Deck 5: Organizing Principles: Lipids, Membranes, and Cell Compartments

Question 1

Purified phospholipids gather together and form membranes only if the appropriate enzyme is present.

Answer 1

False

Question 2

Explain how the basic structure of a phospholipid bilayer is maintained in an aqueous solution, and identify a change you can make that would permanently disrupt the bilayer.

Answer 2

The structure of a phospholipid bilayer is maintained because the hydrophobic fatty acid side chains of the phospholipids are forced together when the hydrophilic polar head groups associate with the water molecules in the aqueous solution.

Question 3

Many environmental factors influence the structure of biological membranes. Which one of the following could permanently disrupt phospholipid bilayers in an aqueous solution?

A)the addition of acid to change the pH
B)physical agitation of the solution
C)slight elevation of the temperature

Answer 3

A

Question 4

The lipid components of cellular membranes often include:

A)phospholipids.
B)phospholipids and fatty acids.
C)fatty acids and cholesterol.
D)phospholipids and cholesterol.

Question 5

Which one of the following is considered an integral membrane protein?

A)a protein with its N-terminus in the cytoplasm and its C-terminus in the extracellular space
B)a protein attached to a transmembrane protein via hydrogen bonding
C)a protein attached to a phospholipid via ionic bonding with the head group of the lipid molecule
D)a protein capable of diffusing throughout the cytoplasm of a cell

Question 6

Freeze fracture is a technique used to visualize membrane proteins. In this technique, cells are rapidly frozen and then split, separating the lipid bilayer into its two component layers. Transmembrane proteins stay associated with one layer and leave a pit in the other. The fluid mosaic model predicts what kind of pattern of proteins and pits?

A)a random arrangement of proteins and pits
B)a random arrangement of proteins, but an ordered arrangement of pits
C)an ordered arrangement of proteins, but a random arrangement of pits

Question 7

Phospholipase is an enzyme that cleaves the phosphate head group off a phospholipid molecule. The plasma membrane is not, however, permeable to the enzyme. Imagine a cell where phospholipid A is present in the layer of phospholipds facing the exterior of the cell, and phospholipid B is present in the layer of phospholipds facing the interior of the cell. After adding phospholipase to the medium in which the cell is growing, what would you expect to find in the fluid surrounding the cell?

A)the phosphate head group from phospholipid A only
B)the phosphate head group from phospholipid B only
C)phosphate head groups from both phospholipids A and B
D)phosphate head groups from neither phospholipids A nor B

Question 8

Of the major taxonomic groups of organisms mentioned in Chapter 1 (Section 1.3), list those whose cells have a plasma membrane.

Question 9

Specific types of lipids assemble into defined areas of a biological membrane referred to as:

A)sphingopatches.
B)lipid rafts.
C)biomembrane aggregation regions (BARs).
D)plaques.
E)cholesterol plugs.

Question 10

Phospholipids spontaneously form a variety of structures in aqueous solution. This property accounts at least in part for which of the following?

A)the first cells
B)formation of lipid bilayers
C)the ability of vesicles to fuse with the plasma membrane (exocytosis)
D)the ability of vesicles to bud off from the plasma membrane (endocytosis)
E)All of the answer options depend on this property of phospholipids.

Question 11

Which one of the following describes the hydrophilic component of cholesterol?

A)a hydroxyl group only
B)a phosphate group only
C)a phosphate group and a chemical group called choline
D)a group of four planar rings and a hydroxyl group
E)a single hydrocarbon tail

Question 12

List the lipid components of cellular membranes.

Question 13

Which component of a phospholipid is found in the interior of a lipid bilayer?

A)glycerol
B)fatty acids
C)phosphate group

Question 14

The first cells were surrounded by a membrane composed largely of lipids synthesized by intracellular proteins.

Question 15

Which property of membrane phospholipids allows membrane proteins involved in the same biochemical pathway to associate with each other?

