Cell Bio Exam 2 Ch. 11-14
44. Movement of phospholipids from one leaflet to the other (a) occurs routinely. (b) requires cholesterol. (c) requires flippases. (d) is impossible.
(c) requires flippases.
40. Diversity among the oligosaccharide chains found in the carbohydrate coating of the cell surface can be achieved in which of the following ways? (a) Varying the types of sugar monomers used (b) Varying the types of linkages between sugars (c) Varying the number of monomers in the chain (d) Varying the number of branches in the chain (e) All of the above
(e) All of the above
27. Which of the following membrane lipids does not contain a fatty acid tail? (a) Phosphatidylcholine (b) A glycolipid (c) Phosphatidylserine (d) Sphingomyelin (e) Cholesterol
(e) Cholesterol
5.Which parts of the phospholipid face the outside of the membrane? A. The head B. The tail C. The belly
A. The head
3. The tails of phospholipids are: A. hydrophobic. B. hydrophilic. C. amphipathic.
A. hydrophobic.
What is the main chemical energy currency in cells? A. Glucose B. NADH C. ATP D. High-energy electrons
ATP
What occurs when ATP synthase pumps H+ across a membrane against the electrochemical proton gradient? A. ATP synthase transports Na+ in the opposite direction across the membrane B. ATP synthase cleaves ATP to form ADP and Pi C. ATP synthase catalyzes the formation of ATP from ADP and Pi
ATP synthase cleaves ATP to form ADP and Pi
D
After a normal overnight fast, most of the acetyl CoA entering the citric acid cycle is derived from what type of molecule? A. Glucose B. Pyruvate C. Glycogen D. Fatty acids
False
All of the carbohydrates in the plasma membrane face the cell exterior, and the carbohydrates on internal cell membranes face the cytosol. False True
Positively charged solutes
All other factors (e.g., concentration and solute size) being equal, which type of solute does a cell tend to pull inside? Negatively charged solutes Positively charged solutes Uncharged solutes
How much of the mass of the plasma membranes is constituted by proteins?
50%
Which of the following drives the production of ATP from ADP and Pi by ATP synthase? A. A proton gradient B. A Na+ gradient C. Phosphorylation
A proton gradient
In general, which of the following will diffuse across a lipid bilayer most rapidly?
A small hydrophobic molecule
False
A symport protein would function as an antiport protein if its orientation in the membrane were reversed.
12. How does cholesterol in animal cell membranes affect the fluidity of the bilayer? A. Cholesterol tends to stiffen the bilayer. B. Cholesterol tends to make the bilayer more fluid. C. Cholesterol has little effect on membrane fluidity.
A. Cholesterol tends to stiffen the bilayer.
D
Intermediates formed in glycolysis and the citric acid cycle are used by the cell to synthesize: A. Amino acids B. Nucleotides C. Lipids D. All of the Above E. A and B, but not C
The Na+-K+ pump in the plasma membrane of animal cells uses the energy from ATP hydrolysis to pump sodium and potassium ions against their electrochemical gradients. In which direction are the ions pumped across the membrane?
K+ in and Na+ out
False
Metabolism can be tightly regulated because the substrates involved in these reactions are each recognized by a single, unique enzyme. True or False
True
Patch-clamp recording can be used to observe the transport of ions through individual ion channels.
hydrophobic
The tails of phospholipids are: amphipathic coated with sugars hydrophilic hydrophobic stiff
A
When food is plentiful, animals can store glucose as: A. Glycogen B. Starch C. Acetyl CoA D. All of the above
A state in which the flow of positive and negative ions across the plasma membrane is precisely balanced
Which of the following statements describes the resting membrane potential of a neuron?
Water passes through the cell membrane only through specialized channels called aquaporins.
false
During an action potential, which of the following actions does not help return the membrane to its resting potential?
the opening of voltage-gated Na+ channels
When a vesicle fuses with the plasma membrane, the monolayer that was facing the inside of the vesicle will face:
the outside of the cell.
In the /alpha helices of transmembrane proteins, the hydrophobic side chains are facing:
the outside of the membrane-spanning helix.
Some solutes are transported across the membrane in tandem with another molecule, both moving from lower concentration to higher concentration.
Which of the following statements is NOT true regarding active transport by transmembrane pumps? Some solutes are moved across a membrane against their concentration gradient using energy from sunlight. Some solutes are moved against their concentration gradient, from one side of a membrane to the other, using energy from ATP hydrolysis. Some solutes are transported across the membrane in tandem with another molecule, both moving from lower concentration to higher concentration.
Calcium levels are kept low in the cytosol compared to outside the cell.
Which of the following statements is true about the concentration of calcium ions in cells?
2. The cell membrane is NOT involved in: A. cell communication. B. import and export of molecules. C. DNA Replication. D. cell growth and motility.
C. DNA Replication.
Which of the following statements is true about the concentration of calcium ions in cells?
Calcium levels are kept low in the cytosol compared to outside the cell.
Double bonds in hydrocarbon tails have what effect on the rigidity of fats and phospholipid bilayers?
Double bonds decrease the ability of hydrocarbon tails to pack together into a rigid mass.
Double bonds decrease the ability of hydrocarbon tails to pack together, which makes the bilayer less stiff.
Double bonds in hydrocarbon tails have what effect on phospholipid tails and the rigidity of the lipid bilayer? Double bonds decrease the ability of hydrocarbon tails to pack together into a rigid mass, which makes the bilayer more stiff. Double bonds decrease the ability of hydrocarbon tails to pack together, which makes the bilayer less stiff. Double bonds have little effect on membrane fluidity. Double bonds increase the ability of hydrocarbon tails to pack together into a rigid mass, which makes the bilayer less fluid. Double bonds increase the ability of hydrocarbon tails to pack together into a rigid mass, which makes the bilayer more fluid.
On what side of the membrane are the carbohydrate chains of glycoproteins, proteoglycans, and glycolipids located?
External (noncytosolic) side
Why does a single molecule of NADH result in the production of more ATP molecules than a single molecule of FADH2 via oxidative phosphorylation? A. NADH donates more electrons to the chain. B. FADH2 feeds its electrons into the electron transport chain further along the chain. C. FADH2 is less likely than NADH to participate in the electron transport chain.
FADH2 feeds its electrons into the electron transport chain further along the chain
The first living cells on Earth-both prokaryotes and primitive eukaryotes-most likely generated ATP by what process? A. Photosynthesis B. Fermentation C. Aerobic cellular respiration
Fermentation
What type of enzyme moves phospholipids from one monolayer to the other in a biological membrane?
Flippase
A
For many anaerobic microorganisms, which metabolic pathway is the principle source of ATP? A. Glycolysis B. The citric acid cycle C. The electron transport chain
Voltage-gated
Which type of ion channel plays the major role in propagating electrical signals in nerve cells?
41. Red blood cells have been very useful in the study of membranes and the protein components that provide structural support. 1) Which of the following proteins is the principal fibrous protein in the cortex of the red blood cell? 2) Which of the following proteins serve as the attachment site for P. falciparum (malaria parasite) (a) fibroin (b) tubulin ( c) actin (d) spectrin (e) keratin (f) glycoporin
(d) spectrin ,(f) glycoporin
36. Which of the following statements regarding membrane proteins is FALSE? (a) Integral membrane proteins often precipitate (form insoluble aggregates) in aqueous solutions lacking detergents. (b) Some hydrophobic amino acids in membrane proteins are not in contact with the lipid bilayer. (c) Peripheral membrane proteins can be dissociated from membranes using a gentle detergent. (d) Strong detergents can completely unfold both membrane and nonmembrane proteins. (e) In transmembrane proteins that form an aqueous pore through the membrane, the pore is lined with hydrophobic amino acid side chains
(e) In transmembrane proteins that form an aqueous pore through the membrane, the pore is lined with hydrophobic amino acid side chains
In one second, a lipid in an artificial bilayer may diffuse as far as what distance?
