L4: Derived lipids & compound lipids

Question 1

What are Compound (Conjugated) Lipids?

Answer 1

❖ Fatty acids + alcohol + other groups.
❖ They are classified according to the other group into:

 Phospholipids: phosphoric acids
 Glycolipids: Sugars
 Sulfolipids: sulfate
 Lipoproteins: proteins

Question 2

What is the structure of phospholipids?

Answer 2

❖ Alcohol + fatty acids + phosphoric acid ± nitrogenous base.

Question 3

What are the types of phospholipids?

Answer 3

Glcrolphospholipids (phosphoglycerides) : Glycerol

Sphingophospholipids (sphingomyelin) : Sphingol (sphingosine)

Question 4

What are examples of glycerophospholipids (phosphoglycerides)?

Answer 4

1. phosphatidic acid: Glycerol + 2 fatty acids +Phosphoric acid (No base)
2. Lecithin (Phosphatidylcholine): Phosphatidic acid + choline base.
3. Cephalin (phosphatidylserine or ethanolamine) :phosphatidic acid + serine or ethanolamine
4. Phospatidyl Inositol (Lipoinositol): phosphatidic acid + Inositol.

Question 5

What is the structure of sphingophospholipids?

Answer 5

❖ Sphingol + unsaturated fatty acid + phosphoric acid + choline.

Question 6

What is the function of phospholipids?

Answer 6

They are amphipathic (hydrophilic part + hydrophobic part) which helps:
 Formation of the lipid bilayer in the cell membrane.
 Micelle formation to help T.G absorption in the small intestine
 The structure of plasma lipoprotein carries lipids in the blood.

2) Di-palmitoyl lecithin (DPL) is a component of lung surfactant (prevent lung collapse).

3) Lecithin is a lipotropic agent (prevent fatty liver).

4) Membrane phospholipids provides arachidonic acid for the synthesis of prostaglandins,
leukotrienes.

5) Essential for blood clotting as platelet-activating factor (PAF) is choline plasmalogen

6) Phosphatidylinositol bisphosphate (PIP2) is 2nd messenger for hormones.

7) sphingomyelin is present in myelin sheath around nerves (electrical insulator

Question 7

What is the structure of glycolipids?

Answer 7

❖ Fatty acids + alcohol + sugar

Question 8

What are glycolipids classified into?

Answer 8

-cerebrosides: ❖ sphingol+ fatty acid +monosaccharide usually galactose (Galacto-cerebrosides), may be glucose (Gluco-cerberosides)

-gangliosides: ❖ sphingol + fatty acid + oligosaccharide chain

Question 9

What is the function of gangliosides?

Answer 9

-Electrical insulator in nervous tissue.
-Gangliosides are receptors for many hormones

Question 10

What is the structure of sulpholipids?

Answer 10

as cerebrosides + sulfate group at C3 of galactose

Question 11

What is the function of sulpholipids?

Answer 11

present in the brain and nervous tissue.

Question 12

What are Lipoproteins formed of?

Answer 12

• lipid part (Triglycerides T.G, cholesterol, phospholipids)
• protein part (Apolipoprotein, may be α or β globulin)

Question 13

What is the function of Lipo proteins?

Answer 13

• Structure of cell membrane
• Lipid transport in the blood.

Question 14

What are the types of Lipo proteins?

Answer 14

1) Chylomicrons (CM)

2) Very Low-Density Lipoprotein (VLDL)

3) Low Density Lipoprotein (LDL)

4) High Density Lipoprotein (HDL)

Question 15

Compare between chylomicrons, VLDL, LDL and HDL

Answer 15

Question 16

What are derived lipids?

Answer 16

Lipids derived from simple lipids and compound lipids by hydrolysis (fatty acids, alcohol) or related to lipids (steroids)

Question 17

What are steroids?

Answer 17

Large group of biologically important compounds contain steroid nucleus.

Question 18

What do steroids include?

Answer 18

They include:
1) Sterols
2) Steroid hormones
3) Vitamin D
4) Bile acids

Question 19

What are sterols?

Answer 19

Cholesterol and ergosterol

Question 20

Compare between cholesterol and ergosterol

Answer 20

Question 21

What are the sources of cholesterol?

Answer 21

Exogenous (dietary cholesterol):
- butter, cream, milk, egg yolk, and meat.

Endogenous: Synthesized in the body

Question 22

What are the sites (occurrence) of cholesterol?

Answer 22

• It is widely present in body tissues.
• largest amounts in brain, liver, skin, small intestinal, and adrenal
  cortex

Question 23

What is a normal level of blood cholesterol?

Answer 23

Normal level of total cholesterol is below 200 mg/dl.

Question 24

What is hypercholesteremia associated with?

Answer 24

atherosclerosis, myocardial infarction and cerebral stroke.

Question 25

What are the forms of blood cholesterol?

Answer 25

• Free Cholesterol
• Cholesterol ester (70%), linked with fatty acids

(75% of cholesterol is carried in LDL, the reminder in HDL)

Question 26

Compare between sex hormones

Answer 26

Question 27

What are adrenal cortex hormones (corticoids)?

Answer 27

❖ Glucocorticoids (21 C):
- Corticosterone & Cortisol (17-OH corticosterone)

❖ Mineralocorticoids (21 C):
- 11-Deoxy corticosterone (DOC)
- 11 deoxy cortisol
- Aldosterone (most active)

Question 28

What are the forms of vitamin D?

Answer 28

• Vitamin D3: derived from 7-dehydrocholesteorl by U.V rays.
• Vitamin D 2: derived from ergosterol by U.V rays.

Question 29

What is the function of vitamin D?

Answer 29

increase Ca absorption from GIT and increase bone ossification

Question 30

Compare between bile acids

Answer 30

Question 31

Formation of bile salts

Answer 31

❖ Bile acids unit with glycine (glycocholic acid) or taurine (taurocholic acid).

❖ Glycocholic acid and Taurocholic acid + Na or K → Na or K -glycocholate and taurocholate (bile salts).