Deck 5: Membrane Transport and Cell Signaling

Question 1

A protein that spans the phospholipid bilayer one or more times is

A) a transmembrane protein.
B) a glycoprotein.
C) a peripheral protein.
D) an extracellular matrix protein.

Answer 1

A

Question 2

A primary function of cholesterol in the plasma membranes of some animals is to

A) make the membrane more rigid, allowing it to resist pressure from outside the cell.
B) facilitate the removal of hydrogen atoms from saturated phospholipids.
C) facilitate cell-cell interactions by binding to receptors on neighboring cells.
D) enable the membrane to stay fluid more easily when the temperature drops.

Answer 2

D

Question 3

How do unsaturated fatty acids help keep any membrane more fluid at lower temperatures?

A) The double bonds form kinks in the fatty acid tails that prevent adjacent lipids from packing tightly together.
B) Unsaturated fatty acids have a higher cholesterol content that prevents adjacent lipids from packing tightly together.
C) Unsaturated fatty acids are more polar than saturated fatty acids.
D) The double bonds result in shorter fatty acid tails and therefore thinner membranes.

Answer 3

A

Question 4

Which of the following provides the most likely explanation for why cell membranes are asymmetrical?

A) Proteins only function on the cytoplasmic side of the cell membrane, which results in asymmetry across the membrane.
B) Cell-to-cell communication requires different proteins on the surfaces of interacting cells.
C) The molecular composition of the inner and outer layers of the cell membrane is determined by genes.
D) The two sides of a cell membrane face different environments and carry out different functions.

Question 5

Which of the following is one of the ways that the membranes of winter wheat are able to remain fluid when it is extremely cold?

A) by increasing the average length of the fatty acid tails in membrane
B) by decreasing the percentage of cholesterol molecules in the membrane
C) by decreasing the number of hydrophobic proteins in the membrane
D) by increasing the percentage of unsaturated phospholipids in the membrane

Question 6

Which of the following are localized on the exterior of a phospholipid bilayer?

A) saturated fatty acids
B) unsaturated fatty acids
C) phosphate groups
D) cholesterol

Question 7

What kinds of molecules pass through a cell membrane most easily?

A) large hydrophobic
B) small hydrophobic
C) large polar
D) small ionic
E) large and hydrophilic

Question 8

Which of the following is a characteristic feature of a carrier protein in a plasma membrane?

A) It is a peripheral membrane protein.
B) It exhibits a specificity for a particular type of molecule.
C) It requires the expenditure of cellular energy to function.
D) It works against a concentration gradient.

Question 9

The fluid mosaic model of the membrane proposed that membranes

A) consist of a phospholipid bilayer composed of a variety of fatty acids.
B) consist of protein molecules embedded in a fluid bilayer of phospholipids.
C) consist of a single layer of phospholipids and proteins.
D) consist of a phospholipid bilayer between two layers of hydrophilic proteins.

Question 10

When biological membranes are frozen and then fractured, they tend to break along the middle of the bilayer. The best explanation for this is that

A) the integral membrane proteins are not strong enough to hold the bilayer together.
B) water that is present in the middle of the bilayer freezes and is easily fractured.
C) the hydrophobic interactions between the fatty acid tails of the two phospholipid monolayers are the weakest interactions in the membrane.
D) the carbon-carbon bonds of the phospholipid tails are easily broken.

Question 11

Why are lipids and proteins free to move laterally in membranes?

A) The interior of the membrane is filled with liquid water.
B) Lipids and proteins repulse each other in the membrane.
C) Phospholipids form hydrogen bonds with water at the membrane surface, which moves the lipids as water moves.
D) Weak hydrophobic interactions in the interior of the membrane are easily disrupted.

Question 12

Which of the following is true of integral membrane proteins?

A) They serve only a structural role in membranes.
B) They are loosely bound to the surface of the bilayer.
C) They are usually transmembrane proteins.
D) They are not mobile within the bilayer.

Question 13

A primary function of polysaccharides attached to glycoproteins and glycolipids of animal cell membranes is to

A) facilitate diffusion of active transport of molecules into the cell.
B) mediate cell-to-cell recognition.
C) maintain the integrity of a fluid mosaic membrane.
D) maintain membrane fluidity at low temperatures.

Question 14

Which of the following is true for the evolution of cell membranes?

