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3/17 生化整理, IMG_F251F88A2078-1, IMG_874BCE21CAE2-1 - Coggle Diagram
3/17 生化整理
lipids
introduction
functions
buoyancy & acoustic
plus density when deep diving
sound energy
membrane
water proof
dry surface
cofactors
vitamin K / coenzyme Q
insulation
high absorption of heat
mechanical protection
low thermal conductivity
signaling
hormones
growth factor
store energy
reduced compounds / hydrophobic
carry more energy / less water
glucose & glycogen fir short term
fats for long term need
pigment
antioxidant
classification
contain fatty acids
what is fatty acids ?
saturated
saturated
no double bonds
extended conformations
unsaturated
mono
poly
Carboxylic acids with hydrocarbon chains
most even number
most unbranched (natural)
Nomenclature
common name
numbering of carbon skeleton
Δ : 雙鍵的部分，從頭數（carbonyl carbon）
ω：雙鍵的部分，從尾數
systematic name
Solubility and Melting Point
Solubility
鏈越長，溶解度越差
Melting Point
鏈越短，溶點越低
雙鍵越多，溶點越低
pack in
saturated :fairly orderly
interaction較強
unsaturated : less orderly
interaction較弱
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Trans Fatty Acids
partial dehydrogenation of unsaturated
increase shelf life or stability（高溫烹煮時）
pack more regularly and show higher melting points
increases risk of 心血管疾病
Triacylglycerols
lipids store
Less soluble in water (esterification of carboxylate)
Less dense
waxes
long chain saturated ester + unsaturated fatty acid
high melting points
function
protection and pliability
waterproof
metabolic fuel store
avoid evaporation
membranes lipids
introduction
diversification
Different organism - different head group compositions
polar head + nonpolar tails
Different tissues - different lipid head group compositions
diversification
Glycerophospholipids
Primary constituents of cell membranes
physiological pH --> phosphate charged
structure
Unsaturated fatty acids - connected to C2
polar phosphate group may be eaterified
head groups
H : phosphatidic acid
NH3 : phosphatidylethanolamine
N : phosphatidylcholine
phosphatidylcholine 卵磷脂
major component in eukaryotic cell membranes
prokaryotes do not synthesize
ether lipids
plasmalogen
analog vinyl ether （ether - linked alkene)
vertebrate heart tissue
some protozoa and anaerobic bacteria
function 不完全被知道
resistant to cleavage by common lipases (few specific can)
other 不確定
platelets - activating factor
analog of phosphatidylcholine
aliphatic ether
acetic acid - esterified position C2
inflammation
sphingolipids
backbone
is not glycerol (甘油）
long - chain amino alcohol sphingosine(鞘氨醇)
connection
fatty acid - via amide linkage
polar head - via glycosidic
sugar-containing glycosphingolipids found in outer face of plasma membranes.
head group
H : ceramide
glucose
phosphocholine
sphingomyelin 鞘磷脂
ceramide + phosphocholine
abundant in myelin sheath (nerve cell)
structure similar to Phosphatidylcholine
glycosphingolipids
blood group determine by type of sugar in glycosphingolipids (head groups)
sugar determined by specific glycosyltransferases
no active glycosyltransferases - O antigen
glycosyltransferases
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degraded in lysosome
Phospholipids are degraded by
phospholipases A−D
Gangliosides are degraded via enzymatic cleavages
failure -> build-up
dysfunction
without fatty acid
sterol
structure
hydroxyl group (polar head) in A-ring
nonpolar side chains
four fused rings
tetracycle structure / planar
Physiological Role
Cholesterol and related sterols --> membranes of eukaryotic
thicken membrane
bacteria no no
fluidity and permeability
mammal obtain from food or synthesize
Cholesterol
transport via blood vessel
low-density cholesterol tends to deposit and clog in arteries
derivatives -- hormone
oxidized sterols -- steroids
more polar than 膽固醇
synthesized from gonads and adrenal gland
carried through the body
many are sex hormones
biologically active lipids
smaller amounts than other lipids
signaling molecules
lipid- soluble
example
Arachidonic Acid
oxidation
prostaglandins -- inflammation
thromboxanes
leukotriwenes
Vitamin D
regulated calcium metabolism
vitamin A
Derived from β-carotene
pigment
Biological Membranes
Lipids Aggregate into Structures
micelles
forms amphipathic molecules
more polar head than tail
composed of dozen to thousand lipid molecule
concentration dependent
bilayers
two leaflets of lipid monolayers
hydrophilic head groups interact on both sides
hydrophobic fatty acid tali inside
polar head group + more than one lipid tail
vesicle
spontaneously sealant spherical vesicles
can be made in vitro
central - aqueous cavity
useful artificial carriers
liposomes
membranes
what?