Question 16

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 northern Ontario, Canada, and the other lives in a pond in southern Florida. If you examined the plasma membranes of both of these populations at the same time of year, what difference would you expect to find between the two populations' cell membranes?

A)The fatty acid side chains in the membrane phospholipids of the Florida Paramecia would generally be longer and would be more saturated compared to those in the membranes of the Canada Paramecia.
B)The fatty acid side chains in the membrane phospholipids of the Florida Paramecia would generally be shorter and would be more saturated compared to those in the membranes of the Canada Paramecia.
C)The fatty acid side chains in the membrane phospholipids of the Florida Paramecia would generally be longer and would be less saturated compared to those in the membranes of the Canada Paramecia.
D)The fatty acid side chains in the membrane phospholipids of the Florida Paramecia would generally be shorter and would be less saturated compared to those in the membranes of the Canada Paramecia.

Question 17

Molecules that have both hydrophilic and hydrophobic regions are referred to as _____.

Question 18

In order for bilayers to form spontaneously, the pH of the solution should be:

A)very acidic.
B)moderately acidic.
C)approximately neutral.
D)moderately basic.
E)very basic.

Question 19

Which of the following would be expected to decrease the fluidity of a membrane?

A)an increase in phospholipid fatty acid chain length and an increase in chain saturation
B)a decrease in phospholipid fatty acid chain length and an increase in chain saturation
C)a decrease in phospholipid fatty acid chain length and a decrease in chain saturation
D)an increase in phospholipid fatty acid chain length and a decrease in chain saturation

Question 20

In response to seasonal changes in temperature, many organisms must alter the composition of their plasma membranes to maintain the proper degree of fluidity. As summer turns to fall and eventually into winter, which of the following would you predict you would observe in the plasma membranes of organisms that are unable to regulate their body temperature?

A)an increase in phospholipid fatty acid side chain length and an increase in side chain saturation
B)a decrease in phospholipid fatty acid side chain length and an increase in side chain saturation
C)a decrease in phospholipid fatty acid side chain length and a decrease in side chain saturation
D)an increase in phospholipid fatty acid side chain length and a decrease in side chain saturation

Question 21

Which of the following lipid composition options has the LEAST membrane fluidity?

A)phospholipids with long-chain, saturated fatty acids
B)phospholipids with long-chain, unsaturated fatty acids
C)phospholipids with short-chain, saturated fatty acids
D)phospholipids with short-chain, unsaturated fatty acids

Question 22

How is a micelle different from a liposome?

A)A micelle is composed of a single layer of phospholipids.
B)Micelle phospholipids have bulky head groups.
C)Micelle phospholipids have a single fatty acid tail.
D)All of these choices are correct.

Question 23

Exposure of purified phospholipids to water results in the spontaneous formation of:

A)lipid bilayers.
B)triacylglycerols.
C)steroids.
D)polypeptides.
E)carbohydrates.

Question 24

Predict how phospholipids arrange themselves when they are placed in a nonpolar solution.

A)The phospholipid heads would orient toward the solution.
B)The phospholipid tails would orient toward the solution.
C)The phospholipids would form a bilayer.
D)The phospholipid would form a liposome.

Question 25

Figure 5.2 shows a common biological phospholipid called phosphatidyl choline. Which of the following is NOT a component of phosphatidyl choline?

A)glycerol
B)choline
C)phosphate
D)three fatty acids
E)None of the answer options is correct.

Question 26

A protein that is temporarily associated with a biological membrane is a(n):

A)transmembrane protein.
B)integral membrane protein.
C)peripheral membrane protein.
D)transmembrane protein and an integral membrane protein.

Question 27

Which of the following is a common function of membrane proteins?

A)catalysis
B)attachment
C)transport
D)signal reception

Question 28

A phospholipid molecule in a membrane can:

A)spin (rotate around its vertical axis).
B)move side to side (lateral movement).
C)flip (rotate between the two halves of the bilayer).
D)both spin (rotate around its vertical axis)and move side to side (lateral movement).

