chat 26 Flashcards
Triacylglycerol
- structure
- function
Structure:
-Glycerol and 3 Fatty acids
Function:
- Long term energy storage
- reduced and anhydrous
Phospholipid
- structure
- function
Structure:
- glyceorl
- two fatty acids
- Polar head group containing phosphate
Function
-membrane component
Sphingolipids
- structure
- function
Structure:
- sphingosine
- 2 fatty acids
- Polar head group containing carbohydrate
Function:
-membrane component especially in cells of CNS
Cholesterol
-function
Membrane component
Precursor:
- Seroid hormones
- Bile salts
- vit D
Synthesis of Phosphatidate
Substrates:
Glycerol 3-Phospahte
-comes from reductions of dihydroxyacetone-3Phosphate or Phosphorylation of Glycerol
2 Acyl CoA molcules
-activated by CoA for synthesis of Fatty acids
Product:
-Phosphatidate (diacyl glycerol 3-Phosphate)
Cellular Localization:
- Cytosolic face of smooth ER
- outer membrane of mitochondria
COMMON INTERMEDIATE IN SYNTHESIS OF TRIACYLGLYCEROLS AND PHOSPHOLIPIDS
Salvage pathway for Phosphatidate
Diacylglycerol Kinase
Diacylglycerol + ATP-> Phosphatidate +ADP
Cellular Localization:
- Cytosolic face of smooth ER
- outer membrane of mitochondria
Triacylglycerol Synthesis
Triacylglycerol Synthetase
2 activities:
- Phosphatase (1)
- Diglyceride acyltransferase (2)
Mechanism:
1) Phosphatidate is hydrolyzed and OH replaces Phosphate group to produce Diacylglycerol (DAG)
2) DAG receives 3rd acyl group to form triacylglycerol (remember 3FAs)
Cellular Localization:
-Cytoplasmic side of Smooth ER
Organ localization:
-Liver
Triacylglycerols are transported from the liver via the blood to muscle (energy) or adipose tissue (storage)
Phospholipid synthesis general ideas
requires activated intermediate=Phosphatidate
2 Routes
1) activation of diacylglycerol by attaching CDP
2) activation of alcohol (inositol or other alcohol) by attaching CDP
- Phosphatidylinositol
- Cariolipin
- Phosphatidylethanolamine
- Phosphatidylcholine
- Phosphatidylserine
Phosphatidylinositol synthesis
1st step) ACTIVATE
Substrates:
-Phosphatidylate
-Cytidine triphosphate (CTP) (really add CMP to form CDP)
Product:
- CDP-diacylglycerol
- -Pyrophosphate which is hydrolyzed to provide energy for reaction
2nd step) Put new head group on
Substrate
-CDP-diacylglycerol
-Alcohol (Ex: inositol)
Product:
- Phosphotidylinositol
- CMP
Inositol can be phosphorylated by specific kinases to phosphotidylinositol 4,5-bisphosphate
How is phosphatidylinositol unusual?
contains specific fatty acids:
C1=Stearic acid
C2=arachidonic acid
Cardiolipin Synthesis
Found in mitochondria
If the CDP-diacylglycerol reacts with phosphotidylglycerol then it forms Cardiolipin (diphosphotidylglycerol)
-2 phosphatidyls hooked together by glycerol
Phosphotidylethanolamine synthesis
1) ethanolamin acitivated by Phosphorylation by the gamma phosphate of ATP
2) Phosphorylethanolamine reacts with CTP to form CDP-ethanolamine
- Pyrophosphate hydrolyzed to provide energy for reaction
3) CDP-ethanolamine reacts with diacylglycerol and CMP acting as a leaving group
Phosphatidylserine synthesis
Synthesized from phosphatidylcholine or phosphatidylethanol amine by exchange of head groups with serine
What is the common precursor for synthesis of Sphingolipids
Ceramide
Ceramide Synthesis
1) Fatty Acid CoA (Palmitoyl CoA) + serine ->3-ketosphinganine
- releasing CO2 + CoA
2) reducing Carbonyl to Hydroxyl producing dihydrosphingosine
- NADPH to NADP+
3) Addition of Second Fatty acids to Alpha Amino group of serine producing dihydroceramide
4) Double bond is formed to the right of OH producing Ceramide
- FAD reduced to FADH2
What are the different sphingolipids
REMEMBER CERAMIDE IS COMMON PRECURSOR for:
- Sphingomyelin
- cerebroside
- gangliosides
Ganglioside Synthesis
containCarbohydrates:
- activated UDP glucose/galactose
- added one at a time to ceramide
Cholesterol Structure
27 carbons
- Four rings called steroid nucleus (A, B, C, D)
- -8carbon chain (20-27C
Cholesterol Synthesis Overview
27 Carbons are derived from Acetyl CoA
Cellular Localization
- Cytoplasm
- Endoplasmic Reticulum
Organ Localization:
- Liver parenchymal cells
- Intestine (secondary site)
3 Stages:
1) Synthesis of isopentenyl pyrophosphate (activate isoprene)-cytoplasm
2) 6 molecules of isopentyl pyrophosphate condense to form squalene- ER
3) Cyclization of squalene-ER
Lipid (Cholesterol) Transport
Lipids are transported in the blood and other bodily fluids as spherical complex with apoproteins. (AKA apolipioproteins)
Apoproteins
- Where are they synthesized
- function
Synthesized in the liver and intestine
Function:
- Solubizile hydrophobic lipids
- contain cell-targeting signals
What is a healthy humans HDL/LDL ratio
3.5
What does excess cholesterol lead to?
formation of atherosclerotic plaques leading to disease and death
How are Lipoprotein (aproprotein) particles classified?
By density:
- as the move throughout the body, there:
- density and protein concentration increases
- size and lipid concentration decrease
Less dense: Chylomicrons Chylomicron remnants VLDL-very low density lipoproteins IDL-intermediate density lipoproteins LDL-low density lipoproteins HDL-high density lipoprotein
