Explain why digestion of large food molecules is essential.

1. Explain why digestion of large food molecules is essential. What sort/size of food do we normally eat? Normally the biggest thing we can fit is a mouth-full! http://www.noticiascadadia.com/uploads/pics/burger_king.jpg Where does our food that we eat get used up? In order to get into here it has to pass through a membrane. http://www.answersingenesis.org/assets/images/articles/nab/human-cell.jpg

2. Making the food go from this big…… …To molecules able to pass through a plasma membrane is called Digestion. http://www.noticiascadadia.com/uploads/pics/burger_king.jpg Lipid molecule Amino acid molecule http://www.reactivereports.com/8/images/nand.jpg http://www.ncl.ac.uk/bmsu/assets/photos/glucose-molecule.jpg http://www.solvias.com/documents/Grafiken/images_services/molecule_weiss.jpg

3. Explain the need for enzymes in digestion. Digestion can be split into 2 types: Mechanical Digestion – The physical breaking of the food. Chemical digestion – the chemical break down of the food into its constituent parts. Can you think of where mechanical digestion takes place? Biting the food Chewing the food Churning in the stomach

4. But even that doesn’t get the food small enough to pass through a phospholipid bilayer and into a cell! If we were to wait till the food naturally fell apart into small enough pieces it would take more than 2 months! Look at this animation of fruit decaying……. http://www.youtube.com/watch?v=oUzV-5h6y_Y&feature=related Or we could always cook it……..

5. Because our body works best at 36oC we can’t cook it and we cant hold it inside us for 2 months so instead…. We use something that speeds up reactions and reduces the temperatures that are needed for reactions……. Enzymes

6. State the source, substrate, products and optimum pH conditions for one amylase, one protease and one lipase.

7. Some of these reactions need very specific conditions. What keeps the mouth from becoming acid? What does the stomach produce to get a pH of 1.5 – 3? Won’t this damage the stomach? How does the stomach normally defend against this damage? When this defense goes wrong……. http://www.helico.com/images/du_gu_1.jpg

8. What does bile do? This is called emulsification. Why is it important to the speed at which Lipase works? How are the different regions of the gut kept separate? There are 2 other sphincters in the gut where are they? http://www.sjhsyr.org/sjhhc/hidc07/graphics/images/en/19223.jpg

9. Diagram of the digestive system. Learn these labels: Mouth Oesophagus Stomach Duodenum Large Intestine Small intestine Rectum Anus http://www.gutenberg.org/files/18559/18559-h/images/figure10.png

10. Now test yourself Mouth Oesophagus Stomach Duodenum Large Intestine Small intestine Rectum Anus http://www.gutenberg.org/files/18559/18559-h/images/figure10.png

11. Outline the function of the stomach, small intestine and large intestine. There are several processes you need to know about; what they are and where they happen. Ingestion: Taking food into the digestive system. Normally happens in the mouth. Digestion: Breaking the food down to soluble bits Happens between the mouth and the start of the small intestine. http://urbanext.illinois.edu/diabetes/images/food_digestion.gif

12. Distinguish between absorption and assimilation. Absorbtion: This is when the soluble food particles which have been digested get passed from the intestines into the blood stream. Assimilation: is when the soluble substances are taken from the blood stream and used in the body cells. Egestion: Is the removal of the bits of food that have not been digested. It normally occurs at the anus!

13. So what happens where? Fill in the following table stating what would happen to a buttered cheese,Ham and lettuce sandwich : Teeth, saliva, biting and chewing Ingestion and Digestion Starch + amylase → Maltose Acid, protease, gastric pits, churning Digestion Protein + Pepsin → Dipeptides Villus, microvillus, length, blood supply, Digestion Pancreatic duct, bile duct. Maltase + maltose → Glucose Trypsin +Dipeptides →Amino acids Lipase+lipids+bile→Fatty acid +glycerol Absorption of digested products. Absorption of water and minerals Egestion

14. Explain how the structure of the villus is related to its role in absorption and transport of the products of digestion. http://www.jpp.krakow.pl/journal/archive/0605_s3/gfx/rys0506_9.jpg http://www.biog1105-1106.org/demos/105/unit6/media/villus.structure.jpg

15. What makes a villus so good at its job? Think about Surface Area. What is the effect of surface area on rate of diffusion? How is the surface area of the gut increased with villi? How is the surface area of the villus increased with microvilli? Think about the distance over which products must diffuse. How does a villus ensure the distance is small? Think about how the absorbed products of digestion are taken away from the gut. What is it in a villus that allows this? The villus is very active. What cellular processes are occurring across the cell membranes that would require lots of energy. What supplies this energy? Find out about a lacteal.