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Topic 6.1 - Digestion

Topic 6.1 - Digestion Digestion is the chemical process of breaking down large particles into smaller usable molecules. The human body needs amino acids (from proteins), polysaccharides (from carbohydrates) and lipids (from fats) in order to carry out the six functions of life. .

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Topic 6.1 - Digestion

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  1. Topic 6.1 - Digestion Digestion is the chemical process of breaking down large particles into smaller usable molecules. The human body needs amino acids (from proteins), polysaccharides (from carbohydrates) and lipids (from fats) in order to carry out the six functions of life.

  2. Digestion is also necessary because the molecules have been made by plants, animals or fungi to perform functions in their bodies. We must break them down and use these building blocks to make molecules to our specifications. *cereals and legumes can provide us with all nine essential amino acids.

  3. Digestive Enzymes There are two types of digestion – chemical and mechanical. Specific enzymes are used in chemical digestion to break down specific molecules.

  4. Digestive enzymes are made in the glands and secreted into the gut. Each enzyme works at an optimal temperature and pH. *see table 1 on page 204

  5. Digestive Organs +mouth +esophagus +anus

  6. The Stomach • Glandular wall that secretes mucus, HCl and protease. • HCl kills bacteria • HCl denatures proteins & pepsin breaks up polypeptides into short chains • Elastic nature of stomach allows expansion • Muscular outer layer used for mechanical digestion

  7. Small Intestine • Protease, amylase and lipase are secreted from the pancreas. • other enzymes, such as nuclease come from the intestinal wall • The villi absorb the broken down molecules • Peyer’s patches contain lymphocytes that detect pathogens and create antibodies

  8. The Villi • Between 0.5 – 1.0mm • Outer Epithelium cells are permeable to digested foods • Dense network of blood capillaries, which have large pores • Part of the lymphatic system called the lacteal absorbs lipoprotein droplets because blood capillaries do this poorly • Small muscle fibers can contract the lacteal to make the villi shorter forcing liquid downward to the lymphatic vessel

  9. Absorption Most harmful substances cannot pass through the intestinal wall. However, blood from the intestine first goes to the liver to be cleaned before it travels to the lungs, and then the tissues.

  10. Assimilation Cells absorb the nutrients they need for energy and to build necessary macromolecules.

  11. Large Intestine 1. The colon stores waste and absorbs water, inorganic salts, minerals and vitamins. 2. Cellulose cleans out your colon.

  12. Draw the human digestive system. Remember the enzymes and their job. Homework: page 209 # 1-9 Next Class Demo: stomach dissection

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