2 microns (the length of a large bacterial cell)
34. Select lipids containing a phosphorous atom from the following list. 1. ceramide 2. sphingosine 3. sphingomyelin 4. diacylglycerol 5. ganglioside 6. phosphatidyl serine 7. cholesterol 8. triacylglycerol
3. sphingomyelin 6. phosphatidyl serine
In mitochondria, with the complete breakdown of glucose, about how many molecules of ATP can be produced for each molecule of glucose oxidized? A. 2 B. 12 C. 30 D. 50
30
30. Fill in the blanks. The specialized functions of different membranes are largely determined by the __________________ they contain. Membrane lipids are __________________ molecules, composed of a hydrophilic portion and a hydrophobic portion. All cell membranes have the same __________________ structure, with the __________________ of the phospholipids facing into the interior of the membrane and the __________________ on the outside. The most common lipids in most cell membranes are the __________________. The head group of a glycolipid is composed of __________________.
30. proteins, amphipathic, lipid bilayer, fatty acid tails, hydrophilic head groups, phospholipids, sugars
increasing the amounts of unsaturated fatty acids in their membranes to help keep their membranes fluid.
Organisms that live in cold climates adapt to low temperatures by: decreasing the amounts of unsaturated fatty acids in their membranes to help keep their membranes fluid. increasing the amounts of saturated fatty acids in their membranes to help decrease the fluidity of their membranes. increasing the amounts of saturated fatty acids in their membranes to help keep their membranes fluid. increasing the amounts of unsaturated fatty acids in their membranes to help decrease the fluidity of their membranes. increasing the amounts of unsaturated fatty acids in their membranes to help keep their membranes fluid.
the movement of water from an area of high solute concentration to an area of low solute concentration.
Osmosis can be described as: the movement of water from an area of high solute concentration to an area of low solute concentration. the movement of water from an area of low solute concentration to an area of high solute concentration. the movement of water from an area of low solvent concentration to an area of high solvent concentration. the movement of water from an area of low water concentration to an area of high water concentration.
Which of the following processes involves a membrane? A. Substrate level phosphorylation B. Oxidative phosphorylation
Oxidative phosphorylation
Sodium ions, oxygen (O2), and glucose pass directly through lipid bilayers at dramatically different rates. Which of the following choices presents the correct order, from fastest to slowest?
Oxygen, glucose, sodium ions
Which statement about phospholipids and detergents is NOT true?
Phospholipids are amphipathic, whereas detergents are hydrophobic.
Hydrophobic
Porin proteins—which form large, water-filled pores in mitochondrial and bacterial outer membranes—fold into β-barrel structures. The amino acids that face the outside of the barrel have what kind of side chains? Hydrophilic Hydrophobic
What do carbohydrates attached to cell-surface proteins and lipids provide a cell?
Protection from mechanical and chemical damage A slimy coat that prevents cells from sticking to one another A distinctive identity in cell-cell recognition
Bacteriorhodopsin is a membrane transport protein that uses sunlight to do what?
Pump H+ out of the cell and generate a H+ gradient across the plasma membrane
Which of the following activities restores the ion gradients across the plasma membrane of an axon after an action potential has occurred?
Pumping by the Na+/K+ ATPase
Mechanically gated
Auditory hair cells in the ear depend on what type of ion channel to detect sound vibrations?
39. Which of the following functions does the cell cortex perform? (a) It influences the passage of small molecules into and out of the cell. (b) It allows cells to change shape and to move. (c) It lubricates the cell. (d) It restricts the movement of certain proteins in the lipid bilayer. (e) It supports and strengthens the membrane.
B, D, E
8. In one second, a lipid in an artificial bilayer may diffuse as far as what distance? A. 2 nanometers (the width of a DNA double helix) B. 2 microns (the length of a large bacterial cell) C. 500 microns (the length of a typical amoeba)
B. 2 microns (the length of a large bacterial cell)
16. How much of the mass of the plasma membranes is constituted by proteins? A. 25% B. 50% C. 75%
B. 50%
24. Which is not a mechanism for restricting the movement of proteins in the membrane? A. Using barriers such as tight junctions B. Coating proteins with carbohydrates C. Tethering proteins to the cell cortex D. Tethering proteins to the extracellular matrix E. Tethering proteins to the surface of another cell
B. Coating proteins with carbohydrates
1. Which is NOT found in a cell membrane? A. Lipid B. DNA C. Protein D. Cholesterol
B. DNA
11. Double bonds in hydrocarbon tails have what effect on the rigidity of fats and phospholipid bilayers? A. Double bonds increase the ability of hydrocarbon tails to pack together into a rigid mass. B. Double bonds decrease the ability of hydrocarbon tails to pack together into a rigid mass. C. Double bonds have little effect on the rigidity of fats and phospholipid bilayers.
B. Double bonds decrease the ability of hydrocarbon tails to pack together into a rigid mass.
25. On what side of the membrane are the carbohydrate chains of glycoproteins, proteoglycans, and glycolipids located? A. Cytosolic side B. External (noncytosolic) side
B. External (noncytosolic) side
14. What type of enzyme moves phospholipids from one monolayer to the other in a biological membrane? A. Phospholipase B. Flippase C. No enzyme-this action happens spontaneously and relatively quickly
B. Flippase
17. Which of the following is NOT a function of membrane proteins? A. Transport molecules across the membrane B. Generate the energy required for lipids to diffuse through the membrane C. Transmit extracellular signals to the cell interior D. Serve as anchors to attach the cell to the extracellular matrix
B. Generate the energy required for lipids to diffuse through the membrane
20. Porin proteins-which form large, water-filled pores in mitochondrial and bacterial membranes-fold into /beta barrel structures. The amino acids that face the outside of the barrel have what kind of side chains? A. Hydrophilic B. Hydrophobic
B. Hydrophobic
21. Which statement about phospholipids and detergents is NOT true? A. Phospholipids have two hydrocarbon tails, whereas detergents have just one. B. Phospholipids are amphipathic, whereas detergents are hydrophobic. C. Phospholipids form bilayers, whereas detergents tend to form micelles.
B. Phospholipids are amphipathic, whereas detergents are hydrophobic.
18. Which is NOT an integral membrane protein? A. A transmembrane protein that spans the lipid bilayer B. A monolayer associated protein tucked into the inner leaflet of the lipid bilayer C. A protein attached to the membrane by non-covalent interactions with other membrane proteins D. A lipid-linked protein anchored to the outer leaflet of the membrane
C. A protein attached to the membrane by non-covalent interactions with other membrane proteins
4. The entire phospholipid molecule is: A. hydrophobic. B. hydrophilic. C. amphipathic.
C. amphipathic.
23. The shape of a cell and the mechanical properties of its plasma membrane are determined by a meshwork of fibrous proteins called: A. basal lamina. B. carbohydrate layer. C. cell cortex. D. tight junction.
C. cell cortex.
Synaptic plasticity is largely dependent on the presence of which ion in the postsynaptic cell?
Ca2+
When an action potential reaches a nerve terminal, what type of voltage-gated channels are opened and result in the fusion of synaptic vesicles with the cell membrane?
Ca2+
What is the difference between transporters and channels?
Channels discriminate between solutes mainly on the basis of size and electric charge; transporters bind their solutes with great specificity in the same way an enzyme binds its substrate.
How does cholesterol in animal cell membranes affect the fluidity of the bilayer
Cholesterol tends to stiffen the bilayer.
Which is not a mechanism for restricting the movement of proteins in the membrane?
