Chapter 3 Flashcards
Cell membranes
Diffusion is best described as the random movement of molecules influenced by:
A: the thermal energy of the environment and the width of the plasma membrane.
B: the width of the plasma membrane of the cell.
C: energy transferred from molecular collisions in the cell.
D: the thermal energy of the environment.
E: the thermal energy of the environment and energy transferred from molecular collisions in the cell.
E: the thermal energy of the environment and energy transferred from molecular collisions in the cell.
Molecules that are ___ and ___ are able to move across the cell membrane via simple diffusion.
A: hydrophobic; small
B: hydrophilic; small
C: hydrophilic; large
D: hydrophobic; large
A: hydrophobic; small
At equilibrium, there will be no net movement of molecules across the cell membrane
A: true
B: false
A: true
simple diffusion of a molecule down its concentration gradient requires an input of energy to the system
A: true
B: false
B: false
which of the answer choices correctly describe the movement of water across a selectively permeable membrane during osmosis?
A: the water will move from low solute concentration to high solute concentration
B: either of these descriptions is correct and equivalent.
C: the water will move from high water concentration to low water concentration
B: either of these descriptions is correct and equivalent.
A container is divided into two compartments by a membrane that is fully permeable to water and small ions. Water is added to one side of the membrane (side A), and a 5% solution of sodium chloride (NaCl) is added to the other (side B).
If allowed to reach equilibrium, which of the answer choices would you predict?
A: the solution level on side B will be higher than on side A.
B: The NaCl concentration on side A and side B will each be 5%
C: The solution level on side A will be higher than on side B
D: The NaCl concentration on side A and side B will be each 2.5%
D: The NaCl concentration on side A and side B will be each 2.5%
A container is divided into two compartments by a membrane that is fully permeable to water but not to larger molecules. Water is added to one side of the membrane (side A), and an equal volume of a 5% solution of glucose is added to the other (side B).
What would you predict will happen?
A: The water level on side B will increase and on side A will decrease.
b: The water level on side A will increase and on side B will decrease.
C: Glucose will diffuse from side A to side B.
D: Glucose will diffuse from side B to side A.
A: The water level on side B will increase and on side A will decrease.
A beaker is divided by a membrane that is permeable to water and glucose, but not to sucrose. Equal volumes of solutions are added to side A and B with the initial concentrations as shown in the diagram. Initially, the liquid levels on both sides are the same.
After the system described reaches equilibrium, what can you predict about the water levels?
A: The water will be higher on side A than on side B.
B: The water will be higher on side B than on side A.
C: The water level will be the same on both sides.
C: The water level will be the same on both sides.
A beaker is divided by a membrane that is permeable to water and glucose, but not to sucrose. Equal volumes of solutions are added to side A and B with the initial concentrations as shown in the diagram. Initially, the liquid levels on both sides are the same.
After the system described reaches equilibrium, what will be the concentration of glucose on side B?
A: 0.5 M
B: 0.75M
C: The answer cannot be determined from the information provided.
D: 1.0M
B: 0.75M
The defining characteristics of active transport are that is category of transport move substances ___ their concentration gradient and requires ___
A: against; energy
B: against; protein transporters
C: against; proton pumps
D: down; protein transporters
E: down; energy
A: against; energy
which of the answer choices be the best analogy for an electrochemical gradient across a cellular membrane?
A: a light bulb
B: an electric generator
C: a water pump
D: a waterfall
E: a battery
E: a battery
The molecules below are examples of ___________________.
A: Fatty acid
B: Monosaccharide
C: Amino acid
C: Amino acid
Which of the following amino acids would you expect to find in the transmembrane domain of an integral membrane protein?
A: C
B: A
C: B
A phospholipid molecule in a membrane can:
A: only flip (rotate between the two halves of the bilayer).
B: flip (rotate between the two halves of the bilayer), spin (rotate around its vertical axis), and move side-to-side (lateral movement)
C: only move side-to-side (lateral movement).
D: both spin (rotate around its vertical axis) and move side-to-side (lateral movement).
E: only spin (rotate around its vertical axis).
D: both spin (rotate around its vertical axis) and move side-to-side (lateral movement).
