Mastering Biology Chapter 7, CHAPTER 7: Membranes & Cell Transport, Chapter 7 Practice Quiz, Ch. 7 Membrane Structure and Function
Consider the currently accepted fluid mosaic model of the plasma membrane. Where in the membrane would carbohydrates most likely be found? 1) on the outside (external) surface of the membrane 2) in the interior of the membrane 3) on the inside (cytoplasmic) surface of the membrane 4) on both hydrophilic surfaces of the membrane but not in the hydrophobic interior 5) Carbohydrates are rarely associated with plasma membranes.
1
Which of the following would be least likely to diffuse through a plasma membrane without the help of a transport protein?
A large polar molecule
Which of the following processes and organelle(s) accounts for the replacement of lipids and proteins lost from the plasma membrane?
Exocytosis and smooth and rough ER
Facilitates the cell membrane's property of selective permeability
Proteins embedded in two layers of phospholipids
Phospholipids
form a selectively permeable structure
The sodium-potassium pump __________.
transports sodium ions out of the cell and transports potassium ions into the cell
Imagine two solutions separated by a selectively permeable membrane that allows water to pass, but not sucrose or glucose. The membrane separates a 0.2-molar sucrose solution from a 0.2-molar glucose solution. With time, how will the solutions change? 1) Nothing happens because the two solutions are isotonic to one another. 2) Water enters the sucrose solution because the sucrose molecule is a disaccharide and thus larger than the monosaccharide glucose. 3) Water leaves the sucrose solution because the sucrose molecule is a disaccharide and thus larger than the monosaccharide glucose. 4) The sucrose solution is hypertonic and will gain water because the total mass of sucrose is greater than that of glucose. 5) After the sucrose dissociates to two monosaccharides, water will be osmotically drawn to that side of the membrane.
1
The concentration of solutes in a red blood cell is about 2%, but red blood cells contain almost no sucrose or urea. Sucrose cannot pass through the membrane, but water and urea can. Osmosis would cause red blood cells to shrink the most when immersed in which of the following solutions? 1) a hypertonic sucrose solution 2) a hypotonic sucrose solution 3) a hypertonic urea solution 4) a hypotonic urea solution 5) pure water
1
Which of the following factors would tend to increase membrane fluidity? 1) a greater proportion of unsaturated phospholipids 2) a greater proportion of saturated phospholipids 3) a lower temperature 4) a relatively high protein content in the membrane 5) a greater proportion of relatively large glycolipids compared with lipids having smaller molecular masses
1
Which of the following would be least likely to diffuse through a plasma membrane without the help of a transport protein? 1) a large polar molecule 2) a large nonpolar molecule 3) dissolved gases such as oxygen or carbon dioxide 4) a small nonpolar molecule 5) Any of the above would easily diffuse through the membrane.
1
Which one of the following cell structures exhibits selective permeability between a cell and its external environment? 1) the plasma membrane 2) mitochondria 3) chloroplasts 4) endoplasmic reticulum 5) lysosomes
1
Which one of the following molecules is most likely to diffuse freely across the lipid bilayer of the plasma membrane without the involvement of a transport protein? 1) carbon dioxide 2) glucose 3) sodium ion 4) DNA 5) hemoglobin
1
Active transport by the sodium-potassium pump follows this cycle:
1. Three Na+ ions from the cytosol bind to the pump. 2. The binding of Na+ stimulates the phosphorylation of the pump protein by ATP. 3. Phosphorylation causes a conformational change in the pump that moves the three Na+ ions against their concentration gradient and releases them outside the cell. 4. The release of the Na+ ions permits two K+ ions from outside the cell to bind to the pump, and the phosphate group is released. 5. Release of the phosphate group causes another conformational change in the pump. 6. The conformational change in the pump moves the two K+ ions against their concentration gradient and releases them into the cytosol.
1. A phospholipid has a "head" made up of a glycerol molecule attached to a single _____ which is attached to another small molecule. 2. Phospholipids vary in the small molecules attached to the phosphate group. The phospholipid shown in the figure has a _____ attached to phosphate. 3. Because the phosphate group and its attachments are either charged or polar, the phospholipid head is _____, which means it has an affinity for water. 4. A phospholipid also has two "tails" made up of two _____ molecules, which consist of a carboxyl group with a long hydrocarbon chain attached. 5. Because the C-H bonds in the fatty acid tails are relatively nonpolar, the phospholipid tails are _____, which means they are excluded from water.