Coating proteins with carbohydrates
Combining CO2 and H2O to make a carbohydrate is an energetically very favorable reaction. A. True B. False
False
The storage of energy in a proton gradient derived from electron transport is a recent evolutionary development. A. True B. False
False
It alters the probability that the channel will be found in its open conformation.
For voltage-gated channels, a change in the membrane potential has what effect on the channel?
B. It alters the probability that the channel will be found in its open conformation.
For voltage-gated channels, a change in the membrane potential has what effect on the channel? A. It changes the width of the channel opening. B. It alters the probability that the channel will be found in its open conformation. C. It either opens the channel or closes it, depending on the voltage.
A
From one glucose molecule, how much net energy (in the form of ATP and NADH) is produced during glycolysis? A. 2 ATP, 2 NADH B. 4 ATP, 4 NADH C. 4 ATP, 2 NADH D. 2 ATP, 4 NADH
It is energetically favorable for protons to flow in which direction? A. From the intermembrane space to the mitochondrial matrix B. From the mitochondrial matrix to the intermembrane space
From the intermembrane space to the mitochondrial matrix
Which of the following is NOT a function of membrane proteins?
Generate the energy required for lipids to diffuse through the membrane
True
Given enough time, virtually any molecule will diffuse across a lipid bilayer. False True
Oxygen, glucose, sodium ions
Sodium ions, oxygen (O2), and glucose pass directly through lipid bilayers at dramatically different rates. Which of the following choices presents the correct order, from fastest to slowest? Glucose, oxygen, sodium ions Glucose, sodium ions, oxygen Oxygen, glucose, sodium ions Oxygen, sodium ions, glucose Sodium ions, oxygen, glucose
Auditory hair cells in the ear depend on what type of ion channel to detect sound vibrations?
Stress-gated
C
Sugars derived from food are broken down by: A. Glycolysis, the citric acid cycle, and gluconeogenesis B. Gluconeogenesis, the citric acid cycle, and oxidative phosphorylation C. Glycolysis, the citric acid cycle, and oxidative phosphorylation D. Biosynthesis, fermentation, and the citric acid cycle
Which term describes a coupled transporter that moves both solutes in the same direction across a membrane?
Symport
What is the name of the specialized junction between a neuron and a target cell?
Synapse
Phospholipids with which of the following hydrocarbon tails will produce the most fluid bilayer
Tails with 18 carbon atoms and two double bonds
B
The NADH generated during glycolysis feeds its high energy electrons to: A. The citric acid cycle B. The electron transport chain C. ADP D. H2O
control their pH, import nutrients such as sugars and amino acids, propagate electrical signals, stimulate muscle cell contraction.
The Na+ electrochemical gradient established by the Na+ pumps in the plasma membrane allows animal cells to:
Na+ out and K+ in
The Na+ pump in the plasma membrane of animal cells uses energy from ATP hydrolysis to pump sodium and potassium ions against their electrochemical gradients. In which direction are the ions pumped across the membrane? Na+ and K+ both in Na+ and K+ both out Na+ in and K+ out Na+ out and K+ in
Na+ out and K+ in
The Na+-K+ pump in the plasma membrane of animal cells uses the energy from ATP hydrolysis to pump sodium and potassium ions against their electrochemical gradients. In which direction are the ions pumped across the membrane? A. Na+ out and K+ in B. K+ out and Na+ in C. Na+ and K+ both out D. Na+ and K+ both in
C
The citric cycle converts the carbon atoms in acetyl CoA to which of the following? A. Pyruvate B. Citrate C. CO2 D. CH4
D
The complete oxidation of glucose to H2O and CO2 produces about how many molecules of ATP per molecule of glucose? A. 2 B. 4 C. 12 D. 30
When glucose moves across a phospholipid bilayer by passive transport, which factor determines the direction of its transport?
The concentrations of glucose on either side of the membrane
the concentration gradient
The direction that glucose is transported across the membrane is determined by: the concentration gradient the membrane potential the molecule's charge the molecule's size
A
The end products of glycolysis are: A. Pyruvate, ATP, and NADH B. Pyruvate, ATP, and NADPH C. Pyruvate, ADP, and NADH D. Citrate, ATP, and NADH E. H2O and CO2
Which organelle is important for controlling the concentration of calcium ions in the cytosol?
The endoplasmic reticulum
B
The energy released by oxidizing glucose is saved in the high-energy bonds of: A. ADP and other activated carrier molecules B. ATP and other activated carrier molecules C. GDP and other activated carrier molecules D. H2O and CO2
amphipathic
The entire phospholipid molecule is: amphipathic apathetic hydropathic hydrophilic hydrophobic
The cells have glucose uniports in their plasma membrane.
The epithelial cells that line the gut have glucose-Na+ symport proteins that actively take up glucose from the lumen of the gut after a meal, creating a high glucose concentration in the cytosol. How do these cells release that glucose for use by other tissues in the body?
True
The glucose-Na+ symport in epithelial cells uses the electrochemical gradient of Na+ to draw glucose into the cell.
False
The glucose-Na+ symport protein uses the electrochemical Na+ gradient to drive the active transport of glucose into the cell. Once this transporter has bound both Na+ and glucose, it preferentially opens toward the cytosol, where it releases both solutes.
Which parts of the phospholipid face the outside of the membrane?
The head
Why do lipids form bilayers in water?
The hydrophilic head is attracted to water while the hydrophobic tail shuns water.
Which of the following inhibits ions from passing through a lipid bilayer
The hydrophobic interior of the lipid bilayer
is slightly more negative than the outside of a cell.
The inside of a cell: has the same charge as the outside of the cell. is slightly more negative than the outside of a cell. is slightly more positive than the outside of a cell.
In eukaryotic cells, new phospholipids are manufactured byenzymes bound to which part of the endoplasmic reticulum membrane?
The monolayer that faces the cytosol
Which of the following scenarios requires an input of energy to occur?
The movement of a solution from a region of lower concentration on one side of a membrane to a region of higher concentration on the other side.
active transport
The movement of an ion against its concentration gradient is called: active transport facilitated diffusion osmosis passive transport
passive transport
The movement of an ion down its concentration gradient is called: active transport osmosis passive transport pumping
are hydrophobic
The oils found in plant seeds and the fats found in an animal's fat (or adipose) cells: are amphipathic are hydrophobic are saturated are unsaturated form a lipid bilayer in water
DNA replication
The plasma membrane is NOT involved in: cell growth and motility. cell recognition. cell signaling. DNA replication import and export of molecules
Margarine is made from vegetable oils in which the hydrocarbon tails have had what treatment?
The removal of double bonds (i.e., changing them to single bonds and adding hydrogen atoms)
cell cortex
The shape of a cell and the mechanical properties of its plasma membrane are determined by a meshwork of fibrous proteins called the: basal lamina cell cortex glycocalyx tight junction
membrane potential
The voltage difference across a membrane of a cell is called the: electrical current electrical potential membrane potential potential balance potential voltage
Which of the following is NOT true of mitochondria? A. They are similar in size and shape to bacteria. B. They contain their own DNA and RNA. C. They contain an outer membrane, and inner membrane, and two internal compartments. D. They are replaced by chloroplasts in plants. E. Inside a cell, they are mobile, constantly changing shape and position.
They are replaced by chloroplasts in plants.
A
They synthesis of ATP in glycolysis occurs by: A. substrate-level phosphorylation B. Oxidative phosphorylation
interact with polar groups in the narrowest part of the channel.
To pass through the pore of an ion channel, an ion must:
Which of the following mechanisms prevents osmotic swelling in plant cells?
Tough cell walls
Mitochondria can change their location, shape, and number in the cell to suit the needs of a cell. A. True B. False
True
The outer membrane of a mitochondrion is permeable to all small molecules, including small proteins. A. True B. False
True
The proton gradient can drive the active transport of metabolites into and out of the mitochondrion. A. True B. False
True
Ubiquinone has a redox potential of +30 mV, while cytochrome c has a redox potential of +230 mV. In the electron transport chain, electrons flow from: A. Ubiquinone to cytochrome c. B. Cytochrome c to ubiquinone.
