Kapitel 19

Question 1

Adherens junctions in epithelia that form a continuous belt (zonula adherens) just beneath the apical face of the epithelium - encircling each of the interacting cells in the sheet.

Answer 1

adhesion belt

Question 2

Dependence of cell growth - proliferation - and survival on attachment to a substratum.

Answer 2

anchorage dependence

Question 3

Cell junction that attaches cells to neighboring cells or to the extracellular matrix. (Table 19–1 - p. 1037)

Answer 3

anchoring junction

Question 4

Referring to the tip of a cell - a structure - or an organ. The apical surface of an epithelial cell is the exposed free surface - opposite to the basal surface. The basal surface rests on the basal lamina that separates the epithelium from other tissue.

Answer 4

apical

Question 5

Situated near the base. Opposite the apical surface.

Answer 5

basal

Question 6

Thin mat of extracellular matrix that separates epithelial sheets - and many other types of cells such as muscle or fat cells - from connective tissue. Sometimes called basement membrane. (Figure 19–51)

Answer 6

basal lamina (plural basal laminae)

Question 7

Thin mat of extracellular matrix that separates epithelial sheets - and many other types of cells such as muscle or fat cells - from connective tissue. Also called basal lamina. (Figure 19–51)

Answer 7

basement membrane

Question 8

Member of the large cadherin superfamily of transmembrane adhesion proteins. Mediates homophilic Ca2+-dependent cell–cell adhesion in animal tissues. (Figure 19–3 and Table 19–1 - p. 1037)

Answer 8

cadherin

Question 9

Family of classical and nonclassical cadherin proteins with more than 180 members in humans.

Answer 9

cadherin superfamily

Question 10

Long - unbranched chains of glucose; major constituent of plant cell walls.

Answer 10

cellulose

Question 11

Highly ordered crystalline aggregate formed from bundles of about 40 cellulose chains - arranged with the same polarity and stuck together in overlapping parallel arrays by hydrogen bonds between adjacent cellulose molecules.

Answer 11

cellulose microfibril

Question 12

Family of cadherin proteins - including E-cadherin - N-cadherin - and P-cadherin - that are closely related in sequence throughout their extracellular and intracellular domains.

Answer 12

classical cadherins

Question 13

Fibrous protein rich in glycine and proline that is a major component of the extracellular matrix in animals - conferring tensile strength. Exists in many forms: type I - the most common - is found in skin - tendon - and bone; type II is found in cartilage; type IV is present in basal laminae. (Figures 3–23 and 19–40)

Answer 13

collagen

Question 14

A higher-order collagen polymer of fibrillar collagens that assemble into thin structures (10–300 nm in diameter) many hundreds of micrometers long in mature tissues.

Answer 14

collagen fibril

Question 15

Any supporting tissue that lies between other tissues and consists of cells embedded in a relatively large amount of extracellular matrix. Includes bone - cartilage - and loose connective tissue.

Answer 15

connective tissue

Question 16

Protein component of gap junctions - a four-pass transmembrane protein. Six connexins assemble in the plasma membrane to form a connexon - or “hemichannel.” (Figure 19–25)

Answer 16

connexin

Question 17

Water-filled pore in the plasma membrane formed by a ring of six connexin protein subunits. Half of a gap junction: connexons from two adjoining cells join to form a continuous channel through which ions and small molecules can pass. (Figure 19–25)

Answer 17

connexon

Question 18

One of a heterogeneous group of branched polysaccharides that help to cross-link cellulose microfibrils into a complex network. Has a long linear backbone of one sugar type (glucose - xylose - or mannose) with short side chains of other sugars.

Answer 18

cross-linking glycan

Question 19

Anchoring cell–cell junction - usually formed between two epithelial cells. Characterized by dense plaques of protein into which intermediate filaments in the two adjoining cells insert. (Figure 19–2)

Answer 19

desmosome

Question 20

Extensible fiber formed by the protein elastin in many animal connective tissues - such as in skin - blood vessels - and lungs - which gives them their stretchability and resilience.

Answer 20

elastic fiber

Question 21

Extracellular protein that forms extensible fibers (elastic fibers) in connective tissues.

Answer 21

elastin

Question 22

Tissues - such as the lining of the gut or the epidermal covering of the skin - in which cells are closely bound together into sheets called epithelia.

Answer 22

epithelial tissues

Question 23

Sheet of cells covering the outer surface of a structure or lining a cavity.

Answer 23

epithelium (plural epithelia)

Question 24

Mediates the interactions of collagen fibrils with one another and with other matrix macromolecules to help determine the organization of the fibrils in the matrix. This collagen (including types IX and XII) has a flexible triple-stranded helical structure and binds to the surface of the fibrils rather than forming aggregates.

Answer 24

fibril-associated collagen

Question 25

Class of fibril-forming collagens (including type I collagen - the most common type and the principal collagen of skin and bone) that have long ropelike structures with few or no interruptions and which assemble into collagen fibrils.

Answer 25

fibrillar collagen

Question 26

Common cell type found in connective tissue. Secretes an extracellular matrix rich in collagen and other extracellular matrix macromolecules. Migrates and proliferates readily in wounded tissue and in tissue culture.