1. phosphate group 2. choline group 3. hydrophilic 4. fatty acid 5. hydrophobic
The internal solute concentration of a plant cell is about 0.8M. To demonstrate plasmolysis, it would be necessary to suspend the cell in what solution?
1.0M
Based on Figure 7.19, which of these experimental treatments would increase the rate of sucrose transport into the cell? 1) decreasing extracellular sucrose concentration 2) decreasing extracellular pH 3) decreasing cytoplasmic pH 4) adding an inhibitor that blocks the regeneration of ATP 5) adding a substance that makes the membrane more permeable to hydrogen ions
2
Consider the currently accepted fluid mosaic model of the plasma membrane. Where in the plasma membrane would cholesterol most likely be found? 1) on the outside (external) surface of the membrane 2) in the interior of the membrane 3) on the inside (cytoplasmic) surface 4) in the interior and on the inside surface, but not on the outside surface 5) on either surface of the membrane, but not in the interior of the membrane
2
If a red blood cell and a plant cell were placed in seawater, what would happen to the two types of cells? 1) The red blood cell would burst, and the plant cell would shrink. 2) Both cells would lose water; the red blood cell would shrivel, and the plant plasma membrane would pull away from the cell wall. 3) Seawater is isotonic to both cells. There will be no change in water content of the cells. 4) Both cells would gain water by osmosis; the red blood cell would burst, and the plant cell would increase in turgor pressure. 5) The red blood cell would shrink, and the plant cell would gain water.
2
In what way do the membranes of a eukaryotic cell vary? 1) Phospholipids are found only in certain membranes. 2) Certain proteins are unique to each membrane. 3) Only certain membranes of the cell are selectively permeable. 4) Only certain membranes are constructed from amphipathic molecules. 5) Some membranes have hydrophobic surfaces exposed to the cytoplasm, while others have hydrophilic surfaces facing the cytoplasm.
2
Which of the following correctly describes a general property of all electrogenic pumps? 1) pumps sodium out of the cell and potassium into the cell 2) creates a voltage difference across the membrane 3) can pump a large variety of solutes across a membrane against their concentration gradient 4) a cell with an interior that is positively charged relative to the outside of the cell 5) a cell with a high internal concentration of protons
2
Which of the following structures is most consistent with the selective permeability property of biological membranes? 1) proteins sandwiched between two layers of phospholipid 2) proteins embedded in two layers of phospholipid 3) a layer of protein coating a layer of phospholipid 4) phospholipids sandwiched between two layers of protein 5) a phospholipid bilayer with proteins scattered on the surfaces of the membranes
2
A single plant cell is placed in an isotonic solution. Salt is then added to the solution. Which of the following would occur as a result of the salt addition? 1) The added salt would enter the cell, causing the cell to take up water and swell. 2) Water would enter the cell by osmosis, and the cell would swell. 3) Water would leave the cell by osmosis, causing the volume of the cytoplasm to decrease. 4) There would be no osmotic movement of water in response to the added salt. 5) The added salt makes the solution hypotonic compared to the cell. Water will enter the cell by osmosis.
3
According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly 1) spread in a continuous layer over the inner and outer surfaces of the membrane. 2) confined to the hydrophobic core of the membrane. 3) embedded in a lipid bilayer. 4) randomly oriented in the membrane, with no fixed inside-outside polarity. 5) free to depart from the fluid membrane and dissolve in the surrounding solution.
3
Cells A and B are the same size, shape, and temperature, but cell A is metabolically quiet and cell B is actively consuming oxygen. Oxygen will diffuse more quickly into cell _____ because _____. 1) A; the diffusion gradient there is shallower 2) A; its membrane transport proteins will not be saturated 3) B; the diffusion gradient in cell B is steeper 4) B; the oxygen molecules inside cell B have a higher kinetic energy 5) B; the gradient of oxygen is oriented in the opposite direction compared to cell A
3
Consider the transport of protons and sucrose into a plant cell by the sucrose-proton cotransport protein. Plant cells continuously produce a proton gradient by using the energy of ATP hydrolysis to pump protons out of the cell. Why, in the absence of sucrose, don't protons move back into the cell through the sucrose-proton cotransport protein? 1) Protons cannot move through membrane transport proteins. 2) Protons are freely permeable through the phospholipid bilayer, so no transport protein is needed for protons. 3) The movement of protons through the cotransport protein cannot occur unless sucrose also moves at the same time. 4) In the absence of sucrose, the ATP-powered proton pump does not function, so there is no proton gradient. 5) Protons, unlike other substances, do not diffuse down their concentration gradient.
