Glycobiology Part 2 Flashcards
WHat are the two classifications of membrane lipids?
Glycerolipids
Sphingolipids
What is the structure of a glycerophosphlipid? What are the most common of those?
There. Is a phosphatidic acid esterified to a phosphate and another compound.
- The most common of these are: Phosphatidylcholine (Lecithin) and Phosphatidylinositol (PI)
General functions of glycerophospholipids
- major constituent of cell membrane
- anchor some proteins in membranes
- intracellular signaling
- components of bile
- components of lipoproteins
- components of surfactant
Phosphatidylcholine (Lecithin)
- can be synthesized de novo, but this isn’t sufficient for our needs
- it is essential that we take it in our diets
What could a deficiency in Lecithin cause?
- gall stones - inadequate solubilization of hydrophobic compounds
- Respiratory Distress Syndrome (RDS)
Respiratory Distress SYndrome
Risk factor for premature infants, where expression and secretion of Lecithin has not reached appropriate levels at the time of birth.
- screening tests of amniotic fluid help asses the extent of surfactant production in the developing fetus.
- they do a Lecithin:sphingomyelin (L:S) ratio in the amniotic fluid to assess extent of surfactant production.
- – 2:1 is good. 1.5:1 is bad.
- – if it is too low they give the mother glucocorticoids shortly before delivery.
Glycolipids
Contain carbs and lipids
- derivative of ceramide
- play large role in nerve tissue
- play a role in cellular interactions, growth, and development
Degradation of glycosphingolipids
Sequential removal of residues in a last on, first off manner
Sphingophospholipids
Backbone is sphingosine rather than the traditional glycerol.
- sphingomyelin is a sphingosine based phospholipid and is important component of myelin in nerve fibers.
- Ceramide is a precursor of sphingomyelin.
Tay-Sachs
- Autosomal recessive
- mutation in beta-Hexosaminidase A
- causes an accusation of gangliosides
- Diagnosis : assay to show decrease levels of beta-hexosaminidase A in serum or leukocyte so
- Symptoms: normal at birth and then deteriorate neurologically. Cherry red spot. Seizures. Loss of vision. Poor growth. Motor retardation. Ataxia
NO TREATMENT
Neimann-Pick Disease
- Autosomal recessive
- defect in the enzyme sphingomyelinase
- assimilation of sphingomyelin
- Diagnosis: Through clinical presentation and DNA testing
- Symptoms: normal at first and then regression of previously acquired motor/social skills. Progressive neurological dysfunction due to progressive demyelination. Hepatosplenomegaly. Cherry red macula. Xanthomas. Pancytopenia (reduction in red and white blood cells)
- distinguishing feature Is foamy due to accumulation of sphingomyelin in the macrophages causing them to look foamy histologically. 3
How do you remember that both Tay-Sachs and Neimann-Pick have a cherry-red macula?
They all have a “-“ in their name
Krabbe disease
- autosomal recessive
- deficient enzyme is beta-galactocerebroside
- diagnosis: clinical presentation + brain imaging + DNA testing
- Symptoms: neurological deficits, hyperactive reflexes, optic atrophy, developmental delays/regressions
- treatment: some say stem cell transplant may work
Globose cells can be seen on histology
Fairy
- X linked recessive
- deficient enzyme is alpha-galactosidase
- accumulation - ceramide trihexoside
- Diagnosis - clinical presentation and alpha-galactosidase activity
- Symptoms: parasthesias in the extremities, corneal clouding, renal failure, proteinurea, angiokeratoma, fatigue, hypertension, cardiomyopathy.
- Treatment: enyme replacement therapy for alpha-galactosidase
F - febrile episodes A - alpha galactosidase B - burning pain/neuropathy R - renal failure Y - youth disease
What is a special feature of lipids
Their hydrophobicity allows them to serve as compartments in polar environments.