Ubiquinone to cytochrome c.
C
Under anaerobic conditions, which metabolic pathway regenerates the supply of NAD+ for glycolysis? A. The citric acid cycle B. The formation of acetly CoA C. Fermentation D. The electron transport chain
Which type of ion channel plays the major role in propagating electrical signals in nerve cells?
Voltage-gated
False
Voltage-gated ion channels are present only in electrically excitable cells, such as neurons and muscle cells.
False
Water passes through the cell membrane only through specialized channels called aquaporins. False True
(D) All of the above
What do carbohydrates attached to cell-surface proteins and lipids provide for a cell? (A) A distinctive identity in cell-cell recognition (B) A slimy coat that prevents cells from sticking to one another (C) Protection from mechanical and chemical damage (D) All of the above
A
What does it mean for a bond to be "high energy" such as between phosphate groups in ATP? A. The hydrolysis of such a bond is particularly energetically favorable B. Such a bond is strong and difficult to break C. The bond involves an extra electron
B
What does the term gluconeogenesis refer to? A. The release of glucose from molecules such as glycogen B. The synthesis of glucose from small organic molecules such as pyruvate C. The breakdown of glucose to glycolysis
They are gated
What is typically true of ion channels?
Scramblase
What type of enzyme moves randomly selected phospholipids from one monolayer of a lipid bilayer to the other? Flippase No enzyme—phospholipids cannot be moved from one monolayer to another No enzyme—this action happens spontaneously and relatively quickly Phospholipase Scramblase
It becomes less negative inside the cell
When Na+ channels are opened in an animal cell, what happens to the membrane potential?
False
When a muscle cell is stimulated, Ca2+ pumps in the sarcoplasmic reticulum use the energy of ATP to move Ca2+ into the cytosol, stimulating the cell to contract.
the outside of the cell
When a vesicle fuses with the plasma membrane, the monolayer that was facing the inside of the vesicle will face: the cell cytoplasm the outside of the cell
Which of the following statements is NOT true of electron transfer in the electron transport chain? A. Each electron transfer is an oxidation-reduction reaction. B. When an electron carrier accepts an electron, it becomes oxidized. C. NADH has a relatively low electron affinity.
When an electron carrier accepts an electron, it becomes oxidized.
It continues to flicker between open and closed states, but spends more time open while the neurotransmitter is bound.
When an individual ion channel is stimulated to open (for example, by the binding of a neurotransmitter), what is the typical activity of the ion channel?
B
When fatty acids are oxidized to acetyl CoA, each cycle of the reaction removes how many carbon atoms from the fatty acid molecule? A. 1 B. 2 C. 3 D. 4
(C) The concentrations of glucose on either side of the membrane
When glucose moves across a phospholipid bilayer by passive transport, which factor determines the direction of its transport? (A) The amount of energy available to fuel the transport process (B) The charge difference across the membrane (C) The concentrations of glucose on either side of the membrane (D) All of the above (E) B and C, but not A
producing membrane lipids with tails that are longer and contain fewer double bonds.
When grown at higher temperatures, bacteria and yeast maintain an optimal membrane fluidity by: adding cholesterol to their membranes. producing membrane lipids with tails that are longer and contain fewer double bonds. producing membrane lipids with tails that are longer and contain more double bonds. producing membrane lipids with tails that are shorter and contain fewer double bonds. producing membrane lipids with tails that are shorter and contain more double bonds.
B
When nutrients are plentiful, plants can store glucose as: A. Glycogen B. Starch C. Adipose D. All of the above
Na+ binds to its binding site.
When the glucose-Na+ symport protein is in its outward-open state, which is more likely to occur?
B
Where does the oxidative breakdown of food molecules occur in a eukaryotic cell? A. The cytosol B. Mitochondria C. The Golgi apparatus D. The endoplasmic reticulum
Vegetable oils
Which has a larger number of double bonds? Butter Lard Margarine Saturated fats Vegetable oils
Coating proteins with carbohydrates
Which is NOT a mechanism for restricting the movement of proteins in the plasma membrane? Coating proteins with carbohydrates Tethering proteins to the cell cortex Tethering proteins to the extracellular matrix Tethering proteins to the surface of another cell Using barriers such as tight junctions
A protein attached to the membrane by noncovalent interactions with other membrane proteins
Which is NOT an integral membrane protein? A lipid-linked protein anchored to the outer leaflet of the membrane A monolayer-associated protein tucked into the inner leaflet of the lipid bilayer A protein attached to the membrane by noncovalent interactions with other membrane proteins A transmembrane protein that spans the lipid bilayer
DNA
Which is NOT found in a cell membrane? Cholesterol DNA Lipid Protein Sugar
Phosphatidylcholine
Which is the most abundant phospholipid in animal cell membranes? Cholesterol Glycolipid Phosphatidylcholine Phosphatidylinositol Triacylglycerol
K+ leak channels
Which membrane transport proteins randomly flicker between open and closed states regardless of the conditions inside or outside of the cell?
It maintains a higher Na+ concentration outside the cell.
Which of the following accurately describes the role of the Na+ pump?
B
Which of the following describes the breakdown proces in which enzymes degrade complex molecules into simpler ones? A. Anabolism B. Catabolism
Channels
Which of the following form tiny hydrophilic pores in the membrane through which solutes can pass by diffusion? Anions Channels Liposomes Pumps Transporters
C
Which of the following generates the largest amount of ATP? A. Glycolysis B. The citric acid cycle C. The electron transport chain
The hydrophobic interior of the lipid bilayer
Which of the following inhibits inorganic ions, like Na+ and Cl-, from passing through a lipid bilayer? The carbohydrate layer on the surface of the lipid bilayer The hydrophilic exterior of the lipid bilayer The hydrophobic interior of the lipid bilayer The ions' large size The watery environment on either side of the lipid bilayer
Na+
Which of the following ions has a larger electrochemical gradient across a cell's plasma membrane? K+ Na+
It takes ~10 amino acids to traverse the membrane
Which of the following is FALSE concerning alpha helices in transmembrane proteins? H-bonds form between the peptide backbone Hydrophobic side chains face the outside of the membrane-spanning helix It takes ~10 amino acids to traverse the membrane They form both single-pass and multi-pass transmembrane proteins
Generate the energy required for lipids to diffuse through the membrane
Which of the following is NOT a function of plasma membrane proteins? Allow specific ions to cross the plasma membrane, thereby controlling its electrical properties Generate the energy required for lipids to diffuse through the membrane Serve as anchors to attach the cell to the extracellular matrix Transmit extracellular signals to the cell interior Transport molecules across the membrane
C
Which of the following is NOT required for glycolysis to occur? A. NAD+ B. ATP C. O2 D. ADP
C
Which of the following is true? A. Sugars are converted to Acetyl CoA in the mitochondria; fats are converted to Acetyl CoA in the cytosol B. Fats are converted to Acetyl CoA in the mitochondria; sugars are converted to Acetyl CoA in the cytosol C. Sugars and fats are both converted to Acetyl CoA in the mitochondria D. Sugars are converted to Acetyl CoA but fats are not
B
Which of the following locations is NOT used for the digestion of polymeric food molecules into monomeric subunits? A. Extracellular space (the lumen of intestines, for example) B. The cytosol of a cell C. Lysosomes
Tough cell walls
Which of the following mechanisms prevents osmotic swelling in plant cells? The activity of Na+ pumps The collection of water in contractile vacuoles The expulsion of water from contractile vacuoles Tough cell walls Turgor pressure
The movement of a solute from a region of lower concentration on one side of a membrane to a region of higher concentration on the other side.
