Lipids

Lipid
group of biological molecules of varying composition that are all soluble in non polar solvents.
Fatty Acid
Long hydrocarbon chains that ends with a carboxylic acid group. (-cooh)
Saturated Fatty Acid
Long chain monocarboxylic acids. contain only carbon to carbon single bonds and carbon hydrogen bonds. General Formula CH3(CH2)nCOOH
Unsaturated Fatty Acid
Long chain monocarboxylic acids that contain one or more carbon to carbon double or triple bonds.
Phospholipid
Combination of a lipid and a phosphate group. Major form of lipid in cells.
Phophogylceride
Phospholipids derived from a gylcerol.
Steroid
nautrally occurring family of lipids. Every steroid contains the same 17 carbon skeleton that spans 4 fused rings. Also, two methyl groups.
Cholesterol
A common fat like sterpid nased alcohol found in animal fats.
Triglyceride (TG)
three mlecules of fatty acids esterfied to glycerol. Also called triacylglycerols.
Gylcerol
liquid alcohol often found as a component of fat or triglycerides. structural backbone onto which fatty acids attatch.
Lipoprotein
Combination of lipid(s) and a protein(s). transportation from of lipids in the bloodstream.
Apolipoprotein
protein component found in plasma lipoproteins. The wide variety of apolipoproteins give each lipoprotein a unique composition.
Adipose
fat stored within the body.
Lipase
enzyme that hydrolyzes the ester linkage between glycerol and the fatty acids of triglycerides.
Glycolipids
Combination of a lipid and a carbohydrate group. i.e. brain and nervous tissue.
Functions of Steroids
critical component of membranes, important to maintain membrane fluidity.
serve as hormones
and intergral component of bile acids.
What is the most important steroid in animals? Why?
Chloesterol, because it is a major component of cell membrane and provides membrane fluidity.
Cortisol
hormone secreted by the adrenal glad, helps the body deal with stress by raising glucose levels, increasing lipolysis, and depressing the immune system.
anabolic steroids
resemble testosterone, artificially stimulate the body to increase the amount of muscle mass, stimule the healing of muscle and incress competitive aggressiveness.
Major Lipids of the body
fatty acid, glycerol, cholesterol, phospholipids, monoglycerides, diglycerides, fat soluble vitamins, steroids.
How much does fat does the average person injest per day?
60-130g of fat, mostly in the form of triglycerides, human body absorbs nearly 100% of fats injested.
What are lipids found in foods composed of?
98-99% triglyceride, of which 92-95% is fatty acid, the remainder is glycerol.
Biosynthesized Lipids
Fatty acids are synthesized in the cytoplasm of the cells of the liver, kidney, brain, lung and adipose tissue.
How are lipoproteins classifed?
Based upon their distinctly different densitites after high speed ultracentrifugation
Chylomicrons
largest and least dense of the lipoprotein, formed after ingestion of dietary fat, in the intestinal mucosam, transport dietary lipids to the liver, causes lipemia.
Very Low-Density Lipoproteins (VLDL)
synthesized in the liver, transport TGs produced in the liver to extrahepatic tissues.
Low-Density Lipoproteins(LDL)
transport cholesterol and cholesteryl to peripheral tissues and regulate synthesis of cholesterol. “bad cholesterol”.
High-Density Lipoproteins (HDL)
synthesized in the liver, transports cholesterol back to the liver for excretion. smallest and most dense lipoprotein particle. “good cholesterol”
Beta Oxidation Pathway Definition
series of biochemical reactions whihc fatty acids are completely oxidized in the mitochondrial matrix, resulting in significant amounts of ATP.
Beta Oxidation STEPS
1)each fatty acid molecule is bound to a CoA molecule.
2)each passage results in the production of a single 2 carbon acetyl CoA and a new fatty acid CoA that has two fewer carbons.
3) the two carbon CoA are consumed in the Krebs Cycle and result in production of ATP.
Other than ATP what is produced in the Beta Oxidation Pathway?
two high-energy electron carries (1 NADH + 1 FAD2H). They enter the mitochondrial electron transport change and are used to make more ATP
What happens to excess Acetyl-CoA?
They are converted into molecules called ketone bodies.
Ketone Bodies
Beta-Hydroxybutyrate, acetone, and acetoacetate. CAn be used as fuel by most tissues, and certain organs.
Ketosis
Excess levels of ketone bodies in the bloodsream.
CAuses of ketosis
low carb diet, starvation, uncontrolled diabetes mellitus.
Ketoacidosis
often accompanies ketosis. Beta-hydroxybutyrate and acetoacetate are strong acids that can alter blood Ph.
What are the steps involed in the anabolism of lipids?
