20

Front 1

20-1 Both multicellular plants and animals have _____________________.

Back 1

(d) tissues composed of multiple different cell types.

Hint 1

(a) cells capable of locomotion.
(b) cells with cell walls.
(c) a cytoskeleton composed of actin filaments, microtubules, and intermediate filaments.
(d) tissues composed of multiple different cell types.

Front 2

20-3 Which of the following statements about plant cell walls is true?

Back 2

(a) The microtubule cytoskeleton directs the orientation in which cellulose is deposited in the cell wall.

Hint 2

(a) The microtubule cytoskeleton directs the orientation in which cellulose is deposited in the cell wall.
(b) The molecular components of the cell wall are the same in all plant tissues.
(c) Because plant cell walls are rigid, they are not deposited until the cell has stopped growing.
(d) The cellulose found in cell walls is produced as a precursor molecule in the cell and delivered to the extracellular space by exocytosis.

Front 3

20-5 Which of the following molecules is not found in plants?

Back 3

(c) collagen

Hint 3

(a) cellulose

Front 4

20-6 Which of the following statements about cellulose is false?

Back 4

(d) Microtubules are directly attached to the outside surface of the plasma membrane to form tracks that help orient the cellulose polymers.

Hint 4

(a) Cellulose synthase enzyme complexes are integral membrane proteins.
(b) An array of microtubules guides the cellulose synthase complex as it moves in the membrane.
(c) The sugar monomers necessary for the synthesis of a cellulose polymer are transported across the plasma membrane.
(d) Microtubules are directly attached to the outside surface of the plasma membrane to form tracks that help orient the cellulose polymers.

Front 5

20-8 Which of the following is not an example of a connective tissue?

Back 5

(b) the layer of photoreceptors in the eye

Hint 5

(a) bone
(b) the layer of photoreceptors in the eye
(c) the jellylike interior of an eye
(d) cartilage

Front 6

20-9 Which of the following statements about animal connective tissues is true?

Back 6

(d) Proteoglycans can resist compression in the extracellular matrix.

Hint 6

(a) Enzymes embedded in the plasma membrane synthesize the collagen in the extracellular matrix extracellularly.
(b) In connective tissue, the intermediate filaments within the cells are important for carrying the mechanical load.
(c) Cells can attach to a collagen matrix by using fibronectin, an integral membrane protein.
(d) Proteoglycans can resist compression in the extracellular matrix.

Front 7

20-11 Which of the following statements about collagen is false?

Back 7

(a) Collagen synthase organizes the mature collagen molecules into ordered collagen fibrils.

Hint 7

(a) Collagen synthase organizes the mature collagen molecules into ordered collagen fibrils.
(b) Collagen is synthesized as procollagen and secreted to the outside of the cell in a secretory vesicle.
(c) The terminal procollagen domains are cleaved by a protease in the extracellular space.
(d) Cells can break down a collagen matrix using matrix proteases.

Front 8

20-12 Fibroblasts organize the collagen of the extracellular matrix by ______________.

Back 8

(d) pulling the collagen into sheets or cables after it has been secreted.

Hint 8

(a) cutting and rejoining the fibrils.
(b) processing procollagen into collagen.
(c) twisting fibrils together to make ropelike fibers.
(d) pulling the collagen into sheets or cables after it has been secreted.

Front 9

20-14 A cell can crawl through a tissue because of the transmembrane ______________ proteins that can bind to fibronectin outside of the cell.

Back 9

(a) integrin

Hint 9

(a) integrin
(b) collagen
(c) gap junction
(d) claudin

Front 10

20-15 Which of the following statements about integrins is false?

Back 10

a) Integrins use adaptor proteins to interact with the microtubule cytoskeleton.

Hint 10

(a) Integrins use adaptor proteins to interact with the microtubule cytoskeleton.
(b) Integrins can switch to an activated state by binding to an extracellular matrix molecule.
(c) Integrins can switch to an activated state by binding to an intracellular protein.
(d) An activated integrin molecule takes on an extended conformation.

Front 11

20-16 Proteoglycans in the extracellular matrix of animal tissues ________________.