Which of the following requires an input of energy to occur? The movement of a solute from a region of higher concentration on one side of a membrane to a region of lower concentration on the other side. The movement of a solute from a region of lower concentration on one side of a membrane to a region of higher concentration on the other side.
Inside the cell, the quantity of positively charged ions is almost equal to the quantity of negatively charged ions.
Which of the following statements is true? Inside the cell, the quantity of positively charged ions is almost equal to the quantity of negatively charged ions. Inside the cell, the quantity of positively charged ions is much greater than the quantity of negatively charged ions. Inside the cell, the quantity of positively charged ions is much less than the quantity of negatively charged ions. Inside the cell, there are no negatively charged ions. Inside the cell, there are no positively charged ions.
Na+ is the most plentiful positively charged ion outside the cell, while K+ is the most plentiful inside.
Which of the following statements is true? K+ and Na+ are both excluded from cells. K+ and Na+ are both maintained at high concentrations inside the cell. K+ and Na+ are present in the same concentration on both sides of the plasma membrane. K+ is the most plentiful positively charged ion outside the cell, while Na+ is the most plentiful inside. Na+ is the most plentiful positively charged ion outside the cell, while K+ is the most plentiful inside.
Phospholipids with tails of 18 carbon atoms and two double bonds
Which of the following will produce the most fluid lipid bilayer? Large amounts of cholesterol Phospholipids with fully saturated tails of 18 carbon atoms Phospholipids with fully saturated tails of 20 carbon atoms Phospholipids with tails of 18 carbon atoms and two double bonds Phospholipids with tails of 20 carbon atoms and two double bonds
Negatively charged ions
Which of the following would be deterred from entering an ion channel with a negatively charged lining?
Inhibitory neurotransmitters such as glycine and GABA make a postsynaptic cell harder to depolarize by:
allowing an influx of Cl-.
When transmitter-gated ion channels in the membrane of a post-synaptic cell open in response to neurotransmitter binding, they:
alter the ion permeability of the postsynaptic membrane, which in turn may depolarize the postsynaptic membrane.
The entire phospholipid molecule is:
amphipathic
ATP synthase: A. can produce ATP but cannot break it down. B. can break down ATP but cannot produce it. C. can either produce or break down ATP depending on the magnitude of the electrochemical proton gradient.
can either produce or break down ATP depending on the magnitude of the electrochemical proton gradient.
The shape of a cell and the mechanical properties of its plasma membrane are determined by a meshwork of fibrous proteins called:
cell cortex.
Channelrhodopsin can be used to manipulate the activity of neurons because:
channelrhodopsin, when activated by light, depolarizes the membrane and stimulates neurons.
NADH has a strong tendency to: A. accept electrons. B. donate electrons. C. either donate or accept electrons depending on the electrochemical proton gradient.
donate electrons
The organelles that produce ATP in eukaryotic cells: A. reproduce sexually. B. harbor eukaryotic-like biosynthetic machinery for making RNA. C. have a separate set of DNA that contains many of the same genes found in the nucleus. D. evolved from bacteria engulfed by ancestral cells billions of years ago.
evolved from bacteria engulfed by ancestral cells billions of years ago.
.An ion channel undergoes conformational changes with each ion it passes.
false
An electrical signal crosses the synaptic cleft between the presynaptic and postsynaptic cells
false
Optogenetics uses transmitter-gated channels that have been introduced by genetic engineering techniques to control neurons.
false
The electron transport chain pumps protons: A. from the intermembrane space to the matrix. B. from the matrix to the intermembrane space. C. from the matrix to the cytosol.
from the matrix to the intermembrane space.
When the difference in redox potential between two pairs of molecules is highly positive, then the transfer of the electrons is: A. highly unfavorable. B. highly favorable. C. highly inefficient. D. prohibited by the laws of thermodynamics.
highly favorable.
Cellular respiration: A. is more efficient at generating energy than a gasoline-powered engine. B. is less efficient at generating energy than a gasoline engine C. operates at about the same efficiency as a gasoline-powered engine D. cannot be compared to the efficiency of a gasoline engine.
is more efficient at generating energy than a gasoline-powered engine.
The inside of a cell:
is more negative than the outside of a cell.
The voltage difference across a membrane of a cell is called the:
membrane potential.
When a neuron is stimulated by a signal, the response is at first spread locally along the membrane by what means?
passive spread
The movement of an ion down its electrochemical gradient is called:
passive transport
All other factors (e.g., concentration, solute size) being equal, which type of solute does a cell tend to pull inside?
positively charged solutes
When protons move down their electrochemical gradient into the mitochondrial matrix, they: A. produce NADH. B. produce ATP. C. consume ATP. D. they move electrons through the respiratory chain.
produce ATP.
the cytosolic face of the endoplasmic reticulum
In eukaryotic cells, new phospholipids are manufactured by enzymes bound to: both monolayers of the endoplasmic reticulum. the cytosolic face of the Golgi apparatus. the cytosolic face of the endoplasmic reticulum. the cytosolic face of the plasma membrane. the inside of the endoplasmic reticulum.
B
In eukaryotic cells, what is the final electron acceptor in the electron transport chain? A. H2O B. O2 C. CO2 D. NADH E. FADH2
H+ pumps
In fungi, plants, and bacteria, which pump helps to drive the import of solutes?
A small hydrophobic molecule
In general, which of the following will diffuse across a lipid bilayer most rapidly? A large hydrophilic molecule A large hydrophobic molecule A small hydrophilic molecule A small hydrophobic molecule Water
B
In humans and other mammals, gluconeogenesis occurs mainly in which type of cell? A. Pancreatic cells B. Liver cells C. Muscle cells D. Red blood cells
K+
In most animal cells, which ion can move through "leak" channels?
2 microns (the length of a large bacterial cell)
In one second, a phospholipid molecule in an artificial bilayer may diffuse as far as what distance? 2 meters (the length of some of the longest nerve cells in the body) 2 microns (the length of a large bacterial cell) 2 nanometers (the width of a DNA double helix) 20 nanometers (the width of a typical ribosome) 200 microns (halfway across a typical amoeba)
its electrochemical gradient.
In passive transport, the net movement of a charged solute across the membrane is determined by: its concentration gradient. its electrochemical gradient. its osmotic gradient alone. the membrane potential.
B
In plants, fats and starch are stored in which part of the cell? A. Vacuole B. Chloroplast C. Cytosol D. Endoplasmic Reticulum
B
In the electron transport chain, the oxygen atoms in O2 become part of which of the following molecules? A. CO2 molecules B. H2O molecules C. NADH molecules D. ATP molecules
In a eukaryotic cell, where are most of the proteins for the electron transport chain located? A. In the plasma membrane B. In the mitochondrial inner membrane C. In the mitochondrial outer membrane D. In the ER membrane
In the mitochondrial inner membrane
the outside of the membrane-spanning helix.
In the α helices of transmembrane proteins, the hydrophobic side chains are facing: the inside of the membrane-spanning helix. the outside of the membrane-spanning helix.
Which of the following statements is true?
Inside the cell the quantity of positively charged ions is almost exactly equal to the quantity of negatively charged ions.
For voltage-gated channels, a change in the membrane potential has what effect on the channel?
It alters the probability that the channel will be found in its open conformation.
When Na+ channels are opened in an animal cell, what happens to the membrane potential?
It becomes less negative.
What is incorrect about a nerve impulse?
It depends on the action of ligand-gated ion channels.
When a neuron opens voltage-gated Na+ channels, what happens to the membrane?
It depolarizes
.When an individual ion channel is stimulated to open (for example, by the binding of a neurotransmitter), what is the typical activity of the ion channel?
It flickers between open and closed states, but spends more time open while the neurotransmitter is bound.
