-
a. __ assemblies in which components are held in __ by __
i. core of membrane consists of __= __ of membrane and provides __that does what?
- lipid-protein
- thin sheet
- noncovalent bonds
- sheet of lipids in bilayer
- structural backbone
- barrier
- prevents random movements of water-soluble materials into and out of cell
-
a. __carry out specific functions
b. each type of cell contains a __, which has special activities
- proteins
- unique complement of membrane proteins
-
a. __ varies depending on type of cell membrane, organism, and type of cell
this is due to __ of these membranes
- ratio of lipid to protein
- basic functions
-
Examples of differences in membrane.
1. ex: mitochondria: high protein/ lipid ratio for transport as opposed to RBC, which are lots of myelin for electrical insulation for the nerve cell it encloses
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The membrane also contains __.
carbs attached to lipids nad proteins
-
a. Membranes contain different __, all of which are __(both hydrophilic and hydrophobic regions);
-
Three typesof lipids
- phosphoglycerides
- sphingolipids
- cholesterol
-
1. phosphoglycerides
a. most membrane lipids contain __, making them __
i. because built on __, they are called __
1. not __(3 fatty acids and not amphipathic), but membrane glycerides are __—only two of the hydroxyl groups are esterfied to __; the third is esterfied to __
- phosphate group
- phospholipids
- glycerol
- phosphoglycerides
- triglycerides
- diglycerides
- fatty acids
- hydrophilic phosphate group
-
a. without any additional substitutions beyond the phosphate and the two fatty acyl chains, the molecule is called __, which is virtually absent in most membranes
phosphatidic acid
-
i. instead, __ have an additional group linked to the phosphate, most commonly either __(4)
1. each of these groups is small and __and can form a highly water-soluble domain at one end of the molecule, called the __
a. PS and PI: __ (charge)
b. PC and PE: __ (charge)
- membrane phsophoglycerides
- choline, ethanolamine, serine, or inositol
- hydrophilic
- head group
- - charge
- neutral
-
a. fatty acyl chains are __ approx. 16-22 carbons
i. a membrane fatty acid may be fully __(no = bonds), __(one =), or __(several =)
b. __often contain one unsaturated and one saturated fatty acyl chain
- hydrophobic, unbranched hydrocarbons
- saturated
- monounsaturated
- polyunsaturated
- phosphoglycerides
-
1. health benefits of unsaturated fatty acids (__ and __)
a. __ and __ and incorporated into __ and __ molecules of certain membranes, in brain and retina
b. they are __ because last = is 3 carbons away from omega (CH3) end of the fatty acid chain
i. with fatty acid chains at one end of the molecule and a polar head group at the other, all __exhibit a distinct __
- EPA and DHA
- five and six double bonds
- PE and PC
- omega-3-fatty acids
- phosphoglycerides
- amphipathic character
-
a. Sphingolipids
i. how abundant
ii. derivatives of __, an amino alcohol that has a long hydrocarbon chain
iii. consists of __linked to a __ by its __group, called a __
less
- sphingosine
- sphingosine
- fatty acid
- amino
- ceramide
-
i. various kinds have different groups esterified to the __ of the __
1. if the substitution is __, the molecule is __¸ which is the only phospholipid of the membrane not built with a __
2. if substitution is carb= __
a. simple sugar: __
b. small clusters that have __: __
- terminal alcoholsphingosine moiety
- phosphorycholine
- sphingomyelin
- glycerol backbone
- glycolipid
- cerebroside
- sialic acid
- ganglioside
-
Sphingolipids cont.
