Lecture 43 Flashcards Preview

MGM (D) > Lecture 43 > Flashcards

Flashcards in Lecture 43 Deck (18)
Loading flashcards...
1
Q

What happens during triglyceride synthesis?

A

1) Two fatty acids are transferred from fatty acyl coenzyme A molecules to glycerol 3-phosphate to yield a phosphatidic acid
2) The phosphate group is hydrolyzed
3) A third fatty acyl group is added to yield a triglyceride (triacylglycerol)

2
Q

What happens during the synthesis of Glycerol 3-phosphate?

A

1) Glycerol 3-phosphate can be formed by the reduction of a glycolytic intermediate, dihydroxyacetone phosphate (DHAP) using NADH as a coenzyme (adipocytes)
2) In the liver, glycerol can be phosphorylated by the action of glycerol kinase to form glycerol 3-phosphate

3
Q

Describe the steps of triglyceride synthesis

A

1) Glycerol phosphate + fatty acid-CoA–> Lysophosphatidic acid + CoA with the use of Acyltransferase
2) Lysophosphatidic acid + fatty acid-CoA –> Phosphatidic acid + CoA with the use of Acyltransferase
3) Phosphatidic acid + H2O –> Diacylglycerol + Pi with the use of a phosphatase
4) Diacylglycerol + fatty acid-CoA –> Triacylglycerol + CoA

4
Q

What are phosphatidyl compounds?

A

Two mechanisms for the formation of phosphatidyl compounds (phophatidyl group attached to a polar head group)

1) Activation of the diacylglycerol group with CDP
2) Activation of the polar head group with CDP
3) In the case of phosphatidyl choline (lecithin) or ethanolamine, there is the intermediate formation of CDP-choline or CDP-ethanolamine, respectively

5
Q

What is the function of phospholipases?

A

Phospholipases selectively hydrolyze specific ester linkages on phosphatidyl compounds

6
Q

What is phospholipase A2?

A

1) Phospholipase A2 is present in many mammalian tissues and pancreatic juice. It is also present in snake and bee venoms
2) Phospholipase A2, acting on phosphotidy-linositol, releases a fatty acid (most likely arachidonic acid, the precursor of the prostaglandins)
3) Pancreatic secretions are especially rich in the phospholipase A2 proenzyme, which is activated by trypsin and requires bile salts for activity
4) Phospholipase A2 is inhibited by glucocorticoids (for example, cortisol)

7
Q

What is phospholipase C?

A

1) Phospholipase C is found in liver lysosomes and the alpha toxin of clostridic and other bacilli
2) Membrane-bound phospho-lipase C acts in the PIP2 system and, thus, plays a role in producing second messengers

8
Q

How are sphingolipids formed?

A

1) The molecule sphingosine is synthesized from palmitoyl CoA and the amino acid serine
2) Acylation with a fatty acid transferred from a fatty acyl CoA results in teh formation of a ceramide
3) Addition of choline phosphate yields sphingomyelin, while the addition of sugars yields cerebrosides and globosides
4) Those glycolipids that contain sialic acid are known as gangliosides

9
Q

What compounds can be formed as ceramide derivatives?

A

1) Cermine + Phosphatidylcholine –> Sphingomyelin + Diacylglycerol
2) a) Ceramide + UDP-galactose –> Galactocerebroside + UDP
b) Galactocerebroside –> Sulfatide (PAPS)
3) Ceramide + UDP-glucose –> Glucocerebroside + UDP
4) a) Ceramide + 2 or more UDP-sugars –> Globoside
b) Globoside + CMP-NANA –> Ganglioside + CMP

10
Q

Phosphatidyl molecules are amphipathic molecules that contribute to:

A

Plasma membranes

11
Q

What is the most common monounsaturated fatty acid in the body?

A

Oleic acid

12
Q

Which is the only sphingolipid that is also a phospholipid instead of a glycolipid?

A

Sphingomyelin

13
Q

Why are sphingolipids important?

A

The spingolipids are important molecules in cell membranes and are particularly rich in nerve tissue

14
Q

What are hereditary defects related to sphingolipids?

A

Hereditary defects in hydrolases required for the degradation of sphingolipids result in their accumulation and frequently involve neurological impairment as in Tay-Sachs disease

15
Q

What is Tay-Sachs disease?

A

1) Deficiency of Beta-Hexosaminidase A
2) Accumulation of gangliosides (GM2)
3) Rapid and progressive neurodegeneration
4) Blindness
5) Cherry-red macula
6) Muscular weakness
7) Seizures

16
Q

What is Metachromatic leukodystrophy?

A

1) Accumulation of sulfatides
2) Cognitive deterioration
3) Demyelination
4) Progressive paralysis
5) Dementia in adult form
6) Nerves stain yellowish-brown with cresyl violet (metachromasia)

17
Q

What is Fabry disease?

A

1) Accumulation of globosides
2) Reddish-purple skin rash
3) Kidney and heart failure
4) Burning pain in lower extremeties
5) Only X-linked sphingolipid hereditary disease

18
Q

What is Gaucher disease?

A

1) Gaucher disease Type 1 is the most common genetic disease in the Ashkenazi Jewish population with an incidence of 1 in every 1000 (Mt. Sinai School of Medicine) or 1 in 450 (NIH)
2) There is an autosomal inheritance of the gene for glucocerebrosidase that is coded on chromosome 1
3) Gaucher disease can be treated by injection of glucocerebrosidase (Cerezyme, imiglucerase)
4) Accumulation of gluco-cerebrosides
5) Most common lysosomal storage disease
6) Hepatosplenomegaly
7) Osteoporosis of long bones
8) CNS involvement in rare infantile and juvenile forms