3
Glucose is a six-carbon sugar that diffuses slowly through artificial membranes. The cells lining the small intestine, however, rapidly move glucose from the gut into their cytoplasm. This occurs whether the gut concentrations of glucose are higher or lower than the glucose concentrations in intestinal cell cytoplasm. Using this information, which transport mechanism is most likely responsible for the glucose transport in intestinal cells? 1) simple diffusion 2) phagocytosis 3) active transport 4) exocytosis 5) facilitated diffusion
3
Which of the following statements about cotransport of solutes across a membrane is correct? 1) Cotransport involves the hydrolysis of ATP by the transporting protein. 2) A cotransport protein is most commonly an ion channel. 3) Cotransport proteins allow a single ATP-powered pump to drive the active transport of many different solutes. 4) The sodium-potassium pump is an example of a cotransport protein. 5) In cotransport, both solutes that are being transported are moving down their chemical gradients.
3
Which of the following types of information is (are) most likely to be derived from freeze-fracture of biological samples? 1) the coded information in DNA 2) thin sections (slices) of fixed and embedded cells 3) proteins embedded in membrane bilayers 4) patterns of movement in living cells 5) all of the above
3
Which one of the following pairs correctly matches a membrane transport process to its primary function? 1) phagocytosis; secretion of large particles from the cell by fusion of vesicles with the plasma membrane 2) exocytosis; the movement of water and solutes out of the cell by vesicle fusion with the plasma membrane 3) pinocytosis; the uptake of water and small solutes into the cell by formation of vesicles at the plasma membrane. 4) osmosis; passive diffusion of water and small solutes across a membrane 5) none of the above
3
Which one of the following statements about diffusion is true? 1) It is very rapid over long distances. 2) It requires expenditure of energy by the cell. 3) It is a passive process. 4) It occurs when molecules move from a region of lower concentration to a region of higher concentration. 5) It always requires integral proteins of the cell membrane.
3
Which one of the following statements about the sodium-potassium pump is correct? 1) The sodium-potassium pump transports Na+ and K+ ions across the plasma membrane in the same direction at the expense of ATP hydrolysis. 2) The sodium-potassium pump creates a hydrogen gradient. 3) The sodium-potassium pump is electrogenic. 4) The sodium-potassium pump causes a pH gradient across the plasma membrane. 5) The sodium-potassium pump creates concentration gradients of O+ and Cl- across the plasma membrane.
3
The internal solute concentration of a plant cell is about 0.8 M. To demonstrate plasmolysis, it would be necessary to suspend the cell in what solution? 1) distilled water 2) 0.4 M 3) 0.8 M 4) 1.0 M 5) none of the above
4
The plasma membrane is referred to as a "fluid mosaic" structure. Which of the following statements about that model is true? 1) The fluid component of the membrane is composed of phospholipids, and the mosaic part is composed of carbohydrates. 2) The fluid aspect of the membrane describes its structure at normal temperatures, and the mosaic aspect describes the membrane as the temperature is lowered. 3) The mosaic comprises the carbohydrate chains on the inner surface of the membrane. 4) The fluid component of the membrane is phospholipid, and the mosaic is protein. 5) Only phospholipids are capable of moving in the membrane.
4
Which of the following enables a cell to pick up and concentrate a specific kind of molecule? 1) passive transport 2) facilitated diffusion 3) osmosis 4) receptor-mediated endocytosis 5) channel proteins
4
Which of the following processes includes all others? 1) osmosis 2) diffusion of a solute across a membrane 3) facilitated diffusion 4) passive transport 5) transport of an ion down its electrochemical gradient
4
Which of the following processes, normally associated with membrane transport, must occur to account for an increase in the surface area of a cell? 1) endocytosis 2) active transport 3) receptor-mediated endocytosis 4) exocytosis 5) flip-flop of phospholipids from one side of the plasma membrane to the other
4
Which of the following statements about the role of phospholipids in forming membranes is correct? 1) Phospholipids are completely insoluble in water. 2) Phospholipids form a single sheet in water. 3) Phospholipids form a structure in which the hydrophobic portion faces outward. 4) Phospholipids form a selectively permeable structure. 5) They are triacylglycerols, which are commonly available in foods.
4
Which of these statements describes some aspect of facilitated diffusion? 1) Facilitated diffusion is another name for osmosis. 2) Facilitated diffusion of solutes occurs through phospholipid pores in the membrane. 3) Facilitated diffusion requires energy to drive a concentration gradient. 4) Facilitated diffusion of solutes may occur through protein pores in the membrane. 5) There is only one kind of protein pore for facilitated diffusion.
