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32 Cards in this Set

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  • Back
fluid mosiac model
proteins are dispersed throughout the phospholipid bilayer with the hydrophobic parts embedded and the hydrophilic parts protruding.
hydrophobic interactions
weak, hold the membrane together
low temperatures
phospholipids solidify, which effects the ability of the membrane to function
unsaturated hydrocarbons
tails have kinks due to double bonds which disallow solidification
in animal cells only, wedged between phospholipids to stabilize the membrane. Makes it less fluid at warm temperatures, but also hinders close packing, lowering solidification temperature
membrane molecules
phospholipids- main structure
cholesterol- maintain fluidity
carbohydrates- attached to outside
proteins- control function
Endoplasmic Reticulum
synthesizes membranes and their proteins
integral proteins
span the membrane, strands of amino acids in alpha helixes are hydrophobic and in the interior. maybe attached to cytoplasm or extracellular fibers to give more stability.
peripheral proteins
not trans membrane, often bound to intergral proteins
enzymatic activity
membrane protein may be an enzyme with active site exposed to substances in the adjacent solution. form an enzymatic pathway.
signal transduction
binding site fits a chemical messenger which causes the protein to change shape and relay the message to the other side
cell-cell recognition
glyco (short branched carbohydrates)-proteins serve as identification tags that are specifically recognized by other cells
intercellular joining
membrane proteins of adjacent cells may hook together in gap junctions or tight junctions
attachment to cytoskeleton or extracellular matrix
microfilaments or other elements may bond to the protein which maintains cell shape and protein position
hydrophilic things (DO NOT ENTER)
large polar molecules (glucose, other sugars), ions with their shell of water
hydrophobic (FREE PASS)
water, ethanol, hydrocarbons, oxygen, carbon dioxide
diffusion of two solutes
each solute diffuses down its own concentration gradient
selectively permeable membrane will not let the solute diffuse so water must. passive transport of water determined by TOTAL solute concentration.
plant, protist, fungi and prokaryotic cells
plant cells have elastic walls and only allow a certain amount of water to enter before they become turgid. cells live in hypotonic environments= turgid. isotonic= flaccid. hypertonic= plasmolysis (plasma membrane pulls away from cell wall)
facilitated diffusion
transport proteins allow hydrophilic molecules (ions or polar molecules) to pass. each protein is specific for what it moves
transport protein
similar to enzyme. specific binding site for its protein, can be saturated, and can be inhibited by imposters
gated channels
electrical or chemical stimulus causes protein to open or close
active transport
pumps against gradient and cell must expend metabolic energy
sodium-potassium pump
3 NA+ in the cytoplasm bind to the protein and a phosphorous is added (phosphorylation) from ATP. This causes the protein to change shape and dispense the 3 NA+ outside of the cell. Then two K+ bind from the outside, triggering the release of a phosphorous. This restores the original conformation and dispenses the 2 K+ to the inside. Net loss of 1+
membrane potential
voltage across a membrane. cytoplasm is negative so anions are favored to enter cell, and cations to exit.
electrochemical gradient
two forces that drive the diffusion of ions. chemical force (concentration grad.) and electrical (membrane potential)
electrogenic pump
a transport protein that generates voltage across a membrane
(sodium-potassium in animals)
(proton pump in plants)
ATP actively transports a substance across a membrane. as the substance leaks back through passive tranport, it takes another substance into the cell with it, even though the substance is moving UP the concentration gradient.
the cell secretes macromolecules by the fusion of vesicles with the plasma membrane
pseudopodia reach out and engulf the particle and package it in a vacuole which is consumed by a lysosome.
droplets of extracellular fluid are incorportaed into the cell in small vesicles (non specific)
receptor mediated endocytosis
coated pits form vesicles when specific molecules (ligand)bind to receptors on the cell surgace. This allows the cell to get the specific things it needs from the outside even if they are not in abundance. Other things are taken in as well.