Chapter 15 Flashcards
outer leaflet mainly (2 things)
phosphatidylcholine + sphingomyelin.
Inner leaflet mainly (2 things)
phosphatidylethanolamine + phosphatidylserine
glycolipids are only in the _____ leaflet
outer
present in about the same molar amounts as phospholipids.
cholesterol
These 2 things are free to diffuse laterally within the membrane.
lipids, proteins
transient structures in which specific proteins can be concentrated to facilitate interactions.
lipid rafts.
two classes of membrane proteins
peripheral, integral
associated with membranes through protein-protein interactions; often ionic bonds.
The bonds can be disrupted by polar reagents
Peripheral membrane proteins
inserted into the lipid bilayer; they can be dissociated only by reagents that disrupt hydrophobic interactions.
Integral membrane proteins
amphipathic molecules with hydrophobic and hydrophilic groups that can solubilize these proteins.
detergents
integral proteins that span the lipid bilayer with portions exposed on both sides.
transmembrane proteins
2 transmembrane protein exmaples
Glycophorin and band 3
These are added to the C terminus of some proteins in the ER.
GPI anchors
carbohydrate coat
Glycocalyx
covered by microvilli that increase surface area for absorption.
apical surface
mediate transfer of absorbed nutrients to the blood.
basolateral surface
separate the apical and basolateral domains.
tight junctions
small lipid rafts that start as invaginations of the plasma membrane, organized by caveolin.
Caveolae
bind molecules on one side of the membrane, then undergo conformational changes that allow the molecule to pass through and be released on the other side.
carrier proteins
form open pores through the membrane, allowing free diffusion of any molecule of the appropriate size and charge.
channel proteins
transporters function by alternating between two
conformational states.
Allow water molecules to cross the membrane more rapidly than they can diffuse through the phospholipid bilayers.
aquaporins
open in response to binding of neurotransmitters or other signaling molecules.
ligand-gated channels
open in response to changes in electric potential across the plasma membrane.
voltage-gated channels
use energy from ATP hydrolysis to actively transport ions across the plasma membrane to maintain concentration gradients.
ion pumps
inside of the cell is ______ with respect to the outside.
negative
As nerve impulses (action potentials) travel along axons, the membrane _______
depolarizes
the Na+ channel pore is too ______ for K+ or larger ions.
narrow
In active transport, molecules are transported against their
concentration gradients.
Ion pumps in bacteria, yeasts, and plant cells actively transport ____ out of the cell.
H+
In both prokaryotic and eukaryotic cells they transport toxic substances out of the cell.
ABC transporters
Uptake of glucose and Na+ is an example of transport of:
two molecules in the same direction.
Phagosomes fuse with lysosomes to form
phagolysosomes
uptake of extracellular fluids in large vesicles.
Macropinocytosis
a mechanism for selective uptake of specific macromolecules.
Clathrin-mediated endocytosis
Cholesterol is transported through the bloodstream mostly in the form of
low-density lipoprotein (LDL)
After internalization, clathrin-coated vesicles shed their coats and fuse with
early endosomes.
. Early endosomes have membrane H+ pumps which maintain ______ internal pH
acidic
