Chapter 01: Cellular Biology
McCance/Huether: Pathophysiology: The Biologic Basis of Disease in Adults and Children, 8th Edition

MULTIPLE CHOICE

	1.	Which statement best describes the cellular function of metabolic absorption?
a.	Cells can produce proteins.	
b.	Cells can secrete digestive enzymes.	
c.	Cells can take in and use nutrients.	
d.	Cells can synthesize fats.	

ANS:	C
In metabolic absorption, all cells take in and use nutrients and other substances from their surroundings. The remaining options are not inclusive in their descriptions of cellular metabolic absorption.

PTS:	1	DIF:	Cognitive Level: Remembering

	2.	Where is most of a cell’s genetic information, including RNA and DNA, contained?
a.	Mitochondria	
b.	Ribosome	
c.	Nucleolus	
d.	Lysosome	

ANS:	C
The nucleus contains the nucleolus, a small dense structure composed largely of RNA, most of the cellular DNA, and the DNA-binding proteins, such as the histones, which regulate its activity. The mitochondria are responsible for cellular respiration and energy production. Ribosomes’ chief function is to provide sites for cellular protein synthesis. Lysosomes function as the intracellular digestive system.

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	3.	Which component of the cell produces hydrogen peroxide (H2O2) by using oxygen to remove hydrogen atoms from specific substrates in an oxidative reaction?
a.	Lysosomes	
b.	Peroxisomes	
c.	Ribosomes	
d.	Endosome	

ANS:	B
Peroxisomes are so named because they usually contain enzymes that use oxygen to remove hydrogen atoms from specific substrates in an oxidative reaction that produces H2O2, which is a powerful oxidant and potentially destructive if it accumulates or escapes from peroxisomes. Ribosomes are RNA-protein complexes (nucleoproteins) that are synthesized in the nucleolus and secreted into the cytoplasm through pores in the nuclear envelope called nuclear pore complexes. Lysosomes are saclike structures that originate from the Golgi complex and contain more than 40 digestive enzymes called hydrolases, which catalyze bonds in proteins, lipids, nucleic acids, and carbohydrates. An endosome is a vesical that has been pinched off from the cellular membrane.

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	4.	Which cell component is capable of cellular autodigestion when it is released during cell injury?
a.	Ribosome	
b.	Golgi complex	
c.	Smooth endoplasmic reticulum	
d.	Lysosomes	

ANS:	D
The lysosomal membrane acts as a protective shield between the powerful digestive enzymes within the lysosome and the cytoplasm, preventing their leakage into the cytoplasmic matrix. Disruption of the membrane by various treatments or cellular injury leads to a release of the lysosomal enzymes, which can then react with their specific substrates, causing cellular self-digestion. The chief function of a ribosome is to provide sites for cellular protein synthesis. The Golgi complex is a network of flattened, smooth vesicles and membranes often located near the cell nucleus. The smooth endoplasmic reticulum is involved in steroid hormone production and removing toxic substances from the cell.

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	5.	Which cAMP-mediated response is related to antidiuretic hormone?
a.	Increased heart rate and force of contraction	
b.	Secretion of cortisol	
c.	Increased retention of water	
d.	Breakdown of fat	

ANS:	C
Antidiuretic hormone leads to increased retention of water in the body. Epinephrine causes increases in heart rate and force of contraction. Increased cortisol secretion is due to ACTH. Breakdown of fat is due to glucagon.

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	6.	During which phase of the cell cycle is DNA synthesized?
a.	G1	
b.	S	
c.	G2	
d.	M	

ANS:	B
The four designated phases of the cell cycle are: (1) the G1 phase (G = gap), which is the period between the M phase (M = mitosis) and the start of DNA synthesis; (2) the S phase (S = synthesis), during which DNA is synthesized in the cell nucleus; (3) the G2 phase, during which RNA and protein synthesis occurs, the period between the completion of DNA synthesis and the next phase (M); and (4) the M phase, which includes nuclear and cytoplasmic division.

