Chapter 8

Front 1

Primary Cell Wall

Back 1

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

Front 2

Pectin

Back 2

A gelatinous polysaccharide found in the primary cell wall of plant cells. Attracts and holds water, forming a gel that helps keep the cell wall moist.

Front 3

Turgor Pressure

Back 3

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

Front 4

Secondary Cell Wall

Back 4

The inner layer of a plant cell wall formed by certain cells as they mature. Provides support or protection.

Front 5

Lignin

Back 5

A substance found in the secondary cell walls of some plants that is exceptionally stiff and strong. Most abundant in woody plant parts.

Front 6

Extracellular Matrix

Back 6

ECM. A complex mesh of proteins and polysaccharides secreted by animal cells and in which the cells are embedded. Most important function is structural support.

Front 7

Collagen

Back 7

A fibrous, pliable, cable-like glycoprotein that is a major component of the extracellular matrix of animal cells. Various subtypes differ in their tissue distribution.

Front 8

Integrin

Back 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.

Front 9

Fibronectin

Back 9

An abundant protein in the extracellular matrix that binds to other ECM components and to integrins in plasma membranes; helps anchor cells in place. Numerous subtypes are found in different tissues.

Front 10

Metastasis

Back 10

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

Front 11

Multicellularity

Back 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 that some cells have specialized functions.

Front 12

Tissue

Back 12

A group of similar cells that function as a unit, such as muscle tissue or epithelial tissue.

Front 13

Middle Lamella

Back 13

A central layer that connects adjacent plant cells. Consists primarily of gelatinous pectins and is sandwiched by primary cell walls of plant cells.

Front 14

Epitehlium

Back 14

An animal tissue consisting of sheet-like layers of tightly packed cells that lines an organ, a duct, or a body surface. Also called epithelial tissue. These cells form sealed layers that separate organs and other structures.

Front 15

Tight Junction

Back 15

A type of cell-cell attachment structure that links the plasma membranes of adjacent animal cells, forming a barrier that restricts movement of substances (watertight) in the space between the cells. Most abundant in epithelial.

Front 16

Desmosome

Back 16

A type of cell-cell attachment structure, consisting of cadherin proteins, that binds the cytoskeletons of adjacent animal cells together. Found where cells are strongly attached to each other.

Front 17

Selective Adhesion

Back 17

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

Front 18

Antibody

Back 18

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. All antibody molecules have a similar Y-shaped structure and, in their monomer form, consist of two identical light chains and two identical heavy chains.

Front 19

Cadherin

Back 19

Any of a class of cell-surface proteins involved in cell adhesion and important for coordinating movements of cells during embryological development. Each cadherin can only bind to a cadherin of the same type. Provide the physical basis for selective adhesion.

Front 20

Plasmodesmata

Back 20

Physical connection between two plant cells, consisting of gaps in the cell walls through which the two cells' plasma membranes, cytoplasm, and smooth ER can connect directly. Functionally similar to gap junctions in animal cells. Communication portals.

Front 21

Gap Junctions

Back 21

A type of cell-cell attachment structure that directly connects the cytoplasms of adjacent animal cells, allowing passage of water, ions, and small molecules between the cells.

Front 22

Hormone

Back 22

Any of numerous different signalling molecules that circulate throughout the body in blood or other body fluids and can trigger characteristic responses in distant target cells at very low concentrations.

Front 23

Receptors

Back 23

Identical receptors in diverse cells allow long-distance signals to coordinate the activities of cells throughout a multicellular organism. They are dynamic.

Front 24

Signal Receptor

Back 24

Any cellular protein that binds to a particular signalling molecule and triggers a response by the cell. It changes its shape and activity after binding. Receptors for water-soluble signals are transmembrane proteins in the plasma membrane; those for many lipid-soluble signals are located inside the cell.

Front 25

Signal Transduction

Back 25

The process by which a stimulus outside a cell is amplified and converted into a response by the cell. Usually involves a specific sequence of molecular events, or signal transduction pathway.

Front 26

G Protein

Back 26

Any of various peripheral membrane proteins that bind GTP and function in signal transduction. Binding of a signal to its receptor triggers activation of the G protein, leading to production of a second messenger or initiation of a phosphorylation cascade.

Front 27

Second Messenger

Back 27

A nonprotein signalling molecule produced or activated inside the cell in response to stimulation at the cell surface. Commonly used to relay the message of a hormone or other extracellular signalling molecule.

Front 28

Protein Kinase

Back 28

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

Front 29

Receptor Tyrosine Kinase

Back 29

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

Front 30

Ras

Back 30

A type of G protein that is activated by binding of signalling molecules to receptor tyrosine kinases and then initiates a phosphorylation cascade, culminating in a cell response.

Front 31

Phosphorylation Cascade

Back 31

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

Front 32

Cross-talk

Back 32

Interactions between signalling pathways that occur as a cell generates a response to multiple signals.

Front 33

Quorum Sensing

Back 33

Cell-cell signalling 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.

Front 34

Capsule

Back 34

A layer of polysaccharides firmly attached to the cell wall of certain prokaryotic cells.

Front 35

Slime Layer

Back 35

A layer of polysaccharides loosely attached to the cell wall of certain prokaryotic cells.

Front 36

Biofilm

Back 36

A community of bacteria attached to a surface with the capsules or slime layers made by some of the cells.