Chapter 5

elastin

gives the matrix resilience

Collagen

gives the matrix strength

Cell recognition proteins

glycoproteins that allow the body's immune system to distinguish between foreign invaders and body cells. A glycoprotein that helps the body defend itself against pathogens.

Proteoglycans

glycoproteins that provide a packing gel that joins the various proteins in matrix and most likely regulate signaling proteins that bind to receptors in the plasma protein. Important in cell differentiation during fetal development

Non-cellulose polysaccharides

harden the wall of mature cells.

Glycolipids

have a structure similar to phospholipids except the hydrophilic head is a variety of sugar; they are protective and assist in various functions. Glycolipids are a lipid in plasma membranes that bears a carbohydrate chain attached to a hydrophobic tail.

Glycoproteins

have an attached carbohydrate chain of sugar that projects externally.

crenation

in animal cells, shrinking of the cell due to water leaving the cell when the environment is hypertonic

hypotonic solution

in cells, solution in which the concentration of dissolved substances is lower in the solution outside the cell than the concentration inside the cell; causes a cell to swell and possibly burst as water enters the cell

hypertonic solution

in cells, solution in which the concentration of dissolved substances outside the cell is higher than the concentration inside the cell; causes a cell to shrink as water leaves the cell

Junction proteins

join animal cells so tissues can function. Assists cell-to-cell communication at the plasma membrane.

Adhesion junctions

junction between cells in which the adjacent plasma membranes do not touch but are held together by intercellular filaments attached to buttonlike thickenings called internal cytoplasmic plaques. They hold cells together where tissues stretch (e.g., in heart, stomach, bladder). These are called desmosomes - an intercellular junction that connects cytoskeletons of adjacent cells.

Anchoring junctions

mechanically attach adjacent cells.

bulk transport

movement of elements in an organism in large amounts

diffusion

movement of molecules or ions from a region of higher to lower concentrations; it requires no energy and tends to an equal distribution

Passive transport

moves molecules across membrane without expenditure of energy; includes diffusion and facilitated transport. Through channel or carrier proteins

Plasmodesmata

narrow membrane-lined channels that pass through cell walls of neighboring cells and connect their cytoplasms, allowing direct exchange of molecules and ions between neighboring plant cells. In plants, plasmodesmata are cytoplasmic strands that extend through the pores in the cell wall and connect the cytoplasm of two adjacent cells.

Osmosis

the diffusion of water across a differentially (selectively) permeable membrane.

Turgor pressure

the force directed against a cell wall after the influx of water and the swelling of a walled cell due to osmosis.

solvent

the liquid portion of a solution that serves to dissolve a solute.

Osmotic pressure

the pressure that develops in such a system due to osmosis. It is the measure of the tendency of water to move across a differentially permeable membrane; visible as an increase in liquid on the side of the membrane with the higher solute concentration.

exocytosis

the process by which a substance is released from the cell through a vesicle that transports the substance to the cell surface and then fuses with the membrane to let the substance out

phagocytosis

the process by which amoeboid-type cells engulf large substances, forming an intracellular vacuole.

Facilitated transport

the transport of a specific solute "down" or "with" its concentration gradient (from high to low), facilitated by a carrier protein; glucose and amino acids move across the membrane in this way.

cytolysis

("cell bursting").

pinocytosis

(cellular drinking); occurs when vesicles form around a liquid or very small particles; this is only visible with electron microscopy. It is the process by which vesicle formation brings macromolecules into the cell.

aquaporin

A transport protein in the plasma membrane of a plant or animal cell that specifically facilitates the diffusion of water across the membrane (osmosis).

endocytosis

It is a process by which substances are moved into the cell from the environment by phagocytosis (cellular eating) or pinocytosis (cellular drinking); includes receptor-mediated endocytosis.

differentially (selectively) permeable

The ability of plasma membranes to regulate the passage of substances into and out of the cell, allowing some to pass through and preventing the passage of others.

Receptor mediated endocytosis

a form of pinocytosis, occurs when specific macromolecules bind to plasma membrane receptors. It is the selective uptake of molecules into a cell by vacuole formation after they bind to specific receptor proteins in the plasma membrane.

concentration gradient

a gradual change in chemical concentration between two areas of differing concentrations.

Cholesterol

a lipid found in animal plasma membranes; it stiffens and strengthens the membrane. A steroid found in animal plasma membranes and from which other types of steroids are derived.

extracellular matrix

a meshwork of polysaccharides and proteins produced by animal cells.

Isotonic solutions

a solution that is equal in solute concentration to that of the cytoplasm of a cell; causes cell to neither lose nor gain water by osmosis.

Lignin

adds strength and is a common ingredient of secondary cell walls in woody plants.

Channel proteins

allow a particular molecule to cross membrane freely (e.g., Cl channels). A protein that forms a channel to allow a particular molecule or ion to cross the plasma membrane.

Pectins

allow the cell wall to stretch and are abundant in the middle lamella that holds cells together.

gap junction

allows cells to communicate; formed when two adjacent identical plasma membrane channels join. 1) They provide strength to the cells involved and allow the movement of small molecules and ions from the cytoplasm of one cell to the cytoplasm of the other cell. 2) Gap junctions permit flow of ions for heart muscle and smooth muscle cells to contract.

Fibronectins and laminins

bind to membrane receptors and permit communication between matrix and cytoplasm; these proteins also form "highways" that direct the migration of cells during development.

Enzymatic proteins

carry out specific metabolic reactions. It catalyzes a specific reaction.

Fluid-Mosaic Model

describes the plasma membrane. A model for the plasma membrane based on the changing location and pattern of protein molecules in a fluid phospholipid bilayer.

tight junctions

plasma membrane proteins attach in zipper-like fastenings; they hold cells together so tightly that the tissues are barriers (e.g., epithelial lining of stomach, kidney tubules, blood-brain barrier). A tight junction is a junction between cells when adjacent plasma membrane proteins join to form an impermeable barrier (junction proteins).

Junctions Between Cells

points of contact between cells that allow them to behave in a coordinated manner.

phospholipid bilayer

regulates the passage of molecules into and out of the cell.

Carrier proteins

selectively interact with a specific molecule so it can cross the plasma membrane (e.g., Na+ K+ pump). A protein that combines with and transports a molecule or ion across the plasma membrane.

Receptor proteins

shaped so a specific molecule (e.g., hormone) can bind to it. A protein located in the plasma membrane or within the cell; binds to a substance that alters some metabolic aspect of the cell.

Plasmolysis

shrinking of the cytoplasm due to osmosis in a hypertonic solution; as the central vacuole loses water, the plasma membrane pulls away from the cell wall. It is contraction of the cell contents due to the loss of water.

Tonicity

strength of a solution with respect to osmotic pressure. It is the osmolality of a solution compared to that of a cell.

Active transport

transport of a specific solute across plasma membranes "up" or "against" (from low to high) its concentration gradient through use of cellular energy (ATP). includes active transport, exocytosis, endocytosis, and pinocytosis.

solute

usually a solid. a substance that is dissolved in a solvent, forming a solution.