3. Membrane Structure Flashcards by huh? yunjin.

encloses the cell, defines its boundaries, and maintains the essential differences between the cytosol and the extracellular environment

Plasma membrane

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maintains the characteristics differences between the contents of each organelle and the cytosol

Plasma membrane

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provides the basic fluid structure of the membrane and serves as a relatively impermeable barrier to the passage of most water-soluble molecules.

lipid bilayer

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Tail of phospholipid

two hydrophobic hydrocarbon tails

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protein sensors which transfer information across membrane

receptors

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main phospholipids, two long-chain fatty acids

Phosphoglycerides

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span the lipid bilayer and mediate nearly all the other functions of the membrane

Membrane proteins

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most abundant membrane lipids

Phospholipids

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50% of the mass of the most animal cell membranes

lipids

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Head of phospholipid

Phosphate group

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most common sphingolipid

Sphingomyelin

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from sphingosine (long acyl chain with an amino group (NH2) & two hydroxyl groups (OH)

Spingolipids

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It creates kink in the tail

cis-double bonds (unsaturated)

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3 types of phospholycerides

Phosphatidylethanolamine
Phosphatidylserine
phosphatidylcholine

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a fatty acid tail is attached to the amino group, and a phosphocholine group is attached to the terminal hydroxyl group

Spingomyelin

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able to diffuse freely within the plane of a lipid bilayer

Lipid bilayer

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phospholipid molecules in synthetic bilayers very rarely migrate from the monolayer on one side to that on the other

Flip-flop

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Hydrophobic tails sandwitched

Bilayers

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Tail inward characteristics

Spherical micelles

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contains a rigid ring structure, to which attached a single polar hydroxyl group and a short nonpolar hydrocarbon chain

Cholesterol

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the lipids tend to rearrange spontaneously to eliminate the free edge

Self-sealing property

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resemble sphingolipids; sugars

Glycolipids

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The lipid bilayer contains an unpaired electron whose spin creates a paramagnetic signal that can be detected by

electron spin resonance (ESR) spectrum

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amphiphilic molecules spontaneously ___ to bury their hydrophobic tails in the interior

Aggregate

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specialized membrane microdomains that serve as to organizing centers for assembly of signaling molecules

Lipid rafts

specialized for lipid storage that contain a giant liquid droplet

Fat cells or adipocytes

___ and ___ of the phospholipid molecules cause them to form bilayers spontaneously in aqueous environments.

Shape and amphiphilic nature

lipid molecules rapidly exchange places with their neighbors within a monolayer

Rapid lateral diffusion

catalyzes the rapid flip flop of phospholipids from one monolayer to the other

phospholipid translocators (flippases)

decrease mobility of the first few CH2 groups – makes lipid bilayer less deformable; decreases the permeability of the bilayer to small water-molecule * prevents the hydrocarbon chains from coming together and crystallizing

cholesterol

The lipid bilayer is a ____ fluid

Two-dimensional

modulates the properties of lipid bilayers and enhances the permeability-barrier properties

Cholesterol

How many carbon-long prenyl chains does archaea have?

20-25

storage of lipid

Lipid droplets

a change from a liquid state to a two-dimensional rigid crystalline state at a characteristic temperature

Phase transition

Outer monolayer of RBC

phosphatidylcholine & sphingomyelin

binds to the cytosolic face of the plasma membrane, where phosphatidylserine is concentrated, and requires this negatively charged phospholipid

protein kinase C (PKC)

assembly of signaling molecules, influence membrane fluidity and trafficking of membrane proteins, and regulate different cellular processes such as neurotransmission and receptor trafficking

Lipid rafts

Lipid bilayers can be built from molecules with similar features but __ __ __

different molecular designs

neutral lipids: exclusively hydrophobic molecules, and therefore aggregate into 3 dimensional droplets

Triacylglycerols and cholesterol esters

Important example of lipid kinase

phosphoinositide 3-kinase (PI 3-kinase)

Lipid droplets forms rapidly when cells are exposed to?

high conc. of fatty acids

Inner monolayer of RBC

phosphatidylethanolamine & phosphatidylserine

What is the importance of lipid asymmetry?