4
Which one of the following statement concerning carbohydrates associated with the plasma membrane is correct? 1) Carbohydrates are only found associated with the membranes of prokaryotic cells. 2) The carbohydrate composition of most eukaryotic plasma membranes is quite similar. 3) Carbohydrates on the plasma membrane are typically short chains of 2-5 monosaccharides. 4) Membrane carbohydrates function primarily in cell-cell recognition. 5) Carbohydrates associated with the plasma membrane are located on both surfaces of the membrane.
4
A cell has a membrane potential of -100 mV (more negative inside than outside) and has 1,000 times more calcium ions outside the cell than inside. Which of the following best describes a mechanism by which Ca2+ enters the cell? 1) movement of Ca2+ into the cell through an ion channel down its concentration gradient 2) passive diffusion of Ca2+ into the cell down its electrochemical gradient 3) cotransport of Ca2+ into the cell with Cl- ions 4) movement of Ca2+ into the cell through a carrier protein down its electrical gradient 5) facilitated diffusion of Ca2+ into the cell down its electrochemical gradient
5
A nursing infant is able to obtain disease-fighting antibodies, which are large protein molecules, from its mother's milk. These molecules probably enter the cells lining the baby's digestive tract via which process? 1) osmosis 2) passive transport 3) exocytosis 4) active transport 5) endocytosis
5
Active transport requires a cell to expend energy. Which of the following statements is true? 1) Active transport often involves an ATP-powered ion pump and a cotransport protein. 2) Active transport usually uses ATP as its energy source. 3) Active transport moves solutes against the concentration gradient. 4) Active transport requires a protein carrier. 5) all of the above
5
Green olives may be preserved in brine, which is a 30% salt solution. How does this method of preservation prevent contamination by microorganisms? 1) Bacterial cells shrivel up in high salt solutions, causing the cell to burst. 2) High salt concentration lowers the pH, thus inhibiting bacterial metabolism. 3) High salt concentration raises the pH, thus inhibiting bacterial metabolism. 4) A 30% salt solution is hypotonic to the bacteria, so they gain too much water and burst. 5) A 30% salt solution is hypertonic to the bacteria, so they lose too much water and cannot survive.
5
The transmission of nerve impulses between adjacent nerve cells requires the release of a neurotransmitter (a molecule or small peptide) by exocytosis. Which of the following would best reverse the process that resulted in the release of neurotransmitter, returning the cell to its original state? 1) endocytosis 2) pinocytosis 3) active transport of the neurotransmitter back into the cell 4) passive transport (by facilitated diffusion) of the neurotransmitter back into the cell 5) receptor-mediated endocytosis
5
Which of the following functional processes result(s) from the presence of proteins in or on the plasma membrane? 1) enzymatic activity 2) cell-cell recognition 3) intercellular joining 4) cell-cell communication 5) all of the above
5
Which of the following is (are) true about facilitated diffusion? 1) Facilitated diffusion requires a concentration gradient. 2) Facilitated diffusion requires a membrane. 3) Facilitated diffusion involves proteins. 4) Facilitated diffusion does not involve an outside energy source. 5) all of the above
5
Which of the following is a correct difference between active transport and facilitated diffusion? 1) Active transport involves transport proteins, and facilitated diffusion does not. 2) Facilitated diffusion can move solutes against a concentration gradient, and active transport cannot. 3) Active transport can move solutes in either direction across a membrane, but facilitated diffusion can only move in one direction. 4) Facilitated diffusion involves transport proteins, and active transport does not. 5) Active transport requires energy from ATP, and facilitated diffusion does not.
5
Which of the following is/are a function of membrane proteins? 1) Membrane proteins attach the membrane to the cytoskeleton. 2) Membrane proteins provide receptors for chemical messengers. 3) Membrane proteins form channels, which move substances across the membrane. 4) Membrane proteins with short sugar chains form identification tags that are recognized by other cells. 5) all of the above
5
Which of the following statements about passive transport is correct? 1) Passive transport operates independently of diffusion. 2) Passive transport operates independently of the concentrations of the substance being transported. 3) In passive transport, all movement of the transported molecule stops when its concentration is the same on both sides of the membrane. 4) Passive transport does not occur in the human body. 5) Passive transport permits the transported molecule to move in either direction, but the majority of transport occurs down the concentration gradient of the molecule.