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	7.	What organic compound facilitates transportation across cell membranes by acting as receptors, transport channels for electrolytes, and enzymes to drive active pumps?
a.	Lipids	
b.	Proteases	
c.	Proteins	
d.	Carbohydrates	

ANS:	C
Proteins have several functions, including acting as receptors, transport channels for electrolytes, and enzymes to drive active pumps Lipids help act as the “glue” holding cell membranes together. Proteases cause the breakdown of protein. Carbohydrates are involved in cellular protection and lubrication and help produce energy via oxidative phosphorylation.

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	8.	Understanding the various steps of proteolytic cascades may be useful in designing drug therapy for which human diseases?
a.	Cardiac and vascular disorders	
b.	Autoimmune and malignant disorders	
c.	Gastrointestinal and renal disorders	
d.	Endocrine and gastrointestinal disorders	

ANS:	B
Understanding the various steps involved in this process is crucial for designing drug interventions. Dysregulation of proteases features prominently in many human diseases, including cancer, autoimmunity, and neurodegenerative disorders. Cardiac, vascular, gastrointestinal, renal, and endocrine disorders do not involve this process.

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	9.	Which structure prevents water-soluble molecules from entering cells across the plasma membrane?
a.	Carbohydrate chains	
b.	Glycoprotein channels	
c.	Membrane channel proteins	
d.	Lipid bilayer	

ANS:	D
The bilayer’s structure accounts for one of the essential functions of the plasma membrane. It is impermeable to most water-soluble molecules (molecules that dissolve in water) because the water-soluble molecules are insoluble in the oily core region. The bilayer serves as a barrier to the diffusion of water and hydrophilic substances while allowing lipid-soluble molecules, such as oxygen (O2) and carbon dioxide (CO2), to diffuse through it readily. Carbohydrate chains, glycoprotein channels, and membrane channel proteins do not prevent water-soluble molecules from entering cells across the cell membrane.

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	10.	A student asks for an explanation of the absolute refractory period of the action potential. What response by the professor is best?
a.	A stronger than normal impulse will evoke another response.	
b.	No stimulus is able to evoke another response at this time.	
c.	Multiple stimuli can produce more rapid action potentials.	
d.	The hyperpolarized state means a weaker stimulus produces a response.	

ANS:	B
During the absolute refractory state of the action potential, no stimulus is able to evoke another response from the cell. A stronger than normal impulse may generate a response in the relative refractory period. This period of time is not related to the number of stimuli. A hyperpolarized state means a stronger than normal stimulus would be needed to generate a response.

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	11.	Which form of cell communication is used to communicate within the cell itself and with other cells in direct physical contact?
a.	Protein channel (gap junction)	
b.	Plasma membrane-bound signaling molecules	
c.	Hormone secretion such as neurotransmitters	
d.	Extracellular chemical messengers such as ligands	

ANS:	B
Cells communicate in three main ways; they display plasma membrane-bound signaling molecules that affect the cell itself and other cells in direct physical contact with it, they affect receptor proteins inside the target cell, and they form protein channels (gap junctions) that directly coordinate the activities of adjacent cells. Neurotransmitters are released by neurons and cross the synaptic cleft to communicate with the cells they innervate. Ligands are involved in binding processes.

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	12.	Which mode of chemical signaling uses blood to transport communication to cells some distance away?
a.	Paracrine	
b.	Autocrine	
c.	Neurotransmitter	
d.	Hormonal	

ANS:	D
Chemical signaling can be classified into three categories: (1) local-chemical mediator, (2) hormone, and (3) neurotransmitter. Hormones are released by one set of cells and travel through tissues or the bloodstream to another set of cells where they produce a response by those cells. In paracrine signaling, cells secrete local chemical mediators that are quickly absorbed, destroyed, or immobilized. Paracrine signaling requires close membrane-to-membrane contact. Paracrine signaling usually involves different cell types; however, cells also may produce signals that they, themselves, respond to, which is called autocrine signaling. Neurotransmitters are released by neurons and cross the synaptic cleft to communicate with the cells they innervate.