Which of the following graphs correctly illustrates the effect of temperature on membrane fluidity?
A: C
B: A
C: B
A: C
Under what conditions would a cell increase the amount of unsaturated fatty acid side chains in the phospholipid bilayer of its membranes?
A: Average temperatures are increasing
B: Average temperatures are decreasing
B: Average temperatures are decreasing
Which is TRUE concerning membrane fluidity
A: Increased fatty acid side chain saturation and decreased temperature increase membrane fluidity
B: Increased fatty acid side chain saturation and increased temperature increase membrane fluidity
C: Decreased fatty acid side chain saturation and increased temperature increase membrane fluidity
D: Decreased fatty acid side chain saturation and decreased temperature increase membrane fluidity
C: Decreased fatty acid side chain saturation and increased temperature increase membrane fluidity
In which container is diffusion taking place?
A: Diffusion is occurring in A, B, and C.
B: Diffusion is occurring in A and B, but not in C.
C: Diffusion is occurring in A, but not in B or C
A: Diffusion is occurring in A, B, and C.
In which container is NET diffusion taking place?
A: Net Diffusion is occurring in A and B, but not in C.
B: Net Diffusion is occurring in A, B, and C.
C: Net Diffusion is occurring in A, but not in B or C.
A: Net Diffusion is occurring in A and B, but not in C.
Sweet tea is ___________ compared to unsweetened tea.
A: isotonic
B: hypotonic
C: hypertonic
D: rarely served at barbeque restaurants
C: hypertonic
The beaker in the illustration contains two solutions of salt with different concentrations (measured by molarity, M). The two solutions are separated by a membrane that is permeable to water but not to salt. What will occur in this container
A: diffusion of both water and salt from B to A
B: diffusion of water from A to B but no diffusion of salt
C: diffusion of water from B to A and of salt from A to B
D: diffusion of salt from B to A but not of water
B: diffusion of water from A to B but no diffusion of salt
Which of these prevent free passage of most substances across the biological membrane
Correct answer:
A: The hydrophobic core
B: The cholesterol in the membrane
C: The integral membrane protein
D: The polar head of the membrane phospholipids
E: The triglycerides in the membrane
A: The hydrophobic core
Which molecules can easily diffuse across a cell membrane?
A: large polar molecules
B: small, charged molecules, such as ions
C: proteins
D: gases like O2 and CO2
D: gases like O2 and CO2
Paramecium is a unicellular organism that lives in fresh water. Suppose you are studying two populations of this organism. One population lives in a pond in a cold environment, and the other lives in a pond in a warm environment. If you examined the phospholipid fatty acid tails in cell membranes of both of these populations, what difference would you expect to find?
A: The fatty acid tails from the cold environment would generally be longer but less saturated compared to fatty acids from the warm environment.
B: The fatty acid tails from the warm environment would generally be shorter and more saturated compared to fatty acids from the warm environment.
C: The fatty acid tails from the cold environment would generally be shorter and less saturated compared to fatty acids from the warm environment.
D: The fatty acid tails from the warm environment would generally be shorter and less saturated compared to fatty acids from the warm environment.
C: The fatty acid tails from the cold environment would generally be shorter and less saturated compared to fatty acids from the warm environment.
Considering the amino acids that are found in various domains of transmembrane proteins, which statement would be true?
A: Nonpolar amino acids face towards the side that forms an ion channel and allows the movement of an ion.
B: Polar or charged amino acids would be prevalent in the transmembrane domain, in contact with lipid bilayer
C: Basic amino acids would be prevalent in the intracellular domain, away from the environment outside of the cell.
D: Polar amino acids would be prevalent in the extracellular domain, in contact with the environment outside of the cell.
D: Polar amino acids would be prevalent in the extracellular domain, in contact with the environment outside of the cell.
Molecular Carbondioxide (CO), which is released after the production of ATP by mitochondria, must pass through at least three membranes to get out. How does CO2
A: CO2 undergoes a chemical reaction that binds it to other substances that are transported across the membranes.
B: CO2 requires a facilitator to travel across membranes.
C: CO2 is nonpolar and very small, so it can move by simple diffusion across the membrane.