Question 29

An amphipathic molecule is one that:

A)contains both polar and nonpolar regions.
B)has a head and tail domain.
C)makes up a membrane.
D)can fully dissolve in water.

Question 30

Some lipid rafts are characterized by an accumulation of cholesterol. What does this mean for the fluidity of the raft domain?

A)These lipid rafts are more fluid than the surrounding membrane at normal temperatures.
B)These lipid rafts are less fluid than the surrounding membrane at normal temperatures.
C)These lipid rafts are equally fluid as the surrounding membrane independent of temperature.
D)These lipid rafts are less fluid than the surrounding membrane at low temperatures.

Question 31

Why does a phospholipid on the cytoplasmic side of the cell membrane rarely flip to the extracellular side if both environments are polar?

A)The polar head group cannot pass through the nonpolar interior.
B)The two sides have different functions and thus the phospholipid would not function properly.
C)The cytoplasmic phospholipid is too big to pass through the membrane.
D)The cholesterol does not allow lipids to move.

Question 32

If FRAP is performed on two membranes, one at 25ºC and the other at 40ºC, which one of the following results would most likely be observed?

A)Only the membrane at the higher temperature would recover fluorescence in the bleached area.
B)Only the membrane at the lower temperature would recover fluorescence in the bleached area.
C)Both membranes would recover fluorescence in the bleached area, but the membrane at the colder temperature would recover more rapidly.
D)Both membranes would recover fluorescence in the bleached area, but the membrane at the warmer temperature would recover more rapidly.
E)Both membranes would recover fluorescence in the bleached area at the same rate.

Question 33

Which part of a cholesterol molecule is polar?

A)the OH group
B)the four interconnected planar rings
C)the hydrocarbon tail
D)both the four interconnected planar rings and the hydrocarbon tail

Question 34

A spontaneously generated enclosed bilayer structure is called a(n) _____.

Question 35

Amino acids with hydrophobic side chains are often found in the region of an integral membrane protein that spans the membrane.

Question 36

The interior region of a phospholipid bilayer is characterized as:

A)hydrophilic.
B)hydrophobic.
C)polar.
D)hydrophilic and polar.

Question 37

A single molecule is always either hydrophobic or hydrophilic, and can never possess (at the same time) a region that is hydrophobic and a region that is hydrophilic.

Question 38

What type of molecule is NOT associated with a cell's plasma membrane?

A)carbohydrate
B)phospholipid
C)RNA
D)protein

Question 39

Which one of the following is NOT a component of an animal cell's plasma membrane?

A)protein
B)lipid
C)nucleic acid
D)carbohydrate

Question 40

Long, saturated fatty acid tails _____ lipid mobility and _____ membrane fluidity.

A)enhance; increase
B)reduce; increase
C)maintain; decrease
D)enhance; maintain
E)reduce; decrease

Question 41

The plasma 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)passive transport.
C)endocytosis.
D)active transport.
E)simple diffusion

Question 42

Which one of the following molecules would MOST likely require a transport protein to cross the plasma membrane of a red blood cell?

A)CO₂
B)H₂O
C)O₂
D)C₆H₁₂O₆

Question 43

The beaker in the illustration below contains two solutions of salt with different concentrations (measured by molarity, M). The two solutions are separated by a membrane that is permeable to both salt and water. Which of the following will occur in this container?

A)Diffusion of water from B to A and of salt from A to B.
B)Net diffusion of water across the membrane, but not of salt.
C)Diffusion of salt across the membrane, but not of water.
D)Net diffusion of salt from B to A, but no net diffusion of water.

Question 44

A beaker contains two solutions of salt dissolved in water. The two solutions have different concentrations (measured by molarity, M) and are separated by a membrane that is permeable to both salt and water. Which of the following statements is TRUE?

A)There will be a net movement of salt from side A to side B
B)There will be a net movement of salt, but net movement of water will not occur.
C)There is more water in side A than there is in side B.

