Digestive System Miss Ulrich

Last Day.. Mechanical Digestion: physical breaking up of food into smaller pieces by the teeth. Tongue manipulates the food into a mass called a bolus Peristalsis is the rhythmic contraction of the longitudinal muscles in the esophagus and small intestine that push food through the digestive tract Villi/Microvilli: finger-like projections that line the folds of the small intestine and serve greatly to increase its absorptive surface area

What IS Chemical Digestion? The chemical break down of food by a process called hydrolysis Hydro = water lysis = to loosen Hydrolysis = to break apart with water Water is used to break compounds at specific points in the molecules While hydrolysis normally is very slow, the three groups of enzymes make the process very fast

Three Major Types of Enzymes Lipase Breaks down lipids into fatty acids and glycerol Carbohydrase Breaks down complex sugars into simple sugar molecules like glucose for use in our cells Protease Breaks down proteins into amino acids Vegetarians lack protease enzymes because their bo

Enzymes- The “Lock and Key” Model Proteins that catalyze (i.e., increase rate of) chemical reactions Highly specific to their substrate Substrates are converted into different molecules (i.e., products)

Enzymes Activity The effect of enzymes are greatly affected by: Temperature (warm = fast, cold = slow) Concentration (more = fast, less = slow) pH (suitable pH levels vary, but most work best under neutral or basic pH conditions) Some may also require specific metal ions to be present

Mouth: Salivary Glands There are 3 sets of salivary glands in the mouth which produce saliva to soften food making it easier to swallow Ducts: secrete saliva into the mouth from the glands Chemical digestion begins in the mouth with Salivary Amylase Breaks down sugars into simple sugars (starch to maltose)

Stomach: Gastric Juices Mechanical Digestion also takes place in the stomach- smooth muscle contracts to break down and mix the food with gastric juices to produce chyme Digestive glands in the stomach are stimulated by nerves and by a hormone called gastrin. Individual glands secrete mucus to moisten food and protect the stomach wall The glands also secrete pepsin, hydrochloric acid, and lipases. Hormone: chemical regulator that is secreted in one part of the body and transported by the bloodstream to another part, where it causes a response The glands that secrete gastrin are in the lower part of the stomach and are ductless. Therefore, the hormone must be transported by the bloodstream until it arrives at the upper part of the stomach before it is able to stimulate the digestive glands to secrete their products

Gastric Juice Contains… Hydrochloric acid (HCl) Lowers the pH to about 2, which is necessary for the digestion of proteins Pepsinogen (an inactive protein) Enters the stomach and comes into contact with HCl and is converted to pepsin (active enzyme) Pepsin breaks protein into polypeptides (chunks of protein). In this stage the enzymes are breaking down food. Minimal absorption occurs

Small Intestine – Chemical Digestion Two major glands involved in digestion in the small intestine: The Pancreas The Intestinal glands

Intestinal Glands Found in the walls of the small intestine They produce the following enzymes Peptidases – converts simple amino acids into polypeptides Lipase – converts fats into fatty acids and glycerol Three enzymes that convert larger sugars into glucose Maltase & Sucrase & Lactase Glucose is the monosaccharide which means it is a simple sugar…. A single molecule…. Maltose is a dissacharide which means two

The Pancreas Produces pancreatic juices which are secreted into the pancreatic duct and to the common bile duct and into the duodenum salivary amylase, pepsin, lipase, pancreatic amylase, maltase, sucrase, lactase Catalyze reactions breaking disacharyides into monosacharydes Produces enzymes like: Pancreatic amylase – converts starch to maltose Lipase – converts fats to fatty acids and glycerol Trypsin- digests proteins

The Liver Action is similar to detergent on greasy pots and pans Creates bile that is stored in the Gall bladder and released into the small intestine as needed Bile: aids the process of digestion of lipids in the small intestine (not an enzyme) Stored in the gall bladder and upon eating is discharged into the duodenum Breaks down fat mechanically into small droplets (emulsification) Action is similar to detergent on greasy pots and pans

The Gallbladder Serves as a storage warehouse for bile produced in the liver. As lipids are absorbed by the intestine, so are the components of bile. They are picked up and carried back to the liver to make more bile

The Duodenum and Related Organs Majority of absorption is done In the duodenum

Large Intestine Function: to absorb water from remaining waste material Enzymes are not secreted here.

Enzymes of the Human Digestive System chart Page 346 Read 10.3 Copy Enzymes from table 10.1 to your human digestion chart