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Digestive system (Essay Sample)


2 Sources 1. Describe the processes involved in the digestion and absorption of carbohydrates, lipids and proteins. 2. Discuss the energy produced from the catabolism of carbohydrates, lipids and fats. Which molecule provides the most energy when metabolized?


The human digestive system is a complex series of organs and glands that processes and converts food into energy and basic nutrients to feed the entire body. The digestive system is essentially a long, twisting tube (The alimentary canal or the gastrointestinal tract (GI tract).) that runs from the mouth to the anus, plus a few other organs like the liver and pancreas that produce or store digestive chemicals
The alimentary canal processes different types of food components every day through the use of enzymes and digestive juices. Carbohydrates, proteins and lipids all pass through the alimentary canal at different pace, and are broken down into unique components and are then absorbed into the body for use as fuel or to repair and build muscles, bones and organs.
Carbohydrates start to digest in the mouth where the process of chewing breaks down food into small pieces then the enzymes in the saliva breaks the complex molecules into simpler sugars which are then swallowed down to the esophagus and stomach with some more digestion. Carbohydrates then move to the small intestine where enzymes produced by the pancreas break down the carbohydrates into the simplest sugar molecules, which are then absorbed by the small intestine walls into the bloodstream and used by the body or sent to the liver for storage for use at a later time. Fiber, an indigestible cell wall which is found in carbohydrate plant foods like brown rice and wheat, passes through the alimentary canal essentially undigested.
Most of lipids that are consumed by the body are fats and oil. Fats and oils do not easily dissolve into the watery digestive juices of the alimentary canal. Most of the Fat digestion takes place in the small intestine where bile a juice produced by the liver breaks up fat globules into smaller particles. This makes it easy for lipase a fat-digesting enzyme to further break down the fat particles into fatty acids and cholesterol. The fatty acids then move into the body cells called mucosa where they are converted back into large particles of fat., The fat is then transported to the veins of the chest through vessels called lymphatic which are near the intestines. Blood then carries the fat to be stored in adipose tissue throughout the body. (Haddad, 2013)
Protein is found in meat, eggs, dairy products and beans, and is used by the body to build muscle and organs. Protein molecules are quite large so they have to be digested into smaller molecules called amino acids before the body can start using them. Chemical protein digestion starts in the stomach with the aid of gastric juices, where the protein molecules are soften. Digestion continues in the small intestine where a number of enzymes, from both the intestine and pancreas further breakdown the protein molecules which are then absorbed through the wall of the small intestine into the bloodstream and distributed throughout the body to repair injuries and replace dying cells. (Haddad, 2013)
When various complex molecules are broken down into smaller units, this is referred to as catabolism. This process is used to provide energy in the body. Complex molecules that constitute Proteins, carbohydrates and fats are the sources of the energy that this process extracts. To be able to extract the energy, the complex molecules are broken down into smaller units. These units then enter the glycolysis cycle at various positions in the body. The glycolysis cycle is where there is the further breakdown of sugars and glucose molecules to produce energy.
Complex carbohydrates compounds, also known as starches are taken into the body cells once they have been digested into monosaccharaides which is mainly glucose and fructose. Once inside the cell, they can be converted to glucose. After that, they are pushed directly into glycolysis cycle for further breakdown.
Proteins on the other hand are digested into amino acids and other simple compounds outside the body cells. Once these amino acids enter t...
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