A) The fluid mosaic nature of cell membranes provides for the rapid evolution of cell membranes.
B) The evolution of cell membranes is driven primarily by the evolution of phospholipids as a result of natural selection.
C) The evolution of cell membranes is driven primarily by the evolution of glycoproteins and glycolipids as a result of natural selection.
D) The evolution of cell membranes is driven by the evolution of all membrane components as a result of natural selection.

Question 15

The cell membranes of Antarctic ice fish might have which of the following adaptations?

A) a high percentage of very long chain saturated fatty acids
B) no cholesterol
C) a high percentage of unsaturated fatty acids
D) a high percentage of trans fatty acids

Question 16

The primary structural components of the cell membrane are

A) phospholipids and cellulose.
B) phospholipids and proteins.
C) cholesterol and proteins.
D) proteins and cellulose.
E) glycoproteins and cholesterol.

Question 17

Which of the following tend to lack hydrophobic regions on their surface?

A) transmembrane proteins
B) integral proteins
C) peripheral proteins
D) integrins
E) cholesterol

Question 18

According to the fluid mosaic model of cell membranes, which of the following is a true statement about membrane phospholipids?

A) They can move laterally along the plane of the membrane.
B) They frequently flip-flop from one side of the membrane to the other.
C) They occur in an uninterrupted bilayer, with membrane proteins restricted to the surface of the membrane.
D) They are free to depart from the membrane and dissolve in the surrounding solution.

Question 19

The movement of the hydrophobic gas nitrous oxide (N2O) (laughing gas) into a cell is an example of

A) active transport across the lipid bilayer.
B) facilitated diffusion through the lipid bilayer.
C) diffusion through the lipid bilayer.
D) osmosis through the lipid bilayer.
E) cotransport across the lipid bilayer.

Question 20

An integral membrane protein would have to be

A) hydrophilic.
B) hydrophobic.
C) amphipathic, with at least one hydrophobic region.
D) exposed to water on only one surface of the membrane.

Question 21

The sodium-potassium pump is called an electrogenic pump because it

A) pumps electrons across the plasma membrane.
B) pumps hydrogen ions out of the cell.
C) contributes to the membrane potential.
D) ionizes sodium and potassium atoms.

Question 22

Which of the following would increase the electrochemical gradient across a membrane?

A) a chloride channel
B) a sucrose-proton cotransporter
C) a proton pump
D) a potassium channel

Question 23

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 lower concentration in a mammalian cell to a higher concentration in the extracellular fluid
D) movement of glucose molecules into a bacterial cell from a medium containing a higher concentration of glucose than inside the cell
E) movement of carbon dioxide out of a paramecium

Question 24

Submerging a red blood cell in distilled water will result in

A) plasmolysis of the cell.
B) lysis of the cell.
C) the cell becoming turgid.
D) the cell becoming flacid.

Question 25

Which of the following statements correctly describes the normal tonicity relationships between typical plant and animal cells and their respective environments?

A) Animal cells are generally in a hypotonic solution, and plant cells are generally in an isotonic solution.
B) Animal cells are generally in an isotonic solution, and plant cells are generally in a hypotonic solution.
C) Animal cells are generally in an isotonic solution, and plant cells are generally in a hypertonic solution.
D) Animal cell are generally in a hypertonic solution, and plant cells are generally in an isotonic solution.
E) Animal cells are generally in a hypertonic solution, the plant cells are generally in a hypotonic solution.

Question 26

Glucose diffuses slowly through artificial phospholipid bilayers. The cells lining the small intestine, however, rapidly move large quantities of glucose from the glucose-rich food into their glucose-poor cytoplasm. Based on this information, which transport mechanism is most likely responsible for glucose transport in the intestinal cells?

A) simple diffusion
B) phagocytosis
C) active transport pumps
D) facilitated diffusion

Question 27

What is the voltage across a membrane called?

A) water potential
B) chemical gradient
C) membrane potential
D) osmotic potential
E) electrochemical gradient

Question 28

Which of the following statements about diffusion is correct?

A) It is very rapid over long distances.
B) It requires an expenditure of energy by the cell.
C) It is a passive process in which molecules move from a region of higher concentration to a region of lower concentration.
D) It is an active process in which molecules move from a region of lower concentration to one of higher concentration.
E) It is a passive process in which molecules move from a region of lower concentration to a region of higher concentration.

