DIGESTION & ABSORPTION 6.1

The Process Ingestion Digestion Absorption Transport Eating! Digestion The series of chemical reactions to break down the food into smaller molecules. Absorption Small molecules are absorbed through the cells in the walls of digestive tissue into blood and lymph (circulatory system). Transport The circulatory system delivers the small molecules to cells around your body.

The problem to solve… Most food molecules (macromolecules) are too large to pass through your cell membrane

Macromolecules Monomers = the smallest building blocks of the molecule Polymer = a large molecule made up of many monomers

Macromolecules Macromolecule: Too big for absorption Monomer: Good size for absorption Carbohydrates  polysaccharides, disaccharides, monosaccharides monosaccharides Lipids  triglycerides glycerol and fatty acids Proteins amino acids Nucleic Acids  DNA, RNA nucleotides

Digestion is like… Playing LEGOS Take Apart Put together (protein in steak) Take Apart (into amino acids) Put back together (into your OWN protein) Take Apart

Enzymes Catalysts: A substance that speeds up the rate of a chemical reaction. How? By lowering the activation energy Enzymes: Proteins that act as biological catalysts.

Essential Enzymes Remember, enzymes don’t MAKE the reaction happen, they just hold the macromolecule in its active site to help the reaction move more quickly.

Enzymes 1. Substrates bind to enzyme Active Site 1. Substrates bind to enzyme 2. Substrates are converted into products 3. Products are released 2 Enzyme -substrate complex

Enzymes – 1st level of breakdown Source Substrate Products Optimum pH Amylase ex. Salivary amylase Salivary glands Starch (amylose) Maltose 7 (neutral) Protease ex. Pepsin Stomach cells Proteins (polypeptides) Amino acids, shorter peptides 3 (acidic) Lipase ex. Pancreatic lipase Pancreas cells Lipids Glycerol & fatty acids Phospholipase Many diff tissues Phospholipids Fatty acids, glycerol, phosphate variable

Enzymes Further breakdown Substrate Products Nuclease Maltase Lactase DNA & RNA nucleotides Maltase Maltose Glucose Lactase Lactose Glucose & galactose Sucrase Sucrose Glucose & Fructose Exopeptidase & Dipeptidase Peptides & dipeptides Amino acids Further breakdown

Digestive Tract Food has two options: 1. Get digested and used by the body 2. Be eliminated as feces

6.1.4 Diagram

Science Museum Proposal ~40 min You have been asked to create a new exhibit for the Seoul Science Museum. The exhibit should be a walk-through giant digestive tract with interactive features along the way. Your exhibit will be permanently built in the science museum and has a generous budget from an anonymous donor.

Overview of the Functions of Stomach, SI, LI Food is churned with the gastric juices for a period of time. Small Intestine 1. In the duodenum, the food mixes with new secretions from the liver, gall bladder, and pancreas. 2. Digested nutrients (monomers) pass through the villi into the circulatory system. Large Intestine 1. Reabsorb the water from the food, concentrating the undigested (& unabsorbed) food into feces. 2. Home to mutualistic bacteria (eg. E. coli )that keep us healthy and produce Vitamin K.

Villus: Designed for absorption & transport Digested Nutrients IN Villus: Designed for absorption & transport Digested nutrients pass through the 1-cell thick epithelium tissue to get to the circulatory system. Most molecules go to the capillary bed and then are transported through the blood. Fatty acids are absorbed into the lacteal and then are transported through the lymph. Blood + Nutrients OUT Blood In

Starch digestion in the small intestine Illustrates many processes that we have learned about Membrane permeability Catalysis Without a catalyst the reactions to digest starch would happen at very slow rates Enzyme specificity

Starch digestion in the small intestine Illustrates many processes that we have learned about Membrane permeability Catalysis Enzyme specificity Three enzymes in villi membranes break the 1,6 bonds and the 1,4 products; dextrinase, maltase, glucosidase Salivary amylase begins the digestion. Most starch digestion happens in the small intestine with enzyme secretions from the pancreas. 1,4 bonds broken by pancreatic amylase These small sections are now broken down into maltose and maltotriose Glucose

Starch digestion in the small intestine Illustrates many processes that we have learned about Membrane permeability Catalysis Glucose is absorbed via: co-transport with sodium ions into the interstitial fluid via facilitated diffusion through large membrane pores into capillaries. Enzyme specificity

Food not absorbed… Is eliminated as feces.

Predict whether the bag will gain or lose mass during the experiment. Cola drinks contain a mixture of substances with different particle sizes. This cola contains glucose, phosphoric acid, and caramel (a complex carbohydrate added to produce a brown color). Predict which substances will diffuse out of the bag, with reasons for your prediction. Predict whether the bag will gain or lose mass during the experiment. Cola, left to go flat before being put in a tube Bags made of dialysis tubing Water