contents. |  | Facilitated Transport (Facilitated Diffusion) | A transport process employing diffusion as the driving forces, but employing special membrane carriers or pores to facilitate the movement of specific molecules across the membrane at a very high rate. | Figure 10.20 | Fats | Triacylglycerols which are solid at room temperature. |  | Fatty Acids | These are the simplest lipids. They contain a hydrophobic tail, typically of 1020 carbons attached to a carboxyl group. | Figure 10.1 | Fluid Mosaic Model | A model, originally proposed by S. J. Singer and G.L. Nicholson, describing cellular membrane structure, according to which the proteins are embedded in a phospholipid bilayer and are free to move in the plane of the membrane. | Figure 10.10 | Gated Channels | A system in nerve cells in which systems for passage of sodium and potassium ions are rigidly controlled. |  | Glucose Transport Protein | A 492 amino acid residue membrane protein in erythrocytes responsible for transporting glucose by facilitated diffusion. |  | Glyceraldehyde Phosphate Dehydrogenase | An enzyme of the glycolytic pathway that also is a peripheral protein of the erythrocyte membrane. |  | Glycerophospholipids (phosphoglycerides) | Glycerol-based lipids, typically containing a phosphate group at position #3 and either one or two fatty acids on the other glycerol carbons. | Figure 10.7 | Glycolipids | Lipids that contain saccharide groups. |  | Glycophorins | Major integral erythrocyte membrane proteins. Each has an external carbohydrate carrying domain that may be involved in cellular recognition. |  | Glycosphingolipids | Sphingolipids containing a carbohydrate moiety. Both cerebrosides and gangliosides are examples. | Figure 10.8 | Goldman Equation | An equation that takes into account the peremability of the membrane to different ions in determining the membrane potential. |  | Gramicidin A | A facilitated transport system produced by the bacterium Bacillus brevis that is an ionophore that permits passage of potassium and (to a lesser extent) sodium ions through it, destroying the cellular gradient for these ions. | Figure 10.22 | Hydrogenation | A process in which double bonds in unsaturated fatty acids are saturated using hydrogen. |  | Hydrophilic | Refers to the ability of an atom or a molecule to engage in attractive interactions with water molecules. Substances that are ionic or can engage in hydrogen bonding have this property. |  | Hydrophobic | The molecular property of being unable to engage in attractive interactions with water molecules. Substances with this property are nonionic and nonpolar; they are nonwettable and do not readily dissolve in water. |  | Hydrophobicity Index | A measure of the hydrophobicity of an amino acid sequence in a polypeptide as a function of distance along it. | Figure 10.16 | Integral Membrane Proteins | Proteins found in cell membranes that are embedded in both halves of the lipid bilayer and project through the membrane. | Figure 10.15 | Ion Pumps | A system of active transport that moves ions against a concentration gradient across a membrane. |  | Ionophores | Transport systems (pores or carriers) which facilitate the transport of ions across a membrane. |  | Lateral Diffusion | A term describing a type of motion in lipid bilayers in which movement occurs parallel to the membrane surface, as opposed to flipping on either side of the surface. |  | Lipid Bilayer | A membrane structure that can be formed by amphipathic molecules in an aqueous environment; it consists of two back-to-back layers of molecules, in each of which the polar head groups face the water and the nonpolar tails face the center of the membrane. The fabric of cellular membranes is a lipid bilayer. | Figure 10.5 | Lipids | A chemically diverse group of biological compounds that are classified together on the basis of their generally apolar structure and resulting poor solubility in water. |  | Lipoproteins | A class of molecules in which lipids are bound to proteins. |  | Micelles | Tiny droplets that form when an amphipathic substance that has a polar head group and a nonpolar tail region (such as a fatty acid) is added to an aqueous medium and shaken. Each droplet consists of a spherical cluster of amphipathic molecules arranged with their polar head groups facing out toward the water and their nonpolar tails facing in toward the center. | Figure 10.5 | Monolayers | An arrangement of molecules, typically on the surface of a liquid, in which only a single layer of such molecules are present. |  | Myelin Sheath | An insulating membrane provided around axons by Schwann cells. | Figure 10.29 | Nernst Equation | An equation that relates the electrical potential across a membrane to the concentrations of ions on either side of the membrane. |  | Neurotoxins | A toxin that acts by disrupting nerve cell function. Fast-acting ones often act by blocking the action of an ion gate necessary for the development of an action potential. |  | Neurotransmitter | A substance which enables nerve impulses to be transmitted from one cell to another. |  | Nodes of Ranvier | Gaps between Schwann cells on an axon. These regions are nonmyelinated. | Figure 10.29 | Oleic Acid/Oleate | An unsaturated fatty acid containing 18 carbons and a single cis double bond. Oleate is the ionized form of oleic acid. The systematic name is cis-9-Octadecenoic acid. | Figure 10.1, Table 10.1 | Ouabain | A glycoside which can inhibit the sodiumpotassium pump by binding to its outer surface. | Figure 10.25 | Passive Transport (Passive Diffusion) | A transport process accomplished by the random wandering of molecules through membranes. The process is the same as the Brownian motion of molecules in any fluid. The driving force is the concentration gradient between the two regions and the process ultimately results in the free concentration of the diffusing substance being the same on both sides of the membrane. |  | Peripheral Membrane Proteins | Proteins found in cell membranes that are embedded in only one half of the lipid bilayer and do not project through the membrane. | Figure 10.10 | Phospholipids | Lipids, such as the glycerophospholipids, which contain a phosphate group. |  | Porefacilitated Diffusion | An example of this type of facilitated transport is exhibited by Band 3 protein of erythrocyte membranes, which preferentially permits chloride and bicarbonate ions to pass through the membrane. | Figure 10.20 | Resting Potential | The voltage difference that exists across the membrane of an excitable cell, such as a nerve cell, except in places where an action potential is in progress. It is a consequence of the ion gradients that are maintained across the membrane. |  | Saponification | The process of making a soap in which a fat is hydrolyzed with an alkali, such as NaOH or KOH. |  | Saturated Fatty Acid | A fatty acid containing no double bonds. |  | Schwann Cell | Specialized cells which envelop an axon in layers of an insulating myelin membrane. | Figure 10.29 | Selective Membrane Permeability | The property of a membrane in which specific 'gates' preferentially promote the passage of materials, often only in one direction. |  | Soap | A class of compounds produced by hydrolyzing a fat with an alkali, such as NaOH or KOH. |  | SodiumPotassium Pump | An ion pump employing the energy of ATP to move three ions of sodium outside of the cell as two ions of potassium are moved in. | Figure 10.25 | Spectrin | A peripheral protein of the erythrocyte membrane with and subunits. Is actually a chainlike fiber linking the components of the membrane skeleton. | Figure 10.18 | Sphingolipids | A major class of membrane constituents built on the longchain amino alcohol sphingosine, rather than on glycerol. |  | Stearic Acid/Stearate | A saturated fatty acid with 18 carbons. Stearate is the ionized form of stearic acid. The systematic name is nOctadecanoic acid. | Table 10.1 | Steroids | A group of substances formed from cholesterol. They include a number of important hormones, including the sex hormones of higher animals. | Figure 10.9 | Symport | A transport system in which two substances are transported in the same direction. |  | Transition Temperature | The temperature at which a lipid bilayer converts between an ordered gellike structure and a less ordered liquidlike structure. |  | Translocase | An enzyme catalyzing transverse movement (flipflopping) of phospholipids across a lipid bilayer. |  | Transport by Modification | An active transport system which moves materials across the membrane against concentration gradients by modifying the molecule in transit. |  | Transverse Diffusion | A term describing a type of motion in lipid bilayers (relatively rare) in which movement occurs by flipping on either side of the surface, as opposed to moving parallel to the surface. |  | Triacylglycerol | A storage form of fatty acids in organisms (also known as fat or oil). These substances are triesters of fatty acids and glycerol. | Figure 10.2 | Tristearin | A triacylglycerol in which all of the acyl groups come from stearic acid. |  | Unsaturated Fatty Acid | A fatty acid containing at least one double bond. Double bonds in fatty acids are almost always in the cis configuration. |  | Valinomycin | A carrier facilitated transport system produced by Streptomyces, which selectively transports potassium ions across a membrane, destroying the concentration gradient for this ion. | Figure 10.23 | Wax | A class of compounds formed by esterification of fatty acids and longchain alcohols. Used as a water repellant by organisms. | Figure 10.4

