Manila, PHILIPPINES
Joined August 19th 2007
Hi there! Welcome!
Recent PostsBiochemistry and Physiology have Fascinated Me LatelyOctober 8th 2008 12:16
The wonders of biochemistry and phsiology have been my center of studies lately. Watch out for my articles and how we can apply knowledge of these to our daily ife...
Shared on
 Steatorrhea and Lipid AbsorptionAugust 29th 2008 05:04
LIPID ABSORPTION AND TRANSPORT INTO THE BLOOD
Small to medium fatty acid chains, together with glycerol goes directly into the intestinal walls and into the bloodstream. This is possible since the cell membranes are lipid-soluble so lipids can pass through them. However for monoglycerides, free cholesterol, phospholipids, and long fatty acid chains, different event happens. These substances retain their association with bile acids, forming structures called micelles (Figure 7). Micelles are essentially small aggregates (4-8 nm in diameter) of mixed lipids and bile acids suspended within the ingesta. As the ingesta is mixed, micelles bump into the brush border of small intestinal enterocytes, and the lipids, including monoglyceride and fatty acids, are taken up into the epithelial cells. Figure 7. Micelles The major products of lipid digestion - fatty acids and 2-monoglycerides - enter the enterocyte by simple diffusion across the plasma membrane. A considerable fraction of the fatty acids and other lipids also enter the enterocyte via a specific transporter protein in the membrane. Once inside the enterocyte, fatty acids and monoglyceride are transported into the endoplasmic reticulum, where they are used to resynthesize triglyceride. Beginning in the endoplasmic reticulum and continuing in the Golgi, triglyceride is packaged with cholesterol, lipoproteins and other lipids into particles called chylomicrons. This is occurring in the absorptive enterocytes of the small intestine. Chylomicrons are extruded from the Golgi into exocytotic vesicles, which are transported to the basolateral aspect of the enterocytes. The vesicles fuse with the plasma membrane and undergo exocytosis, dumping the chylomicrons into the space outside the cells. Instead of being absorbed directly into capillary blood, chylomicrons are transported first into the lymphatic vessel that penetrates into each villus. Chylomicron-rich lymph then drains into the system lymphatic system, which rapidly flows into blood. Blood-borne chylomicrons are rapidly disassembled and their constitutent lipids utilized throughout the body (Figure 8).
Shared on
Steatorrhea and Lipid Digestion Part 2August 21st 2008 09:09
LIPID DIGESTION
The bulk of dietary lipid is triglyceride, composed of a glycerol backbone with each carbon linked to a fatty acid . Foodstuffs typically also contain phospholipids, cholesterol, and others (Figures 1, 2, and 3). Once we have taken in food through our mouth, digestion already takes place. There are two types of digestion: the mechanical and the chemical digestion. And the fats from the food we eat are mechanically digested and broken down into smaller pieces by chewing and by the agitations produced in the walls of the gut. Nevertheless such process at times, is just not enough in order for us to optimally absorb the nutrients. And so chemical digestion has to take place. Figure 1. General Structure of Triglyceride Figure 2. General Structure of Cholesterol Figure 3. Phospholipid The mouth and the stomach may play roles in lipid breakdown. However in the said locations, minimal digestion takes place. The bulk of lipid digestion occurs along the small intestine. Nevertheless in the mouth, an enzyme called the lingual lipase acts on triglycerides with short to medium fatty acid chains. Linguinal lypase is secreted by the Ebners glands located at the root of the tongue and parotid glands. It hydrolyzes triglycerides into a diacylglyceride and a fatty acid. Such action of the lingual lipase continues as the food enters the stomach despite of the acidic environment (since its optimal pH is 4). In the stomach another enzyme exerts its effect on the lipids or triglycerides containing small to medium fatty acid chains by the same hydrolyzing effect. This time the enzyme is called gastric lipase (range of optiml pH is 3 to 6), produced by the gland cells of the fundic stomach. The bigger amount of fats is digested along the small intestine. And so chances are the fats being mobilized from stomach to small intestine remain to be large aggregates of triglycerides, cholesterol ester, and phospholipids, and would need further breakdown. Such role is being performed by the enzymes secreted by the pancreas into the small intestine namely the pancreatic lipase, the phospholipase, and the cholesterol esterase. We all know that the pancreatic enzymes, most especially the lipases are water-soluble enzymes, and therefore are short-lived. And so after meal, these lipases have to be released immediately into the small intestine in huge amount to ensure faster action. However if the fat aggregates are too large for the enzymes, then it may take long before these enzymes finish their jobs. By that time, most of them would have lost their potency. Therefore, the lipid aggregates have to be torn down into smaller bits or droplets. This would increase lipase-lipid interaction thus, increasing efficiency and speed of digestion. This process is being done by the bile/ bile acids from the liver and gall bladder. Bile acids play their first critical role in lipid assimilation by promoting emulsification. As derivatives of cholesterol, bile