Lecture 10 Flashcards
Cholesterol
A steroid alcohol
critically important component of cell membranes
Not digested into CO2 + H2O
Steroid hormones
derived from cholesterol
Hormones derived from the same 4-ring structure as cholesterol
Triglycerides
Formed from one glycerol molecule with three fatty acid molecules attached via ester bonds
How are triglycerides transported?
through the body by chylomicrons and VLDL (very-low-density-lipoproteins)
Phospholipids
Composed of one glycerol molecule with a phosphate group and two fatty acid molecules attached via ester bonds
Create phospholipid bilayer membrane
Chylomicrons
Has largest diameter, but lowest density
enter the circulation and are metabolized into remnant particles for uptake and further modification by the liver
Chylomicron composition
68% triglycerides, 5% cholesterol, 7% phospholipid, and 2% apolipoprotein (B-48)
Very-low-density lipoproteins (VLDL)
secreted into the blood by the liver for metabolism in peripheral tissues
Very-low-density lipoproteins (VLDL) composition
55% triglycerides, 19% cholesterol, 18% phospholipid, 8% apolipoprotein (c-100)
Intermediate-density lipoproteins (IDL)
transitional form, it is made from VLDL and further modified in the liver to LDL
Low-density lipoprotein(LDL)
primary carrier of cholesterol
brings cholesterol to peripheral cells for membrane synthesis and formation of adrenal and reproductive hormones
What is LDL known as?
Known as “bad” cholesterol,”
easily taken up by cells
high levels are associated with increased risk for atherosclerosis
LDL composition
50% cholesterol, 22% phospholipids, 6% triglycerides, and 22% protein and have apoprotein B-100
High-density lipoprotein (HDL)
synthesized in the intestines and liver cells
Smallest Diameter, largest density
What is HDL known as?
Healthy cholesterol
removes excess cholesterol from peripheral tissues and transports it to other catabolic sites
This function has an anti-atherogenic effect
HDL composition
50% protein, 28% phospholipids, 19% cholesterol, and 3% triglycerides
apolipoproteins A-I, mainly, and A-II
Lipids and Lipoproteins: Clinical significance
Abnormal lipid metabolism can be due to genetic defects, or it can be acquired
associated with risk of coronary heart disease and other disorders
Ranges of Cholesterols
Total: Normal: <200, high >240
HDL: Normal: >60, Risk: >40
LDL: Normal <100, Risk: >190
Triglyceride: Normal: <150, Risk: >500
Type I hyperlipoproteinemia
Elevated chylomicrons
Serum appearance: Creamy layer of chylomicrons
Total cholesterol: Normal to moderately elevated
Triglyceride: Extremely elevated
Apo-B-48 increased, Apo A-IV increased
Type IIa hyperlipoproteinemia
Increased LDL
Serum appearance: Clear
Total cholesterol: Generally elevated
Triglyceride: Normal
Apo-B 100 increased
Type Iib hyperlipoproteinemia
Increased LDL and VLDL
Serum appearance: Clear or slightly turbid
Total cholesterol: Elevated
Triglyceride: Elevated
Apo B-100 increased
Type III hyperlipoproteinemia
Increased IDL
Serum appearance: Creamy layer sometimes present over a turbid layer
Total cholesterol: elevated
Triglyceride: elevated
Apo E-II increased, Apo E-III decreased, and Apo E-IV decreased
Type IV hyperlipoproteinemia
Increased VLDL
Serum appearance: Turbid
Total cholesterol: Normal to slightly elevated
Triglyceride: Moderately to severely elevated
Apo C-II either increased or decreased, and Apo B-100 increased
Type V hyperlipoproteinemia
Increased VLDL with chylomicrons
Serum appearance: Turbid with creamy layer
Total cholesterol: Slightly to moderately elevated
Triglyceride: Severely elevated
Apo C-II increased or decreased, Apo B-48 and Apo B-100 increased
Bilirubin
Principal pigment in bile that is derived from hemoglobin breakdown
Delta bilirubin
Bilirubin forms a complex with albumin for transport to the liver
bilirubin is unconjugated
Unconjugated bilirubin
carboxylic acids not derivatized to esters
Not soluble in water
Conjugated bilirubin
Form of bilirubin with two ester groups
soluble in water
Urobilin
an orange-brown pigment that gives stool its characteristic color
Jaundice
a yellow discoloration that occurs when the bilirubin concentration in the blood rises
bilirubin is deposited in the skin and sclera of the eyes
Kernicterus
Elevated bilirubin deposits in brain tissue of infants
affecting the central nervous system and resulting in mental retardation
Pre-Hepatic Jaundice
excessive anemias, spherocytosis, toxic conditions, HDN caused by Rh or ABO incompatibility
increased level of conjugated bilirubin in the serum
Neonatal Jaundice
Level of UDP-glycuronyltransferase is low at birth
takes several days for the liver to synthesis an adequate amount of the enzyme to catalyze bilirubin conjugation
causes increased serum level of unconjugated bilirubin
Hepatic Jaundice
when the liver cells malfunction and cannot take up, conjugate, or secrete bilirubin
Post-Hepatic Jaundice/obstructive jaundice
slow flow of bile due to a partial or complete obstruction of the extrahepatic biliary passage between the liver and duodenum
Gilbert syndrome
Defect in the ability of hepatocytes to take up bilirubin
Crigler-Najjar disease
Partial or complete deficiency of UDP-glycuronyltransferase
Dubin-Johnson syndrome
Defective liver cell excretion of bilirubin due to impaired transport in the hepatocytes of conjugated bilirubin
increased serum level of conjugated bilirubin with a mild increase in unconjugated bilirubin
Bilirubin Ranges
Infants: Total bilirubin 2-6 mg/dL
Adults: Total bilirubin 0.2-1.0 mg/dL
Indirect bilirubin 0.2-0.8 mg/dL
Direct bilirubin 0.0-0.2 mg/dL
Urobilinogen
is the collective term for stercobilinogen, mesobilinogen and urobilinogen
In post-hepatic obstruction, urobilinogen formation is decreased because of what?
impaired bilirubin excretion into the intestines
evidenced by: clay-colored/chalky white stool
