Chapter 11 - Cell to Cell Interactions

Why does a hormone act only on specific cell types in an organism and not others?

A cell must have the appropriate receptor before it can bind to the hormone.

Signal Response

A change in which genes are being expressed in the target cell A change in the activation of deactivation of a particular target protein that already exists in a cell

Cellulose in plants

A polysaccharide that is used to synthesize cell walls, which protects cells and helps to maintain their shape

A signal transduction pathway is initiated when a _____ binds to a receptor.

A signal molecule

Gap junctions

Act as channels between cells Also allow communication

What role does a transcription factor play in a signal transduction pathway?

By binding to DNA it triggers the transcription of a specific gene

Collagen

Cable-like protein Binds together to form fibers Forms a flexible extracellular layer

Animals have a variety of membrane proteins that attach cells together

Cells are held together by tight junctions, desmosomes, and gap junctions

Signal Deactivation

Cells have automatic and rapid mechanisms for signal deactivation Phosphatases - removes phosphate groups from proteins in the phosphorylation cascade These mechanisms allow the cell to remain sensitive to small changes in signaling

The most abundant protein found in the extracellular matrix of animal cells is _____.

Collagen

Tight Junctions

Composed of membrane proteins in adjacent cells, chains of these proteins line up and bind to each other with a water tight deal Dynamic and variable, can open and close Found in epithelial tissue

Desmosomes

Connect the cytoskeletons of cells

Signal Reception

Lipid Soluble Hormones - diffuse across plasma membrane and receptors are in the target cells cytoplasm Lipid Insoluble Hormones- do not cross plasma membrane, receptors are in the cells plasma membrane

The primary role of _____ is to bind animal cells together.

Desmosomes

Cell-cell Signaling

Distant cells can communicate through signaling molecules Neurotransmitters may open/close channels Signal reception Signal processing Signal response Signal deactivation

Apoplast

Extracellular space

_____ aid in the coordination of the activities of adjacent animal cells.

Gap Junctions

Plasmodesmata

Gaps in cell wall Connects cells via membrane linked channels

Hormones

Group of signaling and information carrying molecules Structurally diverse, circulate the body, and act on target cells in other sites

Primary Cell Wall

Helps to maintain cell/tissue structure New plant cells form, they secrete a fiber composite forming long strands of cellulose bundled into cable-like micro fibrils that form a crisscrossed network

Collagen in animals

Long fibers of protein found in extracellular matrix that provide structural support for cells

Extracellular Matrix (ECM)

Most animal cells secrete a fiber composite mostly made up of collagen and proteoglycans Cross-linking proteins such as lamins and integrins of the cell surface attach to the plasma membrane and anchor to the cytoskeleton so that the cell is continuous

How is phosphorylation important in a signal transduction cascade?

Phosphorylation will change the activity of target proteins, which triggers another response in the cell.

Extra cellular space between adjacent plant cells comprises three layers

Primary cell wall Middle lamella - glue Primary cell wall of another plant cell COmprused of gelatinuous pectins

Symplast

Shared cytoplasm

For a tissue or an organ to function as a unit, _____.

There must be cell-cell communication among the cells within a tissue or organ

Which of these cell junctions form a barrier to the passage of materials?

Tight Junctions

Which of these is the second of the three stages of cell signaling?

Transduction

Enzyme-linke receptors

Transmembrane proteins Bind a hormone signal Directly catalyzes a reaction inside the cell

Signal Processing (transductions via G-coupled proteins)

Trigger production of a second messenger when active Can perform a number of activities 1. G-protein is inactive (bound to GDP), signal arrives and binds to receptor 2. Signal - receptor complex changes conformation, G-proteins binds to GTP and splits into two parts 3. Activated G-protein binds to an enzyme and induces production fo a second messenger, which triggers a response

Signal Processing via Enzyme Linked Receptors

Tyrosine Kinases (RTKs) are enzyme linked receptors that cross phosphorylates to activate (puts phosphates on each other) and recruits other proteins and they do stuff

Integrins are integral membrane proteins. They are often attached to _____.

cytoskeletal proteins and proteins in the extracellular matrix

G-proteins

intracellular peripheral membrane proteins (have an on/off switch) Active - GTP Inactive - GDP Activated by signal receptor

A signal molecule is also known as a(n) _____.

ligand

Osteocytes are bone cells. Collagen fibers and calcium salts are found in abundance between and among the osteocytes. The collagen and calcium salts are _____.

part of the extracellular matrix