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Lipids(hydrophobic脂溶性), fatty acids - Coggle Diagram
Lipids(hydrophobic脂溶性)
Functions
biological functions
隔絕外部與內部(因為與水不互溶)
water repellant
儲存能量-->脂肪單位提供熱量>醣類(因為小單元儲存能量較醣類多)
bouyancy(浮力) control and acoustics(聲學、聽覺) in marine mammals
more functions
membrane structure
扮演一些生化活性反應式的輔酶
vitamin K:凝血反應(缺少-->凝血反應出問題)
coenzyme Q:粒線體內的ATP合成
訊息傳遞分子(通常是較小型或是沒有fatty acids的lipids)
paracrine hormones(act locally)
steriod hormones(act body-wide)
growth factors
vitamins A & D (hormone precursors)
antioxidants(抗氧化)
vitamin E
pigments(色素)
contain fatty acids(complex lipids)
storage lipids
Triacylglycerols三酸甘油脂(nonpolar)
the primay storage form of lipids(body fat)
less soluble in water than fatty acids(the esterification酯化 of the carboxylate group)
生物體內大多數脂肪酸存在的形式
oils(liquid)
fats(solid)
less dense than water:fats and oils float
主要功能:儲存能量,非形成membrane
membrane lipids
沒有 fatty acid 的 lipid
Sterols
physiological role of sterols
Mammals obtain cholesterol from food or synthesize it de novo in the liver
Cholesterol and related sterols are present in the membranes of most eukaryotic cells
thicken the plasma membrane
no sterols in most bacteria
modulate fluidity and permeability
Cholesterol, bound to proteins, is transported to tissues via blood vessels
Many hormones are derivatives of sterols
steroid hormones 固醇類賀爾蒙
Steroid
s have the sterol nucleus but lack the alkyl chain found in cholesterol.
more polar
than cholesterol 因為沒有側鏈的結構 (側鏈偏nonpolar)
oxidized derivatives of sterols
不同的氧化型態
Steroid hormones
carried through the body in the bloodstream, usually attached to carrier proteins
male and female sex hormones
synthesized from cholesterol in gonads and adrenal glands
母結構:ABCD四個環
sterols and cholesterol
The tetracycle structure of sterols is almost planar
一端polar,一端nonpolar --> 會出現在細胞膜上
sterol 四環&平坦
hydroxyl group (polar head) in the A-ring
various nonpolar side chains
steroid nucleus: four fused rings
Phospholipids
Glycerophospholipids
general structure
The highly polar phosphate group may be further esterified by analcohol; such substituent groups are called the head groups.
Unsaturated fatty acids are commonly found connected to C2 of glycerol-3-phosphate
examples
Phosphatidylcholine
many prokaryotes, including E. coli, cannot synthesize this lipid; their membranes do not contain ---> 常用來比較原核prokaryotes / 真核eakaryotes
major component of most
eukaryotic
cell membranes
ether lipids; Platelets-Activating Factor(PAF)
與血小板有關,活化的因子
aliphatic ether analog of phosphatidylcholine
acetic acid esterified position C2 (傳遞凝血訊號)
first signaling lipid to be identified (血小板上有許多受體也會分泌傳遞物質)
stimulate aggregation of blood platelets (刺激血小板凝聚在一起)
plays role in mediation of inflammation
Phosphatidylethanolamine
ether lipids: Plasmalogen
common in vertebrate heart tissue
also found in some protozoa and anaerobic bacteria
vinyl ether analog of phosphatidylethanolamine
function is not well understood
about
primary constituents of cell membranes
Two fatty acids form ester linkages with the first and
second hydroxyl groups of L-glycerol-3-phosphate
The phosphate group is charged at physiological pH
Sphingolipids
about
A polar head group is connected to sphingosine by a glycosidic or phosphodiester linkage.
a fatty acid is joined to sphingosine via an amide acid
backbone is a long-chain amino alcohol sphingosine
backbone is not glycerol
the suger-containing glycosphingolipids為了接收訊號,特別表現在外層(使得偏極性)
Sphingomyelin
ceramine(sphingosine + amide-linked fatty acid) + phosphocholine attached to the alcohol
abundant in myelin sheath that surrounds some nerve cells in animals
structurally similar to phosphatidylcholine --> phosphatidylcholine
Glycosphingolipids and Blood Groups
the structure of sugar is determined by an expression of specific glycosyltransferases -> 看他的活性決定是什麼血型
Individuals with a glycosyltransferase that transfers an
N-acetylgalactosamine
group have
A blood group
Individuals with a glycosyltransferase that transfers a
galactose
group have
B blood group
.
Individuals with
no active
glycosyltransferase will have the
O antigen
Glycosphingolipids determine blood groups -> O, A, B差別在於醣(側鍊)
the blood groups are determined in part by
the type of sugars located on the head groups
in glycosphingolipids
Lipids會形成也會降解
不正確降解
protein降解失敗 -> 錯誤堆積 -> 疾病
lipid不正確降解 -> e.g.堆積在lysosome上 -> 先天缺陷、疾病
降解需要一系列酵素(移除醣也需要酵素)
Biologically Active Lipids
signaling molecules
between nearby cells
Arachidonic Acid花生四烯酸
Enzymatic oxidation of
arachidonic acid
yields
thromboxanes (formation of blood clots)
leukotrienes (smooth muscle contraction in lungs)
prostaglandins (inflammation and fever) 服用NSAIDs使之作用力降低
Lipid-soluble vitamins (A, D, E, and K)
Vitamin D
synthesized from cholesterol and regulates calcium metabolism
Vitamins E, K, and other lipid quinones
(b)助凝血, (c)抗凝血--> 互相拮抗
Antioxidants
Vitamin A
Precursor for other hormones involved in signaling
Involved in visual pigment
Vitamin A (retinol) is derived from
β-carotene
(C數減半)
present in much smaller amounts than storage or structural lipids
fatty acids
trans fatty acids
a trans double bond allow a given fatty acid to adopt an extended conformation
因為可密集的堆疊,所以show higher melting points than cis forms
form by partial dehydrogenation of unsaturated fatty acids
consuming trans fat increases risk of cardiovascular disease
about
saturated
no double bonds
unsaturated
(the double bonds are commonly in cis configuration, which kinks the chain)
monounsaturated
one double bond
polyunsaturated
more than one double bond
containing between 4 to 36 carbons(可長可短)
even number of carbons 偶數個碳
unbranched 完全直線型
solubility and melting point
melting point
C數增加-->熔點增加
雙鍵數增加-->熔點降低
solubility
C數增加-->溶解度降低
nomenclature