Topic 4 Cells and Transport second set 51-98

Pseudopodia

A cellular extension of cells used in moving and feeding

Cytoplasmic Streaming

A circular flow of cytoplasm that speeds the distribution of materials within cells

Intermediate Filament

A component of the cytoskeleton that includes all filaments with size between that of microtubules and microfilaments

Primary Cell Wall

A relatively thin and flexible layer first secreted by a young plant cell

Middle Lamella

A thin layer of adhesive extracellular material, primarily pectins, found between the primary walls of adjacent young plant cells

Secondary Cell Wall

A layer of the cell wall that is rigid, used for plant cell protection and support in woody plants

Extracellular Matrix (ECM)

An intricate network of molecules, found outside the cell, that link together to form a stable layer.

Collagen

A glycoprotein in the extracellular matrix of animal cells that forms strong fibers; the most abundant protein in the animal kingdom

Cell junctions

Structures that provide contact between neighboring cells or a cell and the extracellular matrix

Tight junctions

Structures where plasma membranes of neighboring cells are pressed against each other, forming continuous seals around the cell.

Desmosomes

Anchoring junctions that function like rivets. Specialized for cell-cell adhesion.

Gap junctions

Structures that provide cytoplasmic channel connections from one animal cell to an adjacent cell

Plasmodesmata

An open channel in the cell wall of a plant through which the cytosol connects to the cytosol from an adjacent cell

Amphipathic

A molecule that has both a hydrophilic region and a hydrophobic region.

Fluid Mosaic Model

The currently accepted model of cell membrane structure, which envisions the membrane as a mosaic of individually inserted protein molecules drifting laterally in a fluid bilayer of phospholipids.

Integral Proteins

proteins that extend entirely through the membrane with both hydrophobic (embedded) and hydrophilic parts

Peripheral Proteins

Protein loosely bound to the surface of the membrane and not embedded in the lipid bilayer.

Transmembrane Proteins

A protein that goes from one side of the cell membrane to the other side.

Glycolipids

Lipid substances with linked sugar groups

Permeability

A measure of the rate of passive diffusion of molecules through the membrane

Transport Proteins

Protein molecules that help to carry substances throughout the body and across cell membranes.

Channel Proteins

A type of transport protein that functions by having a hydrophilic channel that certain molecules or ions use as a tunnel through the membrane.

Aquaporins

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

Diffusion

The process by which molecules spontaneously move from an area of higher concentration to an area of lower concentration

Concentration Gradient

The difference in the concentrations of a substance across a barrier or membrane.

Passive Transport

The movement of substances with gradient across a cell membrane without the use of energy by the cell.

Osmosis

Diffusion of water molecules through a semipermeable membrane until the concentration on both sides is equal

Isotonic

Having a solute concentration equal to that of another solution

Hypertonic

When comparing two solutions, the solution with the greater concentration of solutes

Hypotonic

When comparing two solutions, the solution with the lesser concentration of solutes

Turgid

Firm. Walled cells become firm as a result of the entry of water from a hypotonic environment.

Flaccid

Limp. Lacking in stiffness or firmness, as in a plant cell in surroundings where there is no tendency for water to enter the cell.

Plasmolysis

When a cell is in a hypertonic environment, the cell will lose water to its surroundings, shrink, and its plasma membrane will pull away from the wall

Facilitated Diffusion

The transport of substances through a cell membrane along a concentration gradient with the aid of transport proteins

Ion Channels

A transmembrane protein channel that allows a specific ion to flow across the membrane down its concentration gradient

Gated Channels

A protein channel in a cell membrane that opens or closes in response to a particular stimulus.

Active Transport

The movement of a substance across a biological membrane against its concentration or electrochemical gradient

Sodium-potassium pump

A special transport protein in the plasma membrane of animal cells that transports sodium out of the cell and potassium into the cell against their concentration gradients.

Membrane Potential

The voltage difference between a cell's cytoplasm and the extracellular fluid, due to the differential distribution of ions.

Electrochemical Gradient

A transport force driven by both a difference in charges and in concentration

Electrogenic pump

A transport protein that generates a voltage across a membrane

Proton Pump

An active transport mechanism in cell membranes that consumes ATP to force hydrogen ions out of a cell

Cotransport

The coupling of the "downhill" diffusion of one substance with the "uphill" transport against its own concentration gradient

Exocytosis

the process by which a substance is released from the cell through a vesicle

Endocytosis

the process by which a cell membrane surrounds a particle and encloses the particle in a vesicle to bring the particle into the cell

Pinocytosis

A type of endocytosis in which the cell ingests extracellular fluid and its dissolved solutes.

Receptor-Mediated Endocytosis

The movement of specific molecules into a cell by the inward budding of vesicles containing proteins with receptor sites specific to the molecules being taken in

Carrier proteins

Proteins that bind to molecules and change shape to shuttle them across the membrane