1. Where it happens, How it works, and Why it’s important
DIGESTION
Where it happens, How it works, and Why it’s important

2. 3 primary functions of the digestive system
Break down food
Is this hydrolysis or dehydration synthesis?
Absorb nutrients (monomers) & water
Remove waste (non-digestible material)

3. Where it happens... Digestive TRACT = Mouth Esophagus Stomach
Small intestine
Large intestine
Digestive SYSTEM Includes organs that contribute digestive juices

4. The Mouth Chewing increases surface area Saliva:
Wets the food & mixes it with mucus
Salivary amylase breaks starches into disaccharides
Kills off dangerous microbes

5. The Esophagus Swallowing closes off the trachea via the epiglottis
Peristalsis begins
NO ENZYMES here

6. The Stomach Here for 2-3 hours Storage Liquifies to form chyme
Pepsin (requires acidic pH of 1...HCl does this)

7. The Small Intestine Duodenum Pancreatic juice (from pancreas)
Amylase
Lipase
Protease
Sodium bicarbonate neutralizes acid
Bile (from liver via gallbladder) salts increase lipid surface area by emulsification
- Intestinal juice (from small intestine)
Maltase, lactase, sucrase
Protease

8. Nutrient Absorption In the small intestine Molecules have to be small
Villi
What is left? Water, cellulose & other non-digestible matter

9. The Appendix For humans, unused in digestion
In other mammals, it stores cellulose and other nutrient remains at this point in digestion
(Fun Fact: current science says it is used in our immune system to help identify antigens in food)

10. The Large Intestine (the Colon)
Water diffuses into the blood
Bacteria live here in symbiosis with us

11. The Breakdown: MOLECULES: Carbohydrates Proteins Lipids
WHERE DIGESTED:
Mouth, small intestine
Stomach, small intestine
Small intestine

12. Gross Facts
Bacteria love the stuff we can’t break down…and gas & flatulence are caused by bacteria metabolizing these nutrients
99% of these gases are odorless
People actually study these gases to find out the 1% of these gases that cause the odors (great job!)
Feces is 1/2 bacteria by weight

13. Gross Facts
Newborns don’t pass gas because they have no bacteria in their intestines yet
Beano breaks down some molecules the bacteria like
Lactaid breaks down lactose
Gas-X reduces the surface tension of gas bubbles, which makes you feel better….but the gas is still there
Passing gas in public in ancient Rome was against the law

14. To see and hear digestion in action: **