D: CO2 is hydrophilic and forms carbonic acid which can now cross the membranes.
C: CO2 is nonpolar and very small, so it can move by simple diffusion across the membrane.
What characteristic does the molecule in this figure have that is similar to the structure and function of molecules that make up cell membranes?
A: it is hydrophobic
B: it is amphipathic
C: it is hydrophilic
D: it can self-assemble into a phospholipid bilayer
B: it is amphipathic
Imagine a cell that has a membrane composed mostly of lipids with saturated fatty acid tails, and that this membrane also has low cholesterol content. What are the characteristics of this cell membrane?
A: Due to its low cholesterol content, the cell membrane would lose its fluidity at cold temperatures.
B: The lipids contained in such a membrane would be highly mobile and in nearly constant flux.
C: The lipids would be able to easily transition between the inner and outer layers of the bilayer constituting the cell membrane.
D: The characteristics of this cell membrane would closely mirror those of a membrane composed of only unsaturated fatty acids.
A: Due to its low cholesterol content, the cell membrane would lose its fluidity at cold temperatures.
A single molecule is aways either hydrophobic or hydrophilic can never possess (at the same time) a region that is hydrophobic, and a region is hydrophilic
A: true
B: false
B: false
Predict how phospholipids would arrange if they were placed in a nonpolar solution rather than a polar solution like water.
A: The phospholipids would form a normal bilayer.
B: The phospholipid heads would orient toward the solution, and the tails would cluster away from the solution.
C: The phospholipid tails would orient toward the solution, and the heads would cluster away from the solution.
D: The phospholipid would form a normal liposome.
C: The phospholipid tails would orient toward the solution, and the heads would cluster away from the solution.
Which part of a cholesterol molecule is polar?
A: the hydrocarbon tail
B: the four interconnected planar rings
C: the OH group
D: both the four interconnected planar rings and the hydrocarbon tail
C: the OH group
A phospholipid molecule in a membrane can:
A: only move side-to-side (lateral movement).
B: only spin (rotate around its vertical axis).
C: only flip (rotate between the two halves of the bilayer).
D: both spin (rotate around its vertical axis) and move side-to-side (lateral movement).
E: flip (rotate between the two halves of the bilayer), spin (rotate around its vertical axis), and move side-to-side (lateral movement).
D: both spin (rotate around its vertical axis) and move side-to-side (lateral movement).
The interior region of a phospholipid bilayer is characterized as:
A: hydrophilic
B: hydrophobic
C: hydrophilic and polar
D: polar
B: hydrophobic
Which choice is considered an integral membrane protein?
A: a protein attached to a transmembrane protein via hydrogen bonding
B: a protein with one end in the cytoplasm and the other end in the extracellular space
C: a protein capable of diffusing throughout the cytoplasm of a cell
D: a protein attached to a phospholipid via ionic bonding with the head group of the lipid molecule
B: a protein with one end in the cytoplasm and the other end in the extracellular space
The plasma membrane is composed of a phospholipid bilayer and associated proteins.
what else is commonly found in the plasma membranes of animal cells?
A: cholesterol
B: amino acids
C: nucleic acids
D: ethanol
A: cholesterol
What type of molecule is sometimes found spanning a cell membrane with part of the molecule on one side of the membrane, part embedded in the membrane, and part on the other side?
A: protein
B: RNA
C: phospholipid
D: carbohydrate
A: protein
Which of the following membrane activities requires energy from ATP hydrolysis?
A: movement of sodium ions from a low concentration in a mammalian cell to a high concentration in the extracellular fluid
B: neither the chloride ion concentration gradient nor the electrical gradient of the cell
C: the chloride ion concentration gradient
D: movement of glucose molecules into a bacterial cell from a medium containing a high concentration of glucose to a low concentration inside the cell
A: movement of sodium ions from a low concentration in a mammalian cell to a high concentration in the extracellular fluid
Why is the energy from a molecule of ATP required by the sodium-potassium pump?
A: It provides the energy required to move sodium and potassium ions against their concentration gradients.
B: It helps the sodium and potassium ions bind to the pump binding sites.
