Digestion and Absorption scroll down to see diagrams An Analogy Suppose you are interested in purchasing a Pizza store and wish to investigate how productive the store is without the present owner knowing because, you fear the owner will raise the price. So, instead of going into the store and watching what happens and asking to examine the books that record expenses and profits, you decide to watch the store from outside. You observe how often trucks arrive with pizza dough, pizza toppings cheese, pepporoni, etc.
The stomach is an important part of the digestive system. Firstly it secretes HCL which kills bacteria and other harmful organisms preventing food poisoning and it also provides the optimum conditions for the enzyme pepsin to work in pH 1.
In addition, the stomach secretes pepsin which starts the digestion of proteins into polypeptides and amino acids.
Theses can then be absorbed by the villi in the small intestine. The small intestine is where the final stages of digestion occur. The intestinal wall secretes enzymes and it also receives enzymes from the pancreas.
However the main function of the small intestine is the absorption of the small food particles resulting from digestion. It contains many villi which increase the surface area for absorption.
The large intestine moves the material that has not been digested from the small intestine and absorbs water. This produces solid faeces which are then egested through the anus. Secretes HCL which kills bacteria. HCL provides optimum pH for pepsin. Secretes pepsin for protein digestion.
Receives enzymes from the pancreas. Has villi for absorption of food particles. Moves material that has not been digested along.
Absorption occurs when the food enters the body as the food molecules pass through a layer of cells and into the bodies tissues. This occurs in the small intestine which has many villi that are specialised for absorption.
Assimilation occurs when the food molecules becomes part of the bodies tissue.
Therefore, absorption is followed by assimilation. The structure of the villus is very specific. Firstly there is a great number of them so this increases the surface area for absorption in the small intestine. In addition the villi also have their own projections which are called microvilli.
The many microvilli increase the surface area for absorption further. These microvilli have protein channels and pumps in their membranes to allow the rapid absorption of food by facilitated diffusion and active transport. Also, the villi contains an epithelial layer which is only one cell layer thick so that food can pass through easily and be absorbed quickly.
The blood capillaries in the villus are very closely associated with the epithelium so that the distance for the diffusion of the food molecules is small. This thin layer of cells contains mitochondria to provide the ATP needed for the active transport of certain food molecules.
Finally, there is a lacteal branch at the centre of the villus which carries away fats after absorption. Epithelium is only one cell layer thick and so food is quickly absorbed.
Microvilli on the villi increase the surface area for absorption further. Protein channels and pumps are present in the microvilli for rapid absorption. The mitochondria in the epithelium provide ATP needed for active transport.
Blood capillaries are very close to the epithelium so diffusion distance is small. The lacteal takes away fats after absorption.timberdesignmag.com> Topics > Food components > Carbohydrates Starch Introduction. Starch is one of the most abundant carbohydrates in nature and present in many food plants.
Starch is by far the most consumed carbohydrates in the human diet.
Traditional staple foods such as cereals, roots and tubers are the main source of dietary starch. Effect Of Ph On Amylase In Starch Digestion. researcher is conducting this experiment to find the optimum temperature and pH for starch on amylase.
The experiment was carried out in one day. The researcher and a partner did the experiment based on a lab manuel from class.
Data was collected from the experiment and to be displayed on graphs. Amylase Amylase is an enzyme which catalyzes the hydrolysis of the polysaccharide starch to the disaccharide maltose. Salivary amylase is produced by the salivary glands and pancreatic amylase is produced by the pancreas.
Compare the effects of HCl on protein digestion by pepsin with the effects of HCl on starch digestion by salivary amylase. Explain the physiological significance of these effects. - HCl, which provided an acidic environment, promoted the action of pepsin; as a result, pepsin was maximally active and fully digested the protein that was present.
The parent chitin is insoluble in most organic solvents, chitosan is readily soluble in dilute acidic solutions below pH due to the quaternisation of the amine groups that have a pKa value of making chitosan a water-soluble cationic polyelectrolyte.
The effect of temperature and pH on the activity of salivary amylase on starch can be studied by using the Iodine test. If we add saliva on starch, the salivary amylase present in saliva gradually acts on starch and converts it into maltose.