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MCDB Midterm 2 terms
terms for Molecular Biology Course
18
Science
Undergraduate 2
11/09/2009

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Term
passive diffusion
Definition
most simple
molecules don't become concentrated on either side
flows with concentration gradient
no carrier molecules
Term
carrier mediated diffusion
Definition
transported molecules helped by "receptor proteins" or "carriers" that can bind to the molecule
no energy required
transport occurs WITH concentration gradient
Term
antiport
Definition
transport two different substances in opposite directions
Term
uniports
Definition
transport one substance in one direction
Term
symports
Definition
transport two different substances in the same direction
Term
simple diffusion
Definition
no energy req
with concentration gradient
no membrane protein required
not specific
Term
facilitated diffusion
Definition
no energy required
with concentration gradient
membrane protein required
specific
Term
active transport
Definition
energy required
ATP hydrolysis (against concentration gradient)
membrane protein required
specific
Term
endocytosis
Definition
the process by which complex molecules and large particles, bacterial cells, and water can enter cells
membrane vesicle is brought into the cell
Term
phagocytosis
Definition
large particles and small cells are engulfed into the lumen of the vesicle; type of endocytosis
Term
pinocytosis
Definition
"cell drinking" cells take up water into vesicles; type of endocytosis
Term
receptor-mediated endocytosis
Definition
specialized form of endocytosis for taking certain kinds of macromolecules into cells;
first - macromolecule binds to specific receptor on cell surface forming a "coated pit"
protein clathrin coats the inside surface of the plasma membrane
clathrin - coated vesicle forms around the macromolecule
vesicle moves into the cell cytoplasm and becomes uncoated - releasing its contents
Term
LDL Endocytosis and Atherosclerosis
Definition
LDL particle binds to LDL receptor @ cell surface leading to formation of coated pit
LDL particle taken up into clathrin coated vesicles
vesicle uncoats
vesicle fuses with lysosome which digests contents of vesicle-releasing the cholesterol which then is inserted into plasma membrane
Term
defects in the regulated uptake of LDL particles causes
Definition
hypercholesterolemia; buildup of cholesterol in blood plasma
deposition of cholesterol on artery walls (artherosclerosis)
one defect leading to hypercholesteremia is genetically determined absence of the LDL receptor
Term
exocytosis
Definition
processes by which complex molecules packed into vesicles in cells fuse with plasma membrane and are dumped out of cells
secretory vesicle inside cell fuses with the plasma membrane
vesicle contents dumped out
Term
tight junctions
Definition
link cells together VERY TIGHTLY
don't allow passage of materials in space between two cells
don't allow movement of membrane proteins inside the membrane itself
Term
desosomes
Definition
allows space between cells
doesn't limit movement in space between cells
Term
gap junctions
Definition
permits passage of large molecules between two cells
made of connexons
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