Lecture 13 - Membrane Lipids

Question 1

3 general types of membrane lipids

Answer 1

• glycerophospholipids - backbone is glycerol 3-phosphate
• sphingolipids - (backbone is sphingosine) (18 C’s long)
• cholesterol

Question 2

Sphingolipids

Answer 2

• backbone is sphingosine (18 C’s long)
• have a single fatty acid either saturated or monounsaturated with 16, 18, 22, or 24 carbon atoms.

Question 3

Ceramide

Answer 3

A single fatty acid in the amide linkage with the amino group of sphingosine

Question 4

Sphingomyelin

Answer 4

• a ceramide where “X” is phosphocholine
• a major component of membranes of the central nervous tissue

Question 5

Cerebroside

Answer 5

uncharged glycosphingolipids with either a molecule of glucose or galactose attached to the ceramide moiety

Question 6

Globoside

Answer 6

uncharged glycosphingolipids with two or more monosaccharide molecules attached to the ceramide moiety

Question 7

Ganglioside

Answer 7

negatively charged glycosphingolipids that have several monosaccharide molecules. The negative charge is due to one or more residues of N-acetyl-neuraminic acid (Neu5Ac, also called sialic acid)

Question 8

Blood group antigens O, A and B

Answer 8

• The A antigen has one more N-acetyl galactosamine than the O antigen
• The B antigen has one more galactose than the O antigen

Question 9

Glycerophospholipids

Answer 9

Glycerophospholipids most often contain a saturated fatty acid at C-1 (most commonly palmitic acid) and an unsaturated fatty acid at C-2 (most commonly stearic acid) of glycerol

Question 10

Glycerophospholipid alcohol groups

Answer 10

Question 11

Cardiolipin

Answer 11

Diphosphatidylglycerol, or cardiolipin, has two molecules

of phosphatidic acid esterified through their

phosphate group to an additional molecule of glycerol.

Cardiolipin is found nearly exclusively in mitochondrial

inner membrane

Question 12

Role of cholesterol in membrane fluidity

Answer 12

reduces the leakiness of the bilayer to small molecules such as water. The presence of cholesterol also makes the membrane more rigid.

Question 13

Mobility of lipids in membrane

Answer 13

Question 14

Explain the role of Phospholipase C (PLC) and PI-3 kinase in signal transduction

Answer 14

In signal transduction - Phospholipase C (PLC) cleaves phosphatidylinositol-4,5 bisphosphate (PIP2) to inositol triphosphate (IP3) and diacylglycerol. inositol triphosphate (IP3) and diacylglycerol are 2nd messengers involved in the action of some hormones.

In response to some hormones, Phosphatidylinositol 4,5-biphosphate PIP2 is phosphorylated to PIP3 by PI-3 kinase.

Question 15

Abnormalities of Cell Membrane Fluidity in Disease

Answer 15

with increasing cholesterol content, the lipid bilayers become less fluid on their outer surface but more fluid in the hydrophobic core

spur cell anemia have increased cholesterol content, a spiny shape, and are destroyed prematurely in the spleen (occurs in severe liver disease such as alcoholic cirrhosis)

Erythrocytes require a high degree of fluidity to pass through the capillaries