Assessment of Lipase Activity in Pancreatic Extracts Essay

Assessment of Lipase Activity in Pancreatic Extracts - Essay Example (Sizer, Piche and Whitney 2011). It binds the fat molecules on one end and the watery compounds on the other end. On binding to the fat, they form micelles. This process is called emulsification. Bile salts are the derivatives of cholesterol having both hydrophobic and hydrophilic domains. (Madenci and Egelhaaf 2010).The bile breaks down the large aggregates of triglycerides by binding them with the hydrophobic ends and separating the molecules from the aggregates. (Jenkins and Hardie, 2008).The droplets become smaller and smaller by binding to the bile. When the food enters the small intestine, the gall bladder contracts and sends the bile into the intestine. The gall bladder stores the end products of liver including bile salts. Pancreas is a long fat gland that is present behind the stomach and opposite to the first lumbar vertebra. Pancreas is made up of glandular epithelial cells. The clusters contain the acini cells called as acinar cells. (Williams 2001). Pancreas consists of a head, body and tail. Pancreas is connected to the duodenum by two ducts. Pancreas is the gland that contains both exocrine and endocrine parts. It has the retort shaped flask. It is 12-15 cm in length and weighs 90 grams. Every day pancreas produces 1200 – 1500 ml of pancreatic juice. (Pandol 2010). ... The exocrine pancreas secretes a juice containing two components: they are pancreatic enzymes and aqueous alkaline solution. The pancreatic enzymes are secreted by the acinar tissue containing the acini epithelial cells. (Williams 2001). The pancreatic enzymes are very important for our body because they can digest almost all the components of the food without the requirement of other enzymes. The aqueous water component is rich in sodium bicarbonate. The pancreatic enzymes are pancreatic amylase, pancreatic lipase, trypsin, chymotrypsin, carboxypeptidase, ribonuclease and deoxyribonulcease. The protein digestive enzymes are produced in the inactive form only. (Pandol 2010). Pancreatic lipases are the only enzyme that can digest the fat. The pancreatic lipase digests the triglycerides into mono glycerides and free fatty acids. The pancreas enzymes are very active in the neutral pH which is provided by the aqueous alkaline solution. Lipase binds to the oil-water interface of the trigl yceride water droplet and hydrolyzes the triglyceride. (Sherwood 2008). Bile acids and colipase are very important for the complete lipase activity. Bile acids increase the surface area for the action of the lipase enzyme. They form micelles with the fatty acid and monoglycerides. By this action the glycerides are removed from the oil-water interface. (Pandol, 2010). The triglycerides are now converted into mono glycerides, free fatty acids and glycerol. These molecules are not absorbed directly by the mucus lining of the digestive tract. The mucus lining have aqueous environment and glycerides are hydrophobic. (Reis et al. 2009). The bile salts shuttles the lipid molecules and enters the adsorptive cells of the intestinal villi. These cells are now

Concrete Constituent and Mix Design Essay Example | Topics and Well Written Essays - 1500 words

Concrete Constituent and Mix Design - Essay Example Natural heavyweight aggregates include materials such as goethite, limonite, barite, illmenite, magnetite, and hematite, with specific gravities (SGs) ranging from about 3.5 up to about 5.3, leading to concretes with unit weights up to about 4100 kg/m3 . For higher unit weight concretes, synthetic materials such as Ferro phosphorous (SG 5.8 to 6.8) or scrap iron and steel punching (SG 7.8) can be used, with resulting concrete unit weights of up to 6100 kg/m3. High-density aggregates are good attenuators of gamma rays and of fast neutrons, hence their use in radiation shielding. Although heavyweight concretes can be proportioned in much the same way as ordinary concretes, the aggregates tend to be harsh and have a tendency to segregate from the rest of the mix. As a result, both higher than usual cement contents and a higher ratio of fine to coarse aggregates are recommended. Normal Weight Aggregates Aggregates make up about 75% of the volume of concrete, so their properties have a la rge in?uence on the properties of the concrete (Alexander and Mindess, 2005). Aggregates are granular materials, most commonly natural gravels and sands or crushed stone. The role of the aggregate is to provide much better dimensional stability and wear resistance; without aggregates, large castings of neat cement paste would essentially self-destruct upon drying. Also, because they are less expensive than Portland cement, aggregates lead to the production of more economical concretes. These aggregates are used to make ordinary concrete having unit weight of 2300 kg/m3. In general, aggregates are much stronger than the cement paste, so their exact mechanical properties are not considered to be of much importance (except for very high-strength concretes). Similarly, they are also assumed to be completely inert in a cement matrix, although this is not always true, as will be seen in the discussion on the alkali–aggregate reaction. Light Weight Aggregates Light weight aggregates , which can be either natural or synthetic materials, are characterized by a high internal porosity. Ordinary concrete has a unit weight of about 2300 kg/m3, but lightweight concretes with unit weights as low as 120 kg/m3 can be produced, although they are accompanied by a significant decrease in concrete strength. Natural lightweight aggregates include pumice, scoria, and tuff; however, most light- weight aggregates are synthetically produced. The most common such lightweight aggregates are made from expanded clay, shale, or slate. The raw material is either crushed to the desired size or ground or then pelletized; it is then heated to 1000 to 1200Â °C. At these temperatures, the material bloats (or puffs up) due to the rapid generation of gas produced by the combustion of the small amounts of organic material that these particles generally contain. (The process is similar to that of popping popcorn.) Other materials, such as volcanic glass (perlite), calcium silicate glasses (sla g), or vermiculite, can similarly be bloated. Lightweight aggregates tend to be angular and irregular in shape and can be quite variable. b) Select one physical property and one mechanical property of aggregate and describe in detail the role and influence of these properties on the overall performance of the concrete. Particle Grading The particle-size distribution in a sample of aggregate, referred to as the grading, is