Question 29

Transport of potassium ions into an animal cell by the sodium-potassium pump requires

A) low intracellular concentrations of sodium.
B) high intracellular concentrations of sodium.
C) high intracellular concentrations of potassium.
D) low intracellular concentrations of potassium.
E) energy from ATP.

Question 30

Submerging a plant cell in distilled water will result in

A) plasmolysis of the cell.
B) lysis of the cell membrane.
C) bursting of the cell.
D) the cell becoming turgid.
E) the cell becoming flaccid.

Question 31

Celery stalks that are immersed in fresh water for several hours become turgid (stiff). Celery stalks left in a 0.15 M salt solution become flaccid (limp). From this we can deduce that

A) the fresh water and the salt solution are both hypertonic to the cells of the celery stalks.
B) the fresh water and the salt solution are both hypotonic to the cells of the celery stalks.
C) the fresh water is hypertonic and the salt solution is hypotonic to the cells of the celery stalks.
D) the fresh water is hypotonic and the salt solution is hypertonic to the cells of the celery stalks.
E) the fresh water is isotonic and the salt solution is hypertonic to the cells of the celery stalks.

Question 32

Proteins that allow the diffusion of ions across membranes in the direction of their concentration gradients are most likely

A) channel proteins.
B) carrier proteins.
C) aquaporins.
D) active transport pumps.

Question 33

Which of the following would diffuse through the lipid bilayer of a plasma membrane most rapidly?

A) glucose
B) starch
C) O₂
D) Na+
E) an amino acid

Question 34

Which of the following would diffuse through the lipid bilayer of a plasma membrane most slowly, if at all?

A) glucose
B) an amino acid
C) O₂
D) CO₂
E) water

Question 35

Water passes quickly through cell membranes because

A) the bilayer is hydrophilic.
B) it moves through hydrophobic channels.
C) water movement is tied to ATP hydrolysis.
D) it is a small, nonpolar molecule.
E) it moves through aquaporin channel proteins.

Question 36

Mammalian blood contains the equivalent of 0.15 M NaCl. Seawater contains the equivalent of 0.45 M NaCl. What will happen if red blood cells are transferred to seawater?

A) Water will leave the cells, causing them to shrivel and collapse.
B) NaCl will be exported from the red blood cells by facilitated diffusion.
C) The blood cells will take up water, swell, and eventually burst.
D) NaCl will passively diffuse into the red blood cells.

Question 37

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 membrane-more acidic outside the cell than inside the cell. Phosphate transport is an example of

A) passive diffusion.
B) facilitated diffusion.
C) active transport.
D) cotransport.
E) receptor-mediated endocytosis.

Question 38

The sodium-potassium pump generates the following concentration gradients across the plasma membrane:

A) high [Na+] and [K+] inside the cell and low [Na+] and [K+] outside.
B) low [Na+] and [K+] inside the cell and high [Na+] and [K+] outside.
C) low [Na+] and high [K+] inside the cell and high [Na+] and low [K+] outside.
D) high [Na+] and low [K+] inside the cell and low [Na+] and high [K+] outside.

Question 39

Which of the following is most likely true of a protein that cotransports glucose and sodium ions into the intestinal cells of an animal?

A) Sodium and glucose bind to the same site on the cotransporter.
B) Transport of glucose against its concentration gradient provides energy for uptake of sodium ions against the electrochemical gradient.
C) Sodium ions can be transported whether or not glucose is present outside the cell, but glucose transport requires cotransport of sodium ions.
D) Transport of sodium ions down their electrochemical gradient facilitates the transport of glucose against its concentration gradient.
E) Following transport of sodium ions into the cell, the cotransporter can also transport potassium ions out of the cell.

Question 40

Submerging a red blood cell in a hypertonic solution will result in

A) plasmolysis of the cell.
B) lysis of the cell.
C) the cell becoming turgid.
D) the cell wall shriveling.

Question 41

The primary function of phosphatases in signal transduction is to

A) transfer a phosphate group from a kinase to the next relay molecule in a series.
B) inactivate protein kinases to turn off signal transduction.
C) amplify signal transduction so it activates multiple relay molecules.
D) amplify the second messenger cAMP.

Question 42

A bacterium engulfed by a white blood cell through phagocytosis will be digested by enzymes contained in

A) peroxisomes.
B) lysosomes.
C) Golgi vesicles.
D) vacuoles.
E) secretory vesicles.