Question 45

Which of the following represents the order that molecules cross a synthetic membrane composed of phospholipids but not proteins, from most easily (freely permeable) to least easily (not permeable)?

A)O₂, sodium ions (Na⁺), water (H₂O), glucose
B)O₂, water (H₂O), glucose, sodium ions (Na⁺)
C)sodium ions (Na⁺), glucose, water (H₂O), O₂
D)water (H₂O), glucose, sodium ions (Na⁺), O₂
E)glucose, water (H₂O), O₂, sodium ions (Na⁺)

Question 46

A researcher is using a modified version of FRAP. She has devised a technique that allows her to label all the peripheral membrane proteins with a fluorescent tag, and has bleached a specific area of the cell membrane. After 24 hours, she notices that fluorescence has returned to the bleached area. What can she deduce from this experiment?

A)Peripheral membrane proteins may not be permanently associated with the cell membrane.
B)Peripheral membrane proteins-like transmembrane proteins-are located within the cell membrane.
C)Peripheral membrane proteins can move freely within the cell membrane.
D)Peripheral membrane proteins are akin to integral membrane proteins.
E)Peripheral membrane proteins can both move freely within the cell membrane and are akin to integral membrane proteins.

Question 47

Explain why the plasma membrane is permeable to some substances, while others require a channel, or carrier, protein to cross the membrane.

Question 48

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)The lipids would be able to easily transition between the inner and outer layers of the bilayer constituting the cell membrane.
B)The lipids contained in such a membrane would be highly mobile, and in near constant flux.
C)Due to its cholesterol content, the cell membrane would remain fluid even at cold temperatures.
D)The characteristics of this cell membrane will closely mirror those of a membrane composed of only unsaturated fatty acids.
E)None of the answer options is correct.

Question 49

The electrical component of an electrochemical gradient is due to:

A)the use of ATP as an energy source to drive primary transport.
B)a greater concentration of positive charges on the side of the membrane with the lowest concentration of protons.
C)a higher pH on the side of the membrane with the highest concentration of protons.
D)a higher pH on the side of the membrane with the lowest concentration of protons.
E)a greater concentration of positive charges on the side of the membrane with the highest concentration of protons.

Question 50

Suppose you are studying the transport of a certain polar molecule across the plasma membrane of cells in culture. Over a period of time, you measure the concentration of a polar molecule inside and outside of the cells. You find that the concentration of the molecule is lower in the cell but is gradually increasing. You also measure the ATP concentration inside the cell and find that it is not changing. Which of the following is probably responsible for the transport of this polar substance into the cell?

A)facilitated diffusion
B)secondary active transport
C)endocytosis
D)active transport
E)simple diffusion

Question 51

Which of the following is responsible, in part, for keeping the cytoplasm of red blood cells isotonic with the blood plasma, and thereby preventing either lysis or shrinking of the cells?

A)facilitated diffusion
B)sodium channels
C)the sodium/potassium pump
D)osmosis

Question 52

If cells had single-layer membranes like micelles, how would the structures of transmembrane proteins be affected?

A)Transmembrane proteins would only possess hydrophobic regions.
B)Transmembrane proteins would only possess hydrophilic regions.
C)Transmembrane proteins would possess a hydrophobic region in the cell interior and a hydrophilic region in the extracellular space.
D)Transmembrane proteins would possess a hydrophilic region in the cell interior and a hydrophobic region in the extracellular space.
E)The structures of transmembrane proteins would remain the same as if cells had lipid bilayers.

Question 53

Some plant cells take advantage of the high concentration of protons outside the cell to move solutes, such as sucrose, across the plasma membrane into the cell where the sucrose concentration is already relatively high. This type of transport is an example of:

A)facilitated diffusion.
B)osmosis.
C)secondary active transport.
D)passive transport.

