Chylomicrons: Structure, Origin and Life Cycle
•
18 gefällt mir•11,808 views
chylomicron and metabolic process
Empfohlen
Weitere ähnliche Inhalte
Was ist angesagt?
Was ist angesagt? (20)
Andere mochten auch
Andere mochten auch (20)
Ähnlich wie Chylomicrons: Structure, Origin and Life Cycle
Ähnlich wie Chylomicrons: Structure, Origin and Life Cycle (20)
Kürzlich hochgeladen
Kürzlich hochgeladen (20)
Chylomicrons: Structure, Origin and Life Cycle
- 2. PRESENTED BY Nosheen Afzal (Bi141014) 11/20/2014 2
- 3. CONTENTS • Etymology • Definition • Structure • Size • Origin • Life cycle 11/20/2014 3
- 4. ETYMOLOGY OF CHYLOMICRON The word "chylomicron" has been derived from two greek words: • "Chylos“ means milky • “Mikros" means small • Chylomicrons= small milky (globules). 11/20/2014 4
- 5. DEFINITION • A large plasma lipoprotein particle, occurring as a droplet consisting primarily of triglycerides and functioning in the transport of neutral lipids from the intestine to the tissues by way of the lymph. 11/20/2014 5
- 6. STRUCTURE OF CHYLOMICRONS • Chylomicrons are considered large lipoproteins because of lipid, phospholipid and protein constituents. • However, the Protein Constituents are extremely low although their role in the chylomicrons metabolism remains vital. 11/20/2014 6
- 7. CHYLOMICRON COMPONENTS Triglycerides 85-92% Phospholipids 6-12% Cholesterol 1-3% protein 1-2% 11/20/2014 7
- 8. STRUCTURE OF CHYLOMICRON 11/20/2014 8
- 9. SIZE OF CHYLOMICRONS • According to Scientists, the diameter of these particles can range from: • 75 to 1200 nm • 1200 nm would be largest at its production in the intestinal cells. 11/20/2014 9
- 10. ORIGIN OF CHYLOMICRONS • Chylomicrons are formed in the endoplasmic reticulum of the mucosal cells within the villi of the duodenum. • Secreted through the baso-lateral membrane into the lymphatic system. • From the lymph to the blood systems 11/20/2014 10
- 11. LIFE CYCLE OF CHYLOMICRONS Life cycle of chylomicrons consist of three stages that differ in the constituency of chylomicrons because some of the protein in the form of Apolipoprotein will enter the chylomicron particles as it reaches its destination via the circulation. 11/20/2014 11
- 12. STAGES OF LIFE CYCLE The Life Cycle of Chylomicrons can be illustrated as having three distinct stages. These stages include: • The Nascent Chylomicrons • The Mature Chylomicrons • The Remnant Chylomicrons 11/20/2014 12
- 13. NASCENT CHYLOMICRONS • initial form • formed in the intestinal epithelial cells or inside the enterocytes. • released by exocytosis • central lacteal of vessels to blood via thoracic duct • They contain mainly Triglycirides , Cholestrol, Phospholipids and Apolipoprotien B-48 11/20/2014 13
- 14. MATURE CHYLOMICRONS • HDL donates apolipoprotein C2 and apolipoprotein E to the nascent chylomicron, and convert it to into mature chylomicron. • Apolipoprotien C2 is the co-factor for lipoprotien lipase activity. 11/20/2014 14
- 15. REMNANT CHYLOMICRONS • Once the store of triglycerides become low,the chylomicron donates it’s Apolipoprotienc2 back to the HDL know it is called remnant chylomicron • much smaller in size • Apolipoprotien B-48 and Apolipoprotien E • break down via endocytosis 11/20/2014 15
- 16. 11/20/2014 16
- 17. 11/20/2014 17
- 18. 11/20/2014 18
- 19. ANY QUESTION? 11/20/2014 19
Hinweis der Redaktion
- CHYLOMICRON HAS A SINGLE MONOMERE OF PHOSPHOLIPIDS AND CHOLESTROL….INSIDE THERE ARE TRIGLYCIRIDES AND THE INTERIGOPROTIEN APO B48 – IT IS NEEDED FOR CHYLOMICRON SYNTHESIS…
- in the absorptive cells of the intestine, which are called and are highly efficient in absorbing and transporting the absorbed nutrients through the circulation or else through the lymphatic system. In the case of chylomicrons, once formed, the large size prevents them from entering the circulation directly and Chylomicrons are formed in the endoplasmic reticulum in the absorptive cells of small intestines, to be specific the mucosal cells within the villi of the duodenum. Newly formed chylomicrons are secreted through the baso-lateral membrane into the lymphatic system. Chylomicrons are released from the lymph to the blood systems, and supply the tissue with fat absorbed from the diet.
- This is the initial form of the chylomicrons, which are formed in the intestinal epithelial cells or inside the enterocytes. It is formed by combining triglycerides, phospholipids, cholesterol esters and an apolipoprotein known as apolipoprotein (apo) B48. Once formed, the particles are secreted into the lymphatic system (and hence the name ‘chyle’) before being carried into the circulation at the site where the major lymphatic vessel (thoracic duct) enters the subclavian vessel. The nascent chylomicrons would further receive cholesterol particles from other apolipoproteins present in the lymph or else in the plasma. At the same time, it would receive an apolipoprotein known as ‘apo C’ from high-density lipoproteins (HDL) which will convert nascent chylomicrons into its mature forms. While nacent chylomicron is circulating in the blood, it exchanges components with high density Lipoprotien (HDL)
- Following receiving apo Cs from HDL (more specifically apolipoprotein C-II) the chylomicrons will have the ability to undergo metabolism at the sites where lipoprotein lipase enzyme activity is abundant. Such sites include skeletal muscles, cardiac muscles, adipose tissues, and mammary glands. One common characteristic of all these tissues is that their high requirement for triglycerides for various needs such as energy, storage or else production of milk. CO-FACTOR FOR THE LIPOPROTIEN LIPASE ACTIVITY:AT THIS POINT THE TRIGLYCIRIDES PRESENT INSIDE THE CHYLOMICRON MUST HYDROLIZE BECOZ OF THEAPOLIPOPROTIEN C2 IS THE CO-FACTOR FOR THE LIPOPROTIEN LIPASE ACTIVITY.
- When mature chylomicrons encounter the enzyme lipoprotein lipase, they will break down the triglycerides into fatty acids and monoglycerides. This will make the large triglyceride core of the chylomicrons to shrink and thus become a triglyceride depleted, cholesterol rich, and protein rich, ‘remnant chylomicrons’. The remnant chylomicrons will exchange the excess apolipoproteins, specifically the apo Cs, with HDL and thereby return apo Cs for re-use. The remaining chylomicron particle would be metabolized in the liver via the LDL receptors and it will be aided by the presence of apo E that it received from various tissues where chylomicrons were metabolized. The clearing up process of remnant chylomicrons takes place within few hours of ingesting fatty diets and therefore is an extremely efficient system in healthy individuals. However, in some individuals, the duration for clearing up may not be so rapid and thereby would contribute to prolonged elevation of triglycerides following a meal. break down via endocytosis once it is return back to the liver.