Enzymes and Digestion
- Created by: ChandiniS
- Created on: 31-07-17 12:33
Cardiac Sphincter
A sphincter can contract to close a biological vessel. Other locations of sphincter muscles include the rectum, bladder, the other end of the stomach and the small arteries that supply the skin. The failure of the cardiac sphincter muscle leads to heartburn, as the acid stomach contents go back into the oesophagus.
Amylase
Amylase is a type of carbohydrase. Note that it is specific for starch, and will not break down other carbohydrates like cellulose because they have a different shape. The amylase in saliva will be denatured in the stomach, explaining why more amylase is added in the small intestine
Bile and its formation
This is the bile duct, that carries bile from the gall bladder, where it is stored, into the small intestine. Bile is made in the liver, and it is mainly involved in neutralising the acidic stomach contents and emulsifying fats to aid their digestion. Note that the fat digesting enzyme lipase is made in the pancreas.
Digestion in the gut
The mouth breaks up food by chewing (mastication), but the prolonged churning that takes place in the stomach is also important for mixing and breaking up food. Physical digestion ensures that the food is thoroughly mixed with the digestive enzymes, and increases the surface area of food exposed.
large intestine
The main role of the large intestine is the absorption of water. As well as the water in what we eat and drink, the body adds a large volume of water in bile and pancreatic juice that needs to be reclaimed.
exocrine glands
Exocrine glands secrete substances outside the body through tubes called ducts. Endocrine glands secrete substances directly into the blood without a duct
digestion
The digestive system is basically a tube passing through the body, along with glands that secrete digestive juices into it e.g. the salivary glands, the pancreas and the gall bladder. Note that the pancreas is also part of the endocrine system.
activation energy
During a chemical reaction, bonds between atoms are broken and reformed to give a different arrangement of atoms in the products. Breaking bonds requires an input of energy, even if the reaction releases energy overall. This energy is the activation energy, and enzymes speed up reactions by lowering the activation energy needed.
proteins
Proteins are polymers made by joining a selection of twenty naturally occurring amino acids into a long chain, often several hundred amino acids long. During digestion by protease, these long chains are broken down again into amino acids that can be absorbed into the blood stream
Temperature and its effects
The temperature of a substance is a measure of the average kinetic energy of all the particles in it. So as heat energy is put into an enzyme solution, the particles - enzyme, substrate and water - acquire more kinetic energy and the temperature increases. This increases the rate of collisions, so the reaction rate increases
enzyme make up
All enzymes are made of protein. Enzymes catalyse (speed up) the thousands of reactions that take place in a cell and that make life happen. The sequence (order) of amino acids that make up proteins are coded for by the DNA in genes. That is why we say that DNA carries the instructions for life.
Amylase experiment
Amylase breaks down starch into simple sugars. These can be detected by heating the sample to 80oC with an equal volume of Benedict's reagent. This will give a brick-red precipitate if glucose or other simple sugars are present.
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