Chapter 10 Flashcards
Lipids
heterogenous macromolecules
grouped by solubility in nonpolar solvents -
(no “formula”) (contain C & H & a little O)
What are some functions of lipids?
- Energy storage
- Insulation, cushioning
- Cell compartmentalization
- Hormones and signaling
______________ are Hydrocarbon Derivatives
Fatty Acids
What is the nomenclature for unbranched fatty acid
Specifies the chain length and number of double bonds, separated by a colon.
(For example, the 16-carbon saturated palmitic acid is abbreviated 16:0)
What is the equation like nomenclature for fatty acids
The positions of any double bonds, designated Δ (delta), are specified relative to C-1 by a superscript number indicating the lower-numbered carbon in the double bond. By this convention, oleic acid, with a double bond between C-9 and C-10, is designated 18:1(Δ9) (ex a 20-carbon fatty acid with one double bond between C-9 and C-10 and another between C-12 and C-13 is designated 20:2(Δ9,12).
Fatty acid are long, unbranched _____________ (some branching in bacteria)
carboxylic acids
Fatty acids usually have ______ - 20 carbons with even number
12
____________ numbering from C-1 at C=O group; Common names based on C=O with adjacent carbons designated alpha, beta, yamma ; terminal –CH3 is w
IUPAC
Double bonds in the fatty acids are _____ conformation
Cis
The double bonds in fatty acids are usually found at C_, C_, & C_
C9, C12, & C15
The longer the fatty acyl chain and the fewer the double bonds, the _________ the solubility in water.
lower
_____________ fatty acids pack with favorable interactions
Saturated
___________cis fatty acid show less ordered packing due to double bond kink
Unsaturated
Less thermal energy disrupts unsaturated fatty acid packing – more unsaturation which results in a _________ melting point
lower
Rancidity
Double bond cleavage occurs with oxygen exposure
____________ are Fatty Acid Esters of Glycerol
Triacylglycerols
The simplest lipids constructed from fatty acids are the ________________
triacylglycerols
___________________ are composed of three fatty acids, each in ester linkage with a single glycerol
Triacylglycerols
Triacylglycerols Provide Stored Energy and ___________________
Insulation
Membrane lipids are _________________: one end of the molecule is hydrophobic, the other hydrophilic
amphipathic
Membrane lipids form __________
Membrane bilayers
Glycerophospholipids
The hydrophobic regions are composed of two fatty acids joined to glycerol
Galactolipids and sulfolipids
Contain two fatty acids esterified to glycerol, but lack the characteristic phosphate of phospholipids
Archaeal tetraether lipids
Two very long alkyl chains are ether-linked to glycerol at both ends
Sphingolipids
In which a single fatty acid is joined to a fatty amine
Sphingosine and sterols
Compounds characterized by a rigid system of four fused hydrocarbon rings
Phospholipids
A polar head group is joined to the hydrophobic moiety by a phosphodiester linkage (ex. glycerophospholipids and some
sphingolipids)
Glycolipids
Sphingolipids lack phosphate but have a simple sugar or complex oligosaccharide at their polar ends
______________________ are Derivatives of Phosphatidic Acid
Glycerophospholipids
Glycerophospholipids (phosphoglycerides)
Are membrane lipids in which two fatty acids are attached in ester linkage to the first and second carbons of glycerol, and a highly polar or charged group is attached through a phosphodiester linkage to the third carbon
Some Glycerophospholipids Have _________-Linked Fatty Acids
Ether
Ether lipids
One of the two acyl chains is attached to glycerol in ether, rather than ester, linkage
Plasmaogens
The ether-linked chains may contain a double bond between C-1 & C-2
Plasmalogen
Have both ester and vinyl-ether links between
glycerol and fatty acids; choline or ethanolamine heads
____________ are enriched in vertebrate heart, muscle & peripheral nerves & may protect against oxidative damage (free radicals) and serve as molecule precursors
Plasmalogen (ex. Platelet-activating factor signals for platelet aggregation)
Sphingolipids
Have a polar head group and two nonpolar tails, but unlike glycerophospholipids and galactolipids they contain no glycerol
_____________ are Derivatives of Sphingosine
Sphingolipids
Ceramide
When a fatty acid is attached in amide linkage to the —NH2 on C-2, the resulting compound
Sphingosine
C18 amino alcohol: C1-OH; C2-NH2, C3-OH & amide link to fatty acid (Abundant in mammalian
CNS lipid membranes)
Fluid mosaic model
Phospholipids form a bilayer in which the nonpolar regions of the lipid molecules in each layer face the core of the bilayer and their polar head groups face outward, interacting with the aqueous phase on either side.
Membrane _____________ require variable lipid and protein composition across organelles, tissue, and organism
functions, (* Selective cell boundaries and compartments for nutrients, waste, and metabolites
* Sensing and producing signals and information
* Storing energy as a proton and ion gradients that supports ATP synthesis)
Asymmetric fatty acid synthesis in ______ or bacterial plasma membrane results
E.R
Membrane Protein _____________ also varies with cell type & tissue
Composition
In the fluid mosaic model, proteins are embedded in this bilayer sheet, their ___________ domains in contact with the fatty acyl chains of membrane lipids
hydrophobic
In fluid mosaic model, membrane thicker in solid ___________ with extended and packed lipid tail
(gel) state
Organisms alter fatty acid __________ and length to maintain fluid, dynamic structure from 10-40oC
saturation (based on fatty acid properties)
_______ cholesterol broadens transition temperatures
Steroid (* Limit movement of fatty acid tails
* Reduce van der Waals interactions)
Lipids move _________ within a bilayers in 2D fluid (like machine oil)
rapidly (lateral diffusion) & transverse diffusion its very slow (flip flop)
____________ lipids spontaneously aggregate in aqueous solutions, Hydrophilic heads interact with water; nonpolar tails bury inside
Amphipathic
Micelles
Form with wider head-groups than hydrophobic tails (make a sphere shape with the hydrophobic head outers & hydrophilic tail inwards) (ex. fatty acids and detergents (~10-1000 lipids above a threshold conc.)
Bilayer
Two lipid monolayers (leaflets) form a two-dimensional sheet where the hydrophobic tails on the inside & the hydrophilic head on the outside
Vesicle (liposome)
Are sealed lipid bilayers with internal aqueous cavities that can fuse with other vesicles; flexible and self-sealing
What are the 3 forms lipid aggregate makes in water?
- Micelles
2.Bilayer - Vesicle (liposome)
Integral membrane proteins
Are embedded within the lipid bilayer and are
removable only by agents that overcome the hydrophobic effect, such as detergents, organic solvents, or denaturants
Peripheral membrane proteins
Associate with the membrane through
electrostatic interactions and hydrogen bonding with hydrophilic domains of integral proteins and with membrane lipids ( globular associated with membrane surfaces via non-covalent
interactions; high ionic strength and ΔpH disrupts)
Amphitropic proteins
Associate reversibly with membranes and are therefore found both in the membrane and
in the cytosol
Hydropathy Index
Globular regions emerge with glycosylated (exterior) or charged (interior)
* Delta G transfer from organic to water solution calculated per 20 amino acid window
Integral protein helical transmembrane sequences are identified by hydropathy plots
hydropathy plots (20amino acids)
The positive inside rule
The positively charged Lys and Arg residues of
membrane proteins occur more commonly on the cytoplasmic face of
membranes
Covalently Attached Lipids Anchor Some __________________
Membrane Proteins