Question 54

The beaker in the illustration below contains two solutions of salt with different concentrations (measured by molarity, M). The two solutions are separated by a membrane that is permeable to both salt and water. Which of the following will occur in this container?

A)Net diffusion of water from B to A and of salt from A to B.
B)Net diffusion of water from A to B and of salt from B to A.
C)Net diffusion of water across the membrane, but not of salt.
D)Diffusion of salt across the membrane, but not of water.
E)Net diffusion of salt from B to A, but no net diffusion of water.

Question 55

G protein-coupled receptors are transmembrane receptors involved in cell signaling. The amino acid sequence of these proteins reveals that the polypeptide chain of the protein has seven hydrophobic regions. Based on this information, what can you conclude about how the protein is associated with the cell membrane?

A)The receptor is likely to be a peripheral membrane protein.
B)The polypeptide chain is likely to span the membrane once.
C)The polypeptide chain is likely to span the membrane seven times.
D)The polypeptide chain is likely to span the membrane fourteen times.
E)The receptor is likely to be synthesized on free ribosomes.

Question 56

Some drugs are now being delivered into cells through liposomes, in which the drug is surrounded by a phospholipid bilayer. Explain how the drugs enter the cell.

Question 57

The active maintenance of a constant internal environment is referred to as:

A)homeostasis.
B)equilibrium.
C)stability.
D)symmetry.
E)balance.

Question 58

Some drugs are now being delivered into cells through liposomes, in which the drug is surrounded by a phospholipid bilayer. How do the drugs enter into the cell?

A)The drug destroys the liposome and diffuses into the cell.
B)The liposome cuts a hole in the cell membrane and injects the drug into the cell.
C)The liposome fuses with the phospholipid bilayer of the cell.
D)Protein channels on the cell surface transport the liposomes into the cell.

Question 59

Suppose you are studying the transport of a certain polar molecule across the plasma membrane of cells in culture. Over a period of time, you measure the concentration of a polar molecule inside and outside of the cells. You find that the concentration of the molecule is higher in the cell and is gradually increasing. You also measure the ATP concentration inside the cell and find that it is decreasing. Which of the following is probably responsible for the transport of this polar substance into the cell?

A)facilitated diffusion
B)secondary active transport
C)endocytosis
D)active transport
E)simple diffusion

Question 60

Some diseases result from defective transport across the membrane. For example, cystic fibrosis results when a chloride ion transporter does not function. Which of the following is affected when this transporter does NOT function?

A)the chloride concentration gradient
B)the electrical gradient of the cell
C)both the chloride concentration gradient and the electrical gradient of the cell
D)neither the chloride gradient nor the electrical gradient of the cell

Question 61

The movement of water into, or out of, a cell is an example of:

A)osmosis.
B)lysis.
C)diffusion.
D)active transport.
E)both osmosis and diffusion.

Question 62

The random movement of molecules is referred to as:

A)transport.
B)osmosis.
C)diffusion.
D)All of these choices are correct.

Question 63

A beaker contains two solutions of glucose dissolved in water. The two solutions have different concentrations (measured by molarity, M) and are separated by a membrane that is permeable to water, but not to glucose. Which of the following statements is TRUE?

A)There will be net movement of glucose from B to A.
B)The volume will increase in side B of the beaker.
C)There will be net movement of water from B to A.
D)The system will not reach equilibrium.

Question 64

Which of the following represents how easily the molecules cross a synthetic membrane composed of phospholipids but not proteins, from most easily (freely permeable) to least easily (not permeable)?

A)hydrophobic molecules, ions, small polar molecules, large polar molecules
B)hydrophobic molecules, small polar molecules, large polar molecules, ions
C)ions, large polar molecules, small polar molecules, hydrophobic molecules
D)small polar molecules, large polar molecules, ions, hydrophobic molecules
E)large polar molecules, small polar molecules, hydrophobic molecules, ions

Question 65

The MOST abundant organic molecule in nature is:

A)water.
B)cellulose.
C)aquaporin.
D)cholesterol.
E)ATP.