Which of the following accurately describes the role of the Na+ pump?
It maintains a high Na+ concentration outside the cell.
In most animal cells, which ion can move through "leak" channels in the plasma membrane and, in so doing, establishes the resting membrane potential?
K+
Na+ and Cl−.
Lipid bilayers are highly impermeable to: carbon dioxide. Na+ and Cl−. oxygen. steroid hormones. water.
Removing the double bonds by adding hydrogen (which converts double bonds to single bonds)
Margarine is made from vegetable oils in which the hydrocarbon tails have had what treatment? Decreasing the length of the tails by removing carbon atoms Freezing Increasing the length of the tails by adding carbon atoms Increasing the number of double bonds in the tails by removing hydrogen (which converts single bonds to double bonds) Removing the double bonds by adding hydrogen (which converts double bonds to single bonds)
In mitochondria, what is the final electron acceptor in the electron transport chain? A. Carbon dioxide (CO2) B. Molecular oxygen (O2) C. Water (H2O) D. NADH and FADH2
Molecular oxygen (O2)
The electron transport chain accepts high-energy electrons from: A. ATP. B. pyruvate. C. NADH and FADH2. D. acetyl CoA.
NADH and FADH2
Which of the following is true? A. NADH has a strong affinity for electrons and a positive redox potential. B. NADH has a weak affinity for electrons and a negative redox potential. C. NADH has a strong affinity for electrons and a negative redox potential. D. NADH has a weak affinity for electrons and a negative redox potential.
NADH has a weak affinity for electrons and a negative redox potential.
Which of the following has a larger electrochemical gradient across a cell's plasma membrane?
Na+
Lipid bilayers are highly impermeable to:
Na+ and Cl-.
Which of the following statements is true?
Na+ is the most plentiful positively charged ion outside the cell, while K+ is the most plentiful inside.
Which of the following would be deterred from entering an ion channel with negatively charged lining?
Negatively charged ions
What electron acceptor allows an organism to completely break down organic molecules into CO2 and H2O and thereby release a large amount of energy that can be harnessed by the cell to do work? A. H2O B. O2 C. CO2 D. Pyruvate E. NAD+
O2
External (noncytosolic) side
On what side of the plasma membrane are the carbohydrate chains of glycoproteins, proteoglycans, and glycolipids located? Cytosolic side External (noncytosolic) side
There are several ways that membrane proteins can associate with the cell membrane. Membrane proteins that extend through the lipid bilayer are called __________________ proteins and have __________________ regions that are exposed to the interior of the bilayer. On the other hand, membrane-associated proteins do not span the bilayer and instead associate with the membrane through an α-helix that is __________________. Other proteins are __________________ attached to lipid molecules that are inserted in the membrane. __________________ membrane proteins are linked to the membrane through noncovalent interactions with other membrane- bound proteins.
35. transmembrane, hydrophobic, amphipathic, covalently, peripheral
43. Cell membranes are fluid, and thus proteins can diffuse laterally within the lipid bilayer. However, sometimes the cell needs to localize proteins to a particular membrane domain. Name four mechanisms that a cell can use to restrict a protein to a particular place in the cell membrane.
43. Tethered to the cell cortex, tethered to extracellular matrix molecules, tethered to molecules in another cell, diffusion barrier (Figure 11-33)
49. Indicate whether the following statements are true or false. If a statement is false, explain why it is false. A. Although cholesterol is a hydrophobic molecule, it has a hydrophilic head group like all other membrane lipids. B. Phosphatidylserine is the most abundant type of phospholipid found in cell membranes. C. Glycolipids lack the glycerol component found in phospholipids. D. The highly ordered structure of the lipid bilayer makes its generation and maintenance energetically unfavorable.
49. A: true, B: false (phosphatidylcholine is the most abundant phospholipid.) C: true, D: false (formation of lipid bilayer is favorable in water.)
In fungi, plants, and bacteria, which pump helps to drive the import of solutes?
H+ pumps
Osmosis can be described as
the movement of water from an area of low solute concentration to an area of high solute concentration.
.What is typically true of ion channels?
they are gated
Prozac, among many other drugs, functions by altering neurotransmitter levels in the brain. How does Prozac work?
By blocking the reuptake of serotonin after it has been released, increasing the amount available in the synapses that use it
Which of the following occur without coupling transport of the solute to the movement of a second solute?
Export of Ca2+ from the cytosol
46. Which of the following classes of lipids is (are) present in biomembranes? (a) phospholipids (b) sphingolipids (c) cholesterol (d) all of the above
(d) all of the above
37. Proteins that form a ß-barrel pore in the membrane have several ß-strands that span the membrane. The amino acid side chains facing the inside of the pore would be hydrophilic whereas the amino acid side chains facing the lipid bilayer would be hydrophobic. Which of the three 10-amino acid sequences listed below is the most likely candidate for a transmembrane ß-strand in a ß-barrel protein? Explain your choice. (a) Ala-Asp-Phe-Lys-Leu-Ser-Val-Glu-Leu-Thr (b) Ala-Phe-Leu-Val-Leu-Asp-Lye-Ser-Glu-Thr (c) Ala-Phe-Asp-Lys-Leu-Val-Ser-Glu-Leu-Thr
(a) Ala-Asp-Phe-Lys-Leu-Ser-Val-Glu-Leu-Thr
31. Which of the following statements is true? (a) Phospholipids will spontaneously form liposomes in nonpolar solvents. (b) In eucaryotes, all membrane-enclosed organelles are surrounded by one lipid bilayer. c) Membrane lipids diffuse within the plane of the membrane. (d) Membrane lipids frequently flip-flop between one monolayer and the other.
(a) Phospholipids will spontaneously form liposomes in nonpolar solvents.
29. Which of the following statements regarding the fatty acid tails of phospholipids is FALSE? (a) Phospholipids with unsaturated tails make the bilayer more fluid because the tails contain fewer hydrogen atoms and thus form fewer hydrogen bonds with each other. (b) Saturated phospholipid tails pack more tightly against each other than do unsaturated tails. (c) Most membrane phospholipids have one fully saturated tail. (d) Phospholipid tails in a membrane can interact with each other via van der Waals interactions. (e) Fatty acid tails vary in length.
(a) Phospholipids with unsaturated tails make the bilayer more fluid because the tails contain fewer hydrogen atoms and thus form fewer hydrogen bonds with each other.
33. A group of membrane proteins, which can be extracted only from membranes using detergents, are all found to have a similar amino acid sequence at their carboxyl terminus: -KKKKKXXC (where K stands for lysine, X stands for any amino acid, and C stands for cysteine). This sequence is essential for their attachment to the membrane. What is the most likely way in which the carboxyl-terminal sequence attaches these proteins to the membrane? (a) The cysteine residue is covalently attached to a membrane lipid. (b) The peptide spans the membrane as an α helix. amphipathic hydrophobic phosphatidylserine cholesterol Lipid bilayer phospholipids Fatty acid tails Lipid monolayer proteins glycolipids lipids sterols Hydrophilic head groups phosphatidylcholine sugars (c) The peptide spans the membrane as part of a β sheet. (d) The positively charged lysine residues interact with an acidic integral membrane protein. (e) The positively charged lysine residues interact with negatively charged phospholipids like phosphatidylserine.
(a) The cysteine residue is covalently attached to a membrane lipid.
38. Porin proteins form large, barrel-like channels in the membrane. Which of the following is not true about these channels? (a) They are made primarily of α helices. (b) They are made primarily of β sheets. (c) They cannot form narrow channels. (d) They have alternating hydrophobic and hydrophilic amino acids.
(a) They are made primarily of α helices.
45. Cholesterol mixes with phospholipids in a biomembrane because cholesterol molecules are (a) amphipathic. (b) steroid derivatives. (c) entirely hydrophobic. (d) phospholipid derivatives.