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	13.	Which mode of chemical signaling uses local chemical mediators that are quickly taken up, destroyed, or immobilized?
a.	Paracrine	
b.	Autocrine	
c.	Neurotransmitter	
d.	Hormone	

ANS:	A
In paracrine signaling, cells secrete local chemical mediators that are quickly taken up, destroyed, or immobilized. Autocrine signaling occurs when the target cells produce signals that they themselves respond to. Neurotransmitters are released by neurons and cross the synaptic cleft to communicate with the cells they innervate. Hormones are released by one set of cells and travel through tissues or the bloodstream to another set of cells where they produce a response by those cells.

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	14.	Neurotransmitters affect the postsynaptic membrane by binding to which structure?
a.	Lipids	
b.	Ribosomes	
c.	Amphipathic lipids	
d.	Receptors	

ANS:	D
In each type of chemical signaling, the target cell receives the signal by first attaching to its receptors. The other options do not correctly describe this process.

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	15.	How do cells receive communication from the extracellular fluid surrounding them?
a.	Protein channel (gap junction)	
b.	Plasma membrane-bound signaling molecules (involving receptors)	
c.	Hormone secretion such as neurotransmitters	
d.	Chemical messengers such as ligands	

ANS:	D
Signal transduction involves incoming signals or instructions from extracellular chemical messengers (ligands) that are conveyed to the cell’s interior for execution. The other options do not correctly describe how cells receive communication from the surrounding extracellular fluid.

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	16.	Which molecule provides the second messenger necessary for extracellular communication to be activated?
a.	Guanosine triphosphate (GTP)	
b.	Adenosine monophosphate (AMP)	
c.	Adenosine triphosphate (ATP)	
d.	Guanosine diphosphate (GDP)	

ANS:	B
The two major second-messenger pathways are cyclic AMP (cAMP) and calcium (Ca++). GTP, ATP, and GDP are not major second-messenger pathways. GTP and GDP are “middlemen” or intermediaries. Nutrients are transformed into energy in the form of ATP.

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	17.	Under anaerobic conditions, what process provides energy for the cell?
a.	Oxidative phosphorylation	
b.	Glycolysis	
c.	Lactolysis	
d.	Passive transport	

ANS:	B
Glycolysis provides energy to the cells when oxygen delivery is insufficient or delayed. Oxidative phosphorylation is the process by which energy produced from nutrients is transferred to ATP. Lactolysis is the breakdown of lactose. Passive transport is the movement of water and small, nonelectrically charge molecules across plasma membranes.

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	18.	What is the mechanism by which the energy produced from carbohydrates, proteins, and lipids is transferred to adenosine triphosphate (ATP)?
a.	Anaerobic glycolysis	
b.	Oxidative cellular metabolism	
c.	Oxidative phosphorylation	
d.	Tricarboxylic acid phosphorylation	

ANS:	C
Oxidative phosphorylation occurs in the mitochondria and is the mechanism by which the energy produced from carbohydrates, fats, and proteins is transferred to ATP. Glycolysis provides energy to the cells when oxygen delivery is insufficient or delayed. Oxidative cellular metabolism and tricarboxylic acid phosphorylation are not involved in transferring energy to ATP.

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	19.	Passive transport is best described with which statement?
a.	Being driven by osmosis, hydrostatic pressure, and diffusion	
b.	Involving receptors that can bind with substances being transported	
c.	Being capable of transporting macromolecules	
d.	Requiring energy generated by the cell	

ANS:	A
Water and small electrically uncharged molecules move easily through pores in the plasma membrane’s lipid bilayer. This process, called passive transport, naturally occurs through any semipermeable barrier. It is driven by osmosis, hydrostatic pressure, and diffusion, all of which depend on the laws of physics and do not require life. The other options do not correctly describe passive transport.

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	20.	Which is the best example of active transport?
a.	Movement across a membrane due to differences in solute concentration	
b.	Movement requiring the expenditure of metabolic energy	
c.	Movement of two molecules simultaneously in one direction	
d.	Movement of two molecules simultaneously in opposite directions	

ANS:	B
Active transport requires a life, biologic activity, and the expenditure of metabolic energy. Movement due simply to differences in concentration gradients is called passive transport. Movement of two molecules in the same direction is called symport, while moving two molecules in opposite directions is called antiport.