5
Which statement(s) about the sidedness of the plasma membrane is (are) correct? 1) Parts of proteins that are exposed on the cytoplasmic side of the endoplasmic reticulum are also exposed on the cytoplasmic side of the plasma membrane. 2) The asymmetrical distribution of membrane proteins, lipids, and carbohydrates across the plasma membrane is determined as the membrane is being constructed. 3) Every integral membrane protein has a specific orientation in the plasma membrane. 4) The two lipid layers may differ in specific lipid composition. 5) all of the above
5
Which of the following plant cells would exhibit the most turgor pressure?
A cell placed in a hypotonic solution
Which of the following plant cells would exhibit the most turgor pressure? A cell placed in a hypotonic solution A cell placed in an isotonic solution A cell placed in a hypertonic solution None of the listed responses is correct. All of the listed responses are correct.
A cell placed in a hypotonic solution
Which of the following would be least likely to diffuse through a plasma membrane without the help of a transport protein? A large polar molecule A large nonpolar molecule Dissolved gases such as oxygen or carbon dioxide A small nonpolar molecule Any of the above would easily diffuse through the membrane.
A large polar molecule
Which of the following substances would be most likely to pass through the plasma membrane without the help of a transport protein?
A nonpolar molecule, such as a hydrocarbon
Which of the following substances would be most likely to pass through the plasma membrane without the help of a transport protein? A large polar molecule A large nonpolar molecule Dissolved gases such as oxygen or carbon dioxide A small nonpolar molecule A nonpolar molecule, such as a hydrocarbon
A nonpolar molecule, such as a hydrocarbon
fatty acid
A phospholipid also has two "tails" made up of two ______________ molecules, which consist of a carboxyl group with a long hydrocarbon chain attached.
phosphate group
A phospholipid has a "head" made up of a glycerol molecule attached to a single ______________ , which is attached to another small molecule.
Which of the following statements is most likely true of a protein that cotransports glucose and sodium ions into the intestinal cells of an animal?
A substance that blocks sodium ions from binding to the cotransport protein will also block the transport of glucose.
phagocytosis
A white blood cell engulfing a bacterium is an example of _____.
embedded in a lipid bilayer
According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly
What is the difference between active transport and facilitated diffusion?
Active transport requires energy from ATP, and facilitated diffusion does not.
Which of the following is a correct difference between active transport and facilitated diffusion?
Active transport requires energy from ATP, and facilitated diffusion does not.
What property of dishwashing liquid (detergent) makes it useful to wash grease from pans?
Amphipathic nature
How does cholesterol affect membrane fluidity?
At body temperature, it makes the membrane less fluid
How does cholesterol affect membrane fluidity?
At body temperature, it makes the membrane less fluid.
Cells A and B are the same size, shape, and temperature, but cell A is metabolically less active than cell B; cell B is actively converting oxygen to water in cellular respiration. Oxygen will diffuse more rapidly into cell __________ because __________.
B; the diffusion gradient in cell B is steeper
Why is energy required for active transport?
Because it moves solutes against their concentration gradient
hydrophobic
Because the C-H bonds in the fatty acid tails are relatively nonpolar, the phospholipid tails are ______________ , which means they are excluded from water.
hydrophilic
Because the phosphate group and its attachments are either charged or polar, the phospholipid head is ______________ , which means it has an affinity for water.
- The diverse proteins found in and attached to membranes perform many important functions - Because membranes are fluid, membrane proteins and phospholipids can drift about in the membrane - The framework of a membrane is a bilayer of phospholipids with their hydrophilic heads facing the aqueous environment inside and outside of the cell and their hydrophobic tails clustered in the center
Biologists use the fluid mosaic model to describe membrane structure. - The diverse proteins found in and attached to membranes perform many important functions - The kinky tails of some proteins help keep the membrane fluid by preventing the component molecules from packing solidly together - Because membranes are fluid, membrane proteins and phospholipids can drift about in the membrane - The framework of a membrane is a bilayer of phospholipids with their hydrophilic heads facing the aqueous environment inside and outside of the cell and their hydrophobic tails clustered in the center - Membranes include a mosaic, or mix, of carbohydrates embedded in a phospholipid bilayer
If a red blood cell and a plant cell were placed in seawater, what would happen to the two types of cells?
Both cells would lose water; the red blood cell would shrivel, and the plant plasma membrane would pull away from the cell wall.
Which of the following molecules is most likely to passively diffuse across the plasma membrane?
