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unit 4

Terms

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endocrine signals
hormonal, long distance. signal released travels through blood vessels to target cell, affects only target cell with correct receptor
amphipathic
molecule that has both a hydrophilic region and a hydrophobic region such as a phosopholipid
isotonic
the solute concentration is the same on both sides
diffusion
passive movement of a substance from an area of high concentration (or activity) to low concentration dur to the random motion of its particles; always toward equilbrium
freeze fracture microscopy
freeze a collection of membranes, fracture them with a dull blade. prepare the fractured surfaces for scanning, electron microscope
peripheral protein
stick on surface of membrane but do not embed within
endocytosis
the cellular uptake of macromolecules and particulate substances by localized regions of the plasma membrane that surround the substance and pinch it off to form an intracellular vesicle using cellular energy
signal transduction pathway
mechanism linking a mechanical or chemical stimulus to a specific cellular response
fatty acid
a long carbon chain carboxylic acid. fatty acids vary in length and in the number and location of double bonds; three fatty acids linked to a glycerol molecule form fat.
glycerol
three carbons with a hydroxyl; eliminating hydrophobia, component of phospholipids
passive transport
simple diffusion and facilitated osmosis/diffusion-downhill, losing free energy, end with less free energy
osmosis
diffusion of water across membranes, most water movement is facilitated diffusion through membrane-bound water channel proteins called aquaporins. solutes affect the net direction of movement. always toward the side of the memebrane where solutes are more concentrated
active transport
use of transport proteins and cellular energy to move against the concentration gradient; moves molecules or ioins across membranes using transport proteins; cell supplies the energy in the form of ATP; the carrier proteins are unidirectional and called pumps
plasmolysis
due loss of water in a hypertonic solution the membrane pulls away from the cell wall
glycoprotein
a protein covalently attached to a carbohydrate
cholesterol
steroid that forms an essentail component of animal cell membranes and acts as a precursor molecule for the synthesis of other biologically important steroids
transport protein
allow diffusion of hydrophilic substances, called channels or carriers; used in facilitated diffusion
integral protein
typically a transmembrane protein with hydrophobic regions that completely spans the hydrophobic region of the interior of the membrane
hypertonic
the side with more solute, making a cell shrivel, loose water, water moves to hypertonic side
pinocytosis
type of endocytosis where liquids are "drank" using smaller vesicles
selective permeability
membranes control the types of substances that can cross, the rate of transport, the direction of transport. they are also dynamic meaning their transport properties can change
receptor-mediated endocytosis
give endocytosis specificity derived from a protein controlled process; movement of specific molecules into a cel by the inward budding of membranous vesicles containing proteins with receptor sites specific to the molecules being taken in; enables a cell to acquire bulk quantities of specific substances
exocytosis
the cellular secretion of macromolecules by the fusion of vesicles witht he plasma membrane using cellular energy
paracrine signals
target cells nearby the signal releasing cell
turgid
very firm, a walled cell becomes this if it has a greater solute concentration than its surroundings, resulting in entry of water
gated channel
a protein channel in a cell membrane that opens or closes in response to a particular stimulus
neurotransmittors
a chemical messenger released from teh synaptic terminal of a neuron at a chemical synapse that diffuses across the synaptic cleft and binds to and stimulates the postsynaptic cell
cotransport
the coupling of downhill diffusion of one substance to the uphill transport of another against its own concentration gradient
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)
electrogenic pump
an ion transport protein that generates voltage across a membrane
fluid mosiac model
proteins are embeded in the phospholipid bilayer and can move laterally within
phospholipid
molecule that is a constituent of the inner bilayer of biological membranes, having a polar, hydrophilic head and a nonpolar, hydrophobic tail. consists of five smaller building blocks attached by dehydration reactions
sodium-potassium pump
found in every animal; Na out of the cell, K into the cell, both normally against concentration gradient
electrochemical gradient
the diffusion gradient of an ion, representing a type of potential energy that accounts for both the concentration difference of the ion across a membrane and its tendency to mvoe relative to the membrane potential
lipid
a class of macromolecules. mostly hydrocarbon, largely nonpolar-hydrophobic, not soluble in water, three most important to living systems are fats, phospholipids and steroids
signal receptors
on the surface of cells where the signal must attach
phagocytosis
type of endocytosis where soilds get encorporated into the cell
phospholipid bilayer
the hydrophilic heads are on the outside in the water and the hydrophobic tails point inside

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