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	21.	Which method of transport uses transmembrane proteins with receptors with a high degree of specificity for the substance being transported?
a.	Active	
b.	Mediated	
c.	Transmembranous	
d.	Passive	

ANS:	B
Mediated transport (passive and active) involves integral or transmembrane proteins with receptors having a high degree of specificity for the substance being transported. Active and passive transport are opposites with active transport requiring the use of energy and passive transport relying on osmosis, hydrostatic pressure, and diffusion and not energy. Transmembranous means “across membranes.”

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	22.	The movement of fluid across the arterial end of capillary membranes into the interstitial fluid surrounding the capillary is an example of which fluid movement process?
a.	Hydrostatic pressure	
b.	Osmosis	
c.	Diffusion	
d.	Active transport	

ANS:	A
Hydrostatic pressure is the mechanical force of water pushing against cellular membranes. Osmosis is the movement of water “down” a concentration gradient, that is, across a semipermeable membrane from a region of higher water concentration to a region of lower water concentration. Diffusion is the movement of a solute molecule from an area of greater solute concentration to an area of lesser solute concentration. Active transport requires a life, biologic activity, and the expenditure of metabolic energy.

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	23.	A student asks why osmolality is preferred over osmolarity as the measurement of osmotic activity in the clinical assessment of individuals. What response by the professor is most accurate?
a.	Plasma contains sodium and chloride, which influence the volume of solution.	
b.	Volume affects perfusion more than the weight of solutes.	
c.	More of the weight of plasma is influenced by solutes rather than by water.	
d.	Osmotic activity depends on the concentration of solutes present in plasma.	

ANS:	C
Osmolality is a measure of the number of milliosmoles per kilogram (mOsm/kg) of water, or the concentration of molecules per weight of water. Osmolarity is a measure of the number of milliosmoles per liter (mOsm/L) of solution, or the concentration of molecules per volume of solution. Osmolality is a measure of the number of milliosmoles per kilogram (mOsm/kg) of water, or the concentration of molecules per weight of water. Osmolarity is a measure of the number of milliosmoles per liter (mOsm/L) of solution, or the concentration of molecules per volume of solution. In plasma, less of the plasma weight is water; therefore the overall concentration of particles is greater. The osmolality will be greater than the osmolarity because of the smaller proportion of water. Osmolality is thus the preferred measure of osmotic activity in clinical assessment of individuals.

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	24.	A patient who has diarrhea receives a 3% saline solution intravenously to replace the sodium and chloride lost in the stool. What effect will this fluid replacement have on cells?
a.	Become hydrated	
b.	Swell or burst	
c.	Shrink	
d.	Divide	

ANS:	C
A hypertonic solution has a concentration of greater than 285 to 294 mOsm/kg. An example of a hypertonic solution is 3% saline solution. Water can be pulled out of the cells by a hypertonic solution; therefore the cells shrink. An isotonic solution will cause the cells to become more hydrated without disrupting the osmolality of either intracellular or extracellular fluid. Hypotonic solutions can cause cells to swell or burst. No solutions lead to cell division.

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	25.	The transport of glucose from the blood to the cell is accomplished by which process?
a.	Hydrostatic pressure	
b.	Active diffusion	
c.	Passive osmosis	
d.	Mediated transport	

ANS:	D
Mediated transport is the means by which glucose is transported from the blood to the cells. This process uses transport proteins. Hydrostatic pressure is the force of water pushing against a cell membrane. Diffusion is a passive process, not active. Osmosis is the movement of water “down” a concentration gradient, that is, across a semipermeable membrane from a region of higher water concentration to a region of lower water concentration and is a passive process.

