Agenda 1/5 and 1/8 Digestion System Notes Practice Diagram Review Tasks Turn in: Video notes and workbook Homework: Digestion Worksheet (posted on website)

Digestion Steps 1. Ingestion- you eat the food 2. Digestion- series of chemical reactions where the food is converted into smaller molecules 3. Absorption- Smaller molecules are absorbed into your bloodstream 4. Transport- Those smaller molecules are moved to where they are needed in your body Digestion breaks molecules down into smaller parts. Those molecules can then be used to make larger molecules we need Ex: Proteins you eat are broken down into amino acids. Those amino acids can then be used during protein synthesis

Food Molecules Starch, glycogen, lipids, and nucleic acids are digested into monomers Cellulose (known as dietary fiber) is undigested by our bodies But bacteria in our gut can digest it!

Enzymes As food travels through your digestive system, enzymes are added along the way to break the food down Enzymes are specific for a specific food type Enzymes act as catalysts for reactions Enzymes work best at 37 degrees Celsius (body temperature) What happens if this temperature increases too much?

Anatomy of Digestive System Basically a long tube called the alimentary canal Two accessory organs: Pancreas and liver Connected to the canal by ducts Begins in the mouth, ends at the anus *draw, label, color your own digestive system diagram!

Digestive System Sketch

Alimentary Canal Smooth muscles in the alimentary canal cause food to move through the digestive system Smooth muscles are control by the autonomic nervous system and are involuntary Meaning you don’t have to think about your digestive system muscles as you sit here! Two layers of muscle: circular and longitudinal

Microscopic Digestive Tissue- Small Intestine

Pancreas The pancreas produces insulin and glucagon which an involved in cellular respiration It also produced three enzymes important to digestion 1. Lipase- breaks down lipids 2. Amylase- breaks down sugars 3. Endopeptidase- breaks down proteins

Small Intestine The pancreas produces juice that goes into the duodenum (the first part of the small intestine) The enzymes in that juice begin to break food particles down into smaller molecules The smaller molecules can be absorbed by the intestines and go into the blood stream so they can be used by your body

Villi in Small Intestines Villi are small folds and projections that increase the surface area that can absorb nutrients in the intestines Epithelial cells have tiny microvilli that extend into the lumen of the intestines and absorb digested particles to be transported through the blood stream Villi absorb: water, glucose, amino acids, nucleotides, glycerol, fatty acids, mineral ions, vitamins

Microscopic Cross-Section of Villi

Active vs. Passive Transport in Villi Molecules move out of the lumen in the villi through active or passive transport Simple Diffusion: Small, non- polar molecules (like fatty acids) Facilitated Diffusion: Large or polar (like glucose) Active: Glucose and amino acids if moving against concentration gradient

Role of Liver in Digestion The liver produces bile which is stored in the gall bladder Bile is used to break down fats The liver has other roles- like storing glycogen for energy outside of digestion

Things to Label on Small Intestines Villi Lumen Circular Muscle Longitudinal Muscle