Term
| How thick are the two phospholipid sheets that are encase the membranes of all living cells? |
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Definition
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Term
| The cell membrane is formed of what? |
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Definition
| a bilayer formed of phospholipids |
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Term
| Who proposed the fluid mosaic model? |
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Definition
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Term
| What was proposed about the proteins according to fluid mosaic model? |
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Definition
| They are inserted into the lipid bilayer with their nonpolar segments are in contact with the nonpolar interior and the polar are protuding out from membrane surface. |
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Term
| What are the two kinds of proteins found in membranes? |
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Definition
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Term
| What are integral membrane proteins located? |
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Definition
| they are embedded in the membrane |
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Term
| Where are peripheral proteins located? |
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Definition
| on the surface of a membrane |
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Term
| Name the four things every cell membrane is composed of. |
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Definition
| Phospholipid bilayer, transmembrane proteins, interior protein network, and cell-surface markers. |
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Term
| Describe the composition, function, and how the phospholipid bilayer works. |
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Definition
| composed of phospholipid molecules, its function consists of providing a permeability barrier and a matrix for proteins, and it excludes water-soluble molecules from the nonpolar interior of the bilayer and cell. |
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Term
| What do animal cell membranes contain? |
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Definition
| cholestrol with an attached hydroxyl group |
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Term
| What three types of proteins is the transmembrane protein composed of? |
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Definition
| carriers, channels, and receptors |
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Term
| What do "carriers" in the transmembrane protein do and how do they work? |
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Definition
| they actively or passively transport molecules across the membrane and they move specific molecules through the membrane in a series of conformational changes |
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Term
| What do "channels" in transmembrane proteins do and how do they work? |
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Definition
| they passively transport molecules across membrane and create a selective tunnel that acts as a passage. |
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Term
| What do receptors in a transmembrane protein do and how do they work? |
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Definition
| they transmit info into the cell and the signal molecules bind to cellsurface portion of the receptor protein |
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Term
| What is the interior protein network composed of? |
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Definition
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Term
| What do the spectrins of an interior protein network do? |
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Definition
| they determine the shape of a cell and form a supporting scaffold beneath the membrane that is anchored to the cytoskeleton and membrane |
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Term
| What do the clathrins of an interior protein network do? |
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Definition
| they anchor certain proteins to specific sites, especially on the exterior plasma membrane in receptor-mediated endocytosis and the proteins line coated pits and facilitate binding to specific molecules |
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Term
| What are two specific cell-surface markers found in the phospholipid bilayer? |
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Definition
| glycoproteins and glycolipids |
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Term
| What do the cell-surface markers glycoproteins do and how do they work? |
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Definition
| they do self recongition and they create a protein/carb chain shape characteristic of an individual |
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Term
| What do the cell-surface markers glycolipids do and how do they work? |
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Definition
| they are used for tissue recognition and they create a lipid/ carb chain shape characteristic of the tissue |
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Term
| What is a distinction that has been found true of the plasma membrane in the last decade? |
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Definition
| it is not homogenous and contains microdomains with distinct lipid and protein composition. |
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Term
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Definition
| a microdomain of the plasma membrane that is enriched with chlosterol and fills space between the phospholipids, packing them more tightly together |
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Term
| What allows biologists to examine the delicate, filmy structure of a cell membrane? |
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Definition
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Term
| Name two types of electron microscopes. |
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Definition
| Transmission electron microscope and scanning electron microscope |
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Term
| What is one way to visualize the inside of a membrane? |
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Definition
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Term
| A phospholipid has a backbone derived from what? |
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Definition
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Term
| What does the third carbon of the glycerol carry? |
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Definition
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Term
| How many fatty acid chains are connected to the backbone of a phospholipid? |
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Definition
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Term
| Phosphate groups are charged, what are the moclecules attached to them? |
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Definition
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Term
| What is the difference in the ends of the phospholipid? |
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Definition
| the phosphate end is hydrophilic and the fatty acid end is hydrophobic |
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Term
| What happens when a collection of phospholipids are placed in water? |
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Definition
| the polar water molecules repel the nonpolar tails of the phospholipids while seeking partners for hydrogen bonding |
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Term
| What is the key biological componet of the lipid bilayer? |
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Definition
| it rejects the passage of any water soluble substances |
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Term
| What is a lipid bilayer stable? |
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Definition
| Because water's affinity for hydrogen bonding never stops |
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Term
| What does saturated fats tend to do to the membranes? |
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Definition
| make them less fluid because they are packed together tightly |
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Term
| What is found in membranes and what effect can it have on membranes? |
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Definition
| sterols, and they can increase or decrease the fluidity. |
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Term
| Increasing temperature makes a membrane _______, and decreasing temperature makes a membrane __________. |
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Definition
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Term
| Bacteria contain which kind of enzyme that can counteract temperature? |
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Definition
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Term
| What are the six classes of protein membranes? |
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Definition
| transporters, enzymes, cell-surface receptors, cell-surface identity markers, cell-to-cell adhesion, and attachments to cytoskeleton |
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Term
| The anchoring molecules are modified lipids that do what? |
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Definition
| they have nonpolar regions that insert into the internal portion of the bilayer, and they have chemical bonding domains that link directly to proteins |
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Term
