Lipid Metabolism Flashcards
How are lipids transported?
by lipoproteins (water soluble)
What is the origin of lipids?
-Exogenous (dietary sources)
-Endogenous (synthesized in the liver)
Definition of lipids?
a biological substance that is insoluble in water, but soluble in
organic solvents such as alcohol, chloroform, ether and acetone.
** some of phospholipids are not soluble in acetone & some have a limited
solubility in H2O
______ is important for reducing in lipid synthesis.
NADPH
What is the primary source of fuel for the body?
lipids
-50% of daily calories
What is the structural functions of lipids?
Components of cell membranes & other cell structures,
giving the cell membrane stability (& rigidity) and allowing
for transmembrane transport of important molecules
What is the hormonal function of lipids?
steroid hormones
Lipids functions for heat retention (brown fat) and ________ conduction (Myeline sheath)
nerve
*Energy can be generated from what major lipid?
(Free) fatty acids
What are the major lipids?
-(Free) Fatty Acids
* Phospholipids
* Cholesterol (Free & Esterified)
* Triglycerides
* Glycolipids
* Prostaglandins
- Consist of glycerol esters combined with free fatty acids
- Constitute majority of Neutral Fat (95% of tissue storage fat)
Triglycerides***
What is esterified cholesterol?
One fatty acid and one cholesterol (becomes hydrophobic)
What is like a hormone but not released into circulation, works locally?
Prostaglandins
What are triglycerides composed of?
3 fatty acids
How much of fatty acids are free?
Only a small percentage
Most are part of triglycerides
___________ supply almost half the calories burned for energy.
Fatty acids
What does saturated fatty acids depend on?
no double bonds
· Mono-Unsaturated, one double bond,
· PolyUnsaturated, 2 or more double bonds
Short chain FA are ______ carbon atoms.
4-6
Medium-chain FA are _____ carbon atoms.
8-12
Long-chain FA are ______ carbon atoms.
greater than 12
-needs special carriers (other than albumin)
Which is flexile, trans or cis form of fatty acids?
cis
Essential component of “Cell Membranes”
Phospholipids
Act as detergents in clearing other fats out of the body
AMPHIPHILIC STRUCTURE ENABLES BOTH FUNCTIONS
Phospholipids
Phospholipids serve as constituents of cell membranes and outer shells of ____________ molecules
lipoprotein
***Important phospholipids include:
✓ Lecithin (phosphatidyl choline) P choline
✓ Cephalins P ethanolamine, inositol, serine
✓ Spingomyelin (Spingolipid)
Spingomyelin (Spingolipid) have a _______ backbone.
Sphingosine
***Phospholipids are synthesized by…
the liver & intestinal epithelium
Lung surfactants are a mixture of _________ that decrease the fluid tension of the alveoli (preventing them from collapse)
lipoproteins
What causes Respiratory Distress Syndrome?
When premature infants do not secrete adequate amounts of lung surfactant thereby making lung expansion difficult
What phospholipids are examined to determine fetal lung maturity?
Amniotic fluid phospholipids
L/S (Lecithin: Sphingomyelin) ratios greater than 2 —-> decreased risk
L/S ratio alone is not a good predictor in…
diabetic, hypertensive and intrauterine growth retardation
***Lung maturity also correlates with the presence of….
Phosphotidyl glycerol
Surfactant containing PG (>2.1 mg/L) —> increase surfactant stability**
Synthesized endogenously from acetyl-CoA
cholesterol
- Unsaturated steroid alcohol
- High molecular weight—
4 perhydrocyclophenanthrone rings with side chain
Cholesterol
What enzyme do most cholesterol drugs work on?
HMG-CoA Reductase
(rate limiting enzyme)
-if this works endogenous cholesterol synthesis goes down. Therefore decreasing cholesterol.
What is found almost exclusively in animals?
cholesterol
***Important functions of cholesterol include:
- Manufacture and repair of cell membranes
- Synthesis of **bile acids
- Synthesis of Vitamin D
- Precursor of five major classes of Steroid Hormones
Precursor of five major classes of Steroid Hormones?
1) Progestins
2) Glucocorticoids
3) Mineralocorticoids
4) Androgen
5) Estrogen
The only fat that cannot be stored in the body
cholesterol *****
-excess gets made to bile acids and goes to intestines
What effect does aldosterone have on Mg, H, K and Na?
excretion of Mg, H, and K
reabsorption of Na
How is mean arterial pressure calculated?
MAP = CO x PR
How does the body obtain cholesterol?
Cholesterol in blood may be absorbed through diet, or endogenously synthesized in the liver
How is cholesterol excreted?
via bile salts into the intestinal tract***
-cannot be stored
About ____% of total body cholesterol is in stationary tissue (skin and muscle)
70
Only about ____% of total body cholesterol is mobile in the plasma.
30
- 1/3 free; 2/3 esterified with FA
How does HDL cholesterol get cleared?
HDL protien –> enzymes (LCAT and ACAT) —> ester —> free cholesterol —> to be cleared via liver –> bile salts –> intestinal tract
What does LCAT stand for?
Lecithin Cholesterol acyltransferase***
-Bound to Lipoprotein (HDL)
- Transfer FA from C2 of phpsphatidylcholin to cholesterol
Lecithin Cholesterol acyltransferase
What does ACAT stand for?
Acyl-CoA:Cholesterol acyltransferase***
Acyl-CoA + Cholesterol <——-> CoA + Cholesterol ester
How is cholesterol esterified?
- Lecithin cholesterol acyltransferase (LCAT)
- Acyl-CoA:Cholesterol acyltransferase (ACAT)
-Esterification of cholesterol by LCAT: _______
-Hydrolysis of cholesterol: ______
plasma
liver
What do TG consist of?
glycerol esters combined with three FAs
-constitutes majority of “neutral fats”
________ from adipose tissue and are the main storage from of fats.
TGs
How is fat used for energy during fasting or between meals?
Stored TGs can be catabolized into FFA
Plasma TG are derived from the…
intestine and liver
-intestinal TG is absorbed from dietary fat
What is the main source of plasma TG?
liver manufacture
What is the difference between vegetable TG and meat TG
veg-more unsaturated FA
meat- more sat FA
sugar-containing lipids
Glycolipids
(cerebroside: ceramide with a sugar at the 1-OH moiety).
What are two groups of glycolipids?
✓ Gangliosides—major membrane lipids of CNS
✓ Membrane glycosphingolipids—important for cell recognition
and blood typing
-Long-chain polyunsaturated FA (eicosanoids) with C20, including a
cyclopentane ring
* Synthesized in many tissues from arachidonic acid & other
polyunsaturated fatty acids
prostaglandins
What are the major classes of prostaglandins?
PGA –> PGI with subscripts indicating number of C=C double bonds PGA2
Prostaglandins and related compounds (thromboxanes, leukotrienes) are potent, and can alter the function of
both synthesizing and adjoining cells (very strong but short half life, regulator functions)
Chemical cell communication
Function like Hormone, but not hormone
Not stored , but synthesized as needed (short half-life)
prostaglandins
What are the three phases of lipid transport though the body?
-Digestive phase (intra luminal phase)
- Absorptive phase (cellular phase)
- Transport phase
Why must fats be “processed” for absorption?
fats are insoluble
Most fats are first emulsified by the action of ________.
bile salts
-then get acted upon by pancreatic enzymes, lipase, cholesterol esterase