Monday, May 7, 2012

May 7th, 2012

Today in class we took some practice quizzes and discussed the calorimetry lab.

  • finish calorimetry lab, due tomorrow
  • design a quiz, due tomorrow
  • study for Tissues, Excretion and Digestion test, Thursday
  • make sure you've read the chapters (21 and 22)

Digestion Notes

There are 4 stages of digestion.
  • Ingestion: eating food
  • Digestion: breaking down the food you eat into small molecules that your body can use
  • Absorption: the cells in the lining of the digestive tract take in the molecules and transport them throughout the body using the bloodstream
  • Elimination: getting rid of undigested wastes
There are 2 types of digestion.
  • Mechanical Digestion: physical processes like chewing and stomach churning
  • Chemical Digestion: breaking down food with enzymes
    • Hydrolysis: breaking down of polymers into monomers using the atoms from water
    • Hydrolases: digestive enzymes that catalyze hydrolysis
    • Enzymes: specific molecules that start chemical reactions
The alimentary canal is a fancy name for the digestive tract. It has hollow cativities where food passes through to be digested and absorbed (in red), accessory organs (in blue) and enzymes (in purple). The process of digestion starts in the mouth...

Mouth (oral cavity)
  • chewing, lubricates food, swallowing into the pharynx (first part of the throat, before the split between the trachea and esophagus
  • attached to the mouth are 3 pairs of salivary glands: release saliva (1 liter a day) and salivary amylase
  • salivary amylase: breaks starches into sugars (maltose)
  • muscular tube, uses muscle contractions called peristalsis to push food into the stomach
  • no enzymes
  • stores food for 2 to 6 hours, can hold 2 liters of food and water
  • muscular, churns food and gastric acid into a mixture called acid chyme
  • contains gastric juice: pH of .8 to 2 (VERY acidic), hydrochloric acid (HCl) that kills bacteria and activates pepsin, pepsin: breaks proteins into amino acids, rennin: breaks down milk proteins
  • stomach lining coated in mucus to protect itself from gastric juice, replaced every 2 to 3 days
  • top of the stomach is closed off by the cardiac sphincter (esophageal sphincter in the picture) and the end of the stomach is closed off by the pyloric sphincter
  • sphincter: muscular ring that contricts a part of the body until materials need to exit or enter
  • produces bile: emulsifies fats, breaking big fat droplets into little fat droplets so they are accessible to enzymes
  • bile is stored, concentrated and released by the neighboring gall bladder
  • bile is secreted into the duodenum
  • pancreatic juice: contains trypsin, lipase and amylase, neutralizes stomach acids in the duodenum
  • trypsin: breaks down proteins into amino acids
  • lipase: breaks down fats (lipids) into glycerol and fructose
  • pancreatic amylase: breaks down starches into sugars (maltose)
  • pancreatice juice is secreted into the duodenum
Small Intestine
  • 2.5 centimeters wide, 6 meters long
  • duodenum: first part of the small intestine, mixes pancreatic juice, bile and intestinal juice, 90% of digestion
  • peptidase: breaks down proteins into amino acids
  • maltase: breaks down maltose (disaccharide) into 2 glucose molecules (monosaccharide)
  • sucrase: breaks down sucrose (disaccharide) into glucose (monosaccharide) and fructose (monosaccharide)
  • lactase: breaks down lactose (disaccharide) into glucose (monosaccharide) and galacatose (monosaccharide)
  • small intestine completes digestion and does most of the aborption
  • villi: tiny projections on the lining of the intestine, increase surface area for absorption, absorbs nutrients and passes them into the sorrounding capillaries
Large Intestine
  • 5 centimeters wide
  • colon: majority of large intestine, absorbs water and excess salts
  • appendix: small projection where the small and large intestines meet, no purpose in humans, possible function: to store extra "good" bacteria that the digestive system needs?
  • rectum: end of the large intestine, stores wastes (feces)
  • anus: final sphincter fo the digestive system



  1. You put in a lot of good pictures and lots of notes. I think it was really helpful. Nice job

  2. I agree with Austin. This post is really detailed and easy to understand. The color coding is extremely helpful also. Nice work!

  3. I agree with Austin and Vinise - the pictures were really good for understanding this unit. I also love the color coding, because that really helped me understand the different categories (hollow cavities, accessory organs, and enzymes) and processes! Great job :)

  4. I agree with the three of them--looks really nice and clean and easy to read. :) The only thing you forgot was the labels I think (with this new format, it was hard for me to figure out how to add them, so no worries). I really like this one!!

  5. WOW Lydia. This is a really great guide! I really liked how you organized it, kind of in the order of the path food takes. With key terms bundled and bolded with each organ, it really made it easy to understand what was happening to the food each step of the way. The tons of visual aid wasn't a bad idea either =D GREAT job.