Back 11

(b) allow cartilage to resist compression.

Hint 11

(a) chiefly provide tensile strength.
(b) allow cartilage to resist compression.
(c) are linked to microtubules through the plasma membrane.
(d) are polysaccharides composed of glucose subunits.

Front 12

20-17 Which of the following statements is false?

Back 12

(c) Proteoglycans are a major component of compact connective tissues but are relatively unimportant in watery tissues such as the jellylike substance in the interior of the eye.

Hint 12

(a) Proteoglycans can act as filters to regulate which molecules pass through the extracellular medium.
(b) The negative charge associated with proteoglycans attracts cations, which cause water to be sucked into the extracellular matrix.
(c) Proteoglycans are a major component of compact connective tissues but are relatively unimportant in watery tissues such as the jellylike substance in the interior of the eye.
(d) Glycosaminoglycans are components of proteoglycan.

Front 13

20-19 A basal lamina ______________________.

Back 13

(b) is a thin layer of extracellular matrix underlying an epithelium

Hint 13

(a) is a thin layer of connective-tissue cells and matrix underlying an epithelium.
(b) is a thin layer of extracellular matrix underlying an epithelium.
(c) is attached to the apical surface of an epithelium.
(d) separates epithelial cells from each other.

Front 14

20-21 Tight junctions ______________________.

Back 14

(c) are formed from claudins and occludins.

Hint 14

(a) allow small, water-soluble molecules to pass from cell to cell.
(b) interact with the intermediate filaments inside the cell.
(c) are formed from claudins and occludins.
(d) are found in cells in connective tissues.

Front 15

20-22 Adherens junctions ______________________.

Back 15

(a) can be used to bend epithelial sheets into tubes.

Hint 15

(a) can be used to bend epithelial sheets into tubes.
(b) are most often found at the basal surface of cells.
(c) are found only in adult tissues.
(d) involve fibronectin and integrin interactions.

Front 16

20-23 At desmosomes, cadherin molecules are connected to ________________.

Back 16

(b) intermediate filaments.

Hint 16

(a) actin filaments.
(b) intermediate filaments.
(c) microtubules.
(d) gap junctions.

Front 17

20-24 Hemidesmosomes are important for ______________________.

Back 17

(d) attaching epithelial cells to the extracellular matrix.

Hint 17

(a) tubulation of epithelial sheets.
(b) linkages to glycosaminoglycans.
(c) forming the basal lamina.
(d) attaching epithelial cells to the extracellular matrix.

Front 18

20-28 A major distinction between the connective tissues in an animal and other main tissue types such as epithelium, nervous tissue, or muscle is _______________.

Back 18

(b) the amount of extracellular matrix in connective tissues.

Hint 18

(a) the ability of connective-tissue cells such as fibroblasts to change shape.
(b) the amount of extracellular matrix in connective tissues.
(c) the ability of connective tissues to withstand mechanical stresses.
(d) the numerous connections that connective-tissue cells make with each other.

Front 19

20-30 Which of the following statements about gap junctions is false?

Back 19

(c) Because gap junctions do not allow ions to pass through, they are not used for electrically coupling cells.

Hint 19

(a) Gap junctions are made of connexons.
(b) Molecules up to 1000 daltons in molecular mass can move across gap junctions.
(c) Because gap junctions do not allow ions to pass through, they are not used for electrically coupling cells.
(d) Gap junctions can close in response to extracellular signals.

Front 20

20-31 Which type of junction involves a connection to the actin cytoskeleton?

Back 20

(a) adherens junctions

Hint 20

(a) adherens junctions
(b) desmosomes
(c) tight junctions
(d) gap junctions

Front 21

20-32 Which type of junction contributes the most to the polarization of epithelial cells?

Back 21

(c) tight junctions

Hint 21

(a) adherens junctions
(b) desmosomes
(c) tight junctions
(d) gap junctions

Front 22

20-33 Cadherins ______________________.

Back 22

(b) mediate cell–cell attachments through homophilic interactions.

