Lipids Flashcards
Defined as biosynthesis of fatty acid
Lipogenesis
Three types of lipogenic pathways based on cellular localization
Extramitochondrial
Microsomal
Mitochondrial
Extramitochondrial lipogenesis pathway occurs in
Cytosol
Microsomal lipogenesis pathway occurs in
Smooth endoplasmic reticulum
Mitochondrial lipogenesis pathway occurs in
Mitochondrion
General principle of lipogenesis is
Add 2 carbon atoms per cycle
Takes place in the cytosol
Conversion of acetyl CoA to malonyl CoA via acetyl CoA carboxylase is the rate limiting step
Uses biotin
Extramitochondrial lipogenesis
In the extramitochondrial lipogenesis pathway, Acetyl CoA is converted to
*rate-limiting step
malonyl CoA
Is the rate-limiting step or committed enzyme in extramitochondrial lipogenesis
Acetyl CoA Carboxylase
Prosthetic group of Acetyl CoA
Biotin
Acetyl CoA carboxylase for conversion of acetyl coa to malonyl coa is inhibited by
palmitic acid
A protein found in raw egg white, inhibits the committed step by binding and removing biotin
Avidin to acetyl carboxylase
Energy source per gram of lipid
9 calories
Adipose ->
Fatty acids -> CO2 + H2O + ATP
Major components of cell membranes
Phosphoglycerides
Sphingolipids
Cholesterol
Lipid classes
Fatty acid derivatives Triacylglycerol (TAG) Phospholipids Sphingolipids Wax esters Isoprenoids (terpenes, steroids) Lipoproteins
2-4 carbon atom Fatty acids
Short
6-10 carbon atom fatty acid
Medium
12-26 carbon atom or more fatty acid
Long
Have only single bonds in hydrocarbon chain
Saturated fatty acid
Are solids at room temperature because the regular nature of their aliphatic chains allows the molecules to be packed in close, parallel alignment
Have only single bonds in hydrocarbon chain
Saturated fatty acids
Have at least one C = C double bond in the chains
In contrast, are all liquid at room temperature because the cis double bonds interrupt the packing of the chains
Thus less energy is required to melt them
Unsaturated fatty acids
The greater the degree of unsaturation,
the lower the melting point
20 Carbon Double-Bonds with Methyl, Oil soluble OMEGA end and a Carboxyl, Water-soluble Delta End
Eicosapenaenoic acid (EPA) Omega 3
22 Carbon Double-Bonds with Methyl, Oil-soluble, Omega End and Carboxyl, Water-Soluble Delta End
Docasahexaenoic Acid (DHA) Omega 3
18 Carbon Double-Bonds with Methyl, Oil-soluble Omega end and Carboxyl, Water-Soluble Delta end
Gamma-linolenic Acid (GLA)
Omega 6
20 Carbon Double-bonds with Methyl, Oil-Soluble Omega End and Carboxyl, Water-Soluble Delta End
Dihomo-gamma-linolenic Acid (DGLA)
Omega 6
Polyunsaturated >2 double bonds
Not synthesized by body
Decrease risk of Cardiovascular Disease
Polyenoic fatty acids
Essential fatty acids
Omega 3
Omega 6
C18 having two double bonds
Linoleic acid
Lady linoleic linolenic
C18 having three
Precursor of EPA (eicosapentaenoic acid) and DHA (docosahexanoic acid)
Linolenic acid
C20 having four double bonds
Arachidonic acid
The main storage forms of fatty acids
The acylglycerols are esters of fatty acids bound to the sugar alcohol glycerol
All three OH groups of glycerol are esterified
They are the most common lipid material
TAG
They are also called neutral fats, because the carboxyl groups of the fatty acids are bound in ester linkage and can no longer function as acids
Mixtures are referred to as fats or oils
TAG
Molecules are classified according to which alcohol becomes esterified to the phosphate group
Phosphoglyceride
Phosphatidylcholine (PC or Lecithin) Phosphatidylethanolamine Phosphatidylserine Diphosphatidylglycerol Phosphatidylinositol
Phosphoglyceride
Surfactants or surface-acting agents
Plays an essential role in reducing surface tension in lung alveoli
Increase pulmonary compliance
Respiratory Distress Syndrome of the newborn
Lecithin
Phosphatidylcholine
Serologic test for syphilis
Utilizes a diphosphatidylglycerol as the antigen
Venereal Disease Research Laboratory
Cardiolipin
With repeating 5-carbon units (isoprene)
Terpenes
Steroids
Isoprenoids
Mixed terpenoids
Vitamin E (alpha tocopherol) Ubiquinone Vitamin K
Complex derivatives of triterpenes
All with 4 fused rings
The essential structural nucleus of the steroids consists of three fused cyclohexane rings joined to a cyclyopentene ring
Steroids
Ovarian steroid
estrogen
18 Carbon atoms
The A ring of the steroid nucleus of estrogen is aromatic
Estrogen
Has OH groups attached to carbons 3 and 17
Estradiol
Produced in the adrenal cortex and the testes
19 Carbon atoms
Testosterone
Dehydroepiandrosterone
Androgens