Ceramide | A sphingolipid made by combining sphingosine with an acyl group, forming an amide bond. | Figure 10.8 | Cerebroside | A sphingolipid which is important in the membranes of brain and nerve cells. These are ceramides onto which a sugar moiety has been added. |  | Cholesterol | An important lipid constituent of membranes that also is implicated in atherosclerosis. It serves as a precursor to the steroid hormones. | Figure 10.9 | Ganglioside | A sphingolipid which is important in the membranes of brain and nerve cells. These are ceramides onto which a complex carbohydrate is attached. |  | Glycerol | A molecule forming the backbone of fats, oils, and glycerophospholipids. |  | Phosphatidic Acid | The simplest class of glyerophospholipids, with fatty acids at carbons #1 and 2 of glycerol and a phosphate on carbon #3. | Figure 10.7 | Phosphatidylcholine | A glycerophospholipid and prominent membrane lipid in which phosphatidic acid is esterified through the phosphate group to choline. | Figure 10.7 | Phosphatidylethanolamine | A glycerophospholipid and prominent membrane lipid in which phosphatidic acid is esterified through the phosphate group to ethanolamine. | Figure 10.7 | Phosphatidylinositol | A glycerophospholipid in which phosphatidic acid is esterified through the phosphate group to inositol. |  | Phosphatidylserine | A glycerophospholipid and prominent membrane lipid in which phosphatidic acid is esterified through the phosphate group to serine. | Figure 10.7 | Saxitoxin | A neurotoxin contained in the marine dinoflagellates responsible for 'red tide.' It binds to the sodium channel of nerve cells. |  | Sodium Dodecyl Sulfate (SDS) | A synthetic detergent that does not precipitate in hard water. |  | Sphingomyelin | A sphingolipid combining a ceramide with a phosphocholine. |  | Sphingosine (D-4-sphinganine) | The backbone of the sphingolipids. |  | Tetrodotoxin | A neurotoxin found in some organs of the puffer fish that acts by preferentially binding to the sodium channel of nerve cells, blocking all ion movement. |  | Triton X-100 | A synthetic non-ionic detergent. |  | Veratridine | A neurotoxin found in the seeds of Schoenocaulon officinale which binds to sodium channels of nerve cells and blocks them in the open configuration. |