Carbon dioxide
Which of the following molecules is most likely to passively diffuse across the plasma membrane? Carbon dioxide Glucose Sodium ion DNA Hemoglobin
Carbon dioxide
What function do carbohydrates fulfill in the plasma membrane?
Cell-to-cell recognition
A nursing infant is able to obtain disease-fighting antibodies, which are large protein molecules, from its mother's milk. These molecules probably enter the cells lining the baby's digestive tract via which process?
Endocytosis
into...membranous vesicles
Endocytosis moves materials _____ a cell via _____.
Which process and organelle accounts for the replacement of lipids and proteins lost from the plasma membrane?
Exocytosis and smooth and rough ER
Sort the phrases into the appropriate bins depending on whether they describe exocytosis, endocytosis, or both.
Exocytosis: requires fusion of vesicles with the plasma membrane, increases the surface area of the plasma membrane, secretes large molecules out of the cell Endocytosis: decreases the surface area of the plasma membrane, forms vesicles from inward folding of the plasma membrane Both: requires cellular energy, transported substances never physically cross the plasma membrane
Which of these statements describes some aspect of facilitated diffusion?
Facilitated diffusion of solutes may occur through channel or transport proteins in the membrane.
Which of these statements describes some aspect of facilitated diffusion? Facilitated diffusion of solutes may occur through channel or transport proteins in the membrane. Facilitated diffusion is another name for osmosis. Facilitated diffusion of solutes occurs through phospholipid pores in the membrane. Facilitated diffusion requires energy to drive a concentration gradient. There is only one kind of protein pore for facilitated diffusion.
Facilitated diffusion of solutes may occur through channel or transport proteins in the membrane.
lipids are mostly nonpolar
How can a lipid be distinguished from a sugar?
If a red blood cell is placed in a salt solution and bursts, what is the tonicity of the solution relative to the interior of the cell?
Hypotonic
hypotonic
If a red blood cell is placed in a salt solution and bursts, what is the tonicity of the solution relative to the interior of the cell?
Endocytosis
Is this true for exocytosis, endocytosis, or both? - decreases the surface area of the plasma membrane
Endocytosis
Is this true for exocytosis, endocytosis, or both? - forms vesicles from inward folding of the plasma membrane
Exocytosis
Is this true for exocytosis, endocytosis, or both? - increases the surface area of the plasma membrane
Both
Is this true for exocytosis, endocytosis, or both? - requires cellular energy
Exocytosis
Is this true for exocytosis, endocytosis, or both? - requires fusion of vesicles with the plasma membrane
Exocytosis
Is this true for exocytosis, endocytosis, or both? - secretes large molecules out of the cell
Both
Is this true for exocytosis, endocytosis, or both? - transported substances never physically cross the plasma membrane
only channels
Is this true for only channels, only carriers, or both? - allow water molecules and small ions to flow quickly across the membrane
both
Is this true for only channels, only carriers, or both? - are integral membrane proteins
only channels
Is this true for only channels, only carriers, or both? - provide a continuous path across the membrane
both
Is this true for only channels, only carriers, or both? - provide a hydrophilic path across the membrane
only carriers
Is this true for only channels, only carriers, or both? - transport primarily small polar organic molecules
both
Is this true for only channels, only carriers, or both? - transport solutes down a concentration or electrochemical gradient
only carriers
Is this true for only channels, only carriers, or both? - undergo a change in shape to transport solutes across the membrane
Which of the following statements about diffusion is true?
It is a passive process.
How can a lipid be distinguished from a sugar?
Lipids are mostly nonpolar.
Which of the following statements concerning carbohydrates associated with the plasma membrane is correct?
Membrane carbohydrates function primarily in cell-cell recognition.
A critical feature of the plasma membrane is that it is selectively permeable. This allows the plasma membrane to regulate transport across cellular boundaries--a function essential to any cell's existence. How does phospholipid structure prevent certain molecules from crossing the plasma membrane freely?
Nonpolar Molecules (ex. hydrocarbons, O2, CO2): Hydrophobic, Can Cross Easily, No Transport Protein Required Polar Molecules (ex. water, sugars): Hydrophilic, Have difficulty crossing the hydrophobic part, Transport protein required to pass efficiently Ions (ex. Na+, K+, Ca2+, Cl-): Hydrophilic, Have difficulty crossing the hydrophobic part, Transport protein required to pass efficiently
Sort the phrases into the appropriate bins depending on whether they are true only for channels, true only for carrier proteins, or true for both channels and carriers.