(a) amphipathic.
47. Phospholipids with short or unsaturated fatty acyl chains (a) decrease membrane fluidity. (b) increase membrane fluidity. (c) cause biomembranes to become thicker. (d) allow hydrophilic molecules to diffuse across the lipid bilayer.
(b) increase membrane fluidity.
48. The ___________________________________________ are transmembrane proteins. (a) lipid-anchored membrane proteins (b) integral membrane proteins (c) peripheral membrane proteins (d) extracellular matrix proteins
(b) integral membrane proteins
28. Which of the following statements regarding lipid membranes is TRUE? (a) Phospholipids will spontaneously form liposomes in nonpolar solvents. (b) In eucaryotes, all membrane-enclosed organelles are surrounded by one lipid bilayer. (c) Membrane lipids diffuse within the plane of the membrane. (d) Membrane lipids frequently flip-flop between one monolayer and the other. (e) The preferred form of a lipid bilayer in water is a flat sheet with exposed edges
(c) Membrane lipids diffuse within the plane of the membrane.
42. Which of the following statements about the carbohydrate coating of the cell surface is FALSE? (a) It is not usually found on the cytosolic side of the membrane. (b) It can play a role in cell-cell adhesion. (c) The arrangement of the oligosaccharide side chains are highly ordered, much like the peptide bonds of a polypeptide chain. (d) Specific oligosaccharides can be involved in cell-cell recognition. (e) It can protect the cell surface from mechanical and chemical damage.
(c) The arrangement of the oligosaccharide side chains are highly ordered, much like the peptide bonds of a polypeptide chain.
32. Why are glycolipids found on the extracellular, but not the cytoplasmic, surface of the plasma membrane? (a) Plasma membrane flippases transport them from the cytosolic face. (b) The enzymes that produce them are present only on the extracellular surface of the plasma membrane. (c) The enzymes that add the sugar groups are confined to the inside of the endoplasmic reticulum and the Golgi apparatus. (d) The oligosaccharides on glycolipids are cleaved off by enzymes found only in the cytosol. (e) They flip spontaneously, after incorporation, due to the hydrophilic sugar head groups.
(c) The enzymes that add the sugar groups are confined to the inside of the endoplasmic reticulum and the Golgi apparatus.
50. Sodium dodecyl sulfate (SDS) and Triton X-100 are both detergents that can be used to lyse cells. A. If the the goal is to study the activity of membrane proteins after cell lysis, explain why SDS would not be a good choice. B. How does Triton X-100 work in cell lysis, and why is it a better choice of detergent to help you extract proteins?
50. A: SDS is a strong ionic detergent. SDS extracts proteins out from the membrane and completely unfolds them. It is impossible to do functional study of the denatured proteins. B: Triton X-100 is a mild detergent having a polar but uncharged portion. Triton X-100 forms a shell around the hydrophobic region of the protein without denaturing. This allows functional characterization of the protein because the protein is in a new, synthetic membrane bilayer.
. Consider the apical location of a particular protein expressed in epithelial cells, illustrated in Figure A. Which type of defect described below is the most likely to cause the redistribution of that protein around the entire cell, shown in Figure B? (A) protein A apical plasma (B) membrane tight junction lateral plasma membrane basal plasma membrane basal lamina (a) (b) (c) (d) a nonfunctional protein glycosylase the deletion of a junctional protein the truncation of a protein found in the extracellular matrix a nonfunctional flippase
51. b
Which of the following statements is NOT true regarding active transport?
A coupled transporter brings two different types of solutes across the membrane, both moving from higher concentration to lower concentration.
membrane domain
A functionally specialized region of a cell membrane, typically characterized by the presence of specific proteins, is called a: carbohydrate layer cell cortex glycocalyx membrane domain retinal corral
An electrochemical gradient has a chemical component and voltage component. Which of the following will have the largest electrochemical gradient?
A positively charged ion present in high concentrations outside the cell
Which is NOT an integral membrane protein?
A protein attached to the membrane by non-covalent interactions with other membrane proteins
Which of the following statements describes a resting membrane potential of a neuron
A state in which the flow of positive and negative ions across the plasma membrane is precisely balanced
In a lipid bilayer, which behaves like a two-dimensional fluid, lipids rapidly diffuse:
A) within the plane of one monolayer in the bilayer.
7. In a lipid bilayer, which behaves like a two-dimensional fluid, lipids rapidly diffuse: A. (A) within the plane of one monolayer in the bilayer. B. (B) back and forth from one monolayer to the other in the bilayer. C. Both A and B D. Neither A nor B
A. (A) within the plane of one monolayer in the bilayer.
B
Although the citric acid cycle itself does not use O2, it requires a functioning electron transport chain (which uses O2) in order to regenerate which molecule for further use in the citric acid cycle? A. NADH B. NAD+ C. H2O D. ATP E. ADP
A positively charged ion, such as Na+, at high concentration outside the cell
An electrochemical gradient has a chemical component and an electrical component. Which of the following will have the largest electrochemical gradient? A negatively charged ion, such as Cl-, at high concentration outside the cell A positively charged ion, such as K+, at high concentration inside the cell A positively charged ion, such as Na+, at high concentration outside the cell
False
An ion channel undergoes conformational changes with each ion it passes.
22. Bacteriorhodopsin is a membrane transport protein that uses sunlight to do what? A. Hydrolyze ATP molecules B. Pump H+ out of the cell and generate a H+ gradient across the plasma membrane C. Pump photons into the cell and generate a deep purple color D. Convert CO2 into sugar during photosynthesis
B. Pump H+ out of the cell and generate a H+ gradient across the plasma membrane
9. Phospholipids with which of the following hydrocarbon tails will produce the most fluid bilayer? A. Tails with 18 carbon atoms, fully saturated B. Tails with 18 carbon atoms and two double bonds C. Tails with 20 carbon atoms, fully saturated D. Tails with 20 carbon atoms and two double bonds
B. Tails with 18 carbon atoms and two double bonds
6. Why do lipids form bilayers in water? A. The hydrophobic head is attracted to water while the hydrophilic tail shuns water. B. The hydrophilic head is attracted to water while the hydrophobic tail shuns water. C. The hydrophobic tail is attracted to water while the hydrophilic head shuns water. D. The hydrophobic head shuns water and the hydrophilic tail attracts water.
B. The hydrophilic head is attracted to water while the hydrophobic tail shuns water.
13. In eukaryotic cells, new phospholipids are manufactured byenzymes bound to which part of the endoplasmic reticulum membrane? A. The monolayer that faces the lumen of the endoplasmic reticulum B. The monolayer that faces the cytosol C. Both monolayers
B. The monolayer that faces the cytosol
10. Margarine is made from vegetable oils in which the hydrocarbon tails have had what treatment? A. Decreasing the number of single bonds (i.e., changing them to double bonds and removing hydrogen atoms) B. The removal of double bonds (i.e., changing them to single bonds and adding hydrogen atoms) C. The addition of carbon atoms D. The removal of carbon atoms
B. The removal of double bonds (i.e., changing them to single bonds and adding hydrogen atoms)
15. When a vesicle fuses with the plasma membrane, the monolayer that was facing the inside of the vesicle will face: A. the cell cytoplasm. B. the outside of the cell.
B. the outside of the cell.
19. In the alpha helices of transmembrane proteins, the hydrophobic side chains are facing: A. the inside of the membrane-spanning helix. B. the outside of the membrane-spanning helix.