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	26.	What transports potassium and sodium across plasma membranes?
a.	Passive electrolyte channels	
b.	Coupled channels	
c.	Adenosine triphosphatase (ATPase) enzyme	
d.	Diffusion	

ANS:	C
The exact mechanism for the transport of Na+ and K+ across the membrane is uncertain. One proposal is that ATPase enzyme induces the transporter protein to undergo several conformational changes, causing Na+ and K+ to move short distances (see Figure 1-29). The remaining options do not correctly describe the means by which K+ and Na+ are transported.

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	27.	What occurs during exocytosis?
a.	Macromolecules can be secreted across eukaryotic cell membranes.	
b.	All substances are secreted into the cellular matrix.	
c.	No repairs in the plasma membrane can take place.	
d.	Solute molecules flow freely into and out of the cell.	

ANS:	A
In eukaryotic cells, secretion of macromolecules almost always occurs by exocytosis. The remaining options do not correctly describe exocytosis.

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	28.	The cellular uptake of the nutrient cholesterol depends on which process?
a.	Receptor-mediated exocytosis	
b.	Antiport system	
c.	Receptor-mediated endocytosis	
d.	Passive transport	

ANS:	C
The cellular uptake of nutrients, such as cholesterol, for example, depends on receptor-mediated endocytosis. Nutrients are not transported via the other options.

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	29.	What causes the rapid change in the resting membrane potential to initiate an action potential?
a.	Potassium gates open, and potassium rushes into the cell, changing the membrane potential from negative to positive.	
b.	Sodium gates open, and sodium rushes into the cell, changing the membrane potential from negative to positive.	
c.	Sodium gates close, allowing potassium into the cell to change the membrane potential from positive to negative.	
d.	Potassium gates close, allowing sodium into the cell to change the membrane potential from positive to negative.	

ANS:	B
When a resting cell is stimulated through voltage-regulated channels, the cell membranes become more permeable to Na+. As Na+ moves into the cell the membrane potential decreases, or moves forward, from a negative value (in millivolts) to zero. The Na+ gates open, and Na+ rushes into the cell, causing the membrane potential to reduce to zero and then become positive (depolarization). The remaining options do not correctly describe the change that initiates an action potential.

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	30.	The action of platelet-derived growth factor is to stimulate the production of which cells?
a.	Platelets	
b.	Epidermal cells	
c.	Connective tissue cells	
d.	Fibroblast cells	

ANS:	C
Different types of cells require different factors to stimulate proliferation; for example, platelet-derived growth factor stimulates the production of connective tissue cells. Platelet-derived growth factor does not stimulate production of platelets, epidermal cells, or fibroblasts.

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	31.	What role do cytokines play in cell reproduction?
a.	Provide growth factor for tissue growth and development	
b.	Block progress of cell reproduction through the cell cycle	
c.	Restrain cell growth and development	
d.	Provide nutrients for cell growth and development	

ANS:	A
Growth factors, also called cytokines, stimulate an increase in cell mass or cell growth by promoting the synthesis of proteins and other macromolecules and inhibiting their degradation.

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	32.	What is the process of cellular reproduction?
a.	The process often takes months or years to complete.	
b.	Cellular reproduction typically has a short interphase.	
c.	Two diploid cells, called daughter cells, have been formed.	
d.	The process involves the interaction of male and female cells.	

ANS:	C
During telophase, the final stage of cellular reproduction, two identical diploid cells, called daughter cells, has been formed from the original cell. The process occurs hundreds of times a second. Interphase is the longest phase of the cell cycle. Male and female cells do not interact in cellular reproduction; each cell is responsible for reproducing itself.

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	33.	Which statement is true about eukaryotic cells?
a.	They lack distinct nucleus.	
b.	They contain compartments called organelles.	
c.	They lack an encasing nuclear membrane.	
d.	They are smaller than the typical prokaryote cell.	

ANS:	B
Eukaryotic cells have a characteristic set of membrane-bound intracellular compartments called organelles that include a well-defined nucleus encased in a nuclear membrane. Eukaryotic cells are also larger than prokaryotes.

