One general feature which characterizes those phyla which we think of as \"highe

ID: 259878 • Letter: O

Question

One general feature which characterizes those phyla which we think of as "higher animals" is a high degree of structural complexity. The bodies of animals like cats and crocodiles are dubdivided into a variety of specialized structures we call "organs." Organs with related functions are interconnected, forming organ systems.

This exercise will focus on just one of those organ systems--one of the most obvious and easy to figure out: the digestive system. The general task of the digestive system is apparently simple. Food, which comes to us in sizeable chunks, must be broken down into its simple molecular components, absorbed into the blood stream and distributed throughout the body to supply the energy and other nutrient needs of the trillions of cells in that body. (The distribution part of that need is fulfilled by another system--the circulatory system.) The parts of the food which aren't useful to us or which can't be broken down must be disposed of.

But this general task isn't as simple as it may sound. Quite a few different operations are necessary on that pathway from snack to cellular nutrients. The various organs of the digestive system are specialized to perform these tasks.

So here's your assignment. Imagine you've just taken a healthy bite of a nice, juicy burger. What happens to the parts of that burger as it travels through your body, from one end to the other?

Just for the record, here's what's in your burger. It's a ground beef patty (good quality, of course--only the best!) inside a bread bun. We don't want just a plain old burger, of course, so we've added a bit of mayonnaise, a couple of leaves of lettuce and a few slices of pickle. Yum!

In the world of biochemistry, that means we've got protein (meat), carbohydrates (bread, lettuce, pickles), and lipids (mayo). There are other things in there as well--vitamins, minerals, trace elements, etc., not to mention DNA. But your assignment will focus on those big three nutrients--protein, carbohydrate and lipid.

In your assignment, you are to discuss what happens to these various components (beginning with the intact bite of burger) as they travel through the mouth, esophagus, stomach, duodenum and small intestines, and the colon. Don't forget what happens at the very end .Along the way, some adjunct structures come into play as well. Don't forget about the salivary glands, the liver, the gall bladder and the pancreas. Also, you need to include specific information about digestive enzymes, including names and sources, and the target molecules they act upon.

A strong hint: The smartest way to go about this is to treat each of these "way stations" in order. Start with the mouth, then follow the food as it passes from one area of the digestive system to another. Keep your narrative organized and easy to follow. And have fun--this is your burger you're talking about.

Explanation / Answer

Food rich in mainly three nutrients:

PATHWAY IN TABULATED FORM:

Part of Digestive system

Enzyme and its Action with products formed

Process

Buccal cavity

Saliva containing enzyme amylase from Salivary Glands

Starch changes to maltose

Crushed by teeth molar and premolars

Rinsed with liquids in mouth called saliva that help in adherence of particles together to form bolus for swallowing

Oesophagus

No action

Being pushed forward through peristaltic movement . No enzyme encounter.

Stomach

Gastric lipase

Fats Fatty acids and glycerol

Pepsinogen Pepsin in presence of HCL

Pepsin

Proteins Peptides

Flushed into gastric juices rich in HCl that cause denaturation of proteins, killing of bacteria,

Moving out of stomach through cardiac sphincter

Small Intestine

Panceratic Juice from Pancreas

Pancreatic lipase/steapsin

Meets juices coming from pancreas that are alkaline in nature and activates different enzyme action

Bile Juice from Liver

Emulsification of fats i.e breakdown of large globules into smaller globules

In intestine also get rinsed with green bile juice from liver

Intestinal Juice from intestine

Peptidase

Peptide Amino acids

Lipase

Di glycerides mono glycerides

Maltase to break maltose to glucose

Sucrose to convert sucrose to glucose and galactose.

Insentinal juice rich in all enzymes breaks all nutrients into smallest particle

Large Intestine

Digestion and absorption of nutrients continue.

Absorption of maximum water from me

Rectum

Undigested part of food stored

Anus

Pathway to outside