Question 43

The difference between pinocytosis and receptor-mediated endocytosis is that

A) pinocytosis brings only water molecules into the cell, whereas receptor-mediated endocytosis brings in other molecules as well.
B) pinocytosis increases the surface area of the plasma membrane, whereas receptor-mediated endocytosis decreases the plasma membrane surface area.
C) pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis is highly selective.
D) pinocytosis requires cellular energy, but receptor-mediated endocytosis does not.
E) pinocytosis can concentrate substances from the extracellular fluid, but receptor-mediated endocytosis cannot.

Question 44

Which of the following characteristics is unique to plant hormones?

A) Plant hormones may be bound by intracellular steroid receptors.
B) Plant hormones may be delivered to target cells through a vascular system.
C) Plant hormones may be delivered to target cells through the air.
D) The target cells for plant hormones may be located large distances from the cells that produce and secrete the hormones.

Question 45

Which of the following is the most likely fate of animal cells that lack receptors for local paracrine signal molecules?

A) They would be unable to grow and divide in response to growth factors from nearby cells.
B) They would be unable to respond to hormone signals delivered through the bloodstream.
C) They would bind locally secreted growth factors, but intracellular signal pathways would be blocked.
D) They would grow and divide normally.

Question 46

Which of the following is true of steroid receptors?

A) The receptor molecules are themselves lipids or glycolipids.
B) The receptor molecules are transmembrane proteins with the ligand binding domain on the outside of the cell.
C) The receptor molecules are transmembrane proteins with the ligand binding domain on the inside of the cell.
D) The receptor molecules are peripheral proteins embedded in the interior layer of the plasma membrane.
E) The receptor molecules may be soluble proteins in the cytoplasm.

Question 47

Proton pumps are used in various ways by members of every domain of organisms: Bacteria, Archaea, and Eukarya. What does this most probably mean?

A) Proton pumps must have evolved before any living organisms were present on Earth.
B) Proton pumps are an essential feature of all cell membranes.
C) Proton gradients across a membrane were used by cells that were the common ancestor of all three domains of life.
D) Cells of each domain evolved proton pumps independently when oceans became more acidic.

Question 48

Which of the following correctly describes the relationship between an enzyme and its function?

A) kinase: addition of a tyrosine
B) phosphatase: removal of a phosphate group
C) glycogen phosphorylase: synthesis of glycogen
D) adenylyl cyclase: conversion of cAMP to AMP

Question 49

Which of the following is the first event that occurs following the binding of a ligand by a membrane receptor protein?

A) An intracellular enzyme is activated by phosphorylation.
B) An intracellular G protein is activated.
C) The membrane receptor protein undergoes a conformational change.
D) The membrane receptor protein enters the cytoplasm.

Question 50

Immediately following binding of a growth factor, an activated receptor would most likely stimulate

A) activation of a protein kinase.
B) activation of adenylyl cyclase.
C) activation of a calcium-binding protein.
D) activation of a protein phosphatase.

Question 51

Which of the following enzymes adds a phosphate group to target proteins?

A) kinase
B) phosphatase
C) glycogen phosphorylase
D) adenylyl cyclase

Question 52

The mechanism by which testosterone alters cell function is by

A) binding to a receptor protein that enters the nucleus and activates specific genes.
B) serving as a transmembrane signal receptor that activates cell-signaling pathways.
C) acting as a steroid signal receptor that activates ion channel proteins.
D) serving as a second messenger that activates cell-signaling pathways.

Question 53

The secretion of a signal molecule by a cell into the local environment, followed by a response by a number of cells in the immediate vicinity, is an example of

A) hormonal signaling.
B) synaptic signaling.
C) endocrine signaling.
D) paracrine signaling.
E) extracellular matrix signaling.

Question 54

Approximately what proportion of human genes are thought to encode protein kinases?

A) 0.01%
B) 0.5%
C) 2%
D) 10%

Question 55

When a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as which part of the signal pathway?

A) receptor
B) relay molecule
C) signal molecule
D) transducer
E) molecule protein

Question 56

Familial hypercholesterolemia is characterized by extremely high levels of cholesterol in the blood, which results from

A) defective cell membranes that cannot incorporate cholesterol.
B) poor attachment of cholesterol to the extracellular matrix of cells.
C) inhibition of the cholesterol active transport system in red blood cells.
D) nonfunctional or missing LDL receptors on cell membranes.