Hint 22

(a) are used to transfer proteins from one cell to another.
(b) mediate cell–cell attachments through homophilic interactions.
(c) are abundant in the plant cell wall.
(d) bind to collagen fibrils.

Front 23

20-34 Plasmodesmata ______________________.

Back 23

(a) permit small molecules to pass from one cell to another.

Hint 23

(a) permit small molecules to pass from one cell to another.
(b) are found only in animal cells.
(c) are closed by the neurotransmitter dopamine.
(d) provide tensile strength.

Front 24

20-35 The plasmodesmata in plants are functionally most similar to which animal cell junction?

Back 24

(c) gap junction

Hint 24

(a) tight junction
(b) adherens junction
(c) gap junction
(d) desmosome

Front 25

20-39 Cells that are terminally differentiated ______________________.

Back 25

(b) can no longer undergo cell division.

Hint 25

(a) will undergo apoptosis within a few days.
(b) can no longer undergo cell division.
(c) are unable to move.
(d) no longer produce RNAs.

Front 26

20-40 When a terminally differentiated cell in an adult body dies, it can typically be replaced in the body by a stock of ________.

Back 26

(a) proliferating precursor cells.

Hint 26

(a) proliferating precursor cells.
(b) cells more apically located than the terminally differentiated cells.
(c) Wnt proteins.
(d) induced pluripotent cells.

Front 27

20-41 An adult hemopoietic stem cell found in the bone marrow ______________________.

Back 27

(c) can undergo self-renewing divisions for the lifetime of a healthy animal.

Hint 27

(a) will occasionally produce epidermal cells when necessary.
(b) can produce only red blood cells.
(c) can undergo self-renewing divisions for the lifetime of a healthy animal.
(d) will express all the same transcription factors as those found in an unfertilized egg.

Front 28

20-42 A pluripotent cell _________.

Back 28

(b) can give rise to all the tissues and cell types in the body.

Hint 28

(a) can only be produced in the laboratory.
(b) can give rise to all the tissues and cell types in the body.
(c) can only give rise to stem cells.
(d) is considered to be terminally differentiated.

Front 29

20-43 Mouse embryonic stem (ES) cells ______________________.

Back 29

(d) come from the inner cell mass of early embryos.

Hint 29

(a) can only be produced through therapeutic cloning.
(b) can give rise to all tissues and cell types in the body except germ cells.
(c) can be implanted in foster mothers to produce cloned cows and other animals.
(d) come from the inner cell mass of early embryos.

Front 30

20-44 How do reproductive cloning and therapeutic cloning differ?

Back 30

(d) Embryos are placed into foster mothers during reproductive cloning but not during therapeutic cloning.

Hint 30

(a) The DNA in the nucleus of cells produced for therapeutic cloning is genetically identical to the donor genome, whereas in cells produced for reproductive cloning it is not.
(b) Reproductive cloning requires a supply of fertilized donor egg cells, whereas therapeutic cloning requires unfertilized egg cells.
(c) Therapeutic cloning requires nuclear transplantation, whereas reproductive cloning does not.
(d) Embryos are placed into foster mothers during reproductive cloning but not during therapeutic cloning.

Front 31

20-45 An individual that arises by reproductive cloning has a nuclear genome that is identical to __________.

Back 31

(b) the adult who donated the cell for nuclear transplantation.

Hint 31

(a) the female who donated the egg.
(b) the adult who donated the cell for nuclear transplantation.
(c) both the female who donated the egg and the adult who donated the cell for nuclear transplantation.
(d) the foster mother in which the embryo is placed.

Front 32

20-46 Induced pluripotent stem (iPS) cells ______________________.

Back 32

(a) are created by the expression of a set of key genes in cells derived from adult tissues so that these cells can differentiate into a variety of cell types.

Hint 32

(a) are created by the expression of a set of key genes in cells derived from adult tissues so that these cells can differentiate into a variety of cell types.
(b) require a supply of donor egg cells, such as embryonic stem cells.
(c) can differentiate into a greater variety of adult tissues than embryonic stem cells.
(d) are created by nuclear transplantation.

