Biology - Week 5 Notes

Biology - Week 5 Notes - Biology 2108 Summer 2008 Dr Davis...

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Biology 2108 – Summer 2008 – Dr. Davis Abbreviated lecture notes from the week starting 6/23/08. Corresponds with Chapter 41-45 in Campbell (7th Edition) 41 – Animal Nutrition Food Processing The main stages of food processing are ingestion, digestion, absorption , and elimination Ingestion , the act of eating is the first stage of food processing Digestion , the second stage of food processing Is the process of breaking food down into molecules small enough to absorb Involves enzymatic hydrolysis (see fig 5.2) of polymers into their monomers Absorption , the third stage of food processing, is the uptake of nutrients by body cells Elimination , the fourth stage of food processing, occurs as undigested material passes out of the digestive compartment Digestion Animals with simple body plans have a gastrovascular cavity that functions in both digestion and distribution of nutrients Animals with a more complex body plan have a digestive tube with two openings, a mouth and an anus This digestive tube is called a complete digestive tract or an alimentary canal The alimentary canal can be organized into specialized regions that carry out digestion and nutrient absorption in a stepwise fashion The Mammalian Digestive System Consists of an alimentary canal and various accessory glands that secrete digestive juices into the canal
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The Oral Cavity, Pharynx, and Esophagus In the oral cavity, food is lubricated by saliva and digestion begins Teeth chew the food into smaller particles These small particles are then exposed to the enzyme amylase secreted by the salivary glands This initiates the breakdown of glucose polymers The pharynx (throat) is the junction that opens to both the esophagus and the windpipe ( trachea ) The esophagus conducts food from the pharynx down to the stomach by peristalsis Peristalsis - Rhythmic waves of contraction of smooth muscles in the wall of the alimentary canal The Stomach The stomach stores food and performs preliminary steps of digestion Secretes gastric juice , made up of hydrochloric acid and the enzyme pepsin The churning action of the smooth muscles in the stomach mix the food and gastric juice mixture, now called acid chyme This mixture breaks up the extracellular matrix and the peptide bonds in the food, and kills bacteria The lining of the stomach is coated with mucus, which prevents the gastric juice (at pH = 2 !!!) from destroying the stomach cells The Small Intestine The small intestine is the longest section of the alimentary canal Is the major organ of digestion and absorption Enzymatic Action in the Small Intestine
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The first portion of the small intestine is the duodenum Acid chyme from the stomach mixes with digestive juices from the pancreas , liver , gallbladder , and intestine itself The pancreas produces proteases , protein-digesting enzymes that are activated once they enter the duodenum Absorption of Nutrients
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This note was uploaded on 07/22/2008 for the course BIOL 2108 taught by Professor Davis during the Spring '08 term at Kennesaw.

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Biology - Week 5 Notes - Biology 2108 Summer 2008 Dr Davis...

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