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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


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


O-linked glycosylation occurs in the


What is the major difference between passive diffusion and facilitated diffusion?

involvement of a transport protein


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


_ 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


membranes are _fluid


factors affecting fluidity

length of fatty acyl tails, presence of double bounds in acyl tails, presence of chloesterol


process of covalently attaching a carbohydrate to a protein or lipid


carbohydrate to lipid


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.


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


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


equal water and solute concentrations on either side of the membrane


solute concentration is higher on one side of the membrane


solute concentration is lower on one side of the membrane


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


shrinking in a hypertonic solution

turgor pressure

pushes plasma membrane against cell wall


plants wilt bc water leaves plant cells

2 classes of transport proteins

channels and transporters


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


carriers that transport solute, principal pathway for the uptake of organic molecules


single molecule


2 or more ions transported in same direction


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


actively transport Na and K against their gradients by using the energy from ATP hydrolysis


material inside cell is excreted into extracellular medium through vesicles


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


formation of membrane vesicles from the pm as a way for cells to internalize the fluid


fornation of an enormous membrane vesicle called a phagosome that engulfs a large particle such as a bacterium

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