Front 33

20-47 The artificial introduction of three key ______________ into an adult cell can convert the adult cell into a cell with the properties of ES cells.

Back 33

(d) transcription factors

Hint 33

(a) chromosomes
(b) viruses
(c) hormones
(d) transcription factors

Front 34

20-50 A malignant tumor is more dangerous than a benign tumor because ______________________.

Back 34

(d) its cells invade other tissues.

Hint 34

(a) its cells are proliferating faster.
(b) it causes neighboring cells to mutate.
(c) its cells attack and phagocytose neighboring normal tissue cells.
(d) its cells invade other tissues.

Front 35

20-51 A metastasis is _________.

Back 35

(a) a secondary tumor in a different part of the body that arises from a cell from the primary tumor.

Hint 35

(a) a secondary tumor in a different part of the body that arises from a cell from the primary tumor.
(b) a cell that is dividing in defiance of normal constraints.
(c) a part of the primary tumor that has invaded the surrounding tissue.
(d) the portion of the cancerous tumor that displays genetic instability.

Front 36

20-52 Which of the following statements about cancer is false?

Back 36

(c) A mutation in even a single cancer-critical gene is sufficient to convert a normal cell into a cancer cell.

Hint 36

(a) Viruses cause some cancers.
(b) Tobacco use is responsible for more than 20% of all cancer deaths.
(c) A mutation in even a single cancer-critical gene is sufficient to convert a normal cell into a cancer cell.
(d) Chemical carcinogens cause cancer by changing the nucleotide sequence of DNA.

Front 37

20-54 Which of the following genetic changes cannot convert a proto-oncogene into an oncogene?

Back 37

(a) A mutation that introduces a stop codon immediately after the codon for the initiator methionine.

Hint 37

(a) A mutation that introduces a stop codon immediately after the codon for the initiator methionine.
(b) A mutation within the coding sequence that makes the protein hyperactive.
(c) An amplification of the number of copies of the proto-oncogene, causing overproduction of the normal protein.
(d) A mutation in the promoter of the proto-oncogene, causing the normal protein to be transcribed and translated at an abnormally high level.

Front 38

20-55 Which of the following statements about tumor suppressor genes is false?

Back 38

(b) Cells with one functional copy of a tumor suppressor gene will usually proliferate faster than normal cells.

Hint 38

(a) Gene amplification of a tumor suppressor gene is less dangerous than gene amplification of a proto-oncogene.
(b) Cells with one functional copy of a tumor suppressor gene will usually proliferate faster than normal cells.
(c) Inactivation of tumor suppressor genes leads to enhanced cell survival and proliferation.
(d) Individuals with only one functional copy of a tumor suppressor gene are more prone to cancer than individuals with two functional copies of a tumor suppressor gene.

Front 39

20-57 Ras is a GTP-binding protein that is often defective in cancer cells. A common mutation found in cancer cells causes Ras to behave as though it were bound to GTP all the time, which will cause cells to divide inappropriately. From this description, the normal Ras gene is _______.

Back 39

(c) a proto-oncogene.

Hint 39

(a) a tumor suppressor.
(b) an oncogene.
(c) a proto-oncogene.
(d) a gain-of-function mutation.

Front 40

20-65 APC is a tumor suppressor and acts in the Wnt signaling pathway to prevent the TCF complex from turning on Wnt-responsive genes. Mice that lack the gene encoding TCF4 do not have the ability to maintain the pool of proliferating gut stem cells needed to renew the gut lining. What do you predict will happen in mice that lack the APC gene?

Back 40

(b) Mice lacking the APC gene will have inappropriate proliferation of gut stem cells.

Hint 40

(a) Mice lacking the APC gene will be like the mice lacking TCF4 and not be able to renew the gut lining.
(b) Mice lacking the APC gene will have inappropriate proliferation of gut stem cells.
(c) Mice lacking the APC gene will have a hyperactive Wnt receptor even though there is no Wnt signal.
(d) Mice lacking the APC gene will be like normal healthy mice, since APC is a tumor suppressor and thus not needed unless there is a tumor present.