The precuresor of synthesis is Acetyl-CoA, each molecule is made by the sequential addition of acetyl groups (2 carbons). Fatty acids can ezymatically combine with glycerol to make TGs
Where does synthesis of fatty acids occur?
Within the cytosol of cells.
Pancreatic Lipase
removes fatty acids from dietary lipids resulting in more polar compounds with ampipathic properties.
Emulsification
polar agents cover small fat particles and prevent monoglycerides, free fatty acids and glycerol.
Sources of Lipase within the body
Pancreas (primary source)
Salivary Galnds (lingual lipase)
Clinical Significance of elevated Lipase
acute pancreatitis, pancreatic carcinoma.
Test methodolgy of Lipase
Measures the fatty acid that is produced by the catalysis of Lipase.
Chylomicron Remnant
remainder of chylomicrons after exposure to LPL
about 95% of Bile acids are?
reabsorbed and reused by the liver to support bile production.
Steps in the metabolism of Dietary Lipoproteins
1) new chylomicrons are secreted into the lymphatic ducts and enter the blood.
2) LPL hydrolyzes triglycerides in chylomicrons.
3) resulting fatty acids and glycerol are taken up by cells and used as energy.
4) excess fatty acids are re-esterfied into triglycerides for long-term storage.
Steps in metabolism of lipoproteins of hepatic origin
1)VLDL is syntheszied in the liver and secreted into circulation where they undergo lipolysis.
2) VLDL loses core lipids causing dissociation and transfer of lipoproteins and phospholipids.
3) VLDL remnants are further transformed into LDL in the liver.
4) Once LDL is bound to receptors they are endocytosed and transported to the lysosome.
5) triglycerides in LDL are converted into free fatty acids and glycerol.
6) fatty acids are metabolized for energy.
7) free cholesterol is used for membrane biosynthesis.
Reverse Cholesterol Pathway
mediated by HDL maintains cholesterol equilibrium.
excess cholesterol is transported back to the liver by HDL, where it is excreted into bile as free cholesterol, or excreted after being converted to bile acids.
3 forms of Hyperlipidemia
Hypertriglyceridemia, Hypercholeserolemia, Hyperlipoproteinemia.
Hypertriglyceridemia
elevated levels of TGs. Results from abnormal lipid metabolism or abormal forms of VLDL. Serum TG >500mg/dL
Hypercholesterolemia
increased level of cholesterol. contributor to atherosclerosis and CAD. abnormally high serum LDL. Common inherited disorder caused by defective or absent LDL receptors.
Hyperlipoproteinemia
increased level of specific lipoproteins. acquired or inherited. caused by underlying diseases, medications, genetic mutations, or poor diet.
Hypolipoproteinemia
very rare condition caused by a decreased level of lipoprotein.
Atherosclerosis
Deposition of lipids, especially cholesterol, in arterial walls.
Atherosclerosis – Disease Process
1)lipid deposition starts with fatty streaks.
2) blood traveling causes small injuries that signal macrophage and platelets.
3) LDL brings cholesterol and a fibrous plaque develops.
4) LDL that has been modified is taken up by macrophages and transform into foam cells.
5) continuous injurt and repair leads to additonal narrowing and increased pressure causing disease.
Coronary Artery Disease
major fibrous plaque develops in the artiers of the heart. (Heart Attack)
Peripheral Vascular Disease
major fibrous plaque develops in the arteries of the arms or legs.
Cerebrovascular disease
majorfibrous plaque develops in the vessels of the brain. (Stroke)
What is the most common type of heart disease?
Coronary Artery Disease, it is the leading cause of death in both men and women in the US.
What are the possible effects of reduced or cut-off blood supply to the heart?
Angina, HEart Attack aslo known as Acute Myocardial Infarction, HEart Failure, Arythmias.
Elevated LDL and Triglyceride
high risk of cardiac disease.
High HDL concentration
decreased risk of cardiac disease.
Low HDL concentrations
increased risk of cardiac disease.
Elevated Triglyceride
contributor to cardiac disease.
Total Cholesterol – Enzymatic Method
quantitation of all the colesterol and colesterol esters present.
PRinciple of Total Cholesterol
hydrolysis of cholesterol esters yiel cholesterol and free fatty acids. Oxidation of total cholesterol yields Hydrogen peroxide,which is oxidatively coupled to 4-aminoantipyrine. When peroxidase is added it forms a product that absorbs light at 500nm.
Friedewald Formula Part 1:
VLDL cholesterol = Triglyceride / 5
Friedewald Formula Part 2
LDL cholesterol = Total Cholesterol – (VLDL Cholesterol + HDL cholesterol.
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