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	34.	Which statement is true about phagocytosis?
a.	Phagocytosis is an example of exocytosis.	
b.	Phagocytosis is dependent on small vesicles.	
c.	Phagocytosis involves the ingestion of bacteria.	
d.	Phagocytosis focuses on solute molecules.	

ANS:	C
Phagocytosis is the engulfment of large particles in phagocytic cells. Phagocytosis is an example of endocytosis, not exocytosis and does not focus on solutes.

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	35.	A muscle cell possesses which specialized function?
a.	Movement	
b.	Conductivity	
c.	Secretion	
d.	Respiration	

ANS:	A
A cell has the potential to differentiation and to gain the ability to perform one of eight specialized functions. Muscle cells can generate forces that produce motion. Nerves cells are capable of conductivity. Cells of the adrenal gland, testis, and ovary can secrete. Respiration is a function that all cells possess.

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	36.	When a mucous gland cell creates a new substance from previously absorbed material, this process is known as which specialized cellular function?
a.	Excretion	
b.	Metabolic absorption	
c.	Reproduction	
d.	Secretion	

ANS:	D
Certain cells, such as mucous gland cells, can synthesize new substances from substances they absorb and then secrete the new substances to serve elsewhere as needed. Excretion occurs when cells rid themselves of waste products. Reproduction is the process of forming new cells.

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	37.	All cells are capable of what process?
a.	Excretion	
b.	Movement	
c.	Conductivity	
d.	Continuous division	

ANS:	A
All cells have the capacity to excrete, thus allowing them to rid themselves of waste products resulting from the metabolic breakdown of nutrients. Muscle cells have the property of movement. Conductivity is a property of nerve cells. Many, but not all, cells are capable of reproduction.

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	38.	What is the best description of cell cycle arrest?
a.	The cell cycle is stopped due to damaged DNA.	
b.	Programmed cell death is suppressed.	
c.	Macromolecule degradation is inhibited.	
d.	Production of growth factors is halted.	

ANS:	A
The DNA damage response occurs when DNA is damaged and several protein kinases are recruited to the site of damage and start a signaling pathway that stops the progression of the cell cycle, or cell cycle arrest. Cell cycle arrest does not involve suppressing programmed cell death, macromolecule degradation, or growth factor production.

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MULTIPLE RESPONSE

	1.	What are the major chemical components of the cell membranes? (Select all that apply.)
a.	Lipids	
b.	Sodium ions	
c.	Carbohydrates	
d.	DNA	
e.	Proteins	

ANS:	A, E
The major chemical components of all cell membranes are lipids and proteins. Sodium ions, carbohydrates, and DNA are not major chemical components of cell membranes.

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	2.	Which statements are true concerning the process of mediated transport? (Select all that apply.)
a.	Can be active or passive	
b.	Only moves one molecule at a time	
c.	Involves transport proteins	
d.	Expends tremendous energy	
e.	Occurs only with hormones	

ANS:	A, C
Mediated transport uses membrane transport proteins and can be either active or passive. Mediated transport systems can move molecules singly or two at a time and may or may not use energy. Many substances can be moved through mediated transport.

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	3.	What is passive transport dependent on? (Select all that apply.)
a.	Semipermeable barrier membrane	
b.	The process of osmosis	
c.	Diffusion as a driving force	
d.	A living host	
e.	Hydrostatic pressure	

ANS:	A, B, C, E
Passive transport naturally occurs through any semipermeable barrier. It is driven by osmosis, hydrostatic pressure, and diffusion, all of which depend on the laws of physics and do not require life.

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	4.	What is the primary function of proteins? (Select all that apply.)
a.	Proteins are binding units.	
b.	Proteins are transport channels.	
c.	Proteins are ribonucleoproteins.	
d.	Proteins provide cell surface markers.	
e.	Proteins are chemical reaction catalysts.	

ANS:	A, B, D, E
Protein functions include (a) recognition and binding units (receptors) for substances moving in and out of the cell; (b) pores or transport channels; (c) enzymes that drive active pumps; (d) cell surface markers, such as glycoproteins; (e) cell adhesion molecules; and (f) catalysts of chemical reactions.

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