Biochemistry Midterm 2.3 - Lipids/Membrane Flashcards
lipids are defined by
solubility properties, fats are lipids, not all lipids are fats
fatty acids description and what they are found in
amphipathic, 3-35 carbons tail
at pH 7 carboxyl group is ionized
found in complex lipids (structural and storage) and micelles
oleic acid systematic name
cis-9-octadecenoic acid
fatty acid nomenclature
numbering of carbons starts from carboxyl end (reactive end) π«
number carbons start from methyl end in nutrition omega Ο
# of carbons: # of double bonds ^ π« # 1st carbon of double bond
ex. 18:1^π«9 = cis-9-octadecenoic acid
linoleic acid in formula
alpha-linolenic acid formula
18:2^π«9,12
18:3^π«9,12,15
melting point increases
solubility decreases
Melting point :
1) decreasing double bonds/increased saturation
2) increasing chain length
Solubility:
1) decreases as chain length increases
saturated fatty acids
pack in an tight, ordered way
increased van der waals interactions
increased melting temp, takes more thermal energy to disrupt forces
cis bonds make for kinks that lower packing/melting temp
process that changes a cis alkene to a trans alkene
partial hydrogenation and cis alkene isomerization
biological health consequences of saturated fat and trans fat
saturated fat increase cholesterol by providing proper packing domains for cholesterol (LDL)
trans fats do the same and increase cell membrane rigidity
we donβt have the enzymes to break down trans fat bonds
simple triacylglycerol
a triglyceride with 3 fatty acids of the same type
enzyme that adds FA to glycerol and takes FA off
type of bond formed
acyl transferase and lipase
between the carboxyl end of a fatty acid and glycerol backbone is an ester bond formed by condensation reaction
fat and oil definition
solid triacylglycerides, liquid triacylglycerides
triacylglycerides description and why they are good for energy storage
storage lipid in animals (fats) and plants (seeds)
non polar, less soluble than fatty acids due to esterification of carboxyl groups
good for energy storage because more energy per carbon (reduced) and carry less water
how to make soap
saponification: add strong base to triglycerides to form glycerol and crude soap
waxes decription
esters of long chain fatty acids (saturated and unsaturated) with long chain alcohols (no glycerol back bone)
used as storage in plankton, waterproofing, and protection from evaporation
high melting point
highest lipid types in plasma, organelles and lysosomes
cholesterol, phosphatidylcholine, and sphingolipids
glycerophospholipids description
glycerol backbone, 2 fatty acids and a phosphate + head group on C3
primary structure in cell membranes
phosphate group is negatively charged at pH 7
phosphatidic acid
base form of glycerophospholipids
glycerophospholipid with 2 fatty acids on C1/C2 and an H attached to phosphate group as the head group
lysophosphatidatic acid
phosphate group attached to a glycerol backbone and 1 FA on C1
head group for phosphatidylethanolamine
amine containing, net charge 0 at pH 7
phosphatidylcholine
bonds
head group
major cell membrane component in most eukaryotes but prokaryotes canβt synthesis it
ester bonds between glycerol and FA and glycerol and phosphate, and phosphoester bond between phosphate and head group
amide containing, net charge of 0 at pH 7
head group for phosphatidylserine
carboxylate and amine containing, net charge -1 at pH 7
head group for phosphatidylglycerol
alcohol groups, net charge -1 at pH 7
head group for phosphatidylinositol
cyclic, net charge -4 at pH 7
cardiolipin head group
the large one, non cyclic, net charge -2 at pH 7
in vitro DNA synthesis requires:
2 Mg2+ ions, incoming nucleotide triphosphate, a 3β-OH group that with act as a Nucleophile, 3 Asp residues
sphingolipids
long chain amino alcohol backbone with a fatty acid connecter via an amide linkage on C2
polar head is attached by glycosidic or phosphodiester linkage
ceramide
sphingolipid with 1 amide linked fatty acid on C2
head group is H
sphinomyelin
sphingosine + phosphocholine at C3
type of phospholipid
cerebroside
mono-sugar group + sphingosine
found in nerve sheaths
type of glycolipid
ganglioside
sugars or oligosaccharides + sphingosine
type of glycolipid
glycosphingolipids
found on outside of plasma membranes for cell-cell recognition, as well as in blood type identification
what phospholipid and sphingolipid are structurally similar?