Question 66

What factors are required for net movement of a substance to occur by facilitated diffusion?

A)a concentration gradient
B)a plasma membrane
C)a transport protein
D)All of these choices are correct.

Question 67

In certain cells, a transport protein moves one calcium ion out of the cell against its concentration gradient while allowing the movement of three sodium ions into the cell down sodium's electrochemical gradient. Which of the following CORRECTLY describes this cotrannsport of calcium and sodium?

A)primary active transport by a symporter
B)secondary active transport by an antiporter
C)secondary active transport by a symporter
D)primary active transport by an antiporter

Question 68

Which of the following have cell walls?

A)plant cells
B)animal cells
C)fungal cells
D)bacterial cells

Question 69

Which of the following organisms have complex carbohydrates as a major component of their cell walls?

A)animals
B)bacteria
C)fungi
D)plants

Question 70

On most bicycles, the tires include a separate inner tube inside the tire itself. When the inner tube is inflated, often to pressure greater than 100 pounds per square inch, it does not burst because the walls of the tire support it. Without the tire, the inner tube would burst long before such high pressures were reached. Similarly, the cytoplasm of plant cells in hypotonic conditions is under relatively high osmotic pressure. However, the cells do not lyse (or burst) due to the presence of the _____ that provides structural support for the _____.

A)cell wall; plasma membrane
B)cell wall; contractile vacuoles
C)plasma membrane; contractile vacuoles
D)contractile vacuoles; plasma membrane
E)contractile vacuole; cell wall

Question 71

A beaker contains two solutions of salt dissolved in water. The two solutions have different concentrations (measured by molarity, M) and are separated by a membrane that is permeable to both salt and water. Which of the following statements is TRUE?

A)Side A is hypotonic relative to side B.
B)Side A is isotonic relative to side B.
C)Side A is hypertonic relative to side B.

Question 72

In intestinal epithelial cells, a transport protein moves glucose into the cytoplasm against its concentration gradient at the same time that it transports Na⁺ into the cell down its electrochemical gradient. Which of the following CORRECTLY describes this cotransport of glucose and sodium?

A)Primary active transport by a symporter.
B)Secondary active transport by an antiporter.
C)Secondary active transport by a symporter.
D)Primary active transport by an antiporter.

Question 73

Passive transport of a molecule across a lipid bilayer only occurs if there is a significant difference in the concentration of that molecule from one side of the bilayer to the other.

Question 74

Which one of the following is LEAST likely to cross a lipid bilayer?

A)O₂
B)CO₂
C)ATP
D)H₂O
E)N₂

Question 75

The sodium-potassium pump is an example of:

A)a symporter.
B)passive transport.
C)an antiporter.
D)channel-mediated diffusion.
E)None of the answer options is correct.

Question 76

Why does active transport require ATP?

A)An input of energy is needed to speed up the rate of facilitated diffusion.
B)An input of energy is needed to allow the movement of molecules from an area of low concentration to one of higher concentration.
C)An input of energy is needed to maintain the conformation of transport proteins.
D)An input of energy is needed to both speed up the rate of facilitated diffusion and maintain the conformation of transport proteins.

Question 77

Which way does the water move if the cell is in a hypotonic environment?

A)out of the cell
B)into the cell
C)Water doesn't move across the hydrophobic core of cell membranes.

Question 78

You are studying the transport of a particular substance into epithelial cells grown in culture. You notice that you can only find the substance inside the cell when ATP is present. How is the protein moving through the membrane?

A)diffusion
B)facilitated diffusion
C)passive transport
D)active transport

Question 79

The movement of water across a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration is referred to as _____.

Question 80

The term homeostasis refers to the ability of:

A)molecules to undergo net movement by diffusion.
B)the cell to seek out an optimal environment.
C)the plasma membrane to control what enters a cell.
D)the cell to control and maintain its internal environment.