C: It provides the energy required to ionize sodium and potassium.
D: It helps prevent other molecules from being transported by the pump.
A: It provides the energy required to move sodium and potassium ions against their concentration gradients.
How is a carrier protein different from a channel protein?
A: Carrier proteins use ATP, but channel proteins do not.
B: Carrier proteins undergo conformational change so that they are open alternately to one side of the membrane or the other.
C: Transport through carrier proteins depends on concentration gradients, but transport through channel proteins does not.
D: Transport through a carrier protein does not depend on the random motion of molecules.
B: Carrier proteins undergo conformational change so that they are open alternately to one side of the membrane or the other.
Which molecules can easily diffuse across a cell membrane?
A: Gases like O2 and CO2
B: Large polar molecules
C: small, charged molecules, such as ions
D: proteins
A: Gases like O2 and CO2
Why does active transport of molecules across a membrane require ATP?
A: An input of energy is needed because the movement of molecules requires the synthesis of additional membrane.
B: An input of energy is needed to move all molecules across a membrane.
C: An input of energy is needed to speed up the rate of facilitated diffusion.
D: An input of energy is needed to speed up the rate of facilitated diffusion.
D: An input of energy is needed to speed up the rate of facilitated diffusion.
Which substance could most easily cross a synthetic membrane composed of phospholipids but not proteins?
A: Sodium ions (NA+)
B: oxygen (O2)
C: water (H2O)
D: glucose (C6H12O6)
B: oxygen (O2)
The cell membranes of some plant cells use transport proteins to move protons out of the cell against their concentration gradient. This is an example of:
A: facilitated diffusion
B: simple diffusion
C: endocytosis
D: active transport
E: passive transport
D: active transport
The protein-assisted movement of a polar molecule across the membrane that does not require ATP or the input of energy occurs through:
A: endocytosis
B: the substances is impermeable to the cell membrane
C: facilitated diffusion
D: simple diffusion
E: active transport
C: facilitated diffusion
Which molecule would most likely require a transport protein to cross the cell membrane of a red blood cell?
A: C6 H12 06
B: O2
C: H20
D: CO2
A: C6 H12 06
The sodium-potassium pump is an example of:
A: an antiporter
B: passive transport
C: none of the other answer options is correct
D: a symporter
E: channel-mediated diffusion
A: an antiporter
The active maintenance of a constant internal environment is referred to as:
A: equilibrium
B: homeostasis
C: stability
B: homeostasis
Some diseases result from defective transport across the membrane. For example, cystic fibrosis results when a chloride ion transporter does not function. What is affected when this transporter does not function?
A: neither the chloride ion concentration gradient nor the electrical gradient of the cell
B: both the chloride ion concentration gradient and the electrical gradient of the cell
C: the chloride ion concentration gradient
D: the electrical gradient of the cell
B: both the chloride ion concentration gradient and the electrical gradient of the cell
Which of these prevent free passage of most substances across a biological
membrane?
A: The hydrophobic core of the lipid bilayer
B: The integral membrane proteins
C: The cholesterol molecules in the membrane
D: The polar head group of the membrane phospholipid
E: The triglycerides in the membrane
A: The hydrophobic core of the lipid bilayer
Considering the amino acids that are found in various domains of transmembrane proteins, which statement would be true?
A: Polar amino acids would be prevalent in the extracellular domain, in contact with the environment outside of the cell.
B: Nonpolar amino acids would be prevalent in the intracellular domain contact with the environment inside of the cell.
C: Polar or charged amino acids would be prevalent in the transmembrane domain, in contact with lipid bilayer
D: Nonpolar amino acids towards the side that forms an ion channel and allows movement of ion.
A: Polar amino acids would be prevalent in the extracellular domain, in contact with the environment outside of the cell.