phosphatidylcholine and sphingomyelin
both have phosphocholine head
blood type is determined by
glycosphingolipids. The structure of the sugar is determined by glycosyltransferase and what it transfers:
Type O antigen - no active glycosyltransferase
Type A antigen - transfer of N-acetylgalactosamine
Type B antigen - galactose group
AB is both
phospholipase A1
phospholipase A2
phospholipase C
phospholipase D
A1: cleaves after O at C1
A2: cleaves after O at C2
C: cleaves before phosphate group (after O at C3)
D: cleaves after phosphate group (before O)
biologically active lipids
no glycerol or fatty acids
steroids - made from acetate or modification of other sterols
ex. bile salts, hormones
prostaglandins - made from modified fatty acids
sterol structure
4 fused rings (almost planar, A-D), hydroxyl group off A ring, and non polar side chains
phytosterols - plants
cholesterol - animals
no sterols in bacteria
steroid hormones
oxidized derivatives of sterols, made from cholesterol in gonads and adrenals
no alkyl hydrophobic chain (and therefore more polar)
carried through blood attached to carrier proteins
eicosanoids
signaling molecules from oxidized arachadonic acid:
prostaglandins - regulate inflammation and fever
thromboxanes - regulate formation of blood clots
leukotrienes - smooth muscle contraction
3 structures lipids aggregate into in water
micelles, lipid bilayers, and liposomes
dependent on type of lipid and concentration
micelles form with
amphipathic molecules with larger polar heads than tails (width, conical shaped)
such as: FFA, detergents, some steroids, lysophospholipids
lipid bilayer forms with
cylindrical shaped lipids (more than one tail)
such as: phospholipids and sphingolipids
made of 2 leaflet monolayers
stabilized by van der waals, hydrophobic effect and electrostatic interactions
liposome
vesicle, made of same as lipid bilayer but in a hollow sphere shape
inside sphere is aqueous to store and transport hydrophilic molecules
trilaminar membrane permeability
impermeable to charged ions and large molecules or proteins
permeable to hydrophobic molecules, neutral gases and small uncharged polar molecules like water
uncatalyzed membrane lipid movement
catalyzed membrane lipid movement
lateral movement and axis spin
transbilayer movement
flippase - outside to inside flip (ATP dependent)
floppase - inside to outside flip (ATP dependent)
scramblase - either direction towards equilibrium
why is it hard for polar molecules to pass through lipid bilayer?
because of hydrophobic phospholipid tails on the inside of the membrane
outer leaflet is often more
positively charged
predominant outer layer phospholipids
phosphatidylcholine and sphingomyelin
predominant inner layer phospholipids
phosphatidylethanolamine, phosphatidylserine
where are lipids made?
made in the ER and move from cis golgi apparatus to trans side for packaging
integral/intrinsic membrane proteins
firmly associated with the membrane, often spanning both leaflets and contain hydrophobic and hydrophilic regions
can be extracted with strong detergents, change in pH, chelating agent, urea and carbonate
Anchored (GPI-linked) membrane proteins
linked during regulatory events and can be removed by detergents or phospholipases
GPI is a carbohydrate motif
Also called amphitropic proteins
Peripheral (non GPI-linked) membrane proteins
weakly associated, easily removed by pH buffers, denaturing agents and chelating agents
monotopic/polytopic
spans 1 or 2 leaflets
membrane phases are and depend on
gel - liquid ordered state, individual molecules donβt move, tails are fully extended and densely packed
liquid - liquid disordered state, fluid phase, individual molecules move, tails are randomly oriented and loosely packed
increased heat increases fluidity
naturally more fluid than gel, necessary for cellular function
how cholesterol works as a fluidity buffer
- amphipathic molecule, acts a buffer by broadening transition temperature (AKA melting temp)
- rigid hydrophobic planar rings and hydrophobic flexible branched hydrocarbon tail with a polar hydroxyl head
1) in cold temperatures, cholesterol decreases packing of lower fatty acid tail ends which decreases melting temp
2) in warm temperatures, cholesterol increases packing of upper ends of hydrocarbon tails by immobilizing methylene groups which increases melting temp
membrane transition temp graph with and without cholesterol
sudden shift from gel to fluid state without cholesterol, gradual shift with cholesterol
kind of FA that contribute to a more fluid membrane and health benefits
short unsaturated fatty acids
also they are more adaptable to temperatures than saturated fatty acids
saturated fatty acid filled membranes are stiffer and more susceptible to rupture
what percentage of membrane proteins are integral vs peripheral
70% integral, 30% peripheral