Question 57

The primary function of transcription factors is

A) to regulate the conversion of ATP into cAMP.
B) to regulate DNA synthesis.
C) to regulate gene expression.
D) to transmit signals from an activated receptor to intracellular G proteins.

Question 58

In general, a signal transmitted via a phosphorylation cascade

A) is initiated by a phosphorylase enzyme.
B) is propagated by a steroid receptor.
C) results in a conformational change in each phosphorylated protein.
D) is turned off by a kinase enzyme.

Question 59

Following activation of a receptor, which sequence below represents the correct order in which components will be involved in a signaling pathway that utilizes the second messenger cAMP?

A) G protein → cAMP → adenyl cyclase → protein kinase
B) G protein → adenyl cyclase → cAMP → protein kinase
C) adenyl cyclase → cAMP → G protein → protein kinase
D) cAMP → adenyl cyclase → protein kinase → G protein
E) protein kinase → G protein → adenyl cyclase → cAMP

Question 60

In receptor-mediated endocytosis, receptor molecules are initially localized on the outer surface of the plasma membrane. Where do the receptors end up following endocytosis?

A) on the inside surface of the plasma membrane
B) on the inside surface of a vesicle
C) on the outer surface of a vesicle
D) on the outer surface of the nucleus
E) on the inside surface of the Golgi apparatus

Question 61

A drug designed to inhibit the response of cells to testosterone would almost certainly result in which of the following?

A) lower cytoplasmic levels of cAMP
B) an increase in receptor tyrosine kinase activity
C) a decrease in transcriptional activity of certain genes
D) a decrease in G protein activity

Question 62

Figure 5.1
For the following questions, match the labeled component of the cell membrane in Figure 5.1 with its description.
Which component in the figure is a peripheral protein?

A) A
B) B
C) C
D) D
E) E

Question 63

Figure 5.1
For the following questions, match the labeled component of the cell membrane in Figure 5.1 with its description.
Which component in the figure is a glycolipid?

A) A
B) B
C) C
D) D
E) E

Question 64

The primary function of G proteins in signal transduction is

A) transducing the signal from an activated receptor to the next protein in the pathway.
B) binding extracellular signal molecules to activate the pathway.
C) converting ATP to cATP to amplify the signal.
D) phosphorylating relay molecules in the pathway.

Question 65

In research on aging (both cellular aging and organismal aging), it has been found that aged cells do not progress through the cell cycle as they had previously. Which of the following would provide evidence that this is related to cell signaling?

A) decreased ATP production in aged cells
B) decreased hormone production in aged cells
C) decreased affinity of growth factor receptors for their respective ligands
D) decreased numbers of cytoplasmic ribosomes

Question 66

Figure 5.2
The solutions in the two arms of this U-tube (Figure 5.2) 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 are equal. Refer to the figure to answer the following question(s).
After the system depicted in the figure reaches equilibrium, what changes are observed with respect to the concentrations of sugars?

A) The concentration of sucrose is equal in sides A and B and the concentrations of glucose are unchanged.
B) The concentrations of glucose and sucrose are equal in sides A and B.
C) The concentration of glucose is equal in sides A and B and the concentrations of sucrose are unchanged.
D) The water levels change, but the concentrations of glucose and sucrose in sides A and B are unchanged.

Question 67

Figure 5.2
The solutions in the two arms of this U-tube (Figure 5.2) 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 are equal. Refer to the figure to answer the following question(s).
After the system depicted in the figure reaches equilibrium, what changes are observed?

A) The concentrations of glucose and sucrose are unchanged.
B) The water level is higher in side A than in side B.
C) The water level is unchanged.
D) The water level is higher in side B than in side A.

Question 68

Figure 5.1
For the following questions, match the labeled component of the cell membrane in Figure 5.1 with its description.
Which component in the figure plays an important role in cell-cell recognition?

