Four guinea pig 豚鼠 adipocytes
Cotyledon子叶cell from a seed of the Arabidopsis拟南芥
TG
lipase
Fatty acid + glycerol
mitochondrion β-oxidation
ATP
▪ Stored fuels Triacylglycerols vs polysaccharides
甘油三酯 TG: Glycerol + FA 腊 Wax: long chain alcohol +FA
O
O
CH2 O C R1
R2 C O CH
O
CH2 O C R3
▪ Compound lipid alcohol + FA+ non lipid component
Phosphlipids 糖脂---saccharide
甘油磷脂
磷脂
鞘氨脂
鞘氨醇
鞘氨脂
糖脂 半乳糖脂，脑苷脂
▪ Derived lipid Derivatives of these compounds
取代烃 fatty acids and their salts 脂肪酸(盐) 固醇类 steroid hormones, sterol固醇, taurocholic
Sperm Whales: Fatheads of the Deep ▪ Head:1/3 body weight ▪ 90% of the head is spermaceti oil, ~4 tons ▪ Triacylglycerols + waxes ▪ Buoyancy
ω-6 PUFA (poly-unsaturated fatty acid), relate to skin disease
Linolenic acid 亚麻酸
18:3Δ9c,12c,15c 顺-9，12，15-十八碳
三烯酸
ω-3 PUFA deficiency ----nerve and heart disease
TG--------
❖Insulation against low temperatures
• warm-blooded polar animals are amply padded with triacylglycerols
• hibernating animals (bears ) insulation and energy storage
French fries, doughnuts and cookies tend to be high in trans fatty acids
▪ melting point of branched FA
Stearic acid
70℃
10-methyl-stearic acid 10 ℃
Essential fatty acids Linoleic acid 亚油酸 顺9，12-十八碳二烯酸 18:2 Δ9c,12c
The hydrocarbon chain
the length degree of unsaturation
Physical properties
The longer the fatty acyl chain, the fewer
the double bonds, thTehelowloenrgiesrtthhee fatty acyslocluhbailnit,ythe fewer the double bonds, the higher is the
▪ Lipid rancid:
oxidative cleavage of the double bonds in unsaturated fatty acids produces aldehydes and carboxylic acids of shorter chain.
Triacylglycerols provide stored energy and insulation
biological function
Classification of biological lipids:
By chemical composition: ▪ Simple lipid ▪ Compound lipid ▪ Derived lipid
▪ Simple lipid: FA+alcohol
Stearic acid 18:0 Palmitic acid 16:0 oleic acid油酸18:1Δ9c Linoleic acid亚油酸18:2Δ9,12c α Linoleic acid亚麻酸18:3Δ9,12,15c
Trans-oleic acid 油酸18:1Δ9t
反式双键不引起键的弯折
▪ Free fatty acids are rarely found in the body
▪ They are transported in the blood complexed to serum albumin血清清蛋白
Common fatty acids----
▪ Carbon atoms: 12-24, even
18:1Δ9c
Physical properties of fatty acids
saturated (no double bonds) unsaturated (contain one or more double bonds)
Almost all biologically produced unsaturated fatty acids contain cis double bonds----a bend in the molecules
lipases脂肪酶
TG
fatty acids + glycerol
triacylglycerols
▪ Simple ▪ Mixed
Nonpolar
O
O
CH2 O C R1
R2 C O CH
O
CH2 O C R3
Hydrophobic molecules
▪ Many Foods Contain Triacylglycerols
a. More reduced----yields more energy b. hydrophobic----unhydrated----not have to
carry the extra weight of water of hydration
stored polysaccharides(2g water per gram of polysaccharides
solubility melting point
melting point
Melting point
At room temperature
Free rotation, Molecules can pack together tightly in nearly crystalline arrays
Saturated fatty acid---a waxy consistency
Unsaturated fatty acid---oily liquids
Kink Takes less thermal energy to disorder markedly lower melting points
▪ The biological functions of the lipids are as diverse as their chemistry.
You should know Representative lipids of each type
chemical structure physical properties
Palmitic acid 棕榈酸，软脂酸 十六烷酸
16-carbon saturated fatty acid 16:0
Stearic acid 硬脂酸
十八烷酸
18-carbon saturated fatty acid 18:0
Oleic acid 油酸，顺9-十八碳烯酸
18-carbon fatty acid, a single double bond
e.g.
Obese people of 15-20kg triacylglycerols meet energy needs for months
15-20kg glycogen-----less than a day’s energy supply
c. Carbohydrates
Ready solubility in water----quick sources of metabolic energy
2. Storage lipid
Storage lipid are derivatives of fatty acids.
▪ Triacylglycerols: fatty acid esters of glycerol
▪ Wax
Fatty acid
▪ 脂肪酸 Fatty acids in the body biosynthesis from acetyl-CoA breakdown of fats and phospholipids
Synthesis of fatty acids, condensation of two-carbon units
▪ Location of double bond: Δ9,Δ12,Δ15,
A simplified nomenclature 18:2 (Δ9c,12c) C-cis T-trans 18-carbon, C-1 being the carboxyl carbon One double bond between C-9 and C-10 Another between C-12 and C-13 Linoleic acid 亚油酸