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58 terms

Cell Bio Chapter 5

STUDY
PLAY
Fatty acid tails of the phospholipids in a bacterium that lives at very high temperatures has
long fatty acid tails
If you removed cholesterol from the membranes of human cells
the membrane would become too fluid, resulting in leakiness
glycolipids and glycoproteins located in the plasma membrane may serves as
recognition signals
In FFEM
the interior of phospholipid bilayers may be analyzed
most membrane phospholipids are synthesized
at the cytosolic leaflet of the smooth ER membranes
N-linked glycosylation occurs in the
ER
O-linked glycosylation occurs in the
Golgi
What is the major difference between passive diffusion and facilitated diffusion?
involvement of a transport protein
osmosis
the movement of water from a hypotonic compartment to a hypertonic compartment
When bacteria use an H+/sucrose symporter, ________ are moving down their concentration gradient, while _________ are moving up their concentration gradient.
H+ ions; sucrose molecules
What is a major different between active transport and passive transport?
energy requirement
transmembrane gradients involving ions have
both an electrical and chemical component
what is the basic framework of the membrane?
phospholipid bilayer
phospholipids are _molecules
amphipathic
_ region faces in. _ region faces out.
hydrophobic, hydrophilic
membrane is considered a mosaic of _ _ and _ molecules
lipid, protein, carbohydrate
transmembrane proteins
one or more regions that are physically embedded in the hydrophobic region of the phospholipid bilayer
lipid anchors
covalent attachment of a lipid to an amino acid side chain within a protein
peripheral membrane proteins
noncovalently bound to regions of integral membrane proteins that project out from the membrane
apprx _ percent of all genes encode membrane proteins
25
membranes are _fluid
semi
factors affecting fluidity
length of fatty acyl tails, presence of double bounds in acyl tails, presence of chloesterol
glycosylation
process of covalently attaching a carbohydrate to a protein or lipid
glycolipid
carbohydrate to lipid
glycoprotein
carbohydrate to protein
synthesis of membrane phospholipids at ER membrane
fatty acids are attivated by CoA
fatty acids bond to GCP and are inserted into cytosolic leaflet of ER membrane via acyl transferase.
phosphate is removed by a phosphatase enzyme.
choline already linked to phosphate is attached via cholin phosphotransferase.
flippaess transfer some of the phospholipids to the other leaflet.
insertion of membrane proteins into ER membrane
protein begins synthesis in ER.
ER signal sequence is cleaved.
Polypeptide synthesis continues, and a hydrophobic transmembrane sequence is made as the polypeptide is being threaded through the channel.
synthsis complete sequence remains.
glycosylation
attachment of carbohydrates to a lipid or protein
N-linked glycosylation
group of 14 sugars is build onto lipid dolichol in the ER membrane.
oligosaccharide transferase removes the carbohydrate tree from dolichol and transfers it toan asparagine.
O-linked glycosylation
occurs only in Golgi. addition of sugars to oxygen atom of serine or threonine
diffusion
movement of solute from an area of higher concentration to an area of lower concentration
passive diffusion
without transport protein
2 types of passive transport
passive diffusion and facilitated diffusion
passive diffusion
diffusion of a solute through a membrane without transport protein
facilitated diffusion
diffusion of a solute through a membrane with the aid of a transport protein
isotonic
equal water and solute concentrations on either side of the membrane
hypertonic
solute concentration is higher on one side of the membrane
hypotonic
solute concentration is lower on one side of the membrane
osmosis
water diffuses through a membrane from an area with more water to an area with less water
osmotic pressure
the tendency for water to move into any cell
crenation
shrinking in a hypertonic solution
turgor pressure
pushes plasma membrane against cell wall
plasmolysis
plants wilt bc water leaves plant cells
2 classes of transport proteins
channels and transporters
channels
form an open passageway for the direct diffusion of ions or molecules across the membrane
different types of channels
ligand-gated, intracellular, phosphorylation, voltage-gated, mechanosensitive
transporters
carriers that transport solute, principal pathway for the uptake of organic molecules
uniporter
single molecule
symporter
2 or more ions transported in same direction
antiporter
2 or more ions or molecules transported in opposite directions
active transport
movement of solute across a membrane against its gradient from a region of low concentration to higher concentration
NA/K ATPase
actively transport Na and K against their gradients by using the energy from ATP hydrolysis
exocytosis
material inside cell is excreted into extracellular medium through vesicles
endocytosis
plasma membrane invaginates to form a vesicle that brings substances into the cell
steps of exocytosis
vesicle loaded with cargo is formed a protein coat wraps around it.
vesicle is released from the golgi
protein coat is shed
vesicle fuses with pm and releases cargo outside
steps of endocytosis
cargo binds to receptor and receptors aggregate causing coat proteins to bind to surrounding membrane.
pm invaginates as coat proteins cause a vesicle to form
vesicle is released
protein coat is shed
vesicle fuses with an internal organelle
pinocytosis
formation of membrane vesicles from the pm as a way for cells to internalize the fluid
phagocytosis
fornation of an enormous membrane vesicle called a phagosome that engulfs a large particle such as a bacterium