A) A
B) B
C) C
D) D
E) E

Question 69

Figure 5.3
The solutions in the arms of a U-tube (Figure 5.3) are separated at the bottom of the tube by a selectively permeable membrane. The membrane is permeable to sodium chloride but not to glucose. Side A is filled with a solution of 0.4 M glucose and 0.5 M sodium chloride (NaCl), and side B is filled with a solution containing 0.8 M glucose and 0.4 M sodium chloride. Initially, the volume in both arms is the same. Refer to the figure to answer the following questions.
At the beginning of the experiment, side A in the figure

A) is hypertonic to side B.
B) is hypotonic to side B.
C) is isotonic to side B.
D) is hypertonic to side B with respect to glucose.
E) is hypotonic to side B with respect to sodium chloride.

Question 70

Which of the following is the greatest advantage of having multiple steps in a transduction pathway?

A) Many of the steps can be used in multiple pathways.
B) Having multiple steps in a pathway requires the least amount of ATP.
C) Having multiple steps provides for greater possible amplification of a signal.
D) Each step can be activated by several G proteins simultaneously.

Question 71

In which of the following ways could signal transduction most probably be explored in research to treat cancer?

A) removal of serine/threonine phosphate acceptors from transduction pathways in colon pre-cancerous growths
B) increase in calcium ion uptake into the cytoplasm in order to modulate the effects of environmental carcinogens
C) alteration of protein kinases in cell cycle regulation in order to slow cancer growth
D) stimulation of cAMP production in cancer cells

Question 72

Figure 5.1
For the following questions, match the labeled component of the cell membrane in Figure 5.1 with its description.
Which component in the figure is a fiber of the extracellular matrix?

A) A
B) B
C) C
D) D
E) E

Question 73

Sutherland discovered that the signaling molecule epinephrine

A) increases concentrations of cyclic AMP in the cytoplasm.
B) causes lower blood glucose by binding to liver cells.
C) binds to a cytosolic receptor inside muscle cells.
D) interacts directly with glycogen phosphorylase.

Question 74

Figure 5.1
For the following questions, match the labeled component of the cell membrane in Figure 5.1 with its description.
Which component in the figure is cholesterol?

A) A
B) B
C) C
D) D
E) E

Question 75

Figure 5.1
For the following questions, match the labeled component of the cell membrane in Figure 5.1 with its description.
Which component in the figure helps membranes resist changes in fluidity at high and low temperatures?

A) A
B) B
C) C
D) D
E) E

Question 76

Figure 5.2
The solutions in the two arms of this U-tube (Figure 5.2) 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 are equal. Refer to the figure to answer the following question(s).
Initially, in terms of tonicity in the figure, the solution in side A with respect to that in side B is

A) hypotonic.
B) hypertonic.
C) isotonic.
D) saturated.

Question 77

The primary function of kinases in signal transduction is to

A) inactivate relay molecule to turn off signal transduction.
B) regulate gene expression by serving as a transcription factor.
C) inactivate second messengers such as cAMP.
D) activate protein kinases or other relay molecules in a series.

Question 78

At puberty, an adolescent female body changes in both structure and function of several organ systems, primarily under the influence of changing concentrations of estrogens and other steroid hormones. How can one hormone, such as estrogen, mediate so many effects?

A) Estrogen is produced in high concentrations by a large number of different cell types.
B) Estrogen binds to common receptors inside several cell types, and each cell responds in the same way to its binding.
C) Estrogen does not affect cells that lack estrogen receptors in the cell membrane.
D) Estrogen binds to specific receptors inside many kinds of cells, each of which has different responses to its binding.

Question 79

Figure 5.1
For the following questions, match the labeled component of the cell membrane in Figure 5.1 with its description.
Which component in the figure is a microfilament of the cytoskeleton?

A) A
B) B
C) C
D) D
E) E

Question 80

Figure 5.3
The solutions in the arms of a U-tube (Figure 5.3) are separated at the bottom of the tube by a selectively permeable membrane. The membrane is permeable to sodium chloride but not to glucose. Side A is filled with a solution of 0.4 M glucose and 0.5 M sodium chloride (NaCl), and side B is filled with a solution containing 0.8 M glucose and 0.4 M sodium chloride. Initially, the volume in both arms is the same. Refer to the figure to answer the following questions.
If you examine side A in the figure after three days, you should find

A) a decrease in the concentration of NaCl and glucose and an increase in the water level.
B) a decrease in the concentration of NaCl, an increase in water level, and no change in the concentration of glucose.
C) no net change in the system.
D) a decrease in the concentration of NaCl and a decrease in the water level.
E) no change in the concentration of NaCl and glucose and an increase in the water level.