Category - Structures

Query - What is the structure of the molecule below?

Reversal

Category - Molecules

Query - What is the name of the molecule with the structure below?

(name on left, structure in middle, figure on right)

Arachidonic Acid/Arachidonate |  |  | Arachidic Acid/Arachidate |  |  | Behenic Acid/Behenate |  |  | Capric Acid/Caprate |  |  | Ceramide |  |  | Cerebroside |  |  | Cerotic Acid/Cerotate |  |  | Cholesterol |  |  | Ganglioside |  |  | Glycerol |  |  | Lactobacillic Acid |  |  | Lauric Acid/Laurate |  |  | Lignoceric Acid/Lignocerate |  |  | Linoleic Acid/Linoleate |  |  | Linolenic Acid/Linolenate |  |  | Myristic Acid/Myristate |  |  | Palmitic Acid/Palmitate |  |  | Palmitoleic Acid/Palmitoleate |  |  | Phosphatidic Acid |  |  | Phosphatidylcholine |  |  | Phosphatidylethanolamine |  |  | Phosphatidylinositol |  |  | Phosphatidylserine |  |  | Saxitoxin |  |  | Sodium Dodecyl Sulfate (SDS) |  |  | Sphingomyelin |  |  | Sphingosine (D-4-sphinganine) |  |  | Tetrodotoxin |  |  | Triton X-100 |  |  | Tuberculosteric Acid |  |  | Veratridine |  |

Category - General

Query - Is contained in the left column below, solution in middle, figure on right

Reversal - there is no reversal

What are three functions of fat storage in animals? | 1. Energy production 2. Heat production 3. Insulation | What compounds are put together to make a fat? | 1. Fatty acids 2. Glycerol | What compounds are put together to make a wax? | 1. Fatty acid 2. Long chain alcohol. | Why does 'hard' water pose a problem for soap users? | Calcium or magnesium ions present in hard water precipitate the fatty acids of soap, leaving a 'scum' and destroying the emulsifying action. | What effect does cholesterol have on the lipid bilayer? | It fits awkwardly into membrane lipids and tends to disrupt regularity in membrane structure. | What effect does cholesterol have on the transition temperature of a lipid bilayer? | It widens the range over which the transition occurs, but does not change the central point of the temperature. | What effect does incorporation of lipids with more unsaturation in a membrane have on the transition temperature of the membrane? | They lower the transition temperature. | What effect does incorporation of lipids with more saturation in a membrane have on the transition temperature of the membrane? | They raise the transition temperature. | What three proteins are associated with the Band 3 (anion channel) protein? | Adducin, ankyrin, and glyceraldehyde-3-phosphate dehydrogenase. | What is the function in erythrocytes of Band 3 (anion channel) protein? | Allow passage of bicarbonate and chloride ions through the membrane and thereby facilitate carbon dioxide transport by the hemoglobin. | What is the free energy change for moving a substance from a region where its concentration is C1 to a place where its concentration is C2? | Equation 10.1 | What are the three circumstances under which a simple free energy calculation may not accurately predict the direction a material may move across a membrane? | 1. If a substance may be preferentially bound by macromolecules confined to one side of the membrane or chemically modified once it crosses. 2. The membrane electrical potential may additionally influence the distribution of ions - Equation 10.2

