IBDP> CORE TOPICS> TOPIC 6 HUMAN HEALTH AND PHYSIOLOGY> 6.1 DIGESTION
Assessment statements6.1.1 Digestion of macromolecules
6.1.2 Enzymes and digestion. 6.1.3 Types of digestive enzyme 6.1.4 Structure of the digestive system 6.1.5 Functions of the stomach. small intestine and large intestine 6.1.6 Absorption and assimilation. 6.1.7 Structure and function of the villus. |
Animations, articles and links |
6.1.1 Digestion of macromolecules
Why digestion of food is essential?The digestion of large food molecules is important due to two reasons.
1. The food we eat is made up of large compounds made by other organisms and therefore these have to be broken down and reassembled so that our bodies can use them. 2. The food molecules have to be small enough to be absorbed by the villi in the intestine through diffusion, facilitated diffusion or active transport and so large food molecules need to be broken down into smaller ones for absorption to occur POINTS TO BE INCLUDED (6 marks) Large molecules cannot be absorbed. Mechanical digestion happens to break down food physically, however enzymes breakdown large molecules into smaller ones (that can be absorbed); Thus many enzymes are required as they are substrate specific they also speed up the rate of digestion considerably. |
6.1.2 Enzymes and digestion.
Enzymes help in breaking down of large food molecules to small subunits that can be absorbed.
Enzymes are biological catalysts that increase the rate of reaction Digestive enzymes are secreted into the lumen of the gut when food is present. Enzyme increase the rate of reaction of the breakdown of large food molecules into smaller forms that can be absorbed by the body. POINTS TO BE INCLUDED(8 marks) Food must be in a small enough to leave the gut and enter the bloodstream. Thus physical breakdown is not enough, chemical breakdown is necessary. Enzymes help in chemical breakdown of food and increase the rate of digestion. Enzymes are biological catalysts and allow digestion to occur at body temperature. Enzymatic digestion is a sequential process (explain this with named examples of enzymes, their substrate and location) |
6.1.3 Types of digestive enzyme
Examples of specific enzymes:
Protease - Eg. trypsin, pepsin, chymotrypsin etc digest proteins into polypeptides / dipeptides / amino acids / peptides; Lipase digest lipids into glycerol / fatty acids; Amylase digest polysaccharides into disaccharides, monosaccharides Place of digestion of different food-
Foods are digested mechanically in mouth and stomach and are digested by enzymes in specific regions of the alimentary canal Carbohydrates are digested in the mouth. Carbohydrates are digested in the small intestine; enzymes that digest carbohydrates include e.g. amylase, maltase, ptyalin, sucrase, lactase. Proteins are partially digested in the stomach. Proteins are digested in the small intestine (into amino acids); enzymes that digest proteins include e.g. proteases,dipeptidase, pepsin, etc. Fats are digested in the small intestine; fat digestion is facilitated by bile; enzymes that digest fats include e.g. lipase. |
6.1.4 Structure of the digestive system
Points for drawing (4 marks)Esophagus – attached to both mouth and stomach;
Stomach – j-shaped sac attached to esophagus and u-shaped portion of small intestine; Large intestine – wider diameter than small intestine, attached to small intestine; Pancreas – leaf-shaped, in u-shaped region of small intestine with small duct connected to small intestine; Liver – large, triangular, to left of stomach; Gall bladder – small sac drawn on top of liver with tube connected to small intestine at same region as duct from pancreas; Anus – at end of large intestine but narrower in diameter |
Functions of the parts of the digestive system
6.1.5 Functions of the stomach, small intestine and large intestine
Stomach
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Small intestine
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6.1.6 Absorption and assimilation.
Large food molecules are digested to small products in the lumen of the gut. This facilitates absorption.
Absorption:
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6.1.7 Structure and function of the villus.
Structure of villusThe 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.
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Adaptations of the villus
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Draw and label the diagrams
Digestive system
class presentation |
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References-
Damon, Alan et al, Higher level Biology for the IB diploma. Pearson Baccalaureate
Clegg, CJ, Biology for the IB diploma. London: Hodder Murrray, 2007, 978-0340926529
Taylor, Stephan, Science Video resources Wordpress,
Burell, John. Click 4Biology(online)
All pictures have been downloaded from Google images for educational purpose only.
Damon, Alan et al, Higher level Biology for the IB diploma. Pearson Baccalaureate
Clegg, CJ, Biology for the IB diploma. London: Hodder Murrray, 2007, 978-0340926529
Taylor, Stephan, Science Video resources Wordpress,
Burell, John. Click 4Biology(online)
All pictures have been downloaded from Google images for educational purpose only.