B. the outside of the membrane-spanning helix.
Which of the following organisms do not have mitochondria in their cells? A. Plants B. Animals C. Bacteria D. Eukaryotic microorganisms
Bacteria
Pump H+ out of the cell to generate a H+ gradient across the plasma membrane
Bacteriorhodopsin is a membrane transport protein that uses sunlight to do what? Convert CO2 into sugar during photosynthesis in archaea that live in salt marshes Hydrolyze ATP molecules to allow salt-dwelling, anaerobic archaea to produce energy Pump H+ out of the cell to generate a H+ gradient across the plasma membrane Pump photons into the cell to generate a deep purple color
26. What do carbohydrates attached to cell-surface proteins and lipids provide a cell? A. Protection from mechanical and chemical damage B. A slimy coat that prevents cells from sticking to one another C. A distinctive identity in cell-cell recognition D. All of the above
D. All of the above
Which is NOT found in a cell membrane?
DNA
The cell membrane is NOT involved in
DNA replication
In passive transport, a charged solute moves spontaneously in which way?
Down its electrochemical gradient
Which of the following statements is true about the electron transport chain? A. Electrons start out at very high energy and lose energy at each transfer step. B. Electrons start out at very low energy and gain energy at each transfer step. C. Electrons gain and release energy as they move from one complex to another in the electron transport chain.
Electrons start out at very high energy and lose energy at each transfer step.
Which of the following is not a direct source of fuel for mitochondria? A. Glucose B. Pyruvate C. Fatty acids
Glucose
In the electron transport chain, what provides the main reservoir for protons that are pumped across the membrane? A. NADH B. H2O C. Glucose
H2O
What is the ratio of ATP and ADP concentrations in the cytosol of a cell? A. High ATP/ADP ratio B. High ADP/ATP ratio
High ATP/ADP ratio
Channels discriminate between solutes mainly on the basis of size and electric charge; transporters bind their solutes with great specificity in the same way an enzyme binds its substrate.
How do transporters and channels select which solutes they help move across the membrane? Both channels and transporters discriminate between solutes mainly on the basis of size and electric charge. Channels allow the passage of solutes that are electrically charged; transporters facilitate the passage of molecules that are uncharged. Channels discriminate between solutes mainly on the basis of size and electric charge; transporters bind their solutes with great specificity in the same way an enzyme binds its substrate. Channels will allow the passage of any solute as long as it has an electric charge; transporters bind their solutes with great specificity in the same way an enzyme binds its substrate. Transporters discriminate between solutes mainly on the basis of size and electric charge; channels bind their solutes with great specificity in the same way an enzyme binds its substrate.
Cholesterol tends to stiffen the bilayer
How does cholesterol in animal cell membranes affect the bilayer? Cholesterol has little effect on the properties of a lipid bilayer. Cholesterol makes the bilayer more flexible. Cholesterol makes the lipid bilayer more permeable. Cholesterol tends to make the lipid bilayer more fluid. Cholesterol tends to stiffen the bilayer.
B
How much ATP must be invested during the first part of glycolysis for each molecule of glucose broken down? A. 1 B. 2 C. 4
50 atoms
How thick is the plasma membrane? 50 µm 50 atoms 50 meters 50 mn 50nm
False
Human red blood cells contain no internal membranes other than the nuclear membrane. False True
Porin proteins-which form large, water-filled pores in mitochondrial and bacterial membranes-fold into /beta barrel structures. The amino acids that face the outside of the barrel have what kind of side chains?
Hydrophobic
The tails of phospholipids are:
Hydrophobic
within the plane of their own monolayer.
In a lipid bilayer, lipids rapidly diffuse: back and forth from one monolayer to the other in the bilayer. both within the plane of one monolayer and back and forth between the monolayers. in and out of the bilayer None of the above: lipids remain in place within the bilayer within the plane of their own monolayer.
There will be more lipids than proteins.
In a patch of animal cell membrane about 10 µm2 in area, which will be true? Given the fluidity of the lipid bilayer, there is no way to predict the relative numbers of proteins and lipids in any patch of cell membrane. There will be an equal number of proteins and lipids. There will be more carbohydrates than lipids. There will be more lipids than proteins. There will be more proteins than lipids.
50%
In a typical animal cell, approximately how much of the mass of the plasma membrane is constituted by proteins? 2% 25% 50% 75% 98%
The movement of an ion against its electrochemical gradient is called:
active transport
The endoplasmic reticulum
Which organelle is important for controlling the concentration of calcium ions in the cytosol?
The head
Which portion of a membrane phospholipid faces the outside of the membrane? None—phospholipids are confined to the inside of a membrane. The amphipathic portion The fatty acids The head The tail
Phospholipids are amphipathic, whereas detergents are hydrophobic.
Which statement about phospholipids and detergents is NOT true? Detergents are shaped like cones, whereas phospholipids are more cylindrical. Phospholipids are amphipathic, whereas detergents are hydrophobic. Phospholipids form bilayers in water, whereas detergents tend to form micelles. Phospholipids have two hydrocarbon tails, whereas detergents have just one.
Symport
Which term describes a coupled transporter that moves both solutes in the same direction across a membrane?
Transporters
Which type of membrane transport protein can perform either passive or active transport? Both channels and transporters Channels No membrane transport protein can perform both passive and active transport Transporters
Phospholipids
Which types of lipids are most abundant in the plasma membrane? Phospholipids Glycolipids Sterols Triacylglycerides
Because oxygen dissolves readily in lipid bilayers
Why do cells lack membrane transport proteins that are specific for the movement of O2? Because oxygen concentration must be kept low inside cells to avoid creating reactive superoxide radicals that can damage DNA and proteins Because oxygen dissolves readily in lipid bilayers Because oxygen is transported in and out of the cell by special oxygen-binding proteins such as hemoglobin Because oxygen, dissolved in water, can enter cells via aquaporins Because transport of oxygen across cell membranes is energetically unfavorable
The hydrophilic head is attracted to water while the hydrophobic tail shuns water.
Why do phospholipids form bilayers in water? The hydrophilic head is attracted to water while the hydrophobic tail shuns water. The hydrophilic head is insoluble in water. The hydrophobic head is attracted to water while the hydrophilic tail shuns water. The hydrophobic head shuns water and the hydrophilic tail attracts water. The hydrophobic tail is attracted to water while the hydrophilic head shuns water.
As electrons move through the electron transport chain, they are passed from: A. a carrier molecule of lower electron affinity to a carrier molecule of higher electron affinity. B. a carrier molecule of higher electron affinity to a carrier molecule of lower electron affinity. check my answer
a carrier molecule of lower electron affinity to a carrier molecule of higher electron affinity.
Which of the following membrane transport proteins forms tiny hydrophilic pores in the membrane through which solutes can pass by diffusion?
a channel
In the electron transport chain, as electrons move along a series of carriers, they release energy that is used to: A. pump protons across a membrane. B. phosphorylate ADP to form ATP. C. split water into protons and oxygen.
pump protons across a membrane.
The movement of electrons through the electron transport chain: A. consumes ATP. B. produces NADH. C. pumps protons across the inner mitochondrial membrane. D. pumps ATP across the inner mitochondrial membrane.
pumps protons across the inner mitochondrial membrane.
When O2 accepts electrons in the electron transport chain, O2 becomes _______. A. oxidized B. reduced
reduced
During very active periods of photosynthesis, the glyceraldehyde-3-phosphate generated by carbon fixation in the stroma is stored as: A. ATP. B. starch. C. glycogen. D. pyruvate.
starch.
The direction that glucose is transported across the membrane is determined by:
the concentration gradient.
Which type of membrane transport protein can perform either passive or active transport?
transporter
Given enough time, virtually any molecule will diffuse across a lipid
true
Mice that abuse channelrhodopsin and light are ten times more likely to beat their wives.
true
The communication between neurons involves the conversion between electrical and chemical signals.
true
The glucose-Na+ symport in epithelial cells uses the electrochemical gradient of Na+ to draw glucose into the cell.
true