i. __and similar structure to __
1. fatty acyl chains of sphingolipids are __and more __ than __
- amphipathic
- phosphoglycerides
- longer
- highly saturated
- phosphoglycerides
-
i. Glycolipids
1. crucial roles in cell function
a. __system rich in them
2. role in certain __; the toxins that cause __ and __ enter their target cell by first binding to cell-surface gangliosides, as does the flu
- nervous
- infectious diseases
- cholera and botulism
-
a. Cholesterol
i. may be up to __% of the lipid molecules in the plasma membrane
ii. plant cells contain __, but biologists disagree
iii. cholesterol molecules are oriented with their __outward membrane surface and remainder in __
1. __rings of a cholesterol molecule are __ and __,and they interfere with the __
- 50
- cholesterol-like sterols
- small hydrophilic hydroxyl group
- bilayer
- hydrophobic
- flat and rigid
- movements of the fatty acid tails of the phospholipids
-
a. Nature of Lipid Bilayer
i. each type of cell membrane has own characteristic __composition, differing in __, __, and particular species of __
1. estimated that some membranes have hundreds of different phospholipids
- lipid
- types of lipids
- nature of head groups
- fatty acyl chains
-
i. __ are more simple structural elements; important in biological properties
1. lipid composition etermines __ of membrane and __
membrane lipids provide precursors for__that regulate cellular function
- membrane lipids
- physical state
- activity
- highly active chemical messengers
-
a. Measurements
i. combined fatty acyl chains of lipid bilayer= about __
ii. each row of head groups= __
iii. total of about __
- 30 angstroms
- 15 angstroms
- 60
-
i. presence in membranes of the __lipid molecules
1. never have a __--> form __
ii. because of __ of lipid bilayer, membranes are __and their overall shape can change, as occurs during __or __
1. facilitates regulated __ or __ of membranes
- amphipathic
- free edge; unbroken
- interconnected networks
- flexibility
- deformable
- locomotion
- cell division
- fusion or budding
-
Importance in terms of maintenance
maintaining proper internal composition of a cell, in separating electric charges across the plasma membrane, etc
-
Ability to __
ex: phospholipid molecules assemble spontaneously to form walls of vesicles, called __
-
a. liposome walls have __ that is organized similarly to membrane bilayer
b. membranes can be inserted into __and their functions studied iin simpler environment than membrane
- continuous lipid bilayer
- liposomes
-
a. liposomes develop as __ to deliver __ or __ within the body, which can be linked to the __ or contained at high concentration within its __
i. the walls are constructed to contain __ that allow the liposomes to __ to the surfaces of particular target cells where the drug or DNA is intended to go
- vehicles drugs or DNA molecules
- wall of the liposome
- lumen
- specific proteins
- bind selectively
-
i. Asymmetry of Membrane Lipids
1. lipid bilayer: __
a. __ cannot penetrate the plasma membrane and are only able to digest lipids that reside in the __
- two distinct leaflets have distinctly different lipid composition
- lipid-digesting enzymes
- outer leaflet of the bilayer
-
i. compared to the inner leaflet, the outer leaflet has a high concentration of__ and a low concentration of __
1. it follows that the lipid bilayer can be thought of as composed of __ having different physical and chemical properties
- PC (and sphingomyelin)
- PE and PS
- two more or less stable, independent monolayers
-
1. different classes of lipids have different properties
a. all glycolipids of plasma membrane are in __ and serve as __
b. phosphatidylethanolamine, which is in the __, tends to promote the __, which is important in __ and __
- outer leaflet
- receptors for extracellular ligands
- inner leaflet
- curvature of the membrane
- membrane budding and fusion
-
a. phosphatidylserine in the __ has a net __charge at physiologic pH, which makes it a candidate for __
b. appearace of PS on the outer surface of aging lymphocytes does what, whereas its appearance on the outer surface of platelets leads to __
- inner leaflet
- negative
- binding positively charged lysine and arginine residues
- marks the cells for destruction by macrophages
- blood coagulation
-
a. PI in the __ can be __at different sites on the __ring, which converts the lipid into a __
play a key role in __ from plasma membrane to cytoplasm and __ to the cytosolic face of the plasma membrane
- inner leaflet
- phosphorylated
- inositol
- phosphoinositide
- transfer of stimuli
- recruitment of proteins
-
a. Membrane Carbs
i. depending on species and cell type, carbs in membrane range between __% by weight
1. more than __% of membrane carbs are linked to proteins to form __; remaining are __ to form __
- 2-10
- 90
- glycoproteins
- covalently linked to lipids
- glycolipids
-
i. all carbs of plasma membrane face outward into __; carbs of internal cell membrane face away from __
- extraellular space
- cytosol
-
1. addition of carb, __, is the most complex
2. carbohydrate of glycoproteins are short, branched, __
a. these __attached to membrane proteins and lipids can display extensive variability in __ and __
- glycosylation
- hydrophilic oligosacchardies
- oligosaccharides
- composition and structure
-
a. even the same protein can display __in different cells and tissues
b. oligosaccharides may be attached to several different __ by two major types of __
i. important role in __ of a cell with its environment and __ to different cellular compartments
1. ex: blood type determined by this
- different chains of sugars
- amino acids
- linkages
- mediating interactions
- sorting of membrane proteins
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