in converting extracellular signals into intracellular one

phospholipids in the cytosolic monolayer

phosphatidylinositol (PI)

cleaves an inositol phospholipid in the cytosolic monolayer of the plasma membrane to generate two fragments, one of which remains in the membrane and helps activate protein kinase C, while the other is released into the cytosol and stimulates the release of Ca2+ from the endoplasmic reticulum

Phospholipase C

translocate from the inner monolayer to the outer monolayer when cells undergo apoptosis

Phosphatidylserine

Sugar-containing lipid molecules that have the most extreme asymmetry in their membrane distribution. are found exclusively in the monolayer facing away from the cytosol

Glycolipids

charged glycolipids; important because of their electric effects

Gangliosides

exposed apical surface; may help to protect the membrane against the harsh conditions

Epithelial cells

asymmetric distribution of glycolipids in the bilayer results from the ____________ in the lumen of the Golgi apparatus

addition of sugar groups to the lipid molecules

performs most of the membrane’s specific tasks and therefore give each type of cell membrane its characteristic functional properties

Membrane proteins

Membrane proteins that extend through the lipid bilayer

Transmembrane proteins

Archor used by the membrane proteins that are entirely exposed at the external cell surface, by a covalent linkage

glycosylphosphatidylinositol; GPI anchor

do not extend into the hydrophobic interior of the lipid bilayer at all; they are instead bound to either face of the membrane by noncovalent interactions with other membrane proteins

membrane-associated proteins

do not extend into the hydrophobic interior of the lipid bilayer; bound to either face of the membrane by noncovalent interactions

Peripheral proteins

Membrane protein attachment by a fatty acid chain or a prenyl group

Myristoyl anchor Palmitoyl anchor Farnesyl anchor

always has a unique orientation in the membrane, reflects both the asymmetric way it is inserted into the lipid bilayer in the ER during its biosynthesis

Transmembrane protein

strands of a polypeptide chain to be arranges as a β sheet that is rolled up into a cylinder

multiple transmembrane

The hydrogen-bonding between peptide bonds is maximized if the polypeptide chain forms a regular α helix as it crosses the bilayer

How most membrane-spanning segments traverse the bilayer

Transmembrane proteins, the polypeptide chain crosses only once

single-pass transmembrane proteins

the polypeptide chain crosses multiple times

multipass transmembrane proteins

small amphiphilic molecules; more soluble in water than lipids

Detergents

used to localize potential α– helical membrane spanning segments in a polypeptide chain

hydropathy plots

Glycosylated: always present on the noncytosolic side of the membrane

oligosaccharide chains

Nanodiscs can be analyzed _____ to determine their structure

by single particle electron microscopy techniques

____ extensively coat the surface of all eukaryotic cells

Carbohydrates

Glycosylated: form on the noncytosolic side, where they can help stabilize either the folded structure of the polypeptide chain or its association with other polypeptide

Disulfide bonds

ionic (sodium dodecyl sulfate) or nonionic (octylglucoside and Triton)

Polar side

small, uniformly sized patches of membrane that are surrounded by a belt of protein, which covers the exposed edge of the bilayer to keep the patch in solution

Nanodiscs

surfactant concentration at which micelle formation is first seen in the solution

critical micelle concentration (CMC)

function to capture light energy and use it to pump H+ across the membrane

photosynthetic reaction center

able to move laterally within the membrane

Lateral diffusion

involves marking the membrane protein of interest with a specific fluorescent group (GFP)

fluorescence recovery after photobleaching (FRAP)

measures lateral diffusion rates of membrane proteins

fluorescence recovery after photobleaching (FRAP)

labeling individual membrane molecules and track their movement by video microscopy

single-particle tracking

certain plasma membrane enzymes and transport proteins are confined to the apical surface of the cells

epithelial cells

create nanoscale raft domains that function in signaling and membrane trafficking

protein-protein interactions in membranes

vesicle budding, cell movement, and cell division

shape is controlled dynamically

long, thin, flexible rod; it maintains the structural integrity and shape of the plasma membrane

Spectrin

enables the red cell to withstand the stress on its membrane as it is forced through narrow capillaries

spectrin-based cytoskeleton

vesicle budding, cell movement, and cell division

shape is controlled dynamically