Biological Membranes Ch. 5

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phospholipids

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P. Any of various phosphorus-containing lipids, such as lecithin, that are composed mainly of fatty acids, a phosphate group, and a simple organic molecule such as glycerol. Phospholipids are the main lipids in cell membranes.

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peripheral protein

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PP.proteins that adhere only temporarily to the biological membrane with which they are associated. These molecules attach to integral membrane proteins, or penetrate the peripheral regions of the lipid bilayer. On the water soluble side.

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permeability

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P.selectively-permeable membrane, a partially-permeable membrane or a differentially-permeable membrane, is a membrane that will allow certain molecules or ions to pass through it by diffusion and occasionally specialized "facilitated diffusion." The rate of passage depends on the pressure, concentration, and temperature of the molecules or solutes on either side, as well as the permeability of the membrane to each solute

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transport protein

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TP. A type of [[protein that actively transports materials across a [[cell membrane that would not otherwise allow this to occur.

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osmosis

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Diffusion of a solvent (usually water molecules) through a semipermeable membrane from an area of low solute concentration to an area of high solute concentration.

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hypotonic solution

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solution that contains less solute (more water) compared to the cytoplasm of the cell.

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aquaporin

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A. proteins embedded in the cell membrane that regulate the flow of water. They are "the plumbing system for cells

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facilitated diffusion

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FD.process of diffusion, a form of passive transport facilitated by transport proteins. Facilitated diffusion is the spontaneous passage of molecules or ions across a biological membrane passing through specific transmembrane transport proteins.

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cotransport

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C. coupled transport, refers to the simultaneous or sequential passive transfer of molecules or ions across biological membranes in a fixed ratio

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pinocytosis

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form of endocytosis in which small particles are brought into the cell suspended within small vesicles which subsequently fuse with lysosomes to hydrolyze, or to break down, the particles. This process requires energy in the form of adenosine triphosphate (ATP)

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cell signaling

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part of a complex system of communication that governs basic cellular activities and coordinates cell actions.[1] The ability of cells to perceive and correctly respond to their microenvironment is the basis of development, tissue repair, and immunity as well as normal tissue homeostasis

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protein kinase

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kinase enzyme that modifies other proteins by chemically adding phosphate groups to them (phosphorylation).

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adhering junction

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P.Desmosomes - between cells. Cells subject to abrasion or other mechanical stress, such as those of the surface epithelia of the skin, have junctions that adhere cells to one another and to the extracellular matrix.

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plasmodesmata

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small channels that directly connect the cytoplasm of neighboring plant cells to each other, establishing living bridges between cells

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amphipathic

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term describing a chemical compound possessing both hydrophilic and lipophilic properties.

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glycoprotein

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A molecule that consists of a carbohydrate plus a protein.

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diffusion

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net transport of molecules from a region of higher concentration to one of lower concentration by random molecular motion.

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osmotic pressure

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pressure that must be applied to a solution to prevent the inward flow of water across a semipermeable membrane.

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turgor pressure

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Turgor is a force exerted outward on a plant cell wall by the H2O contained in the cell. This force gives the plant rigidity, and may help to keep it erect.

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gated channel

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are one type of ionotropic receptor or channel-linked receptor. They are a group of transmembrane ion channels that are opened or closed in response to the binding of a chemical messenger (i.e., a ligand),[1] such as a neurotransmitter.[2]

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active transport

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mediated process of moving particles across a biological membrane against a concentration gradient

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exocytosis

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durable process by which a cell directs the contents of secretory vesicles out of the cell membrane

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clathrin

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c. a protein which plays a major role in the formation of coated vesicles

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first messenger

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messenger

1. That which carries a message.

2. Having message-carrying properties.

first messenger, a hormone that binds to a receptor on the surface cell and, in so doing, communicates with intracellular metabolic processes

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cell junction

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cj. type of structure that exists within the tissue of a multicellular organism

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cadherins

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c. are a class of type-1 transmembrane proteins. They play important roles in cell adhesion, ensuring that cells within tissues are bound together. They are dependent on calcium (Ca2+) ions to function, hence their name

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fluid mosaic model

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A model conceived by S.J. Singer and Garth Nicolson in 1972 to describe the structural features of biological membranes

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signal transduction

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st. refers to any process by which a cell converts one kind of signal or stimulus into another

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concentration gradient

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cg.a gradual change in the concentration of solutes in a solution as a function of distance through a solution.