Chapter 13 Lipids - Ventura College Chemistry, Malia Rose ... · Chapter 8: Lipids. Functions of...
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Chapter 8: Lipids
Transcript of Chapter 13 Lipids - Ventura College Chemistry, Malia Rose ... · Chapter 8: Lipids. Functions of...
Chapter 8: Lipids
Functions of Lipids
- Storage Fats are long term energy (9 kcal/g) while carbohydrates are quick energy (4 kcal/g). - Membrane Components Lipid barriers keep water out. - Messengers Hormones process signals.
Classifications
LIPIDS
SAPONIFIABLE LIPIDS NONSAPONIFIABLE LIPIDS
SIMPLE COMPLEX
Waxes Triglycerides Phosphoglycerides Sphingolipids
Steroids Prostaglandins
Structure of Lipids Fatty Acids: long-chain carboxylic acids
oleic acid: cis-octadecanoic acid, C18H34O2
palmitic acid: hexadecanoic acid, C16H32O2
Always in even numbers.
Micelles Micelle: spherical cluster of molecules
casein in milk drug carriers
Saturation and Unsaturation
saturated: maximum number of hydrogens - labeled “fats” - considered “less” healthy - higher m.p. unsaturated: fewer than the maximum number of hydrogens - labeled “oils” - considered “more” healthy - lower m.p.
Fats and Oils At room temperature, animal fats are typically solids while oils are liquids.
Polyunsaturated fat: more than one double bond per fatty acid
In general, melting point increases with: - saturation - increasing molecular weight
Triglycerides Triglyceride: triesters of glycerol (alcohol) and fatty acids (carboxylic acid)
Some monoglycerides and diglycerides exist.
OH
OH
OH
1,2,3-propanetriol, "glycerol"
+ROH
O
3
O
O
O
O
O
R
R
O
R
triglyceride
2-oleoylglycerol
Physical Properties
Triglycerides are hydrophobic, making them insoluble in water.
Left: Immiscible lipid and water mixture. Right: Adding bile salts (ionic compounds) allows them to dissolve in water.
Hydrolysis
Hydrolysis (lipolysis): addition of water to split an ester in acidic conditions
Opposite of esterification
Takes place during: - digestion - breakdown after storage
O
O
O
O
O
R
R
O
R
triglyceride
+ 3 OH2
OH
OH
OH
+ROH
O
3
glycerol fatty acids
H+
or lipase
Saponification Saponification: splitting esters in basic conditions
NOT the opposite of esterification.
3 NaOH Na+3
triglyceride glycerol 3 sodium carboxylate salts (soap)
O R
O
O
O
R
O R
O
O
O
O
O
OH
OH
OH
R O–
O
++ 3 NaOH Na+3
triglyceride glycerol 3 sodium carboxylate salts (soap)
O R
O
O
O
R
O R
O
O
O
O
O
OH
OH
OH
R O–
O
++
NaOHH2O
Na+R O R
O
R O–
O
OH R++ NaOH
H2O
Na+R O R
O
R O–
O
OH R++
Base must be added in stoichiometric amounts. Reaction is irreversible.
soaps: fatty acid salts
Soaps
+ =
hard soap: made with NaOH, sodium carboxylates soft soap: made with KOH, potassium carboxylates
Hydrogenation Hydrogenation: adding H2 with a metal catalyst
oleic acid
linoleic acid
linoleic acid
5 H2Pt
steric acid
O CH3
O
O
O
(CH2)7
(CH2)7
O CH3
O
(CH2)7
(CH2)4
O CH3
O
(CH2)7
(CH2)4
O CH3
O
(CH2)16
O CH3
O
(CH2)16
O CH3
O
O
O
(CH2)16
+
oleic acid
linoleic acid
linoleic acid
5 H2Pt
steric acid
O CH3
O
O
O
(CH2)7
(CH2)7
O CH3
O
(CH2)7
(CH2)4
O CH3
O
(CH2)7
(CH2)4
O CH3
O
(CH2)16
O CH3
O
(CH2)16
O CH3
O
O
O
(CH2)16
+
Partial hydrogenation changes the consistency to softer, malleable solids but
also produces trans fats.