acids have both hydrophilic and hydrophobic domains (i.e. they are amphipathic- Figure 4). On exposure to a large aggregate of triglyceride, the hydrophobic portions of bile acids intercalate into the lipid, with the hydrophilic domains remaining at the surface. Such coating with bile acids aids in breakdown of large aggregates or droplets into smaller and smaller droplets (Figure 5). The "detergent" function of bile salts is essential to fat digestion, for the lipase can "attack" the fat globules only on their surfaces. The smaller the fat particles, the better digestion. Figure 4. Bile Acids Figure 5. Emulsification After lipid emulsification, the pancreatic enzymes finally would have optimal effect on digestion. The pancreatic lipase breaks triglyceride down to one 2-monoglyceride and two fatty acid chains (Figure 6). In order for the lipase to carry out such function, it should not be inhibited by bile acid action. And so upon emulsification of a lipid particle, bile acids have to be displaced away from the emulsified lipids. Displacement of such is done by the colipase, which is also a protein found in pancreatic secretions. Figure 6 Phospholipids are in turn broken down into components by the phospholipase. Phospholipids are broken down into glycerol, fatty acids, phosphoric acid and others (e.g. choline). The dietary cholesterol, which occurs frequently as cholesterol ester, has do be broken down into its fatty acid and free cholesterol components. This has to be done in order for the cholesterol to be effectively absorbed later on. And this is the job of the cholesterol esterase. The whole process of digestion in the small intestine is triggered by the release of cholecystokinin hormones, thus stimulating the pancreas and liver to release their respective secretions.
Shared on
Steatorrhea and Lipid DigestionAugust 7th 2008 13:54
INTRODUCTION
Steatorrhea is the formation of non-solid feces. Stools may also float due to excess fat from malabsorption, and have an oily appearance and be foul smelling. In this state an oily anal leakage or some level of fecal incontinence may occur. It is not a disease entity per se, but a symptom of a variety of diseases that compromise lipid or fat digestion and absorption. Among the causes of such diseases and compromised condition maybe the following: (1) defect in the production or action of the enzymes directed at digesting lipids from the food we eat; (2) bile deficiency; or (3) defective intestinal epithelium involved in lipid absorption.
Shared on
Issues on Adolescence (Part 3)July 12th 2008 03:21
Physical Changes
Puberty is a physical process of change characterized by the development of secondary sex characteristics. We must understand that puberty differs from adolescence. Puberty happens synchronous with adolescence, but adolescence does not only highlight physical changes, but (largely) also psychological ones
Shared on
Issues on Adolescence ContinuedJuly 9th 2008 12:26
Adolescence is commonly divided into three periods: early (11 to 14 years of age), middle (14 to 17 years old), and late (17 to 20 years). These divisions may overlap each other. And development taking place in each phase varies from one individual to another. And so this discourse shall discuss the typical growth and development an individual goes through along adolescence as a whole. Discussion of such will be two-fold: physical and psychosocial.
Before we proceed, it is nice to know that societies have their own ways, rites, or icons that mark an individuals entry to adolescence. As adolescence is a transition between being a child and assuming the duties and responsibilities of an adult, some societies would test an adolescents (especially male) bravery and endurance by providing a challenge or activity (Atkinson). In Jewish rites, the bar mitzvah would entitle an adolescent into engaging in early marriage (Jewish Encyclopedia, 1901-1906). In the Philippines, one of important markers of adolescence among male is circumcision. Nevertheless, almost all societies in the world would unquestionably associate adolescence with puberty. As a matter of fact, puberty may somehow summarize all the significant physical changes an adolescent may undergo
Shared on
Issues on AdolescenceJuly 7th 2008 12:22
Adolescence
As an individual reaches the late phase of his childhood, he or she now enters a new and more challenging milestone in his life- being an adolescent. In this stage, an individual is expected to grow more maturely, not only physically but also psychosocially. And meeting such expectation is a must, for this has something to do with achieving a more stable life once an individual reaches adulthood
Shared on
On Knee Pain IIJuly 2nd 2008 15:42
Here are some exercises we can do:
1. Place a pillow in between knees, while your back lies flat on a surface and both knees are bent. Try to squeeze the pillow using both knees and hold it for 10 seconds. repeat the procedure initially for ten times, gradually increasing repititions depending on your capability.
Shared on
On Knee PainJune 20th 2008 14:11
E.W., from HongKong asks:
"I am a 16 year old student. And I need to go to my classroom on the second floor every weekday morning. But as I climb the stairs, I usually feel pain on my right knee- after two or three steps. What may be the possible problem on my knee? Thank you!"
Shared on
|
Recent CommentsComment by Physiotherapy
|
Comments (1)
Add Comments
Read More
Comment by Physiotherapy
on On Knee Pain
Living Healthfully
Masahista pala ha!!!
On the Lighter Side