Chapter 20

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

D

The artificial introduction of three key ______________ into an adult cell can convert the adult cell into a cell with the properties of ES cells. a. hormones b. chromosomes c. viruses d. transcription factors

D

Which of the following statements about integrins is false? 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. An activated integrin molecule takes on an extended conformation. d. Integrins can switch to an activated state by binding to an intracellular protein.

A

A major distinction between the connective tissues in an animal and other main tissue types such as epithelium, nervous tissue, or muscle is _______________. Select one: a. the ability of connective-tissue cells such as fibroblasts to change shape. b. the amount of extracellular matrix in connective tissues. c. the numerous connections that connective-tissue cells make with each other. d. the ability of connective tissues to withstand mechanical stresses.

B

An adult hemopoietic stem cell found in the bone marrow ______________________. a. will express all the same transcription factors as those found in an unfertilized egg. b. can undergo self-renewing divisions for the lifetime of a healthy animal. c. will occasionally produce epidermal cells when necessary. d. can produce only red blood cells.

B

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

B

Which of the following statements about animal connective tissues is true? a. Cells can attach to a collagen matrix by using fibronectin, an integral membrane protein. b. Proteoglycans can resist compression in the extracellular matrix. c. Enzymes embedded in the plasma membrane synthesize the collagen in the extracellular matrix extracellularly. d. In connective tissue, the intermediate filaments within the cells are important for carrying the mechanical load.

B

Cells that are terminally differentiated ______________________. a. are unable to move. b. will undergo apoptosis within a few days. c. can no longer undergo cell division. d. no longer produce RNAs.

C

Which of the following statements about cancer is false? a. Tobacco use is responsible for more than 20% of all cancer deaths. b. Viruses cause some cancers. 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.

C

Which type of junction contributes the most to the polarization of epithelial cells? a. adherens junctions b. desmosomes c. tight junctions d. gap junctions

C