DIGESTIVE SYSTEM CHAPTER 38-1 PG Organization: how does our body get nutrients?

What nutrients do our bodies need?  Carbohydrates – energy  Lipids – energy, cell membranes, insulation/ protection  Proteins – Many different functions!

What else do our bodies need?  Water – our cells are filled with cytoplasm, which is made of mostly water  Vitamins – Molecules our bodies cant make, but need  Minerals – ions such as iron (Fe 2+ ), Calcium (Ca 2+ ), Sodium (Na + ), and Potassium (K + )

How do we get nutrients?  The function of the digestive system:  Break up complex molecules (food) into smaller pieces that our bodies can use

4 steps to get nutrients  Ingestions – take in food  Digestions – break down food  Absorption – move monomers to blood stream  Elimination – get rid of waste

Primary & Accessory Organs  Primary: organs the food passes through  Accessory: food does not pass through, but help in digestion

The Organs

Mouth  Mechanical digestions: physically breaks apart food  Teeth  chew!  Chemical digestion: breaks chemical bonds  Saliva: contains amylase  an enzyme that breaks down polysaccharides Moistens food

Esophogus  Peristalsis: the contraction of muscles in waves to move and crush the bolus, chewed food.  /watch?v=rJS-Kh5wCQU /watch?v=rJS-Kh5wCQU  Epiglottis: flap that prevents food from going down your trachea (windpipe) when you swallow.

Stomach  Chemical: HCl kills bacteria and activates pepsin enzymes  Pepsin breaks down polypeptides (protein)  Mechanical: muscles crush and mix food into chyme

Small Intestine  Chemical:  Where most digestion takes place  pancreas and liver secrete enzymes into small intestine  Vili: many folds in the walls, which increase surface area for absorption

Pancreas  Accessory organ  Has different types of cells to produce hormones and enzymes  Secretes (produces) enzymes into small intestine:  Amylase – breaks down starch  Trypsin – breaks down polypeptides  Lipase – breaks down triglycerides

Liver  Accessory organ  Connect to the small intestine through the common bile duct  Secretes bile:  Bile emulsifies fats = bile breaks up clumps of fat

Gall Bladder  Accessory organ  Stores bile

Large Intestine  No digestion  Removes water  Stores waste

More Digestive Enzymes What chemical reaction do these enzymes catalyze ?

Practice Essay  Can you describe what would happen to a slice of pepperoni pizza as it moves through your digestive system?  What macromolecules are in which parts of the pizza?  Where would those macromolecules be digested?