Only Channels: provide a continuous path across the membrane, allow water molecules and small ions to flow quickly across the membrane Only Carriers: undergo a change in shape to transport solutes across the membrane, transport primarily small polar organic molecules Both: provide a hydrophilic path across the membrane, transport solutes down a concentration or electrochemical gradient, are integral membrane proteins
Which of the following particles could diffuse easily through a cell membrane?
Oxygen (O2)
Which of the following statements about passive transport is correct?
Passive transport permits the solute to move in either direction, but the net movement of the population of solute molecules occurs down the concentration gradient of the molecule.
Which molecule is most abundant in the plasma membrane?
Phospholipids
Which of the following molecules are most abundant in the plasma membrane?
Phospholipids
Which of the following statements about the role of phospholipids in the structure and function of biological membranes is correct?
Phospholipids form a selectively permeable structure.
choline group
Phospholipids vary in the small molecules attached to the phosphate group. The phospholipid shown in the figure has a ____________ attached to phosphate.
Which cell structure exhibits selective permeability between a cell and its external environment?
Plasma membrane
Which of the following cell structures exhibits selective permeability between a cell and its external environment?
Plasma membrane
Which of the following structural arrangements of the components in biological membranes facilitates the cell membrane's property of selective permeability?
Proteins embedded in two layers of phospholipids
How does the "fluid mosaic model" describe the structure of the plasma membrane?
Proteins in the membrane contribute to the mosaic quality of the membrane while the lateral and rotational movements of phospholipids contribute to its fluidity.
Proton pumps are used in various ways by members of every domain of organisms: Bacteria, Archaea, and Eukarya. What does this fact most probably mean?
Proton gradients across a membrane were used by cells that were the common ancestor of all three domains of life.
Red blood cells contain approximately a 2% concentration of solutes. A red blood cell is placed into a solution that contains a 4% concentration of solutes to which the cell is not permeable. What will happen to the red blood cell?
The cell will decrease in size as water flows out of it.
Which of the following statements correctly describe(s) the driving forces for diffusion of Na+ and K+ ions through their respective channels?
The diffusion of Na+ ions into the cell is facilitated by the Na+ concentration gradient across the plasma membrane. The diffusion of K+ ions out of the cell is impeded by the electrical gradient across the plasma membrane. The electrochemical gradient is larger for Na+ than for K+.
Which of the following factors does not affect membrane permeability?
The polarity of membrane phospholipids
A cell is placed into a solution and the cell shrinks.
The solution is hypertonic.
A cell is placed into a solution and the cell shrinks. Which of the following is true regarding the solution?
The solution is hypertonic.
The solutions in the two arms of this U-tube are separated by a membrane that is permeable to water and glucose but not to sucrose. Side A is half-filled with a solution of 2 M sucrose and 1 M glucose. Side B is half-filled with 1 M sucrose and 2 M glucose. Initially, the liquid levels on both sides are equal. Which of the following will be true when the system reaches equilibrium?
The water level will be higher in side A than in side B.
Which of the following is correct regarding peripheral proteins?
These proteins are found only on the surface of the plasma membrane.
Which of the following is correct regarding peripheral proteins? These proteins are found only on the surface of the plasma membrane. They span the entire phospholipid bilayer. They exhibit only hydrophobic properties. They have no specific function in the plasma membrane. These proteins exhibit both hydrophilic and hydrophobic properties.
These proteins are found only on the surface of the plasma membrane.
Which of the following is correct regarding integral proteins?
These proteins exhibit both hydrophilic and hydrophobic properties.
Which of the following is correct regarding integral proteins? These proteins exhibit both hydrophilic and hydrophobic properties. These proteins are found only on the surface of the plasma membrane. They exhibit only hydrophilic properties. They exhibit only hydrophobic properties. They have no specific function in the plasma membrane.
These proteins exhibit both hydrophilic and hydrophobic properties.
In facilitated diffusion, what is the role of the transport protein?
Transport proteins provide a hydrophilic route for the solute to cross the membrane.
True or false? The water-soluble portion of a phospholipid is the polar head, which generally consists of a glycerol molecule linked to a phosphate group.
True
True or false? Osmosis is a type of diffusion.
True (Osmosis is the diffusion of water across a selectively permeable membrane.)
True
True or false? Osmosis is a type of diffusion.
True
True or false? The water-soluble portion of a phospholipid is the polar head, which generally consists of a glycerol molecule linked to a phosphate group.
What happens when two solutions separated by a selectively permeable membrane reach osmotic equilibrium?
