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The cell membrane is involved in what 3 key functions?
1)receiving information (receptors) 2)Import and export of molecules (channels and pumps) 3)Capacity for movement and expansion
What functions do cell membrane formed compartments(organelle's) serve?
1) separate chemical run's 2)protects vital structure(DNA)
What two organelles are enclosed by two membranes?
Nucleus and Mitochondria
What are the most most abundant membrane lipids?
phospholipids
What is the most common phospholipid in cell membranes?
Phospatidylcholine
What components make up the hydrophilic head and hydrophobic tail of phosphatidylcholine?
Head=Choline,Phosphate, Glycerol Tail=Hydrocarbon Tail
Fat molecules are _______ and phospholipids are ______?
Hydrophobic and amphipathic
Phospholipid bilayers spontaneously______?
close, because it is energetically favorable to hide hydrophobic region of the bilayer
Liposomes are?
Pure phospholipids added to water (Artificial bilayers can be created in lab)
Phospholipids can move within the plane of the membrane easily which 3 ways?
1)lateral diffusion(exchange places w/ neighbors) 2)flexion 3)rotation(rotate along long axis)
Fluidity is?
the ease with which lipid molecules move within the plane of the bilayer
Lipid rafts are?
These specialized membrane microdomains compartmentalize cellular processes by serving as organizing centers for the assembly of signaling molecules, influencing membrane fluidity and membrane protein trafficking, and regulating neurotransmission and receptor trafficking. Lipid rafts are …
What are the 2 properties of Hydrocarbon Tails that effect how tight they pack in the bilayer (Fluidity)?
Length and Number of double bonds they contain
Choleseterol?
-Stiffens the membrane -About 20% of the lipids in membrane by weight -Short and rigid, fills spaces made by kinks
Membrane Fluidity does what 4 IMPORTANT things?
1)Enable rapid diffusion of membrane proteins 2)Membrane lipids and proteins move around the membrane 3)Membranes can fuse with each other and mix molecules 4)Ensures even distribution of membrane molecules between daughter cells.
Lipid bilayer's distribution is?
Asymmetrical -two halves of bilayer have diff sets of phospholipids and glycolipids
Phosphatidylcholine is?
mainly structural found on outside
sphingomyelin is?
myelin sheathing, most outside, signaling
Phosphatidylserine is?
found on inside, flips to outside during apoptosis
Phosphatidylethanolamine is?
found on inside, involved in membrane fusion
glycolipids?
provide energy and acts as cell surface marker
Cholesterol?
maintain fluidity and structure of the membrane
Inositol phospholipids
important signaling molecules
New membrane synthesis occurs?
In the ER
New membrane exported to other membranes by _____ and _____?
budding and fusion
_____ catalyze the transfer of phospholipid molecules to opposite monolayer
Flippases
In membranes ___ is preserved?
Orientation,
Cytosolic face is always____ to the _____?
adjacent, cytosol
Noncytosolic face is?
exposed to either cell exterior or the interior space of an organelle
What are the four types of membrane proteins?
Transporters, Anchors, Receptors, Enzymes
proteins equal _____% of the mass of most plasma membranes
50
What are the two types main types of membrane proteins?
Integral and Peripheral
What are the three types of integral proteins?
1)Transmembrane 2)Monolayer Associated (alpha helix) 3)Lipid-Linked
What is the one type of peripheral membrane protein?
Protein-Attached
Transmembrane proteins?
They extend through the bilayer and have both hydrophobic and hydrophilic regions A-helix and B-pleated sheet(barrel)
Monolayer-Associated?
-located entirely in the cytosol -Associated with inner layer of lipid bilayer -Amphipathic a-helix expose on the surface of the protein
Lipid-Linked
-Lie Entirely outside of the bilayer -On the cytosolic or extracellular side -One or more covalently bound lipid groups
Protein-Attached?
-bound indirectly by interactions with other membrane proteins -One or the other face of the membrane
_____ determines how polypeptide chain crosses the bilayer as alpha helices
Hydrophobicity
Alpha helix regions of an transmembrane protein will have______ on the outside which attract them to the membrane(hydrocarbon tails)?
hydrophobic
Peptide bonds are____ and therefore ____?
polar, hydrophilic
______ parts of the polypeptide backbones form hydrogen bonds with one another in the interior of the helix
Hydrophilic
Transmembrane proteins act as _____ to relay signals from the extracellular environment to the cell?
receptors, ex: cannabinoid receptor
Membrane pores can be formed by _____(most common) or ______?
alpha helices, beta sheets
Alpha helix can form ___ pores?
tight pores that can be "opened and closed"
B-barrel?
-B sheet curved into a cylinder -A.A. facing inside =hydrophilic -A.A. facing outside=hydrophobic -Less versatile than a-helix, limit to how tight B-sheet can be curved to form barrel
Detergents ____ lipid bilayer allowing _____ of membrane proteins?
destroy, release -disrupt hydrophobic associations -Used to break open membranes when making a cell lysate for SDS-Page
Hydrophobic ends of detergent bind to membrane-spanning _______ region of transmembrane proteins and _________ tails of lipid bilayer which separates the membrane proteins.
hydrophobic and hydrophilic
Plasma membrane reinforce by?
Cell Cortex
Cell membranes strengthened and supported by framework of _____ attached to membrane via _______ proteins?
Proteins, transmembrane
Cell cortex?
meshwork of fibrous proteins that is attached to the cytosolic face of the membrane
Red Blood Cells, main component of cortex is ____?
spectrin,
_____ cortex is relatively simple and the most researched?
Red blood cells
spectrin?
Provides support for plasma membrane and maintains cell’s shape
Mutations in spectrin in RBC's?
Anemia
______ proteins like spectrum to specific transmembrane proteins?
Intracellular attachment
Anemia?
Genetic abmormalities in spectrin, fewer RBC's and RBC's that are incorrectly shaped and fragile.
What two cells were shown to explain who proteins can move freely within the lipid bilayer?
Rhodamine (mouse cell) labeled membrane protein, and flourescein (human cell) labeled membrane protein!
Membrane domains?
functionally specialized regions on the cell or organelle surface
What two ways do cells confine proteins to localized areas within the bilayer?
Membrane domains, and lipid rafts
4 ways to restrict protein movements in the membrane?
1) Tether to cell cortex inside cell 2)Extracellular matrix molecules outside cell 3)Tether to proteins from another cell 4)Diffusion barriers restrict proteins to specific domain (tight junctions)
Tight junctions?
forms barrier allowing for asymmetric distribution of membrane proteins, proteins can diffuse between cells but not beyond tight junctions -Ex blood brain barrier, gut lining, lungs
Glycoproteins?
proteins in plasma membrane with oligosaccharides(short chains of sugars) linked to them
Proteoglycans?
One or more long chain polysaccharide chains attached to membrane proteins
Carbohydrate layer is located on?
noncytosolic side
Function of Carbohydrate Layer?
-Protect cell surface(mechanical and chemical damage) -Absorb water(slimy) -helps motility -stops cells from sticking together -Cell recognition and adhesion

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