Hydrogenation increases a fat’s solidity.
Waxes wax: ester of fatty acids and long-chain alcohols
Waxes are: - insoluble in water - not easily hydrolyzed - used as protective coatings
Classifications
LIPIDS
SAPONIFIABLE LIPIDS NONSAPONIFIABLE LIPIDS
SIMPLE COMPLEX
Waxes Triglycerides Phosphoglycerides Sphingolipids
Steroids Prostaglandins
Lipid Bilayer lipid bilayer: outer membrane
Hydrophilic ends point outward. Hydrophobic ends point inward.
Fluid Mosaic Model fluid mosaic model: Free, lateral motion of the bilayers makes membranes “liquid-like” to allow transport through it
Phosphoglycerides phosphoglycerides: triester of glycerol with two fatty acids and one phosphoric acid linked to an aminoalcohol
plasmalogen
The aminoalcohol can be: - choline (lecithins) - ethanolamine (cephalins) - serine (cephalins)
Sphingolipids sphingolipids: contain sphingosine instead of glycerol
Classifications
LIPIDS
SAPONIFIABLE LIPIDS NONSAPONIFIABLE LIPIDS
SIMPLE COMPLEX
Waxes Triglycerides Phosphoglycerides Sphingolipids
Steroids Prostaglandins
Steroids steroid: Contain 3 cyclohexane (phenathrene) and 1 cyclopentane fused together
C17H28, cyclopentaphenanthrene
gonane: simplest steroid, contains only core structure
Steroids differ by the number of methyl and functional groups attached to the core structure.
cholic acid
medrogestone
Cholesterol cholesterol: most abundant steroid in the human body, builds and maintains membranes
In a day, 1000-mg cholesterol is made to keep a total body
content of 35-g.
Typical daily cholesterol intake is 200-300 mg.
HDL vs. LDL
HDL has a high ratio of protein to cholesterol. It moves cholesterol to the liver and is considered “good”. LDL has a low ratio of protein to cholesterol. It moves cholesterol to artery walls and is considered “bad”.
HDL vs. LDL
High LDL and low LDL are considered “desirable”.
Recommended levels of HDL, LDL, and total cholesterol
Heart Disease
Hormones Cholesterol is the starting material for a wide range of
steroid hormones.
Progesterone
cholesterol progesteroneOH
O
Ocholesterol progesteroneOH
O
O
Progesterone is produced in the ovaries, adrenal glands, and the placenta as one of the “female” sex hormones.
It has been commercially synthesized from diosgenin.
Estradiol
testosterone keto tautomer
enol tautomer, estradiol
O
OH
CH3
H
OH
O OH
OH
testosterone keto tautomer
enol tautomer, estradiol
O
OH
CH3
H
OH
O OH
OH
estradiol: female sex hormone generated from the aromatization of the A ring in testosterone.
Testosterone
testosterone: promotes maturation of male characteristics
Testosterone promotes anabolic effects, including growth of muscle mass, increased bone density, and stimulation of linear growth and bone maturation.
Anabolic steroids cause muscle fibers to become larger and repair more quickly than normal
Glutocorticoids glucocorticoids: control carbohydrate metabolism and control inflammation and the immune system.
cortisol: released due to stress to increase blood sugar levels by converting fatty acids and amino acids in the liver to glucose.
cortisone: oxidized ketone derivative of cortisol
Classifications
LIPIDS
SAPONIFIABLE LIPIDS NONSAPONIFIABLE LIPIDS
SIMPLE COMPLEX
Waxes Triglycerides Phosphoglycerides Sphingolipids
Steroids Prostaglandins
Prostaglandins prostaglandin: fatty acid synthesized from arachidonic acid
Induce labor, lower blood pressure, relaxes muscles, inflames tissue around injuries.
thromboxane: ring is a cyclic acetal
Induces platelet aggregation to start blood clotting.
leukotriene: oxidized arachdionic acid, without ring closure
Occur mainly in white blood cells to produce long-lasting muscle contractions, inflammation, and fever.
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