Answer 26

fibroblast

Question 27

Extracellular matrix protein involved in adhesion of cells to the matrix and guidance of migrating cells during embryogenesis. Integrins on the cell surface are receptors for fibronectin.

Answer 27

fibronectin

Question 28

Communicating channel-forming cell–cell junction present in most animal tissues that allows ions and small molecules to pass from the cytoplasm of one cell to the cytoplasm of the next.

Answer 28

gap junction

Question 29

Long - linear - highly charged polysaccharide composed of a repeating pair of sugars - one of which is always an amino sugar. Mainly found covalently linked to a protein core in extracellular matrix proteoglycans. Examples include chondroitin sulfate - hyaluronan - and heparin. (Figure 19–32)

Answer 29

glycosaminoglycan (GAG)

Question 30

Binding between molecules of the same kind - especially those involved in cell–cell adhesion. (Figure 19–5)

Answer 30

homophilic

Question 31

Type of nonsulfated glycosaminoglycan with a regular repeating sequence of up to 25 -000 identical disaccharide units - not linked to a core protein. Found in the fluid lubricating joints and in many other tissues. (Figures 19–33 and 19–34)

Answer 31

hyaluronan (hyaluronic acid)

Question 32

Large and diverse family of proteins that contain immunoglobulin domains or immunoglobulin-like domains. Most are involved in cell–cell interactions or antigen recognition. (Figure 24–48)

Answer 32

immunoglobulin (Ig) superfamily

Question 33

Transmembrane adhesion protein that is involved in the attachment of cells to the extracellular matrix and to each other. (Figure 19–3 and Table 19–1 - p. 1037)

Answer 33

integrin

Question 34

Extracellular matrix fibrous protein found in basal laminae - where it forms a sheetlike network. (Figures 19–52 and 19–53)

Answer 34

laminin

Question 35

Network of cross-linked phenolic compounds that forms a supporting network throughout the cell walls of xylem and woody tissue in plants.

Answer 35

lignin

Question 36

Ca2+- or Zn2+-dependent proteolytic enzyme present in the extracellular matrix that degrades matrix proteins. Includes the collagenases.

Answer 36

matrix metalloprotease

Question 37

Large family of cadherins that are more distantly related in sequence than classical cadherins and include proteins involved in adhesion (including protocadherins - desmocollins - and desmogleins) and signaling.

Answer 37

nonclassical cadherins

Question 38

Protein-binding domain present in many scaffold proteins - and often used as a docking site for intracellular tails of transmembrane proteins. (Figure 19–22)

Answer 38

PDZ domain

Question 39

Mixture of polysaccharides rich in galacturonic acid which forms a highly hydrated matrix in which cellulose is embedded in plant cell walls. (Figure 19–63)

Answer 39

pectin

Question 40

Plant equivalent of a gap junction. Communicating cell–cell junction in plants in which a channel of cytoplasm lined by plasma membrane connects two adjacent cells through a small pore in their cell walls.

Answer 40

plasmodesma (plural plasmodesmata)

Question 41

In epithelia - that the basal end of a cell - adherent to the basal lamina below - differs from the apical end - exposed to the medium above; thus - all epithelia and their individual cells are structurally polarized.

Answer 41

polarized

Question 42

The first cell wall produced by a developing plant cell; it is thin and flexible - allowing room for cell growth. (Figure 19–63)

Answer 42

primary cell wall

Question 43

Molecule consisting of one or more glycosaminoglycan chains attached to a core protein. (Figure 19–35)

Answer 43

proteoglycan

Question 44

Tripeptide sequence of arginine-glycine-aspartic acid that forms a binding site for integrins; present in fibronectin and some other extracellular proteins. (Figure 19–47C)

Answer 44

RGD sequence

Question 45

Permanent rigid cell wall that is laid down underneath the thin primary cell wall in certain plant cells that have completed their growth.

Answer 45

secondary cell wall

Question 46

Member of a family of cell-surface carbohydrate-binding proteins that mediate transient - Ca2+-dependent cell–cell adhesion in the bloodstream—for example between white blood cells and the endothelium of the blood vessel wall. (Figure 19–28)

Answer 46

selectin

Question 47

Type of protease that has a reactive serine in the active site. (Figures 3–12 and 3–39)

Answer 47

serine protease

Question 48

Cell–cell junction that seals adjacent epithelial cells together - preventing the passage of most dissolved molecules from one side of the epithelial sheet to the other. (Figures 19–2 and 19–21)

Answer 48

tight junction

Question 49

Cytoskeleton-linked transmembrane molecules with one end linking to the cytoskeleton inside the cell and the other end linking to other structures outside it.

Answer 49

transmembrane adhesion proteins

Question 50

Large hydrostatic pressure developed inside a plant cell as the result of the intake of water by osmosis; it is the force driving cell expansion in plant growth and it maintains the rigidity of plant stems and leaves.

Answer 50

turgor pressure

Question 51

The major repeat domain in fibronectin - it is about 90 amino acids long and occurs at least 15 times in each subunit. The repeat is among the most common of all protein domains in vertebrates.

Answer 51

type III fibronectin repeat

Question 52

An essential component of mature basal laminae consisting of three long protein chains twisted into a ropelike superhelix with multiple bends. Separate molecules assemble into a flexible - felt-like network that gives the basal lamina tensile strength.

Answer 52

type IV collagen