Water molecules move between the two solutions, but there is no net movement of water across the membrane.
Phospholipids
What can be identified by its head and two tails?
polarity of membrane phospholipids
What factor does not affect membrane permeability?
Cholesterol
What has the function of stabilizing the phospholipids?
Glycoprotein
What is composed of a carbohydrate and a protein?
osmosis
What name is given to the process by which water crosses a selectively permeable membrane?
amphipathic nature
What property of dishwashing liquid (detergent) makes it useful to wash grease from pans?
Which of the following molecular movements is due to diffusion or osmosis?
When a plant cell is placed in concentrated salt water, water moves out of the cell.
greater proportion of unsaturated phospolipids
Which of the following factors would tend to increase membrane fluidity? - a greater proportion of unsaturated phospholipids - a greater proportion of relatively large glycolipids compared with lipids having smaller molecular masses - a greater proportion of saturated phospholipids - a relatively high protein content in the membrane - a lower temperature
covalent interactions between the phospholipid and protein components of the membrane
Which of the following is least likely to be important in holding the components of a biological membrane together? - covalent interactions between the phospholipid and protein components of the membrane - polar interactions among the phospholipid head groups on the same surface of the membrane - hydrophobic interactions among the fatty acid tails of phospholipids on the same side of the membrane - hydrophobic interactions among the fatty acid tails of phospholipids on opposite sides of the membrane - hydrophobic interactions between the phospholipid tails and the surface of integral membrane proteins buried in the membrane
When a plant cell is placed in concentrated salt water, water moves out of the cell
Which of the following molecular movements is due to diffusion or osmosis? - Cells of the pancreas secrete insulin into the bloodstream - When a plant cell is placed in concentrated salt water, water moves out of the cell - The sodium-potassium pump pumps three sodium ions out of a neuron for every two potassium ions it pumps in
- lipids - oxygen - carbon dioxide - water
Which of the following molecules can cross the lipid bilayer of a membrane directly, without a transport protein or other mechanism? Select all that apply. - lipids - oxygen - ions - proteins - sucrose - carbon dioxide - water
oxygen (O2)
Which of the following particles could diffuse easily through a cell membrane? - oxygen (O2) - sodium ion (Na+) - glucose - hydrogen ion (H+)
passive transport
Which of the following processes includes all others? - transport of an ion down its electrochemical gradient - osmosis - facilitated diffusion - passive transport - diffusion of a solute across a membrane
the similarity of the drug molecule to other molecules that are transported into the target cells
Which of the following would be a factor that determines whether the molecule selectively enters the target cells? - the similarity of the drug molecule to other molecules that are transported into the target cells - the nonpolar, hydrophobic nature of the drug molecule - the concentration of the drug molecule that is transported in the blood - the phospholipid composition of the target cells' plasma membrane
- water - glucose - ions
Which of these can not rapidly pass directly through the phospholipids of the plasma membrane? - lipid solute molecules - water - glucose - ions
Transport Proteins
Which proteins allows solute molecules to enter the cell?
The force driving simple diffusion is ________, while the energy source for active transport is ________.
a concentration gradient; ATP hydrolysis
In facilitated diffusion, __________ proteins provide openings in the plasma membrane for substances to flow through without changing structure, and __________ proteins allow passage of substances through the plasma membrane after undergoing a subtle change in shape.
channel; carrier
The phosphate transport system in bacteria imports phosphate into the cell even when the concentration of phosphate outside the cell is much lower than the cytoplasmic phosphate concentration. Phosphate import depends on a pH gradient across the membranemore acidic outside the cell than inside the cell. In this bacterial cell, phosphate transport is an example of ________.
cotransport
Membrane carbohydrates
function primarily in cell-cell recognition
diffusion
is a passive process
All cells have voltages across their membranes. This voltage is called a(n) __________ and is often maintained by __________.
membrane potential; electrogenic pumps
Facilitated diffusion is a type of _______.
passive transport
Which of the following processes includes all others? facilitated diffusion osmosis passive transport transport of an ion down its electrochemical gradient diffusion of a solute across a membrane
passive transport
Passive transport
permits the solute to move in either direction, but the net movement of the population of solute molecules occurs down the concentration gradient of the molecule.
The plasma membrane exhibits selective permeability. This means that __________.
the plasma membrane allows some substances to flow through it more easily than others
Which of the following molecules can cross the lipid bilayer of a membrane directly, without a transport protein or other mechanism?
water, oxygen, lipids, carbon dioxide