lipids + proteins
eukaryotic cells -- internal membranes
lipid-based & pliable sheets
functions
boundaries
import nutrients + export waste
retain metabolites and ions
signals
compartmentalization within the cell
proton gradient & synthesis ATP
asymmetric 不對稱性
two leaflets different compositions
outer leaflets more positively compositions
Phosphatidylserine多在內層
Fluid Mosaic Model
proteins be embedded in or associated with the membrane
integral proteins pften spanning the bilayer
peripheral proteins weakly associated
composition
tissues
organelles
organisms
varies ratio
abundance of sterols
phospholipid types
archaea
Unique glycerol chirality
L-glycerol in archaea
D-glycerol in bacteria
D-glycerol in bacteria
archaea : isoprene chains
bacteria : unbranched fatty acid chains
Unique linkages
archaea : ether
bacteria : ester
topology
monolayer
proteins
function
Channels, gates, pumps
enzymes
receptors : detect signal
hormones
neurotransmitters
light
pheromone
three types membrane protein
amphitrophic and GPI-linked proteins
attached to membrane by covalent interaction
specific regulatory , can be reversibly removed
lipid anchor
some lipoproteins
covalently linked
protein anchored to the membrane
reversible
target ok
farnesylation
protein target to inner leaflet
lipidation intermediate
Primary sequence contains
C : Cys
aliphatic amino acid
X
catalyzed by farnesyl transferase
integral membrane proteins
span entire membrane
asymmetry
need strong detergent to removed
tightly associated
after purified : still have phospholipids associated with them
Selectively Placed Nonpolar Amino Acids Within the Membrane
Hydropathy Plots
預測穿膜次數
peripheral membrane proteins
Associate with the polar head
loosely associated
dissociated fairly easily during changes
after purified --> no longer associated with any lipid
Physical Properties
Not permeable to large solutes & ions
Permeable to smaller compounds
undergo phase transitions
liquid-disordered state
physiological conditions : fluid-like
liquid-ordered statel
Permeable 可透過化學方法增加
Dynamic and flexible
organisms adjust composition
fluidity determined by the fatty acid
fluid membranes require shorter、unsaturated fatty acids
Membrane Rigidity and Permeability
sterols
animals : cholesterol
plants : phytosterols
fungi : ergosterol
hopanols
dynamics
lateral diffusion
study
Fluorescence recovery after photobleaching --> monitor the return rate
diffusion coefficient
lateral diffusion are high
step
fluorescent probe on lipid
photobleaching
recovering
transverse diffusion
from one leaflet to another ; rare --> transverse the hydrophobic region
Flippases
enzymes catalyze (原本非常慢）
some use energy (ATP) to against concentration gradient
step
flippase
floppase
scrambles
rafts
lipids rafts
ordered
segregation
contain clusters of glycosphingolipids
caveolin
Membrane Curvature
lipid distribution isn't random or uniform
Curvature
amphipathic helices inserted into one leaflet
force membrane bend
BAR domains polymerize superstructure
protein with intrinsic curvature
concave surface --> high density+positive charge
intact with negatively charged