| What do transmembrane proteins do? |
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Definition
| they span the lipid bilayer |
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|
Term
| what is a transmembrane protein? |
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Definition
| each membrane-spanning region |
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Term
| What are transmembrane domains composed of? |
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Definition
| hydrophobic amino acids arranged into alpha helices |
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Term
| What do proteins need in order to be anchored in the membrane? |
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Definition
| only a single transmembrane domain |
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Term
|
Definition
| they are openings that allow molecyles to pass through the membrane |
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Term
| What are the three types of transport across the plasma membrane? |
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Definition
| passive, active, and endocytosis |
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Term
| Which type of transport doesn't require the cell to expand energy? |
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Definition
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Term
| Some molecules and ions can move fairly easy through the membrane because of what? |
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Definition
|
|
Term
| What is concentration gradient? |
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Definition
| a difference between the concentration of the inside and outside of the membrane |
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Term
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Definition
| the net movement from areas of high to low concentration regions |
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Term
| What is faciliated diffusion? |
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Definition
| the molecules hook to a carrier protein or specific channel protein |
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Term
| What do channel proteins do? |
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Definition
| they have an aqueous channel and hydrophillic interior for the polar molecules |
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Term
| What do carrier proteins do? |
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Definition
| they bind specifcally to a molecule like an enzyme and they are selective to one type of molecule |
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Term
| Cell membranes are said to be what? |
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Definition
|
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Term
| What do ion channels possess? |
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Definition
| a hydrated interior that ions can diffuse through |
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Term
| What do gated channels do? |
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Definition
| they open and close in response to a stimulus. |
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Term
| The net movement of ions depend on what three things? |
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Definition
| the concetration on either side of the membrane, the voltage difference, and the state of the gate channel |
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Term
| Ion channels play a specific role in what? |
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Definition
| signaling for the nervous system |
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Term
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Definition
| the diffusion of water molecules across the membrane |
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Term
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Definition
| specialized channels for water |
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Term
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Definition
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Term
| What is an aqueous solution? |
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Definition
| sugars and amino acids dissolved in water |
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Term
| Water and solutes tend to do what? |
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Definition
| diffuse down their concentration gradients |
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Term
| Most solutes are unable to do what? |
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Definition
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|
Term
| What is an osmotic concentration? |
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Definition
| the concentration of all solutes in a solution |
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Term
|
Definition
| solutions with higher concentrations |
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Term
|
Definition
| solutions with lower concentration |
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Term
|
Definition
| two solutions with equal osmotic concentration |
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Term
| What is the difference in a hypertonic and hypotonic cell? |
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Definition
| the hypertonic cell is shriveled up, and the hypotonic swells and bursts |
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Term
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Definition
| the force needed to stop osmotic flow |
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Term
| What are the three ways in which cells survive an aqueous enviornment? |
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Definition
| extrusion, cell wall, and isotonic body |
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Term
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Definition
| unicellular organsims have contractile vacules that remove water |
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Term
| How does the cell wall allow cells to survive in aqueous enviornments? |
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Definition
| the rigid structure prevents the cell from over expanding |
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Term
| What is active transport? |
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Definition
| requires energy, usually derived from ATP |
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Term
|
Definition
| they trasnport a single type of molecule |
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Term
|
Definition
| transport 2 molecules in the same direction |
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Term
|
Definition
| thye transport 2 molecules in different directions |
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|
Term
| What is a sodium-potassium pump? |
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Definition
| it actively pumps Na+ out of the cell and K+ into the cell |
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Term
| What is an important characteristic of the sodium-potassium pump? |
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Definition
| transports from areas of low concentration to high, opposite of passive transport |
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Term
| Name the 6 steps of the sodium-potassium pump. |
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Definition
| three Na+ bind to the cytoplasmic side of the protein, ATP links with a phosphate creating ADP and the ADP is released leaving phosphorylation, phosphorylation translocates the Na+ across the membrane, there is now a high affinity for K+ and it binds to the extracellular side of the protein, the binding of K+ results in hydrolysis, hydrolysis results in a low affinity for K+ and K+ diffuses back into the cell, cycle repeats |
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Term
| What is coupled transport? |
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Definition
| it allows the energy from one molecule to be moved down and captured, and allows a different molecule to go against its gradient |
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Term
| What are the two processes involved in the bulk transport? |
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Definition
| endocytosis and exocytosis |
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Term
| Cells use what three major types of endocytosis? |
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Definition
| phagocytosis, pinocytosis, and receptor-mediated endocytosis |
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Term
| What happens in endocytosis? |
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Definition
| a molecule bumps into the cell and it ends up in a vesicle |
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Term
|
Definition
| if the material takes in a particle that can't dissolve in water |
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Term
|
Definition
| soluble particles being brought in, or liquids |
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|
Term
| What is receptor-mediated endocytosis? |
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Definition
| they are specific and only have one "target molecule" |
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|
Term
|
Definition
| it is in the protein on the inner surface of the receptor |
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|
Term
| What happens in exoctyosis? |
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Definition
| the secretory vesicle fuses with the plasma membrane and releases the product |
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