The lipid component of the cellular membrane include _______
A: Fatty acid and phospholipid
B: Cholesterol and fatty acid
C: Cholesterol and phospholipid
D: Phospholipids
C: Cholesterol and phospholipid
Imagine you are a bacterium. As with any cell, fluidity of plasma membrane is important for you to function. As season changes from summer to fall to winter,
which of the following will you do to maintain the fluidity of your plasma membrane
A: Increase the saturation of the fatty acid chain in the membrane by increasing the number of double bonds
B: Decrease the saturation of the fatty acid chain in the membrane by increasing the number of double bonds
C: Increase the saturation of the fatty acid chain in the membrane by decreasing the number of double bonds
D: Decrease the saturation of the fatty acid chain in the membrane by decreasing the number of double bonds
B: Decrease the saturation of the fatty acid chain in the membrane by increasing the number of double bonds
A peripheral membrane protein penetrates the membrane bilayer
A: True
B: False
B: False
What is the relation of cholesterol to membrane fluidity?
A: Cholesterol decreases the fluidity of the membrane at moderate to high temperature
B: Cholesterol increases the fluidity of the membrane at high temperatures.
C: Cholesterol has no effect on the fluidity of the membrane at normal temperatures
D: Cholesterol is too polar to become part of the phospholipid bilayer.
A: Cholesterol decreases the fluidity of the membrane at moderate to high temperature
Which of the following membrane activities requires energy from ATP
hydrolysis?
A: Facilitated diffusion of chloride ions across the membrane through a chloride channel
B: movement of water into a cell through aquaporins
C: movement of sodium ions from a low concentration in a mammalian cell to a high concentration in the extracellular fluid
D: movement of glucose molecules into a bacterial cell from a medium containing a high concentration of glucose to a low concentration inside the cell
E: movement of carbon dioxide out of a paramecium
C: movement of sodium ions from a low concentration in a mammalian cell to a high concentration in the extracellular fluid
Which of these describes osmosis?
A: Movement of water from a high concentration of solute to low concentration of solute
B: Movement of water from a low concentration of solute to high concentration of solute
C: Movement of water from a hypertonic solution to hypotonic solution
D: Movement of water from a low concentration of water to high concentration of water
B: Movement of water from a low concentration of solute to high concentration of solute
Which molecules can easily diffuse across a cell membrane
A: Nonpolar gases like O2 and CO2
B: Large polar molecules
C: Small charged molecules, such as ions
D: Proteins
A: Nonpolar gases like O2 and CO2
How is a carrier protein different from a channel protein?
A: Carrier proteins use ATP, but channel proteins do not
B: Carrier proteins undergo conformational change so that they are open alternately to one side of the membrane or the other.
C: Transport through carrier proteins depends on concentration gradients, but transport through channel proteins does not.
D: Transport through a carrier protein does not depend on the random motion of molecules.
B: Carrier proteins undergo conformational change so that they are open alternately to one side of the membrane or the other.
Transport of very large molecule into the cell across the plasma membrane is called_____
A: Facilitated diffusion
B: Endocytosis
C: Exocytosis
D: Active transport
B: Endocytosis
Which of the following is an example of passive transport
A: The sodium-potassium pump
B: Phagocytosis
C: Facilitated diffusion
D: Exocytosis
C: Facilitated diffusion
Which of the following characterizes the sodium-potassium pump?
A: Sodium ions are pumped out of a cell against their gradient.
B: Potassium ions are pumped into a cell against their gradient.
C: An integral membrane protein undergoes conformational change.
D: A and B
E: A, B and C
E: A, B and C
What of the following is the driving force for diffusion
A: Concentration gradient
B: Energy from ADP hydrolysis
C: Energy from ATP hydrolysis
A: Concentration gradient
What of the following is the driving force for active transport
A: Concentration gradient
B: Energy from ADP hydrolysis
C: Energy from ATP hydrolysis
C: Energy from ATP hydrolysis
Which of the following membrane activities requires energy from ATP hydrolysis/breakdown?
A: facilitated diffusion of chloride ions across the membrane through a chloride channel
B: movement of water into a cell from high to low concentration through aquaporins
C: movement of sodium ions from a low concentration in a mammalian cell to
a high concentration in the extracellular fluid
D: movement of glucose molecules into a bacterial cell from a medium containing a high concentration of glucose to a low concentration inside the cell
E: diffusion of carbon dioxide out of a paramecium
C: movement of sodium ions from a low concentration in a mammalian cell to
a high concentration in the extracellular fluid
