chapter 8

Question 1

primary cell wall

Answer 1

the outermost layer of a plant cell wall made of cellulose fibers and gelatinous polysaccharides that defines the shape of the cell and withstands the turgor pressure of the plasma membrane

Question 2

pectins

Answer 2

a gelatinous polysaccharide found in the primary cell wall of plant cells, attracts and holds water forming a gel that keeps the cell wall moist

Question 3

turgor pressure

Answer 3

the outward pressure exerted by the fluid contents of a plant cell against its cell wall

Question 4

secondary cell wall

Answer 4

the inner layer of a plant cell wall formed by certain cells as they mature, provides support or protection

Question 5

lignin

Answer 5

a substance found in the secondary cell walls of some plant cells that is exceptionally stiff and strong , most abundant in woody plants

Question 6

extracellular matrix

Answer 6

a complex meshwork of proteins and polysaccharides secreted by animal cells and in which they are embedded

Question 7

collagen

Answer 7

a fibrous, pliable cable-like glycoprotein that is a major component of the extracellular matrix of animal cells

Question 8

integrins

Answer 8

any of a class of cell-surface proteins that bind to fibronectins and other proteins in the extracellular matrix thus holding cells in place

Question 9

fibronectins

Answer 9

an abundant protein in the extracellular matrix that binds to other ECM components and to integrins in the plasma membrane helps anchor cells in place

Question 10

metastasis

Answer 10

the spread of cancerous cells from their site of origin to distant sites in the body where they may establish additional tumors

Question 11

multicellularity

Answer 11

the state of being composed of many cells that adhere to each other and do not all express the same genes with the result of specialized cell functions

Question 12

tight junction

Answer 12

a type of cell to cell attachment where the plasma membrane of adjacent animal cells are attached, forming a barrier to restrict movement in the space between the cells

Question 13

desmosomes

Answer 13

a type of cell to cell attachment consisting of cadherin proteins that binds the cytoskeleton of adjacent animal cells together

Question 14

selective adhesion

Answer 14

the tendency of cells of one tissue type to adhere to other cells of the same type

Question 15

antibody

Answer 15

an immunoglobulin protein produced by B cells that can bind to a specific part of an antigen tagging it for attack by the immune system

Question 16

cadherins

Answer 16

any of a class of cell surface proteins involved in cell adhesion and important for coordinating movements of cells during embryological development

Question 17

plasmodesmata

Answer 17

physical connection between two plants cells consisting of gaps in the cell walls through which the plasma membranes, cytoskeletons, and smooth ER can connect directly

Question 18

hormones

Answer 18

any of many different signaling molecules that circulate throughout the body in blood and other body fluids and can trigger characteristic responses in distant target cells at very low concentrations

Question 19

signal receptor

Answer 19

any cellular protein that binds to particular signaling molecule and triggers a response by the cell

Question 20

signal transduction

Answer 20

the process by which a stimulus outside a cell is amplified and is converted to a response by the cell

Question 21

G proteins

Answer 21

guanine nucleotide-binding proteins, are a family of proteins that act as molecular switches inside cells, and are involved in transmitting signals from a variety of stimuli outside a cell to its interior.

Question 22

second messenger

Answer 22

a nonprotein signaling molecule produced or activated inside the cell in response to a stimulus at the cell surface

Question 23

protein kinases

Answer 23

an enzyme that catalyzes the addition of a phosphate group to another protein, typically activating or inactivating the substrate protein

Question 24

receptor tyrosine kinases

Answer 24

any of a class of cell surface signal receptors that undergo phosphorylation after binding a signaling molecule. The activated phosphorylated receptor then triggers a signal transduction pathway inside the cell

Question 25

Ras protein

Answer 25

G protein that is activated by the binding of a signaling molecule to receptor tyrosine kinases and then initiates a phosphorylation cascade

Question 26

phosphorylation cascade

Answer 26

a series of enzyme-catalyzed phosphorylation reactions commonly used in signal transduction pathways to amplify and convey a signal inward from the plasma membrane

Question 27

cross-talk

Answer 27

interactions among signaling pathways that modify a cellular response

Question 28

quorum sensing

Answer 28

cell to cell signaling in bacteria in which cells of the same species communicate via chemical signals. It is often observed that cell activity changes dramatically when the population reaches a threshold size or quorum

Question 29

biofilms

Answer 29

a hard, polysaccharide rich layer secreted by bacterial cells which allows them to attach to a surface