3. If some thermodynamically favored process (such as active transport) counters the concentrations used in the simple calculation of free energy. Here, Equation 10.3 predicts the amount of alteration of the simple free energy, G by a factor G'.

What is the ultimate outcome of a passive-diffusion-driven process?
The process ultimately results in the free concentration of the diffusing substance being the same on both sides of the membrane.
What is the net rate of transport of a passive diffusion-driven process?
Equation 10.4, where J is the net rate of transport, K is the partition coefficient for the diffusing material between lipid and water, D1 is the diffusion coefficient of the diffusing substance in the membrane, and l is the thickness of the membrane. Since K, D1, and l are not usually known, the rate is calculated by J = -P (C2-C1), where P is the permeability coefficient, which is measured by direct experiment and is equal to KD1/l.
How can facilitated diffusion be distinguished from passive diffusion?
If one measures the rate of transport at increasingly high concentration differences of a substance transported across the membrane, a limiting rate is approached for facilitated diffusion carriers or pores (Figure 10.23). The rate of passive transport, on the other hand, increases linearly with the concentration difference. In passive transport there are no sites to saturate, at least at any concentrations of transported molecules usually studied.
Describe three systems for active transport of materials across a biological membrane.

1. Ion pumps, such as the sodium-potassium pump.

2. Cotransport systems, which employ ATP hydrolysis energy in an indirect way, such as the sodium-glucose transport system, which cotransports sodium ions as a driving force. The sodium gradient is created by ATP hydrolysis in the sodium-potassium pump.

3. Transport by modification, in which a concentration gradient for a compound is destroyed by modifiying the compound as it crosses the membrane. An example is the phosphotransferase system of E. coli, which phosphorylates sugars as they pass through the membrane.

Category - General

Query - What transport mechanism does the following system employ?

Reversal - there is no reversal

(system on left, transport mechanism in middle, figures on right)

Band 3 (anion channel) protein | Pore-facilitated transport |  | Oxygen transport across membranes | Passive Diffusion |  | Carbon Dioxide Transport | Passive Diffusion |  | Glucose Transport Protein (Band 4.5 protein) | Pore-facilitated transport |  | Gramicidin A | Pore-facilitated transport |  | Valinomycin | Carrier-facilitated transport |  | Monensin | Carrier-facilitated transport |  | Sodium-Potassium pump | Ion pump - Active Transport |  | Sodium-Glucose Pump | Cotransport - Active Transport |  | Phosphotransferse System | Active Transport by Modification |

Category - General

Query - What molecule(s) are preferentially transported by the following transport system?

Reversal - there is no reversal

(transport system on left, molecules transported in middle, figures on right)

Valinomycin | Potassium ions |  | Gramicidin A | Potassium and sodium ions |  | Glucose transporter | Glucose |  | Band 3 (anion channel) Protein | Chloride and bicarbonate ions |  | Sodium-Glucose Transporter | Sodium and glucose transported into cell. |  | Sodium-Postassium Transporter | 3 sodium ions outside of the cell and 2 potassium ions into the cell. |  | Phosphotransferase system | Sugars transported into cell |

Category - General

Query - Is the following transport system a symport or antiport?

Reversal - there is no reversal

(transport system on left, sym/antiport in middle, figures on right)

Band 3 (anion channel) protein | Antiport |  | Sodium-Potassium pump | Antiport |  | Sodium-Glucose Pump | Symport |

Category - General

Query - Are the following transport systems ionophores?

Reversal - there is no reversal

(transport system on left, solution in middle, figures on right)

Band 3 (anion channel) protein | No |  | Sodium-Potassium pump | Yes |  | Sodium-Glucose Pump | Yes |  | Gramicidin A | Yes |  | Valinomycin | Yes |  | Glucose transport protein | No |  | What is the Nernst equation? | Equation 10.8 |