Compound lipids -Glycolipids-from P.35 to P.43

What are glycolipids?

Glycolipids are lipids that contain carbohydrate residues such as lactose, glucose, galactose, or aminosugars. They have sphingosine as an alcohol and a fatty acid.

How are glycolipids classified based on carbohydrate residues?

Glycolipids are classified based on the number and nature of carbohydrate residues present.

What are Cerebrosides?

Cerebrosides are a type of glycolipids that contain one sugar molecule. The sugar molecule is commonly ß-galactose, but it may also be lactose or glucose.

What are Sulfatides?

Sulfatides, also known as Sulfated cerebrosides, are a type of glycolipids that contain a sulfate group attached to C3 or C6 of the sugar of the cerebroside.

What are Globosides?

Globosides are a type of glycolipids that contain more than one sugar molecule.

What are Gangliosides?

Gangliosides are a type of glycolipids that contain more than one sugar molecule and sugar amines.

Where are Cerebrosides present?

1-Cerebrosides are present in the myelin sheath of nerves.

2-They are found in the white matter of the brain.

3-Cerebrosides are also present in cell membranes.

How are glycolipids classified based on the nature of carbohydrate residue?

Glycolipids are classified based on the nature of the carbohydrate residue into:

1- Glucoside: If the carbohydrate residue is glucose.

2- Galactoside: If the carbohydrate residue is galactose (most common).

3- Lactoside: If the carbohydrate residue is lactose.

How are glycolipids classified based on the type of fatty acid?

Glycolipids are classified based on the type of fatty acid into:

1- Kerasin: Contains lignoceric acid.

2- "Phrenosin" Cerebron: Contains cerebronic acid (2-hydroxyl lignoceric acid).

3- Nervon: Contains nervonic acid.

4- Oxynervon: Contains oxynervonic acid (2-hydroxy nervonic acid).

What is the importance of these glycolipids?

These glycolipids are important for nerve conduction.

What are lipoproteins?

Lipoproteins are complexes of lipids combined with proteins. The lipid component of lipoproteins can include various lipid molecules such as phospholipids, triglycerides, and cholesterol (either free cholesterol or cholesterol esters).

What are the types of lipoproteins?

There are two main types of lipoproteins:

1- Structural lipoproteins: These are found in cellular and subcellular membranes.

2- Plasma lipoproteins (Transport lipoproteins): These will be discussed in detail in the cardiovascular block.

Eicosanoides are:

OXidation products of linoleic, arachdonic or higher unsaturated fatty acids.

Types of eicosanoides are:

1-Synthesis eicosanoides

2-Corticosteriods

3-Non-steroidal anti-inflammatory drugs (NSAIDs)

How are eicosanoids synthesized?

Eicosanoids are synthesized from polyunsaturated fatty acids in membrane phospholipids. This process occurs after the release of these fatty acids by phospholipase A2. Subsequently, cyclooxygenase produces prostanoids, and lipoxygenase produces leukotrienes and lipoxins.

How do corticosteroids exert their anti-inflammatory effects?

Corticosteroids exert their anti-inflammatory effects by inhibiting both phospholipase A2 and the cyclo-oxygenase involved in the synthesis of prostaglandins.

How do Non-steroidal Anti-inflammatory Drugs (NSAIDs) exert their anti-inflammatory effects?

NSAIDs exert their anti-inflammatory effects by inhibiting cyclo-oxygenase, which is involved in the synthesis of prostaglandins.

What is Prostacyclin (PG12)?

Prostacyclin, also known as PG12, is a type of prostaglandin.

What are the actions of Prostacyclin?

Prostacyclin has several actions:

1- It increases cAMP (cyclic Adenosine monophosphate).

2- It is produced by vascular endothelium.

3- It causes vasodilation.

4- It prevents platelet aggregation.

5- It exhibits cytoprotective properties.

What is Thromboxane A2 (TXA2)?

Thromboxane A2 (TXA2) is a type of eicosanoid.

What are the effects of Thromboxane A2?

Thromboxane A2 has several effects:

1- It decreases cAMP (cyclic Adenosine monophosphate).

2- It is produced by platelets.

3- It causes vasoconstriction.

4- It stimulates platelet aggregation and thrombosis.

5- It is cytotoxic and is implicated in inflammation and ulcers.

What are Prostaglandins (PGs)?

Prostaglandins (PGs) are derived lipids that were first discovered in seminal plasma and the prostatic gland, which is the origin of their name. They are derived from the oxidation of linoleic, arachidonic, or higher unsaturated fatty acids.

What is the chemistry of Prostaglandins?

Structurally, prostaglandins are related to prostanoic acid.

How are Prostaglandins classified based on distribution of functional groups?

Prostaglandins are classified based on the distribution of the ketonic group (C\=O), hydroxyl group (OH), and the position of the double bond in the ring.

How are Prostaglandins further sub-classified based on aliphatic side chain?

Prostaglandins are further sub-classified based on the number of double bonds in the aliphatic side chain into three series (series I, II, and III).

What is one physiological effect of PGs on cAMP levels?

PGs increase cAMP in most tissues, but decrease it in renal and adipose tissues.

What is the sleep-promoting effect of PGD2?

PGD2 is a potent sleep-promoting substance.

How do PGs contribute to inflammation?

PGs are natural mediators of inflammation due to their chemotactic and vasodilator effects.

What role do PGs play in peptic ulcers?

PGs inhibit gastric acid secretion in patients with peptic ulcers and promote the healing of peptic ulcers.

What are the reproductive roles of specific PGs?

PGF2a induces labor, while PGE is required for male fertility.

What is the role of PGs in regulating systemic blood pressure?

PGE, PGF, and PGA cause vasodilation, leading to decreased systemic blood pressure, while other PGs cause vasoconstriction, leading to increased systemic blood pressure.

How do PGs affect platelet aggregation and thrombosis?

PG12 (Prostacyclins) inhibit platelet aggregation and thrombosis, while PGE2 and TXA2 stimulate platelet aggregation and thrombosis.

What are Steroids?

Steroids are cyclic compounds containing a steroid nucleus or ring known as "Cyclo-pentano-perhydro-phenan-threne."

What are examples of Steroids?

Examples of Steroids include:

1- Sterols: e.g., cholesterol and ergosterol.

2- Adrenal cortical hormones: glucocorticoids, mineralocorticoids, and adrenal androgens.

3- Male and female sex hormones: testosterone, estrogen, and progesterone.

4- Bile acids and bile salts.

5- Vitamin D group: e.g., Vit.D2 and Vit.D3.

6- Cardiac glycosides.

What are the physical properties of Cholesterol?

Cholesterol exhibits the following physical properties:

1- It appears as odorless white to yellow crystalline rhombic plates.

2- Cholesterol is insoluble in water.

3- It is soluble in ether, benzene, and chloroform.

What are the chemical properties of Cholesterol?

Cholesterol demonstrates the following chemical properties:

1- It is unsaponifiable, meaning it is not hydrolyzed by alkali.

2- Cholesterol undergoes reduction and oxidation in the body:

* Reduction:

- Cholesterol is reduced by the action of intestinal bacteria, producing Coprostanol ("fecal sterol").

* Oxidation:

- Cholesterol is oxidized in the skin's fat layer to form 7-dehydrocholesterol, which serves as a precursor to Vitamin D3. - In the liver, cholesterol is also oxidized to form bile acids and bile salts.

What is the typical plasma cholesterol level?

The typical plasma cholesterol level is 150-220 mg/dl, with 2/3 of it being esterified and 1/3 in its free form.